Onto Innovation (ONTO) 10-K 26 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Feb. 20, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	NANOMETRICS INC
Entity Central Index Key	704,532
Document Type	10-K
Document Period End Date	Dec. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	NANO
Current Fiscal Year End Date	--12-30
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		23,761,304
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 468.3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 34,899	$ 47,062
Marketable securities	82,130	82,899
Accounts receivable, net of allowances of $126 and $73, respectively	62,457	39,457
Inventories	52,860	38,837
Inventories-delivered systems	1,534	2,457
Prepaid expenses and other	6,234	5,667
Total current assets	240,114	216,379
Property, plant and equipment, net	44,810	44,226
Goodwill	10,232	8,940
Intangible assets, net	2,206	412
Deferred income tax assets	11,924	17,399
Other assets	413	474
Total assets	309,699	287,830
Current liabilities:
Accounts payable	13,857	11,342
Accrued payroll and related expenses	12,901	12,656
Deferred revenue	7,408	9,168
Other current liabilities	7,249	8,047
Income taxes payable	2,680	813
Total current liabilities	44,095	42,026
Deferred revenue	1,661	816
Income taxes payable	860	841
Deferred tax liability	179	20
Other long-term liabilities	521	353
Total liabilities	47,316	44,056
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 3,000,000 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.001 par value, 47,000,000 shares authorized: 24,628,722 and 25,070,889, respectively, issued and outstanding	26	25
Additional paid-in capital	255,368	271,969
Retained earnings (deficit)	9,113	(22,174)
Accumulated other comprehensive income (loss)	(2,124)	(6,046)
Total stockholders’ equity	262,383	243,774
Total liabilities and stockholders’ equity	$ 309,699	$ 287,830

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowances for doubtful accounts	$ 126	$ 73
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	47,000,000	47,000,000
Common stock, shares issued	24,628,722	25,070,889
Common stock, shares outstanding	24,628,722	25,070,889

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Net revenues:
Products	$ 214,877	$ 185,066	$ 146,945
Service	43,744	36,063	40,422
Total net revenues	258,621	221,129	187,367
Costs of net revenues:
Cost of products	100,910	85,391	76,224
Cost of service	20,804	20,160	19,450
Amortization of intangible assets	206	1,454	2,026
Total costs of net revenues	121,920	107,005	97,700
Gross profit	136,701	114,124	89,667
Operating expenses:
Research and development	36,716	31,443	32,701
Selling	30,839	30,181	28,055
General and administrative	26,340	23,381	22,444
Amortization of intangible assets		24	114
Restructuring charge			1,380
Total operating expenses	93,895	85,029	84,694
Income from operations	42,806	29,095	4,973
Other (income) expense:
Interest income	8	35	71
Interest expense	(92)	(285)	(289)
Other income, net	576	290	813
Total other income, net	492	40	595
Income before income taxes	43,298	29,135	5,568
Provision for (benefit from) income taxes	13,096	(14,900)	2,663
Net income	$ 30,202	$ 44,035	$ 2,905
Net income per share:
Basic (in dollars per share)	$ 1.19	$ 1.79	$ 0.12
Diluted (in dollars per share)	$ 1.17	$ 1.75	$ 0.12
Weighted average shares used in per share calculation:
Basic (in shares)	25,334	24,655	24,059
Diluted (in shares)	25,919	25,153	24,375

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 30,202	$ 44,035	$ 2,905
Other comprehensive income (loss):
Change in foreign currency translation adjustment	4,170	(869)	(2,344)
Employee benefit plan adjustment	(160)	(17)	(76)
Net change on unrealized (losses) gains on available-for-sale investments	(88)	42	(13)
Other comprehensive income (loss)	3,922	(844)	(2,433)
Comprehensive income	$ 34,124	$ 43,191	$ 472

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning Balance Value at Dec. 27, 2014	$ 179,537	$ 24	$ 251,396	$ (69,114)	$ (2,769)
Beginning Balance Shares at Dec. 27, 2014		23,813,729
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,905			2,905
Employee benefit plan adjustment	(76)				(76)
Foreign currency translation adjustments	(2,344)				(2,344)
Unrealized gain (loss) on investments, net of tax	(13)				(13)
Issuance of common stock under stock-based compensation plans	2,792		2,792
Issuance of common stock under stock-based compensation plans, Shares		521,607
Stock-based compensation expense	6,248		6,248
Repurchases and retirement of common stock under share repurchase plans	$ (1,721)		(1,721)
Repurchases and retirement of common stock under share repurchase plans, Shares	(111,050)	(111,050)
Ending Balance Value at Dec. 26, 2015	$ 187,328	$ 24	258,715	(66,209)	(5,202)
Ending Balance Shares at Dec. 26, 2015		24,224,286
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,035			44,035
Employee benefit plan adjustment	(17)				(17)
Foreign currency translation adjustments	(869)				(869)
Unrealized gain (loss) on investments, net of tax	42				42
Issuance of common stock under stock-based compensation plans	6,625	$ 1	6,624
Issuance of common stock under stock-based compensation plans, Shares		846,603
Stock-based compensation expense	7,666		7,666
Excess tax benefit related to stock options	(1,036)		(1,036)
Ending Balance Value at Dec. 31, 2016	$ 243,774	$ 25	271,969	(22,174)	(6,046)
Ending Balance Shares at Dec. 31, 2016	25,070,889	25,070,889
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 30,202			30,202
Adjustment due to adoption of ASU 2016-09 Improvements to Employee Share-Based Payment Accounting | Accounting Standards Update 2016-09 [Member]	1,224		139	1,085
Employee benefit plan adjustment	(160)				(160)
Foreign currency translation adjustments	4,170				4,170
Unrealized gain (loss) on investments, net of tax	(88)				(88)
Issuance of common stock under stock-based compensation plans	1,441	$ 1	1,440
Issuance of common stock under stock-based compensation plans, Shares		623,681
Stock-based compensation expense	8,819		8,819
Repurchases and retirement of common stock under share repurchase plans	$ (26,999)		(26,999)
Repurchases and retirement of common stock under share repurchase plans, Shares	(1,065,848)	(1,065,848)
Ending Balance Value at Dec. 30, 2017	$ 262,383	$ 26	$ 255,368	$ 9,113	$ (2,124)
Ending Balance Shares at Dec. 30, 2017	24,628,722	24,628,722

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Cash flows from operating activities:
Net income	$ 30,202	$ 44,035	$ 2,905
Reconciliation of net income to net cash provided by operating activities:
Depreciation and amortization	6,920	8,295	9,075
Stock-based compensation	8,819	7,666	6,248
Excess tax benefit from equity awards		1,036
Disposal of fixed assets	631	478	1,121
Inventory write-down	2,020	2,110	2,645
Deferred income taxes	6,858	(16,783)	345
Changes in fair value of contingent payments to Zygo Corporation		(1,175)	(56)
Changes in assets and liabilities:
Accounts receivable	(19,523)	(2,707)	(12,610)
Inventories	(18,037)	4,526	(16,431)
Inventories-delivered systems	923	399	(943)
Prepaid expenses and other	(230)	905	3,271
Accounts payable, accrued and other liabilities	1,049	2,462	4,167
Deferred revenue	(915)	(3,634)	1,006
Income taxes payable	1,886	(1,928)	828
Net cash provided by operating activities	20,603	45,685	1,571
Cash flows from investing activities:
Payment for acquisition of certain assets	(2,000)
Sales of marketable securities	53,030	5,955	3,383
Maturities of marketable securities	77,250	38,775	41,863
Purchases of marketable securities	(129,766)	(82,864)	(41,449)
Purchases of property, plant and equipment	(5,204)	(3,999)	(1,846)
Net cash (used in) provided by investing activities	(6,690)	(42,133)	1,951
Cash flows from financing activities:
Payments to Zygo Corporation related to acquisition		(315)	(851)
Proceeds from sale of shares under employee stock option plans and purchase plan	5,576	8,447	3,974
Excess tax benefit from equity awards		(1,036)
Taxes paid on net issuance of stock awards	(4,135)	(1,822)	(1,182)
Net cash (used in) provided by financing activities	(25,558)	5,274	220
Effect of exchange rate changes on cash and cash equivalents	(518)	82	(264)
Net (decrease) increase in cash and cash equivalents	(12,163)	8,908	3,478
Cash and cash equivalents, beginning of period	47,062	38,154	34,676
Cash and cash equivalents, end of period	34,899	47,062	38,154
Supplemental disclosure of cash flow information:
Cash paid (refund) for income taxes, net	3,040	3,767	(826)
Supplemental disclosure of non-cash investing activities:
Transfer of inventory to property, plant and equipment, net	2,451	2,345	1,469
Property, plant and equipment included in accounts payable	957	$ 683	36
Share Repurchase Plans [Member]
Cash flows from financing activities:
Repurchases of common stock	$ (26,999)		$ (1,721)

Nature of Business, Basis of Pr

Nature of Business, Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business, Basis of Presentation and Significant Accounting Policies	Note 1. Nature of Business, Basis of Presentation and Significant Accounting Policies Description of Business – Nanometrics Incorporated (“Nanometrics” or the “Company”) and its wholly-owned subsidiaries design, manufacture, market, sell and support optical critical dimension ("OCD"), thin film and overlay dimension metrology and inspection systems used primarily in the manufacturing of semiconductors, solar photovoltaics (“solar PV”) and high-brightness LEDs (“HB-LED”), as well as by customers in the silicon wafer and data storage industries. Nanometrics' metrology systems precisely measure a wide range of film types deposited on substrates during manufacturing to control manufacturing processes and increase production yields in the fabrication of integrated circuits. The Company’s OCD technology is a patented critical dimension measurement technology that is used to precisely determine the dimensions on the semiconductor wafer that directly control the resulting performance of the integrated circuit devices. The thin film metrology systems use a broad spectrum of wavelengths, high-sensitivity optics, proprietary software, and patented technology to measure the thickness and uniformity of films deposited on silicon and other substrates as well as their chemical composition. The overlay metrology systems are used to measure the overlay accuracy of successive layers of semiconductor patterns on wafers in the photolithography process. Nanometrics' inspection systems are used to find defects on patterned and unpatterned wafers at nearly every stage of the semiconductor production flow. The corporate headquarters of Nanometrics is located in Milpitas, California. Basis of Presentation – The consolidated financial statements include Nanometrics Incorporated and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. Fiscal Year – The Company utilizes a 52/53 week fiscal year ending on the last Saturday of the calendar year. For each of fiscal years ended December 30, 2017, December 31, 2016, and December 26, 2015, the period presented consisted of a 52-week year, 53-week year and 52-week year, respectively. Upgrade Revenue and Related Cost - Beginning the first quarter of 2016, revenues associated with upgrade sales are now included under Products Revenues, and the related costs in Cost of Products Revenue. This change was due to the types of upgrades currently being sold, which are primarily system software and hardware performance upgrades to extend the features and functionality of a product. Previously upgrades consisted of a group of parts and/or software that change the existing configuration of a product. For the twelve months ended December 30, 2017, and December 31, 2016, $12.1 million and $11.0 million, respectively, of upgrade sales and $2.7 million and $2.4 million of costs, respectively, are included in Products Revenues and Cost of Products Revenues. For the year ended December 26, 2015, $7.9 million related to upgrade sales, and $3.0 million of costs, are included in Service Revenues and Costs of Service Revenues, respectively, in the accompanying Condensed Consolidated Statement of Operations. Use of Estimates – The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("U.S. GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ materially from those estimates. Estimates are used for, but not limited to, revenue recognition, the provision for doubtful accounts, the provision for excess, obsolete, or slow-moving inventories, valuation of intangible and long-lived assets, warranty accruals, income taxes, valuation of stock-based compensation, and contingencies. Foreign Currency Translation – The assets and liabilities of foreign subsidiaries are translated from their respective local functional currencies at exchange rates in effect at the balance sheet date and income and expense accounts are translated at average exchange rates during the reporting period. Resulting translation adjustments are reflected in “Accumulated other comprehensive income,” a component of stockholders’ equity. Foreign currency transaction gains and losses, as well as remeasurement of assets and liabilities denominated in a currency other than the functional currency are reflected in “Other income (expense)” in the consolidated statements of operations in the period incurred, and consists of a $0.6 million loss, a $0.4 million loss and a $0.5 million gain for the years ended December 30, 2017, December 31, 2016, and December 26, 2015, respectively. Revenue Recognition – The Company derives revenue from the sale of process control metrology and inspection systems and related upgrades (“product revenue”) as well as spare part sales, billable service and service contracts (together “service revenue”). Upgrades are system software and hardware performance upgrades that extend the features and functionality of a product. As discussed above, commencing in the first quarter of 2016, upgrades are included in product revenue, which consists of sales of complete, advanced process control metrology and inspection systems (the “system(s)”). Nanometrics’ systems consist of hardware and software components that function together to deliver the essential functionality of the system. Arrangements for sales of systems and upgrades often include defined customer-specified acceptance criteria. In summary, the Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller's price is fixed or determinable, and collectability is reasonably assured. For repeat product sales to existing customers, revenue recognition occurs at the time title and risk of loss transfer to the customer, which usually occurs upon shipment from the Company's manufacturing location, if it can be reliably demonstrated that the product has successfully met the defined customer specified acceptance criteria and all other recognition criteria have been met. For initial sales where the product has not previously met the defined customer specified acceptance criteria, product revenues are recognized upon the earlier of receipt of written customer acceptance or expiration of the contractual acceptance period. In Japan, where contractual terms with the customer specify risk of loss and title transfers upon customer acceptance, revenue is recognized upon receipt of written customer acceptance, provided that all other recognition criteria have been met. The Company warrants its products against defects in manufacturing. Upon recognition of product revenue, a liability is recorded for anticipated warranty costs. On occasion, customers request a warranty period longer than the Company's standard warranty. In those instances, where extended warranty services are separately quoted to the customer, the associated revenue is deferred and recognized as service revenue ratably over the term of the extended warranty period. The portion of service contracts and extended warranty services agreements that are uncompleted at the end of any reporting period are included in deferred revenue. As part of its customer services, the Company sells software that is considered to be an upgrade to a customer's existing systems. These standalone software sales are not essential to the tangible product's functionality and are accounted for under software revenue recognition rules which require vendor specific objective evidence (“VSOE”) of fair value to allocate revenue in a multiple element arrangement. Revenue from software sales is recognized when the software is delivered to the customer, provided that all other recognition criteria have been met. The majority of other upgrades are sold based on published specifications. For simple upgrades that do not require major configuration, revenue is recognized at the time title and risk of loss transfer to the customer, which is usually upon shipment. For complex and extensive upgrades, specific acceptance or prior acceptance for a similar upgrade is required in order to recognize revenue. Revenue related to spare parts is recognized upon shipment. Revenue related to billable services is recognized as the services are performed. Service contracts may be purchased by the customer during or after the warranty period and revenue is recognized ratably over the service contract period. Frequently, the Company delivers products and various services in a single transaction. The Company's deliverables consist of tools, installation, upgrades, billable services, spare parts, and service contracts. The Company's typical multi-element arrangements include a sale of one or multiple tools that include installation and standard warranty. Other arrangements consist of a sale of tools bundled with service elements or delivery of different types of services. The Company's tools, upgrades, and spare parts are generally delivered to customers within a period of up to six months from order date. Installation is usually performed soon after delivery of the tool. The portion of revenue associated with installation is deferred based on relative selling price and that revenue is recognized upon completion of the installation and receipt of final acceptance. Billable services are billed on a time and materials basis and performed as requested by customers. Under service contract arrangements, services are provided as needed over the fixed arrangement term, which terms can be up to twelve months. The Company does not grant its customers a general right of return or any refund terms and imposes a penalty on orders cancelled prior to the scheduled shipment date. The Company regularly evaluates its revenue arrangements to identify deliverables and to determine whether these deliverables are separable into multiple units of accounting. The Company allocates the arrangement consideration among the deliverables based on relative selling prices. The Company has established VSOE for some of its products and services when a substantial majority of selling prices falls within a narrow range when sold separately. For deliverables with no established VSOE, the Company uses best estimate of selling price to determine standalone selling price for such deliverable. The Company does not use third party evidence to determine standalone selling price since this information is not widely available in the market as the Company's products contain a significant element of proprietary technology and the solutions offered differ substantially from competitors. The Company has established a process for developing estimated selling prices, which incorporates historical selling prices, the effect of market conditions, gross margin objectives, pricing practices, as well as entity-specific factors. The Company monitors and evaluates estimated selling price on a regular basis to ensure that changes in circumstances are accounted for in a timely manner. When certain elements in multiple-element arrangements are not delivered or accepted at the end of a reporting period, the relative selling prices of undelivered elements are deferred until these elements are delivered and/or accepted. If deliverables cannot be accounted for as separate units of accounting, the entire arrangement is accounted for as a single unit of accounting and revenue is deferred until all elements are delivered and all revenue recognition requirements are met. Cash, Cash Equivalents and Marketable Securities – The Company considers all highly liquid investments with original maturities of three months or less, when purchased, to be cash equivalents. Marketable securities are classified as “available-for-sale” and are reported at fair value with unrealized gains and losses reported in stockholders' equity as a component of other comprehensive income. The cost of securities sold is based on the specific identification method. The Company classifies its investments as current based on the nature of the investment and their availability for use in current operations. The Company reviews its investment portfolio quarterly to determine if any securities may be other-than-temporarily impaired due to increased credit risk, changes in industry or sector of a certain instrument or ratings downgrades. Fair Value of Financial Instruments – Financial instruments include cash and cash equivalents, accounts receivable and accounts payable. Cash equivalents are stated at fair market value based on quoted market prices. The carrying values of accounts receivable and accounts payable approximate their fair values because of the short-term maturity of these financial instruments. Derivatives – The Company enters into foreign currency forward exchange contracts to protect against currency exchange risks associated with existing assets and liabilities. A foreign currency forward exchange contract acts as a hedge by increasing in value when underlying assets decrease in value or underlying liabilities increase in value due to changes in foreign exchange rates. Conversely, a foreign currency forward exchange contract decreases in value when underlying assets increase in value or underlying liabilities decrease in value due to changes in foreign exchange rates. These forward contracts are not designated as accounting hedges, so the unrealized gains and losses are recognized in other income, net, in advance of the actual foreign currency cash flows with the fair value of these forward contracts being recorded as accrued liabilities or other current assets. The Company does not use forward contracts for trading purposes. Allowance for Doubtful Accounts – The Company maintains allowances for estimated losses resulting from the inability of its customers to make required payments. Credit limits are established through a process of reviewing the financial history and stability of its customers. Where appropriate and available, the Company obtains credit rating reports and financial statements of customers when determining or modifying their credit limits. The Company regularly evaluates the collectability of its trade receivable balances based on a combination of factors such as the length of time the receivables are past due, customary payment practices in the respective geographies and historical collection experience with customers. The Company believes that its allowance for doubtful accounts adequately reflects the risk associated with its receivables. If the financial conditions of a customer were to deteriorate, resulting in their inability to make payments, the Company may need to record additional allowances, which would result in additional general and administrative expenses being recorded for the period in which such determination was made. Inventories – Inventories are stated at the lower of cost, which approximates actual cost on a first-in, first-out basis, or net realizable value. The Company is exposed to a number of economic and industry factors that could result in portions of inventory becoming either obsolete or in excess of anticipated usage, or saleable only for amounts that are less than their carrying amounts. These factors include, but are not limited to, technological changes in the market, the Company’s ability to meet changing customer requirements, competitive pressures in products and prices, and the availability of key components from suppliers. The Company has established inventory reserves when conditions exist that suggest that inventory may be in excess of anticipated demand or is obsolete based upon assumptions about future demand for the Company’s products and market conditions. Once a reserve has been established, it is maintained until the part to which it relates is sold or is otherwise disposed of. The Company regularly evaluates its ability to realize the value of inventory based on a combination of factors including the following: historical usage rates, forecasted sales of usage, product end-of-life dates, estimated current and future market values and new product introductions. For demonstration inventory, the Company also considers the age of the inventory and potential cost to refurbish the inventory prior to sale. Demonstration inventory is amortized over its useful life and the amortization expense is included in total inventory write down on the statements of cash flows. When recorded, reserves are intended to reduce the carrying value of the Company’s inventory to its net realizable value. If actual demand for the Company’s products deteriorates, or market conditions are less favorable than those that the Company projects, additional reserves may be required. Inventories – delivered systems – The Company reflects the cost of systems that were invoiced upon shipment but deferred for revenue recognition purposes separate from its inventory held for sale as “Inventories – delivered systems.” Property, Plant and Equipment – Property, plant and equipment are stated at cost. Depreciation and amortization is computed using the straight–line method over the following estimated useful lives of the assets: Building and Improvements 5-40 years Machinery and equipment 3-10 years Furniture and fixtures 3-10 years Software 3-7 years Goodwill and Intangible Assets – Goodwill is initially recorded when the purchase price paid for an acquisition exceeds the estimated fair value of the net identified tangible and intangible assets acquired. Intangible assets with finite lives are amortized over their respective useful lives on a straight-line basis and are also evaluated annually for impairment or whenever events or circumstances occur which indicate that those assets might be impaired. Goodwill and indefinite lived assets are not amortized but tested annually for impairment. The Company’s impairment review process is completed during the fourth quarter of each year or whenever events, or circumstances occur which indicate that an impairment may have occurred. The Company assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. If, after assessing the qualitative factors, the Company determines that it is not likely that the fair value of a reporting unit is less than its carrying value, then performing the two-step impairment test is unnecessary. However, if the Company concludes otherwise, then it is required to perform the first step of the two-step goodwill impairment test. The first step requires a comparison of the fair value of Nanometrics’ reporting unit to its net book value. If the fair value of the reporting unit is greater than its carrying value, then no impairment is deemed to have occurred. If the fair value is less, then the second step must be performed to determine the amount, if any, of actual impairment. Amortization of intangible assets with finite lives is computed using the straight-line method over the following estimated useful lives of the assets: Developed technology 5-10 years Customer relationships 2-10 years Brand name 5-10 years Patented technology 7-10 years Trademark 5 years Long-Lived Assets – The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When the sum of the undiscounted future net cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount, impairment may exist. To determine the amount of impairment, the Company compares the fair value of the asset to its carrying value. If the carrying value of the asset exceeds its fair value, an impairment loss equal to the difference is recognized. See Note 7, "Goodwill and Intangible Assets" for further details. Income Tax Assets and Liabilities – The Company accounts for income taxes such that deferred tax assets and liabilities must be recognized using enacted tax rates for the effect of temporary differences between the book and tax accounting for assets and liabilities. Also, deferred tax assets are reduced by a valuation allowance to the extent that management cannot conclude that it is more likely than not that a portion of the deferred tax asset will be realized in the future. The Company evaluates the deferred tax assets on a continuous basis throughout the year to determine whether or not a valuation allowance is appropriate. Factors used in this determination include future expected income and the underlying asset or liability which generated the temporary tax difference. The income tax provision is primarily impacted by federal statutory rates, state and foreign income taxes and changes in the valuation allowance. Product Warranties – The Company sells the majority of its products with a twelve-month repair or replacement warranty from the date of acceptance, which generally represents the date of shipment. The Company provides an accrual for estimated future warranty costs based upon the historical relationship of warranty costs to the cost of products sold. The estimated future warranty obligations related to product sales are reported in the period in which the related revenue is recognized. The estimated future warranty obligations are affected by the warranty periods, sales volumes, product failure rates, material usage and labor and replacement costs incurred in correcting a product failure. If actual product failure rates, material usage, labor or replacement costs differ from the Company’s estimates, revisions to the estimated warranty obligations would be required. For new product introductions where limited or no historical information exists, the Company may use warranty information from other previous product introductions to guide it in estimating the warranty accrual. The warranty accrual represents the best estimate of the amount necessary to settle future and existing claims on products sold as of the balance sheet date. The Company periodically assesses the adequacy of its recorded warranty reserve and adjusts the amounts in accordance with changes in these factors. Shipping and Handling Costs – Shipping and handling costs are included as a component of cost of net revenues. Advertising Costs – The Company expenses advertising costs as incurred. Advertising costs were $0.2 million in 2017, $0.2 million in 2016, and $0.3 million in 2015. Defined Employee Benefit Plans – The Company maintains a defined benefit pension plan in Taiwan for which current service costs are charged to operations as they accrue based on services rendered by employees during the year. Pension benefit obligations are determined by using management’s actuarial assumptions, including discount rates, assumed asset rates of return, compensation increases and employee turnover rates. Net Income Per Share - Basic net income per share excludes dilution and is computed by dividing net income by the number of weighted average common shares outstanding for the period. Diluted net income per share reflects the potential dilution from outstanding dilutive stock options (using the treasury stock method), restricted stock units subject to vesting and shares issuable under the employee stock purchase plan. In applying the treasury stock method 0.6 million, 0.5 million and 0.3 million stock option shares for fiscal year 2017, 2016 and 2015, respectively, were included in the calculation of diluted shares. Certain Significant Risks and Uncertainties – Financial instruments that potentially subject us to a concentration of credit risk consist of cash, cash equivalents, marketable securities, and accounts receivable. The Company's cash and cash equivalents are primarily invested in deposit accounts and money market accounts with large financial institutions. At times, these deposits and securities may exceed federally insured limits; however, the Company has not experienced any losses on such accounts. The Company invests its cash not required for use in operations in high credit quality securities based on the Company's investment policy. The Company's investment policy provides guidelines and limits regarding credit quality, investment concentration, investment type, and maturity that the Company believes will provide liquidity while reducing risk of loss of capital. Investments are of a short-term nature and include investments in commercial paper, corporate debt securities, U.S. Treasury, U.S. Government, and U.S. Agency debt. The Company sells its products primarily to end users in the United States, Asia and Europe and, generally, does not require its customers to provide collateral or other security to support accounts receivable. Management performs ongoing credit evaluations of its customers’ financial condition and maintains an allowance for estimated potential bad debt losses. The Company’s customer base is highly concentrated and historically, a relatively small number of customers have accounted for a significant portion of its revenues. Aggregate revenue from the Company's top five largest customers in 2017, 2016 and 2015 consisted of 73%, 73% and 69%, respectively, of its total net revenues. The Company participates in a dynamic high technology industry and believes that changes in any of the following areas could have a material adverse effect on its future financial position, results of operations or cash flows: advances and trends in new technologies and industry standards; competitive pressures in the form of new products or price reductions on current products; changes in product mix; changes in the overall demand for products offered; changes in third-party manufacturers; changes in key suppliers; changes in certain strategic relationships or customer relationships; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; fluctuations in foreign currency exchange rates; risk associated with changes in domestic and international economic and/or political regulations; availability of necessary components or sub-assemblies; disruption of manufacturing facilities; and its ability to attract and retain employees necessary to support its growth. Certain components and sub-assemblies used in the Company’s products are purchased from a sole supplier or a limited group of suppliers. In particular, the Company currently purchases its spectroscopic ellipsometer and robotics used in its advanced measurement systems from a sole supplier or a limited group of suppliers located in the United States. Any shortage or interruption in the supply of any of the components or sub-assemblies used in its products or its inability to procure these components or sub-assemblies from alternate sources on acceptable terms could have a material adverse effect on its business, financial condition and results of operations.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 30, 2017
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Pronouncements	Note 2. Recent Accounting Pronouncements Accounting Standards Adopted In March 2016, the FASB issued an accounting standard update that simplifies several aspects of the accounting for share-based payment award transactions, including income tax consequences, classification of awards as equity or liability, and classification on the statement of cash flows. The new standard requires adoption of certain amendments relevant to the Company to be applied using a modified retrospective transition method by means of cumulative effect adjustment to retained earnings as of the beginning of the fiscal year 2017. The new standard permits entities to make an accounting policy election related to how forfeitures will impact the recognition of compensation cost for stock-based compensation. The Company has elected to account for forfeitures as they occur and adopted this change on a modified retrospective basis. The cumulative effect of this change resulted in a $0.1 million increase to accumulated deficit as of January 1, 2017. Furthermore, the standard requires excess tax benefits and tax deficiencies to be recorded in the income statement when the awards vest or are settled rather than paid-in capital. The Company recorded the cumulative effect of this change as a $1.2 million reduction to accumulated deficit in the first quarter of fiscal 2017 to reflect the recognition of excess tax benefits in prior years, with a corresponding adjustment to deferred tax assets and long-term tax liabilities. The Company adopted the guidance related to the recognition of excess tax benefits and deficiencies as income tax expense or benefit on a modified retrospective basis. In addition, the Company elected to report cash flows related to excess tax benefits on a prospective basis. The presentation requirements for cash flows related to employee taxes paid for withheld shares had no impact to the Company’s statement of cash flows since such cash flows have historically been presented as a financing activity. In July 2015, the FASB issued an accounting standard update which simplifies the measurement of inventory by requiring inventory to be measured at the lower of cost and net realizable value. The new standard applies only to inventories for which cost is determined by methods other than last-in-first-out and the retail inventory method. Effective in the first quarter of fiscal 2017, the Company adopted this guidance. The adoption of this guidance did not have a significant impact on the Company’s consolidated financial condition and results of operation. Accounting Standards Not Yet Adopted In January 2017, the Financial Accounting Standards Board (the "FASB") issued an accounting standard update which simplifies the subsequent measurement of goodwill and removes step 2 from the goodwill impairment test. Instead, an entity should record an impairment charge based on excess of a reporting unit’s carrying amount over its fair value. The standard is effective for public companies for fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The adoption of this guidance is not expected to have a significant impact on the Company’s consolidated financial condition and results of operations. In October 2016, the FASB issued an accounting standard update which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. This standard will be effective for annual reporting periods beginning after December 15, 2017, including interim reporting period within those annual periods. Early adoption is permitted. This standard update is required to be adopted using the modified retrospective approach, with a cumulative catch-up adjustment to retained earnings in the period of adoption. The Company is currently evaluating the impact of adopting this standard on its consolidated financial condition and results of operations. In August 2016, the FASB issued an accounting standard which addresses eight specific cash flow classification issues. This update is effective for public companies for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years. Early adoption is permitted, including in an interim period. If early adopted in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period, and all the amendments must be adopted in the same period. The standard is to be applied through a retrospective transition method to each period presented. If it is impracticable to apply retrospectively for some of the issues, the amendments for those issues would be applied prospectively as of the earliest date practicable. The adoption of this guidance is not expected to have a significant impact on the Company’s consolidated statement of cash flows. In June 2016, the FASB issued an accounting standard which requires measurement and timely recognition of expected credit losses for financial assets. The update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The standard is to be applied through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The Company is currently evaluating the effect of this update on its consolidated financial condition and results of operations. In February 2016, the FASB issued an accounting standard update which requires lessees to record a right-of-use asset and a corresponding lease liability on the balance sheet (with the exception of short-term leases). For lessees, leases will continue to be classified as either operating or financing in the income statement. The standard is effective for public companies for annual reporting periods beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. This standard is required to be applied with a modified retrospective transition approach. The Company generally does not finance purchases of equipment or other capital, but does lease some equipment and facilities. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures but anticipates most its existing operating lease commitments will be recognized as operating lease liabilities and right-of-use assets. In May 2014, the FASB issued an accounting standard update which requires an entity to recognize the amount of revenue to which it expects to be entitled to for transferring promised goods or services to customers. The updated standard replaces most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method (“modified retrospective” method). In August 2015, the FASB deferred for one year the effective date of the new revenue standard, with early adoption permitted but not earlier than the original effective date. Consequently, the new standard will be effective for the Company on December 31, 2017 and the Company has determined it will not adopt early. Based on the Company’s assessment, the Company will adopt the new guidance in the first quarter of fiscal 2018 by using the modified retrospective method of transition. While the Company is concluding its assessment of the impact of the new standard, the Company believes that the timing of revenue recognition for certain systems and performance obligations, will generally occur earlier than under current revenue recognition guidance. Under current U.S. GAAP, revenue for certain systems or performance obligations is delayed until formal customer sign-off has occurred and/or contractual obligations have been met, whereas under the new standard, revenue should be recorded when transfer of control has occurred, which is normally upon shipment. While the Company expects revenue related to these arrangements to remain unchanged in total, the nature of when control transfers may change the timing of revenue recognition. Nanometrics expects the full-year positive impact to the opening balance of retained earnings related to the adoption of the new standard to be in the range of $0.7 million to $1.2 million. This amount reflects the margin related to revenue deferred as of December 30, 2017, that will not be reported as revenue in fiscal 2018. The amount of this revenue is estimated to be between $1.5 million and $2.5 million. This amount will also be reflected as a reduction to the beginning backlog of the first quarter of fiscal 2018. This amount is comprised of goods shipped in fiscal 2017 but deferred due to either lack of customer acceptance or failure of the customer to meet certain contractual commitments. Under the new standard, the Company has determined that transfer of control occurs at the time of shipment for these items and that the deferral of revenue associated with the unbilled amount is no longer appropriate per the new standard. Additionally, the Company believes the adoption of the new standard will not result in a different set of performance obligations, when compared to current GAAP. The Company further believes that required changes to its current business processes and IT systems, to comply with the new standard, will be minor in nature. Other aspects of the standard, including the capitalization of costs related to the acquisition and/or fulfillment of the Company’s contracts are still being evaluated, but the Company believes impacts are immaterial. The Company is concluding its evaluation of the impact of the new standard on the Company’s contracts with customers and will continue to monitor industry activities and other guidance provided by the accounting profession and regulators and adjust its approach and implementation plans as required.

Fair Value Measurements and Dis

Fair Value Measurements and Disclosures	12 Months Ended
	Dec. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements and Disclosures	Note 3. Fair Value Measurements and Disclosures The Company determines the fair values of its financial instruments based on the fair value hierarchy established in FASB Accounting Standards Codification ("ASC") 820, Fair Value Measurement Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 — Unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Such unobservable inputs include an estimated discount rate used in the Company's discounted present value analysis of future cash flows, which reflects the Company's estimate of debt with similar terms in the current credit markets. As there is currently minimal activity in such markets, the actual rate could be materially different. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard assumes that the transaction to sell the asset or transfer the liability occurs in the principal or most advantageous market for the asset or liability and establishes that the fair value of an asset or liability shall be determined based on the assumptions that market participants would use in pricing the asset or liability. The following tables present the Company’s assets and liabilities measured at estimated fair value on a recurring basis, excluding accrued interest components, categorized in accordance with the fair value hierarchy (in thousands), as of the following dates: December 30, 2017 December 31, 2016 Fair Value Measurements Using Input Types Fair Value Measurements Using Input Types Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 256 $ — $ — $ 256 $ 959 $ — $ — $ 959 Commercial paper and corporate debt securities — — — — — 2,499 — 2,499 Total cash equivalents $ 256 $ — $ — $ 256 $ 959 $ 2,499 $ — $ 3,458 Marketable securities: U.S. Treasury, U.S. Government and U.S. Government agency debt securities — 1,495 — 1,495 — 17,072 — 17,072 Certificate of deposits — 14,497 — 14,497 — 23,019 — 23,019 Commercial paper — 7,949 — 7,949 — 22,402 — 22,402 Municipal securities and corporate debt securities — 47,968 — 47,968 — 14,943 — 14,943 Asset backed securities — 10,221 — 10,221 — 5,463 — 5,463 Total marketable securities $ — $ 82,130 $ — $ 82,130 $ — $ 82,899 $ — $ 82,899 Total (1) $ 256 $ 82,130 $ — $ 82,386 $ 959 $ 85,398 $ — $ 86,357 (1) Excludes $34.6 million and $43.6 million held in operating accounts as of December 30, 2017, and December 31, 2016, respectively. The fair values of the marketable securities that are classified as Level 1 in the table above were derived from quoted market prices for identical assets or liabilities in active markets that the Company has the ability to access. The fair value of marketable securities that are classified as Level 2 in the table above were derived from non-binding market consensus prices that were corroborated by observable market data, quoted market prices for similar instruments, or pricing models, such as discounted cash flow techniques with all significant inputs derived from or corroborated by observable market data. There were no transfers of instruments between Level 1, Level 2 and Level 3 during the financial periods presented. Derivatives The Company uses foreign currency forward contracts to mitigate variability in gains and losses generated from the re-measurement of certain monetary assets and liabilities denominated in foreign currencies. These derivatives are carried at fair value with changes recorded in other income, net in the consolidated statements of operations. Changes in the fair value of these derivatives are largely offset by re-measurement of the underlying assets and liabilities. The derivatives have maturities of approximately 30 days. The settlement result of forward foreign currency contracts included in the fiscal year ended December 30, 2017 and December 31, 2016, was a gain of $1.4 million and a loss of $1.7 million, respectively, and these balances are included in other income, net, in the consolidated statements of operations. The following table summarizes the Company’s outstanding derivative instruments on a gross basis: As of December 30, 2017 As of December 31, 2016 Notional Amount Fair Value Notional Amount Fair Value (in millions) Asset Liability (in millions) Asset Liability Undesignated Hedges: Forward Foreign Currency Contracts Purchase $ 27.5 — $ 0.1 $ 12.6 — — Sell $ 16.8 0.1 — $ 1.3 — —

Cash and Investments

Cash and Investments	12 Months Ended
	Dec. 30, 2017
Investments Debt And Equity Securities [Abstract]
Cash and Investments	Note 4. Cash and Investments The following table presents cash, cash equivalents, and available-for-sale investments as of the following dates (in thousands): December 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Market Value Cash $ 34,643 $ — $ — $ 34,643 Cash equivalents: Money market funds 256 — — 256 Marketable securities: U.S. Government agency securities 1,500 — (5 ) 1,495 Certificates of deposits 14,498 — (1 ) 14,497 Commercial paper 7,952 — (3 ) 7,949 Corporate debt securities 48,073 — (105 ) 47,968 Asset-backed securities 10,240 — (19 ) 10,221 Total cash, cash equivalents, and marketable securities $ 117,162 $ — $ (133 ) $ 117,029 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Market Value Cash $ 43,604 $ — $ — $ 43,604 Cash equivalents: Money market funds 959 — — 959 Commercial paper and corporate debt securities 2,499 — — 2,499 Marketable securities: U.S. Treasury securities 5,667 — — 5,667 U.S. Government agency securities 11,412 — (7 ) 11,405 Certificates of deposits 23,000 19 — 23,019 Commercial paper 22,402 — — 22,402 Corporate debt securities 14,194 — (6 ) 14,188 Municipal securities 756 — (1 ) 755 Asset-backed securities 5,466 — (3 ) 5,463 Total cash, cash equivalents, and marketable securities $ 129,959 $ 19 $ (17 ) $ 129,961 Available-for-sale marketable securities, readily convertible to cash, with maturity dates of 90 days or less are classified as cash equivalents, while those with maturity dates greater than 90 days are classified as marketable securities within short-term assets. All marketable securities as of December 30, 2017, and December 31, 2016, were available-for-sale and reported at fair value based on the estimated or quoted market prices as of the balance sheet date. Gross realized gains and losses on sale of securities are recorded in other income, net, in the Company’s statement of operations. Net realized gains and losses for fiscal 2017, 2016, and 2015 was $1.3 million, $0.5 million and $0.2 million, respectively. Unrealized gains or losses, net of tax effect, are recorded in accumulated other comprehensive income (loss) within stockholders' equity. Both the gross unrealized gains and gross unrealized losses for the fiscal years ended December 30, 2017, and December 31, 2016 were insignificant and no marketable securities had other than temporary impairment. All marketable securities as of December 30, 2017, and December 31, 2016, had maturity dates of less than two years.

Accounts Receivable

Accounts Receivable	12 Months Ended
	Dec. 30, 2017
Receivables [Abstract]
Accounts Receivable	Note 5. Accounts Receivable The Company maintains arrangements under which eligible accounts receivable in Japan are sold without recourse to unrelated third-party financial institutions. These receivables were not included in the consolidated balance sheets as the criteria for sale treatment had been met. After a transfer of financial assets, an entity stops recognizing the financial assets when control has been surrendered. The agreement met the criteria of a true sale of these assets since the acquiring party retained the title to these receivables and had assumed the risk that the receivables will be collectible. The Company pays administrative fees as well as interest ranging from 0.61% to 1.68% based on the anticipated length of time between the date the sale is consummated and the expected collection date of the receivables sold. The Company sold $18.6 million and $31.5 million of receivables during fiscal years ended December 30, 2017, and December 31, 2016, respectively. There were no material gains or losses on the sale of such receivables. There were no amounts due from such third party financial institutions at December 30, 2017, and December 31, 2016.

Financial Statement Components

Financial Statement Components	12 Months Ended
	Dec. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Financial Statement Components	Note 6. Financial Statement Components The following tables provide details of selected financial statement components as of the following dates (in thousands): At December 30, 2017 December 31, 2016 Inventories: Raw materials and sub-assemblies $ 32,187 $ 23,506 Work in process 13,498 10,347 Finished goods 7,175 4,984 Inventories 52,860 38,837 Inventories-delivered systems 1,534 2,457 Total inventories $ 54,394 $ 41,294 Property, plant and equipment, net: (1) Land $ 15,573 $ 15,568 Building and improvements 20,880 20,532 Machinery and equipment 36,380 35,659 Furniture and fixtures 2,420 2,282 Software 9,558 9,756 Capital in progress 4,418 2,748 Total property, plant and equipment, gross 89,229 86,545 Accumulated depreciation and amortization (44,419 ) (42,319 ) Total property, plant and equipment, net $ 44,810 $ 44,226 (1) Total depreciation and amortization expense for the years ended December 30, 2017, December 31, 2016 and December 26, 2015 was $6.7 million, $6.8 million, and $6.9 million, respectively. Other Current Liabilities: Accrued warranty $ 4,863 $ 3,838 Accrued taxes 813 706 Customer deposits — 581 Accrued professional services 534 424 Accrued royalties — 1,233 Other 1,039 1,265 Total other current liabilities $ 7,249 $ 8,047 Components of Accumulated Other Comprehensive Income (Loss) Foreign Currency Translations Defined Benefit Pension Plans Unrealized Income (Loss) on Investment Accumulated Other Comprehensive Income Balance as of December 26, 2015 $ (4,948 ) $ (210 ) $ (44 ) $ (5,202 ) Current period change (869 ) (17 ) 42 (844 ) Balance as of December 31, 2016 (5,817 ) (227 ) (2 ) (6,046 ) Current period change 4,170 (160 ) (88 ) 3,922 Balance as of December 30, 2017 $ (1,647 ) $ (387 ) $ (90 ) $ (2,124 ) The items above, except for unrealized income (loss) on investment, did not impact the Company’s income tax provision. The amounts reclassified from each component of accumulated other comprehensive income into income statement line items were insignificant.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Note 7. Goodwill and Intangible Assets The following table summarizes the activity in the Company’s goodwill during the years ended December 30, 2017 and December 31, 2016, respectively (in thousands): Amounts Balance as of December 26, 2015 $ 9,415 Foreign currency movements (475 ) Balance as of December 31, 2016 8,940 Foreign currency movements 1,292 Balance as of December 30, 2017 $ 10,232 There were no business acquisitions made by the Company during fiscal years 2017, 2016 and 2015. Goodwill Impairment and Long-lived Asset Impairment The Company’s impairment review process is completed during the fourth quarter of each year, or whenever events or circumstances occur that indicate that an impairment may have occurred. The goodwill impairment assessment involves three tests, Step 0, Step 1 and Step 2. The Company performs a Step 0 test, which involves an initial qualitative assessment to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. If, after assessing the qualitative factors, the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then performing the two-step impairment test is necessary. Otherwise, no further testing is necessary. The Company completed its annual goodwill impairment assessment during the fourth quarter of 2017 by first performing a Step 0 qualitative assessment. As part of this assessment, the Company considered the trading value of the Company's stock, the industry trends, and the Company's sales forecast and products plans. The Company concluded that it was more likely than not that the fair value was more than the carrying values of the Company's reporting unit and therefore did not proceed to the Step 1 goodwill impairment test. The process of evaluating the potential impairment of long-lived assets is highly subjective and requires significant judgment. In estimating the fair value of these assets, the Company made estimates and judgments about future revenues and cash flows. The Company’s forecasts were based on assumptions that are consistent with the plans and estimates the Company is using to manage its business. Changes in these estimates could change the Company’s conclusion regarding impairment of the long-lived assets and potentially result in future impairment charges for all or a portion of their balance at December 30, 2017. The Company did not record any impairment charges related to goodwill in fiscal year 2017. The Company assesses if there have been triggers that may require it to evaluate the reasonableness of the remaining estimated useful lives of its intangible assets. No such triggers were identified during fiscal year 2017. Finite-lived intangible assets are recorded at cost, less accumulated amortization. Finite-lived intangible assets as of December 30, 2017, and December 31, 2016 consisted of the following (in thousands): December 30, 2017 Adjusted cost Accumulated amortization Net carrying amount Developed technology $ 18,887 $ (16,681 ) $ 2,206 Customer relationships 9,438 (9,438 ) — Brand names 1,927 (1,927 ) — Patented technology 2,252 (2,252 ) — Trademark 80 (80 ) — Total $ 32,584 $ (30,378 ) $ 2,206 December 31, 2016 Adjusted cost Accumulated amortization Net carrying amount Developed technology $ 15,726 $ (15,380 ) $ 346 Customer relationships 9,322 (9,322 ) — Brand names 1,927 (1,927 ) — Patented technology 2,252 (2,186 ) 66 Trademark 80 (80 ) — Total $ 29,307 $ (28,895 ) $ 412 The amortization of finite-lived intangibles is computed using the straight-line method. Estimated lives of finite-lived intangibles range from two to ten years. Total amortization expense for the fiscal years ended December 30, 2017, December 31, 2016 and December 26, 2015, was $0.2 million, $1.5 million and $2.1 million, respectively. There were no impairment charges related to intangible assets recorded during the year ended December 30, 2017. The estimated future amortization expense of finite intangible assets as of December 30, 2017, is as follows (in thousands): Fiscal Years Amounts 2018 283 2019 352 2020 286 2021 286 2022 286 Thereafter 713 Total future amortization expense 2,206

Warranties

Warranties	12 Months Ended
	Dec. 30, 2017
Product Warranties Disclosures [Abstract]
Warranties	Note 8. Warranties Product Warranty – The Company sells the majority of its products with a 12 months repair or replacement warranty from the date of acceptance or shipment date. The Company provides an accrual for estimated future warranty costs based upon the historical relationship of warranty costs to the cost of products sold. The estimated future warranty obligations related to product sales are recorded in the period in which the related revenue is recognized. The estimated future warranty obligations are affected by the warranty periods, sales volumes, product failure rates, material usage, and labor and replacement costs incurred in correcting a product failure. If actual product failure rates, material usage, labor or replacement costs were to differ from the Company’s estimates, revisions to the estimated warranty obligations would be required. For new product introductions where limited or no historical information exists, the Company may use warranty information from other previous product introductions to guide it in estimating its warranty accrual. The warranty accrual represents the best estimate of the amount necessary to settle future and existing claims on products sold as of the balance sheet date. The Company periodically assesses the adequacy of its reported warranty reserve and adjusts such amounts in accordance with changes in these factors. Components of the warranty accrual, which were included in the accompanying consolidated balance sheets with other current liabilities, were as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 Balance as of beginning of period $ 3,838 $ 4,504 Accruals for warranties issued during period 5,247 4,509 Settlements during the period (4,222 ) (5,175 ) Balance as of end of period $ 4,863 $ 3,838

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9. Commitments and Contingencies Intellectual Property Indemnification Obligations – The Company will, from time to time, in the normal course of business, agree to indemnify certain customers, vendors or others against third party claims that Nanometrics’ products, when used for their intended purpose(s), or the Company’s intellectual property, infringe the intellectual property rights of such third parties or other claims made against parties with whom it enters into contractual relationships. It is not possible to determine the maximum potential amount of liability under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances that are likely to be involved in each particular claim. Historically, the Company has not made payments under these obligations and believes that the estimated fair value of these agreements is immaterial. Accordingly, no liabilities have been recorded for these obligations in the accompanying consolidated balance sheets as of December 30, 2017, and December 31, 2016. Contractual Obligations – The Company maintains certain open inventory purchase agreements with its suppliers to ensure a smooth and continuous supply availability for key components. The Company’s liability under these purchase commitments is generally restricted to a forecasted time-horizon as mutually agreed upon between the parties. This forecasted time-horizon can vary among different suppliers. The Company estimates its open inventory purchase commitment as of December 30, 2017, was approximately $50.7 million. Actual expenditures will vary based upon the volume of the transactions and length of contractual service provided. In addition, the amounts paid under these arrangements may be less in the event that the arrangements are renegotiated or cancelled. The Company leases facilities and certain equipment under non-cancelable operating leases. Rent expense, which is recorded on a straight-line basis over the term of the respective lease, for 2017, 2016 and 2015 was approximately $1.8 million, $1.8 million and $1.7 million, respectively. Future minimum lease payments under its operating leases are as follows (in thousands): Operating Leases 2018 1,664 2019 935 2020 313 2021 54 2022 2 Thereafter — Total $ 2,968 Legal Proceedings – From time to time, the Company is subject to various legal proceedings or claims arising in the ordinary course of business. On August 2, 2017, the Company was named as defendant in a complaint filed in New Hampshire Superior Court (“Complaint”). The Complaint, brought by Optical Solutions, Inc. (“OSI”), alleges claims arising from a purported exclusive purchase contract between OSI and the Company pertaining to certain product. On September 18, 2017, the Company removed the action to the United States District Court for the District of New Hampshire. On September 25, 2017, the Company moved to transfer the Complaint to the Northern District of California and to dismiss all claims in the Complaint for lack of personal jurisdiction and for failure to state a claim. On September 27, 2017, OSI filed a motion to remand. On January 31, 2018, the District Court of New Hampshire denied OSI’s motion to remand. OSI has not yet responded to the Company’s motions to transfer or dismiss, but is scheduled to on February 19, 2018. The Company records a provision for a loss when it believes that it is both probable that a loss has been incurred and the amount can be reasonably estimated. Based on current information, the Company believes it does not have any probable and reasonably estimable losses related to any current legal proceedings and claims. Although it is difficult to predict the outcome of legal proceedings, the Company believes that any liability that may ultimately arise from the resolution of these ordinary course matters will not have a material adverse effect on the business, financial condition and results of operations.

Net Income Per Share

Net Income Per Share	12 Months Ended
	Dec. 30, 2017
Earnings Per Share [Abstract]
Net Income Per Share	Note 10. Net Income Per Share The Company presents both basic and diluted net income per share on the face of its consolidated statements of operations. Basic net income per share excludes the effect of potentially dilutive shares and is computed by dividing net income by the weighted-average number of shares of common stock outstanding for the period. Diluted net income per share is computed using the weighted-average number of shares of common stock outstanding for the period plus the effect to all potentially dilutive common shares outstanding during the period, including contingently issuable shares and certain stock options, calculated using the treasury stock method. A reconciliation of the share denominator of the basic and diluted net income per share computations is as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Weighted average common shares outstanding used in basic net income per share calculation 25,334 24,655 24,059 Potential dilutive common stock equivalents, using treasury stock method 585 498 316 Weighted average shares used in diluted net income per share calculation 25,919 25,153 24,375 For the year ended December 30, 2017, December 31, 2016, and December 26, 2015, the Company had securities outstanding which could potentially dilute basic earnings per share in the future. For the years ended December 30, 2017, December 31, 2016 and December 26, 2015, the weighted average common share equivalents consisting of stock options and restricted stock units included in the calculation of diluted net income per share were 0.6 million, 0.5 million and 0.3 million shares, respectively.

Stockholders' Equity and Stock-

Stockholders' Equity and Stock-Based Compensation	12 Months Ended
	Dec. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stockholders' Equity and Stock-Based Compensation	Note 11. Stockholders' Equity and Stock-Based Compensation Stockholders' Equity Preferred and Common Stock The authorized capital stock of Nanometrics consists of 47,000,000 shares of common stock, par value $0.001 per share, and 3,000,000 shares of preferred stock, par value $0.001 per share. Stock Repurchase On May 29, 2012, our Board of Directors authorized the repurchase of up to $20.0 million of our common stock of which $4.4 million remained as of December 31, 2016. On November 15, 2017, the Company's Board of Directors approved a program to repurchase up to $50.0 million of its common stock which superseded the 2012 repurchase program. This new plan is referred to as the Stock Repurchase Plan with an effective date of November 20, 2017. Stock repurchases under this plan may be made through open market and privately negotiated transactions, at times and in such amounts as management deems appropriate. The timing and actual number of shares repurchased is dependent on a variety of factors including price, corporate and regulatory requirements and other market conditions. Shares repurchased and retired for fiscal year 2017, 2016 and 2015, with the associated cost of repurchase and amount available for repurchase at the end of the respective periods are as follows (in thousands, except number of shares and weighted average price per share): Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Number of shares of common stock repurchased 1,065,848 — 111,050 Weighted average price per share $ 25.33 — $ 15.49 Total cost of repurchase $ 26,999 — $ 1,721 Amount available for repurchase at end of period $ 23,001 — $ 4,397 The Stock Repurchase Plan was completed in February 2018, with purchases since December 30, 2017 of 896,187 shares of our common stock at the weighted average price of $25.65 for a cost of $23.0 million. Stock Option Plans The Nanometrics option plans are as follows: Plan Name Participants Shares Authorized 2005 Equity Incentive Plan Employees, consultants and directors 8,292,594 2000 Employee Stock Option Plan Employees and consultants 2,450,000 2000 Director Stock Option Plan Non-employee directors 250,000 Accent Optical Technologies, Inc. Stock Incentive Plan Employees and consultants 205,003 Employee Stock Purchase Plan Under the 2003 Employee Stock Purchase Plan (“ESPP”), eligible employees are allowed to have salary withholdings of up to 10% of their base compensation to purchase shares of common stock at a price equal to 85% of the lower of the market value of the stock at the beginning or end of each six-month offering period, subject to an annual statutory limitation. At the end of the fiscal year ended December 30, 2017, the Company had 0.5 million shares remaining for issuance under the ESPP. Shares purchased under the ESPP were 122,298 shares, 212,619 shares and 125,504 shares in 2017, 2016 and 2015 at a weighted average price of $21.19, $14.29 and $13.98, respectively. Stock-based Compensation The Company measures and recognizes compensation expense for all share-based payment awards made to employees and directors including employee stock options, restricted stock units and employee stock purchases related to the Employee Stock Purchase Plan (collectively “Employee Stock Purchases”) based on estimated fair values. The fair value of share-based payment awards is estimated on the date of grant using an option-pricing model. The value of the portion of the award that is ultimately expected to vest is recognized as expense over the requisite service periods in the Company's consolidated statement of operations. Valuation and Expense Information The fair value of stock-based awards to employees is calculated using the Black-Scholes option pricing model, which requires subjective assumptions, including future stock price volatility and expected time to exercise. The expected life was calculated using the simplified method allowed by the SAB 107. The risk-free rates were based on the U.S Treasury rates in effect during the corresponding period. The expected volatility was based on the historical volatility of the Company's stock price. These factors could change in the future, which would affect the stock-based compensation expense in future periods. The weighted-average fair value of stock-based compensation to employees is based on the single option valuation approach. Forfeitures are estimated and it is assumed no dividends will be declared. The estimated fair value of stock-based compensation awards to employees is amortized over the vesting period. The weighted-average fair value calculations are based on the following average assumptions: Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Employee Stock Purchase Plan: Expected life 0.5 years 0.5 years 0.5 years Volatility 37.2% 38.7% 36.9% Risk free interest rate 0.91% 0.44% 0.12% Dividends — — — Stock Options and Restricted Stock Units (“RSUs”) On May 23, 2017, the Company approved further amendments to the 2005 Equity Incentive Plan including: increasing the number of shares of common stock authorized by 1.0 million shares and extending the term of the 2005 Equity Incentive Plan through 2027. All other terms remained the same. Stock Options No stock options were granted in fiscal years 2017, 2016 and 2015. A summary of activity of stock options is as follows: Number of Shares Outstanding (Options) Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Options Outstanding at December 26, 2015 1,059,471 $ 14.61 2.47 $ 1,920 Exercised (442,339 ) 13.66 Cancelled/Forfeited (176,587 ) 15.83 Outstanding at December 31, 2016 440,545 15.06 2.12 $ 4,405 Exercised (223,364 ) 13.35 Cancelled/Forfeited (855 ) 16.63 Outstanding at December 30, 2017 216,326 $ 16.82 1.76 $ 1,752 Exercisable at December 30, 2017 215,620 $ 16.81 1.76 $ 1,748 The aggregate intrinsic value in the above table represents the total pretax intrinsic value, based on the Company’s closing stock price of $24.92 as of December 30, 2017, which would have been received by the option holders had all option holders exercised their options as of that date. The total intrinsic value of options exercised during 2017, 2016 and 2015 was $3.1 million, $2.7 million and $1.6 million, respectively. The fair value of options vested during 2017, 2016 and 2015 was $0.3 million, $0.7 million and $1.5 million, respectively. The following table summarizes ranges of outstanding and exercisable options as of December 30, 2017. Options Outstanding Options Exercisable Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $12.98-$15.00 23,383 1.83 $ 14.64 23,383 $ 14.64 $15.08-$15.65 27,697 1.37 15.62 27,697 15.62 $15.74-$15.74 3,333 0.40 15.74 3,333 15.74 $15.85-$15.85 60,000 2.20 15.85 60,000 15.85 $16.00-$17.33 31,700 1.82 17.00 31,700 17.00 $17.70-$18.08 6,613 1.55 17.92 6,588 17.92 $18.22-$18.22 3,600 3.16 18.22 3,449 18.22 $18.51-$18.51 9,000 3.14 18.51 8,583 18.51 $18.79-$18.79 1,000 3.23 18.79 887 18.79 $19.03-$19.03 50,000 1.13 $ 19.03 50,000 $ 19.03 $12.98-$19.03 216,326 215,620 As of December 30, 2017, the total unrecognized compensation costs related to unvested stock options was less than $0.1 million and is expected to be recognized as an expense over a weighted average remaining amortization period of 0.10 years. Restricted Stock Units (“RSUs”) Each RSU counts against the Company’s “2005 Equity Incentive Plan” at a ratio of one and seven tenths shares for each unit granted but represents an amount equal to the fair value of one share of the Company’s common stock. The Company granted 454,600 and 476,667 RSUs during the years ended December 30, 2017, and December 31, 2016, respectively, to key employees with vesting periods up to three years. A summary of activity for RSUs is as follows: Summary of activity for RSUs Number of RSUs Weighted Average Fair Value Outstanding RSUs as of December 26, 2015 713,243 $ 15.99 Granted 476,667 17.45 Released (315,872 ) 16.05 Cancelled (54,253 ) 16.29 Outstanding RSUs as of December 31, 2016 819,785 16.79 Granted 454,600 27.12 Released (387,592 ) 16.81 Cancelled (96,494 ) 19.01 Outstanding RSUs as of December 30, 2017 790,299 $ 22.46 As of December 30, 2017, the total unrecognized compensation costs related to RSU's was $12.5 million and is expected to be recognized as an expense over a weighted average remaining amortization period of 1.75 years. Market-Based Performance Stock Units (“PSUs”) In addition to granting RSUs that vest on the passage of time only, the Company granted PSUs to certain executives. The PSUs will vest in tranches over one, two, and three years based on the relative performance of the Company’s stock during those periods, compared to a peer group over the same period. If target stock price performance is achieved, 66.7% of the shares of the Company’s stock subject to the PSUs will vest, and up to a maximum of 100% of the shares subject to the PSUs will vest if the maximum stock price performance is achieved for each tranche. For certain shares granted in fiscal 2017, 62,500 shares are the cumulative maximum number of shares that may vest for all measurement periods. A summary of activity for PSUs is as follows: Summary of activity for PSUs Number of PSUs Weighted Average Fair Value Outstanding PSUs as of December 26, 2015 60,000 $ 12.23 Granted 67,500 8.52 Released (13,333 ) 12.03 Cancelled (6,667 ) 12.03 Outstanding PSUs as of December 31, 2016 107,500 9.94 Granted 122,050 20.51 Released (38,500 ) 10.41 Cancelled (61,100 ) 19.41 Outstanding PSUs as of December 30, 2017 129,950 $ 15.60 Valuation of PSUs On the date of grant, the Company estimated the fair value of PSUs using a Monte Carlo simulation model. The assumptions for the valuation of PSUs are summarized as follows: 2017 Award 2016 Award 2015 Award Grant Date Fair Values Per Share $14.57-$26.75 $ 8.52 $ 12.23 Weighted-average assumptions/inputs: Expected Dividend — — — Range of risk-free interest rates 1.74%-1.84% 0.92% 0.25%-1.1% Range of expected volatilities for peer group 22%-66% 22%-93% 23%-65% The number of RSUs granted during fiscal year 2017 was 454,600, which counted as 772,820 shares, and PSUs granted during fiscal year 2017 was 122,050, which counted as 207,485 against the 2005 Equity Incentive Plan. The number of RSUs cancelled during fiscal year 2017 was 96,494, which counted as 164,040 shares, and PSUs cancelled during fiscal year 2017 was 61,100, which counted as 103,870, against the 2005 Equity Incentive Plan. Each RSU represents an amount equal to the fair value of one share of the Company's common stock. A summary of activity under the Company’s stock option plans including options, RSUs and PSUs during fiscal year 2017, 2016 and 2015 and shares available for grant as of the respective period end dates, is as follows: Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Shares available for grant at beginning of fiscal year 1,334,581 1,916,589 2,464,082 Additional Shares Authorized 1,000,000 — — Options – cancelled 855 176,587 94,012 Options - expired plan shares (116,192 ) (1,800 ) RSUs – granted (772,820 ) (810,334 ) (860,980 ) RSUs – cancelled 164,040 92,230 202,356 RSUs - shares issued to satisfy tax withholding obligations 251,724 179,117 120,919 PSUs – granted (207,485 ) (114,750 ) (102,000 ) PSUs – cancelled 103,870 11,334 — Shares available for grant at end of fiscal year 1,874,765 1,334,581 1,916,589 Stock-based Compensation Expense Stock-based compensation expense recognized during the period is based on the value of the portion of share-based payment awards that is ultimately expected to vest during the period. Effective January 1, 2017, as a result of the adoption of ASU No. 2016-09 “ Improvements to Employee Share-Based Payment Accounting Tax benefits resulting from tax deductions in excess of the compensation cost recognized for those options are required to be separately classified in the consolidated statements of cash flows. The Company recognized $1.0 million of excess tax benefit in fiscal year 2016, and none in both fiscal years 2017 and 2015, respectively. Stock-based compensation expense for all share-based payment awards made to the Company’s employees and directors pursuant to the employee stock option and employee stock purchase plans by function were as follows (in thousands): Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Cost of products $ 842 $ 403 $ 274 Cost of service 616 509 309 Research and development 1,720 1,408 1,036 Selling 2,323 2,046 1,881 General and administrative 3,318 3,300 2,748 Total stock-based compensation expense related to employee stock options and employee stock purchases $ 8,819 $ 7,666 $ 6,248

Defined Benefit Pension Plan

Defined Benefit Pension Plan	12 Months Ended
	Dec. 30, 2017
Compensation And Retirement Disclosure [Abstract]
Defined Benefit Pension Plan	Note 12. Defined Benefit Pension Plan Nanometrics sponsors a statutory government mandated defined benefit pension plan (the “Benefit Plan”) in Taiwan for its local employees. The fair value of plan assets was $0.3 million for fiscal year ended 2017, and $0.2 million for each of fiscal years 2016 and 2015, respectively; and the net funding deficiency of the Benefit Plan was $0.5 million, $0.4 million, and $0.3 million for the fiscal years ended December 30, 2017, December 31, 2016, and December 26, 2015, respectively. Based on the nature and limited extent of the pension plan, we determined this pension plan was not material for separate disclosure.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 13. Income Taxes Income Tax Assets and Liabilities - The Company accounts for income taxes whereby deferred tax assets and liabilities are recognized using enacted tax rates for the effect of temporary differences between the book and tax accounting for assets and liabilities. Also, deferred tax assets are reduced by a valuation allowance to the extent that management cannot conclude that it is more likely than not that a portion of the deferred tax asset will be realized in the future. The Company evaluates the deferred tax assets on a continuous basis throughout the year to determine whether or not a valuation allowance is appropriate. Factors used in this determination include future expected income and the underlying asset or liability which generated the temporary tax difference. The income tax provision is primarily impacted by federal statutory rates, state and foreign income taxes, and changes in the valuation allowance. Income (loss) before provision for income taxes consists of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Domestic $ 34,238 $ 25,372 $ 178 Foreign 9,060 3,763 5,390 Income (loss) before income taxes $ 43,298 $ 29,135 $ 5,568 The provision (benefit) for income taxes consists of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Current: Federal $ 3,250 $ 697 $ 148 State 9 85 3 Foreign 2,998 2,111 2,266 6,257 2,893 2,417 Deferred: Federal 6,314 (16,641 ) 190 State 53 (320 ) 3 Foreign 472 (832 ) 53 6,839 (17,793 ) 246 Provision (benefit) for income taxes $ 13,096 $ (14,900 ) $ 2,663 Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands): At December 30, 2017 December 31, 2016 Deferred tax assets: Reserves and accruals $ 5,797 $ 11,043 Deferred revenue 240 349 Shared based compensation 1,483 2,590 Tax credit carry-forwards 9,669 10,112 Net operating losses 9,755 8,434 Depreciation & amortization (1,525 ) (2,898 ) Other 207 (1,252 ) Total deferred tax assets 25,626 28,378 Less: Valuation allowance (13,702 ) (10,980 ) Total deferred tax assets net of valuation allowance 11,924 17,398 Deferred tax liabilities: Depreciation & amortization (12 ) (6 ) Other (167 ) (14 ) Total deferred tax liabilities (179 ) (20 ) Net deferred tax assets $ 11,745 $ 17,378 As of December 30, 2017, the Company had net operating loss carryforwards of $25.6 million in California, $3.0 million in other states, and $35.0 million in foreign countries, which begin to expire in 2018. As of December 30, 2017, the Company had available carryforward Federal and California R&D tax credits of $7.0 million and $8.9 million, respectively. Federal R&D tax credit carryforwards begin to expire in 2032. State R&D tax credits carryforward indefinitely. During the years ended December 30, 2017, and December 31, 2016, the change in valuation allowances was $1.5 million and $(25.8) million, respectively. The valuation allowance increase in 2017 was primarily related to the increase net benefit of the California deferred tax assets from lower federal rates, offset by a valuation allowance release against a portion of the Company’s foreign deferred tax assets. The realization of deferred tax assets is primarily dependent on the Company generating sufficient U.S. and foreign taxable income in future fiscal years. The Company regularly assesses the need for a valuation allowance against its deferred tax assets. In making that assessment, the Company considers both positive and negative evidence related to the likelihood of realization of the deferred tax assets to determine, based on the weight of available evidence, whether it is more-likely-than-not that some or all of the deferred tax assets will not be realized. For the year ended December 30, 2017, the Company possessed enough positive evidence to determine that is was more-likely-than-not that the Company would utilize a significant portion of its Singapore deferred tax assets. Therefore, the Company released $0.3 million of valuation allowance in that jurisdiction. The Company continues to maintain valuation allowances against its California and certain foreign deferred tax assets as a result of uncertainties regarding the realization of the asset due to cumulative losses and uncertainty of future taxable income. The Company will continue to assess the realizability of the deferred tax assets in each of the applicable jurisdictions and maintain the valuation allowances until sufficient positive evidence exists to support a reversal. In the event the Company determines that the deferred tax assets are realizable, an adjustment to the valuation allowances will be reflected in the tax provision for the period such determination is made. Changes in tax laws and tax rates could affect the Company's recorded deferred tax assets and liabilities in the future. The Company's tax liabilities involve dealing with uncertainties in the application of complex tax laws and regulations in a multitude of jurisdictions across its global operations. Management will account for any such changes or factors in the period in which such law changes are enacted. On December 22, 2017, H.R.1, formerly known as the Tax Cuts and Jobs Act (“The Act”), was signed into law. Among other items, H.R.1 reduces the federal corporate tax rate from 35% to 21% effective January 1, 2018. As a result, the Company revalued its net deferred tax asset to the lower enacted rate. The Company's net deferred tax asset represents differences between the carrying amounts and tax bases of assets and liabilities carried on the Company's balance sheet. In addition to the revaluation of deferred tax assets and liabilities in reflecting the lower tax rates, the Act also imposes a deemed repatriation tax on the Company’s total post-1986 deferred foreign income. During the year ended December 30, 2017, the company recognized $0.6 million as a provisional estimate for income taxes under the U.S. Securities and Exchange Commission Accounting Bulletin No. 118. The provisional estimate is subject to revisions as we complete our analysis of the Act, collect and prepare necessary data, and interpret any additional guidance issued by the U.S. Treasury Department, Internal Revenue Service (“IRS”), FASB, and other standard-setting and regulatory bodies. Our accounting for the tax effects of the Act will be completed during the measurement period, which should not extend beyond one year from the enactment date. Differences between income taxes computed by applying the statutory federal income tax rate to income (loss) before income taxes and the provision (benefit) for income taxes consist of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Income taxes computed at U.S. statutory rate $ 15,153 $ 10,197 $ 1,949 State income taxes 227 223 28 Foreign tax rate differential 794 3,502 342 Change in valuation allowance 1,490 (25,738 ) 1,648 Equity compensation (1,803 ) 380 311 Tax credits (2,336 ) (3,191 ) (1,834 ) Domestic production activities deduction (608 ) (354 ) — Liabilities for uncertain tax positions 18 67 74 Other, net 161 14 145 Provision (benefit) for income taxes $ 13,096 $ (14,900 ) $ 2,663 As of December 30, 2017, The Company has provided U.S income taxes on all its foreign earnings. The Company still continues to permanently reinvest the cash held offshore to support its working capital needs. Accordingly, no additional foreign withholding taxes that may be required from certain jurisdictions in the event of a cash distribution have been provided thereon. The Company recognizes tax liabilities for uncertain tax positions and adjusts these liabilities when its judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company's current estimate of the tax liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which they are determined. The accounting for uncertainty in income taxes recognized in an enterprise's financial statements prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken on a tax return, and the derecognition of tax benefits, classification on the balance sheet, interest and penalties, accounting in interim periods, disclosure, and transition. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Rollforward Table (at Gross): As of December 30, 2017 December 31, 2016 December 26, 2015 Unrecognized tax benefits - beginning of the period $ 6,477 $ 6,961 $ 6,442 Gross increases-tax positions in prior period 32 23 127 Gross decreases-tax positions in prior period — (1,193 ) (306 ) Gross increases-current-period tax positions 723 686 698 Lapse of statute of limitations (81 ) — — Unrecognized tax benefits - end of the period $ 7,151 $ 6,477 $ 6,961 The unrecognized tax benefit at December 30, 2017, was $7.2 million, of which $4.0 million would impact the effective tax rate if recognized. The Company accrues interest and penalties related to unrecognized tax benefits in its provision for income taxes. The total amount of penalties and interest were not material as of December 30, 2017, December 31, 2016, and December 26, 2015. The Company does not expect a material change in its unrecognized tax benefits within the next 12 months. The Company is subject to taxation in the U.S. and various states including California, and foreign jurisdictions including Korea, Japan, Taiwan, and China. Due to tax attribute carry-forwards, the Company is subject to examination for tax years 2003 forward for U.S. tax purposes. The Company was also subject to examination in various states for tax years 2002 forward. The Company is subject to examination for tax years 2009 forward for various foreign jurisdictions.

Segment, Geographic, Product an

Segment, Geographic, Product and Significant Customer Information	12 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Segment, Geographic, Product and Significant Customer Information	Note 14. Segment, Geographic, Product and Significant Customer Information The Company has one operating segment, which is the sale, design, manufacture, marketing and support of thin film and optical critical dimension systems. The Chief Executive Officer has been identified as the Chief Operating Decision Maker (“CODM”) because he has the final authority over resource allocation decisions and performance assessment. The CODM does not receive discrete financial information about individual components of the Company's business. For the years ended December 30, 2017, December 31, 2016, and December 26, 2015, the Company recorded revenue from customers primarily in the United States, Asia and Europe. The following tables summarize total net revenues and long-lived assets (excluding intangible assets) attributed to significant countries (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Total net revenues (1): South Korea $ 94,082 $ 44,735 $ 30,572 China 29,826 43,460 17,373 Singapore 21,810 37,096 17,395 United States 33,983 29,887 36,720 Taiwan 20,147 27,189 46,715 Japan 41,979 26,604 31,140 Other 16,794 12,158 7,452 Total net revenues $ 258,621 $ 221,129 $ 187,367 (1) December 30, 2017 December 31, 2016 Long-lived tangible assets: United States $ 43,427 $ 42,688 Taiwan 510 818 South Korea 576 554 Japan 60 57 All Other 237 109 Total long-lived tangible assets $ 44,810 $ 44,226 The Company’s product lines differ primarily based on the environment in which the systems will be used. Automated systems are used primarily in high-volume production environments. Materials characterization products are primarily used to measure the composition, band gap, structure, and other physical and electrical properties of semiconducting materials for discrete electronic industry, high brightness LED and solar/photovoltaic structures in both development and high-volume environments. Integrated systems are installed inside wafer processing equipment to provide near real-time measurements for improving process control and increasing throughput. Revenues by product type were as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Automated Systems $ 151,401 $ 127,378 $ 102,386 Integrated Systems 42,183 43,846 31,579 Materials Characterization Systems 21,293 13,842 12,980 Total product revenues $ 214,877 $ 185,066 $ 146,945 The following customers accounted for 10% or more of total accounts receivable, net: Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Taiwan Semiconductor Manufacturing Company Limited *** 20 % 26 % Samsung Electronics Co. Ltd. 13 % 14 % *** Micron Technology, Inc. 18 % 12 % *** Intel Corporation *** 11 % *** Toshiba Corporation 31 % 10 % 27 % *** The customer accounted for less than 10% of total accounts receivable, net, as of that period end. The following customers accounted for 10% or more of total net revenue: Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Samsung Electronics Co. Ltd. 26 % *** 13 % SK Hynix 13 % 15 % 11 % Micron Technology, Inc. 12 % 20 % 16 % Intel Corporation 11 % 18 % *** Toshiba Corporation 11 % *** 10 % Taiwan Semiconductor Manufacturing Company Limited *** 10 % 19 % *** The customer accounted for less than 10% of total net revenue during the period.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 30, 2017
Valuation And Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II - Valuation and Qualifying Accounts as of and for the years ended December 30, 2017, December 31, 2016 and December 26, 2015 Our allowance for doubtful accounts receivable consists of the following (in thousands): Year Ended Balance at beginning of period Additions to Allowance Charges Utilized/Write-offs Balance at end of period December 30, 2017 $ 73 $ 78 $ (25 ) $ 126 December 31, 2016 $ 150 $ — $ (77 ) $ 73 December 26, 2015 $ 253 $ 10 $ (113 ) $ 150 Our valuation allowance for deferred tax assets consists of the following (in thousands): Year Ended Balance at beginning of period Additions to Allowance Charges Utilized/Write-offs Balance at end of period December 30, 2017 $ 10,980 $ 2,984 $ (262 ) $ 13,702 December 31, 2016 $ 36,786 $ 1,643 $ (27,449 ) $ 10,980 December 26, 2015 $ 35,835 $ 951 $ — $ 36,786

Nature of Business, Basis of 23

Nature of Business, Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	Description of Business – Nanometrics Incorporated (“Nanometrics” or the “Company”) and its wholly-owned subsidiaries design, manufacture, market, sell and support optical critical dimension ("OCD"), thin film and overlay dimension metrology and inspection systems used primarily in the manufacturing of semiconductors, solar photovoltaics (“solar PV”) and high-brightness LEDs (“HB-LED”), as well as by customers in the silicon wafer and data storage industries. Nanometrics' metrology systems precisely measure a wide range of film types deposited on substrates during manufacturing to control manufacturing processes and increase production yields in the fabrication of integrated circuits. The Company’s OCD technology is a patented critical dimension measurement technology that is used to precisely determine the dimensions on the semiconductor wafer that directly control the resulting performance of the integrated circuit devices. The thin film metrology systems use a broad spectrum of wavelengths, high-sensitivity optics, proprietary software, and patented technology to measure the thickness and uniformity of films deposited on silicon and other substrates as well as their chemical composition. The overlay metrology systems are used to measure the overlay accuracy of successive layers of semiconductor patterns on wafers in the photolithography process. Nanometrics' inspection systems are used to find defects on patterned and unpatterned wafers at nearly every stage of the semiconductor production flow. The corporate headquarters of Nanometrics is located in Milpitas, California.
Basis of Presentation	Basis of Presentation – The consolidated financial statements include Nanometrics Incorporated and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.
Fiscal Year	Fiscal Year – The Company utilizes a 52/53 week fiscal year ending on the last Saturday of the calendar year. For each of fiscal years ended December 30, 2017, December 31, 2016, and December 26, 2015, the period presented consisted of a 52-week year, 53-week year and 52-week year, respectively.
Upgrade Revenue and Related Cost	Upgrade Revenue and Related Cost - Beginning the first quarter of 2016, revenues associated with upgrade sales are now included under Products Revenues, and the related costs in Cost of Products Revenue. This change was due to the types of upgrades currently being sold, which are primarily system software and hardware performance upgrades to extend the features and functionality of a product. Previously upgrades consisted of a group of parts and/or software that change the existing configuration of a product. For the twelve months ended December 30, 2017, and December 31, 2016, $12.1 million and $11.0 million, respectively, of upgrade sales and $2.7 million and $2.4 million of costs, respectively, are included in Products Revenues and Cost of Products Revenues. For the year ended December 26, 2015, $7.9 million related to upgrade sales, and $3.0 million of costs, are included in Service Revenues and Costs of Service Revenues, respectively, in the accompanying Condensed Consolidated Statement of Operations.
Use of Estimates	Use of Estimates – The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("U.S. GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ materially from those estimates. Estimates are used for, but not limited to, revenue recognition, the provision for doubtful accounts, the provision for excess, obsolete, or slow-moving inventories, valuation of intangible and long-lived assets, warranty accruals, income taxes, valuation of stock-based compensation, and contingencies.
Foreign Currency Translation	Foreign Currency Translation – The assets and liabilities of foreign subsidiaries are translated from their respective local functional currencies at exchange rates in effect at the balance sheet date and income and expense accounts are translated at average exchange rates during the reporting period. Resulting translation adjustments are reflected in “Accumulated other comprehensive income,” a component of stockholders’ equity. Foreign currency transaction gains and losses, as well as remeasurement of assets and liabilities denominated in a currency other than the functional currency are reflected in “Other income (expense)” in the consolidated statements of operations in the period incurred, and consists of a $ 0.6 million loss, a $0.4 million loss and a $0.5 million gain for the years ended December 30, 2017, December 31, 2016, and December 26, 2015, respectively.
Revenue Recognition	Revenue Recognition – The Company derives revenue from the sale of process control metrology and inspection systems and related upgrades (“product revenue”) as well as spare part sales, billable service and service contracts (together “service revenue”). Upgrades are system software and hardware performance upgrades that extend the features and functionality of a product. As discussed above, commencing in the first quarter of 2016, upgrades are included in product revenue, which consists of sales of complete, advanced process control metrology and inspection systems (the “system(s)”). Nanometrics’ systems consist of hardware and software components that function together to deliver the essential functionality of the system. Arrangements for sales of systems and upgrades often include defined customer-specified acceptance criteria. In summary, the Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller's price is fixed or determinable, and collectability is reasonably assured. For repeat product sales to existing customers, revenue recognition occurs at the time title and risk of loss transfer to the customer, which usually occurs upon shipment from the Company's manufacturing location, if it can be reliably demonstrated that the product has successfully met the defined customer specified acceptance criteria and all other recognition criteria have been met. For initial sales where the product has not previously met the defined customer specified acceptance criteria, product revenues are recognized upon the earlier of receipt of written customer acceptance or expiration of the contractual acceptance period. In Japan, where contractual terms with the customer specify risk of loss and title transfers upon customer acceptance, revenue is recognized upon receipt of written customer acceptance, provided that all other recognition criteria have been met. The Company warrants its products against defects in manufacturing. Upon recognition of product revenue, a liability is recorded for anticipated warranty costs. On occasion, customers request a warranty period longer than the Company's standard warranty. In those instances, where extended warranty services are separately quoted to the customer, the associated revenue is deferred and recognized as service revenue ratably over the term of the extended warranty period. The portion of service contracts and extended warranty services agreements that are uncompleted at the end of any reporting period are included in deferred revenue. As part of its customer services, the Company sells software that is considered to be an upgrade to a customer's existing systems. These standalone software sales are not essential to the tangible product's functionality and are accounted for under software revenue recognition rules which require vendor specific objective evidence (“VSOE”) of fair value to allocate revenue in a multiple element arrangement. Revenue from software sales is recognized when the software is delivered to the customer, provided that all other recognition criteria have been met. The majority of other upgrades are sold based on published specifications. For simple upgrades that do not require major configuration, revenue is recognized at the time title and risk of loss transfer to the customer, which is usually upon shipment. For complex and extensive upgrades, specific acceptance or prior acceptance for a similar upgrade is required in order to recognize revenue. Revenue related to spare parts is recognized upon shipment. Revenue related to billable services is recognized as the services are performed. Service contracts may be purchased by the customer during or after the warranty period and revenue is recognized ratably over the service contract period. Frequently, the Company delivers products and various services in a single transaction. The Company's deliverables consist of tools, installation, upgrades, billable services, spare parts, and service contracts. The Company's typical multi-element arrangements include a sale of one or multiple tools that include installation and standard warranty. Other arrangements consist of a sale of tools bundled with service elements or delivery of different types of services. The Company's tools, upgrades, and spare parts are generally delivered to customers within a period of up to six months from order date. Installation is usually performed soon after delivery of the tool. The portion of revenue associated with installation is deferred based on relative selling price and that revenue is recognized upon completion of the installation and receipt of final acceptance. Billable services are billed on a time and materials basis and performed as requested by customers. Under service contract arrangements, services are provided as needed over the fixed arrangement term, which terms can be up to twelve months. The Company does not grant its customers a general right of return or any refund terms and imposes a penalty on orders cancelled prior to the scheduled shipment date. The Company regularly evaluates its revenue arrangements to identify deliverables and to determine whether these deliverables are separable into multiple units of accounting. The Company allocates the arrangement consideration among the deliverables based on relative selling prices. The Company has established VSOE for some of its products and services when a substantial majority of selling prices falls within a narrow range when sold separately. For deliverables with no established VSOE, the Company uses best estimate of selling price to determine standalone selling price for such deliverable. The Company does not use third party evidence to determine standalone selling price since this information is not widely available in the market as the Company's products contain a significant element of proprietary technology and the solutions offered differ substantially from competitors. The Company has established a process for developing estimated selling prices, which incorporates historical selling prices, the effect of market conditions, gross margin objectives, pricing practices, as well as entity-specific factors. The Company monitors and evaluates estimated selling price on a regular basis to ensure that changes in circumstances are accounted for in a timely manner. When certain elements in multiple-element arrangements are not delivered or accepted at the end of a reporting period, the relative selling prices of undelivered elements are deferred until these elements are delivered and/or accepted. If deliverables cannot be accounted for as separate units of accounting, the entire arrangement is accounted for as a single unit of accounting and revenue is deferred until all elements are delivered and all revenue recognition requirements are met.
Cash and Cash Equivalents	Cash, Cash Equivalents and Marketable Securities – The Company considers all highly liquid investments with original maturities of three months or less, when purchased, to be cash equivalents.
Marketable Securities	Marketable securities are classified as “available-for-sale” and are reported at fair value with unrealized gains and losses reported in stockholders' equity as a component of other comprehensive income. The cost of securities sold is based on the specific identification method. The Company classifies its investments as current based on the nature of the investment and their availability for use in current operations. The Company reviews its investment portfolio quarterly to determine if any securities may be other-than-temporarily impaired due to increased credit risk, changes in industry or sector of a certain instrument or ratings downgrades.
Fair Value of Financial Instruments	Fair Value of Financial Instruments – Financial instruments include cash and cash equivalents, accounts receivable and accounts payable. Cash equivalents are stated at fair market value based on quoted market prices. The carrying values of accounts receivable and accounts payable approximate their fair values because of the short-term maturity of these financial instruments.
Derivatives	Derivatives – The Company enters into foreign currency forward exchange contracts to protect against currency exchange risks associated with existing assets and liabilities. A foreign currency forward exchange contract acts as a hedge by increasing in value when underlying assets decrease in value or underlying liabilities increase in value due to changes in foreign exchange rates. Conversely, a foreign currency forward exchange contract decreases in value when underlying assets increase in value or underlying liabilities decrease in value due to changes in foreign exchange rates. These forward contracts are not designated as accounting hedges, so the unrealized gains and losses are recognized in other income, net, in advance of the actual foreign currency cash flows with the fair value of these forward contracts being recorded as accrued liabilities or other current assets. The Company does not use forward contracts for trading purposes.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts – The Company maintains allowances for estimated losses resulting from the inability of its customers to make required payments. Credit limits are established through a process of reviewing the financial history and stability of its customers. Where appropriate and available, the Company obtains credit rating reports and financial statements of customers when determining or modifying their credit limits. The Company regularly evaluates the collectability of its trade receivable balances based on a combination of factors such as the length of time the receivables are past due, customary payment practices in the respective geographies and historical collection experience with customers. The Company believes that its allowance for doubtful accounts adequately reflects the risk associated with its receivables. If the financial conditions of a customer were to deteriorate, resulting in their inability to make payments, the Company may need to record additional allowances, which would result in additional general and administrative expenses being recorded for the period in which such determination was made.
Inventories	Inventories – Inventories are stated at the lower of cost, which approximates actual cost on a first-in, first-out basis, or net realizable value. The Company is exposed to a number of economic and industry factors that could result in portions of inventory becoming either obsolete or in excess of anticipated usage, or saleable only for amounts that are less than their carrying amounts. These factors include, but are not limited to, technological changes in the market, the Company’s ability to meet changing customer requirements, competitive pressures in products and prices, and the availability of key components from suppliers. The Company has established inventory reserves when conditions exist that suggest that inventory may be in excess of anticipated demand or is obsolete based upon assumptions about future demand for the Company’s products and market conditions. Once a reserve has been established, it is maintained until the part to which it relates is sold or is otherwise disposed of. The Company regularly evaluates its ability to realize the value of inventory based on a combination of factors including the following: historical usage rates, forecasted sales of usage, product end-of-life dates, estimated current and future market values and new product introductions. For demonstration inventory, the Company also considers the age of the inventory and potential cost to refurbish the inventory prior to sale. Demonstration inventory is amortized over its useful life and the amortization expense is included in total inventory write down on the statements of cash flows. When recorded, reserves are intended to reduce the carrying value of the Company’s inventory to its net realizable value. If actual demand for the Company’s products deteriorates, or market conditions are less favorable than those that the Company projects, additional reserves may be required. Inventories – delivered systems – The Company reflects the cost of systems that were invoiced upon shipment but deferred for revenue recognition purposes separate from its inventory held for sale as “Inventories – delivered systems.”
Property, Plant and Equipment	Property, Plant and Equipment – Property, plant and equipment are stated at cost. Depreciation and amortization is computed using the straight–line method over the following estimated useful lives of the assets: Building and Improvements 5-40 years Machinery and equipment 3-10 years Furniture and fixtures 3-10 years Software 3-7 years
Goodwill and Intangible Assets	Goodwill and Intangible Assets – Goodwill is initially recorded when the purchase price paid for an acquisition exceeds the estimated fair value of the net identified tangible and intangible assets acquired. Intangible assets with finite lives are amortized over their respective useful lives on a straight-line basis and are also evaluated annually for impairment or whenever events or circumstances occur which indicate that those assets might be impaired. Goodwill and indefinite lived assets are not amortized but tested annually for impairment. The Company’s impairment review process is completed during the fourth quarter of each year or whenever events, or circumstances occur which indicate that an impairment may have occurred. The Company assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. If, after assessing the qualitative factors, the Company determines that it is not likely that the fair value of a reporting unit is less than its carrying value, then performing the two-step impairment test is unnecessary. However, if the Company concludes otherwise, then it is required to perform the first step of the two-step goodwill impairment test. The first step requires a comparison of the fair value of Nanometrics’ reporting unit to its net book value. If the fair value of the reporting unit is greater than its carrying value, then no impairment is deemed to have occurred. If the fair value is less, then the second step must be performed to determine the amount, if any, of actual impairment. Amortization of intangible assets with finite lives is computed using the straight-line method over the following estimated useful lives of the assets: Developed technology 5-10 years Customer relationships 2-10 years Brand name 5-10 years Patented technology 7-10 years Trademark 5 years
Long-Lived Assets	Long-Lived Assets – The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When the sum of the undiscounted future net cash flows expected to result from the use of the asset and its eventual disposition is less than its carrying amount, impairment may exist. To determine the amount of impairment, the Company compares the fair value of the asset to its carrying value. If the carrying value of the asset exceeds its fair value, an impairment loss equal to the difference is recognized. See Note 7, "Goodwill and Intangible Assets" for further details.
Income Tax Assets and Liabilities	Income Tax Assets and Liabilities – The Company accounts for income taxes such that deferred tax assets and liabilities must be recognized using enacted tax rates for the effect of temporary differences between the book and tax accounting for assets and liabilities. Also, deferred tax assets are reduced by a valuation allowance to the extent that management cannot conclude that it is more likely than not that a portion of the deferred tax asset will be realized in the future. The Company evaluates the deferred tax assets on a continuous basis throughout the year to determine whether or not a valuation allowance is appropriate. Factors used in this determination include future expected income and the underlying asset or liability which generated the temporary tax difference. The income tax provision is primarily impacted by federal statutory rates, state and foreign income taxes and changes in the valuation allowance.
Product Warranties	Product Warranties – The Company sells the majority of its products with a twelve-month repair or replacement warranty from the date of acceptance, which generally represents the date of shipment. The Company provides an accrual for estimated future warranty costs based upon the historical relationship of warranty costs to the cost of products sold. The estimated future warranty obligations related to product sales are reported in the period in which the related revenue is recognized. The estimated future warranty obligations are affected by the warranty periods, sales volumes, product failure rates, material usage and labor and replacement costs incurred in correcting a product failure. If actual product failure rates, material usage, labor or replacement costs differ from the Company’s estimates, revisions to the estimated warranty obligations would be required. For new product introductions where limited or no historical information exists, the Company may use warranty information from other previous product introductions to guide it in estimating the warranty accrual. The warranty accrual represents the best estimate of the amount necessary to settle future and existing claims on products sold as of the balance sheet date. The Company periodically assesses the adequacy of its recorded warranty reserve and adjusts the amounts in accordance with changes in these factors.
Shipping and Handling Costs	Shipping and Handling Costs – Shipping and handling costs are included as a component of cost of net revenues.
Advertising Costs	Advertising Costs – The Company expenses advertising costs as incurred. Advertising costs were $ 0.2 million in 2017, $0.2 million in 2016, and $0.3 million in 2015.
Defined Employee Benefit Plans	Defined Employee Benefit Plans – The Company maintains a defined benefit pension plan in Taiwan for which current service costs are charged to operations as they accrue based on services rendered by employees during the year. Pension benefit obligations are determined by using management’s actuarial assumptions, including discount rates, assumed asset rates of return, compensation increases and employee turnover rates.
Net Income Per Share	Net Income Per Share - Basic net income per share excludes dilution and is computed by dividing net income by the number of weighted average common shares outstanding for the period. Diluted net income per share reflects the potential dilution from outstanding dilutive stock options (using the treasury stock method) , restricted stock units subject to vesting and shares issuable under the employee stock purchase plan. In applying the treasury stock method 0.6 million, 0.5 million and 0.3 million stock option shares for fiscal year 2017, 2016 and 2015, respectively, were included in the calculation of diluted shares.
Certain Significant Risks and Uncertainties	Certain Significant Risks and Uncertainties – Financial instruments that potentially subject us to a concentration of credit risk consist of cash, cash equivalents, marketable securities, and accounts receivable. The Company's cash and cash equivalents are primarily invested in deposit accounts and money market accounts with large financial institutions. At times, these deposits and securities may exceed federally insured limits; however, the Company has not experienced any losses on such accounts. The Company invests its cash not required for use in operations in high credit quality securities based on the Company's investment policy. The Company's investment policy provides guidelines and limits regarding credit quality, investment concentration, investment type, and maturity that the Company believes will provide liquidity while reducing risk of loss of capital. Investments are of a short-term nature and include investments in commercial paper, corporate debt securities, U.S. Treasury, U.S. Government, and U.S. Agency debt. The Company sells its products primarily to end users in the United States, Asia and Europe and, generally, does not require its customers to provide collateral or other security to support accounts receivable. Management performs ongoing credit evaluations of its customers’ financial condition and maintains an allowance for estimated potential bad debt losses. The Company’s customer base is highly concentrated and historically, a relatively small number of customers have accounted for a significant portion of its revenues. Aggregate revenue from the Company's top five largest customers in 2017, 2016 and 2015 consisted of 73%, 73% and 69%, respectively, of its total net revenues. The Company participates in a dynamic high technology industry and believes that changes in any of the following areas could have a material adverse effect on its future financial position, results of operations or cash flows: advances and trends in new technologies and industry standards; competitive pressures in the form of new products or price reductions on current products; changes in product mix; changes in the overall demand for products offered; changes in third-party manufacturers; changes in key suppliers; changes in certain strategic relationships or customer relationships; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; fluctuations in foreign currency exchange rates; risk associated with changes in domestic and international economic and/or political regulations; availability of necessary components or sub-assemblies; disruption of manufacturing facilities; and its ability to attract and retain employees necessary to support its growth. Certain components and sub-assemblies used in the Company’s products are purchased from a sole supplier or a limited group of suppliers. In particular, the Company currently purchases its spectroscopic ellipsometer and robotics used in its advanced measurement systems from a sole supplier or a limited group of suppliers located in the United States. Any shortage or interruption in the supply of any of the components or sub-assemblies used in its products or its inability to procure these components or sub-assemblies from alternate sources on acceptable terms could have a material adverse effect on its business, financial condition and results of operations.

Nature of Business, Basis of 24

Nature of Business, Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Estimated useful lives of property, plant and equipment	Depreciation and amortization is computed using the straight–line method over the following estimated useful lives of the assets: Building and Improvements 5-40 years Machinery and equipment 3-10 years Furniture and fixtures 3-10 years Software 3-7 years
Estimated Useful Lives of Intangible Assets	Amortization of intangible assets with finite lives is computed using the straight-line method over the following estimated useful lives of the assets: Developed technology 5-10 years Customer relationships 2-10 years Brand name 5-10 years Patented technology 7-10 years Trademark 5 years

Fair Value Measurements and D25

Fair Value Measurements and Disclosures (Tables)	12 Months Ended
	Dec. 30, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measurements at estimated fair value on recurring basis excluding accrued interest components	The following tables present the Company’s assets and liabilities measured at estimated fair value on a recurring basis, excluding accrued interest components, categorized in accordance with the fair value hierarchy (in thousands), as of the following dates: December 30, 2017 December 31, 2016 Fair Value Measurements Using Input Types Fair Value Measurements Using Input Types Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 256 $ — $ — $ 256 $ 959 $ — $ — $ 959 Commercial paper and corporate debt securities — — — — — 2,499 — 2,499 Total cash equivalents $ 256 $ — $ — $ 256 $ 959 $ 2,499 $ — $ 3,458 Marketable securities: U.S. Treasury, U.S. Government and U.S. Government agency debt securities — 1,495 — 1,495 — 17,072 — 17,072 Certificate of deposits — 14,497 — 14,497 — 23,019 — 23,019 Commercial paper — 7,949 — 7,949 — 22,402 — 22,402 Municipal securities and corporate debt securities — 47,968 — 47,968 — 14,943 — 14,943 Asset backed securities — 10,221 — 10,221 — 5,463 — 5,463 Total marketable securities $ — $ 82,130 $ — $ 82,130 $ — $ 82,899 $ — $ 82,899 Total (1) $ 256 $ 82,130 $ — $ 82,386 $ 959 $ 85,398 $ — $ 86,357 (1) Excludes $34.6 million and $43.6 million held in operating accounts as of December 30, 2017, and December 31, 2016, respectively.
Outstanding derivative instruments	The following table summarizes the Company’s outstanding derivative instruments on a gross basis: As of December 30, 2017 As of December 31, 2016 Notional Amount Fair Value Notional Amount Fair Value (in millions) Asset Liability (in millions) Asset Liability Undesignated Hedges: Forward Foreign Currency Contracts Purchase $ 27.5 — $ 0.1 $ 12.6 — — Sell $ 16.8 0.1 — $ 1.3 — —

Cash and Investments (Tables)

Cash and Investments (Tables)	12 Months Ended
	Dec. 30, 2017
Investments Debt And Equity Securities [Abstract]
Cash, Cash Equivalents and Available-for-Sale Investments	The following table presents cash, cash equivalents, and available-for-sale investments as of the following dates (in thousands): December 30, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Market Value Cash $ 34,643 $ — $ — $ 34,643 Cash equivalents: Money market funds 256 — — 256 Marketable securities: U.S. Government agency securities 1,500 — (5 ) 1,495 Certificates of deposits 14,498 — (1 ) 14,497 Commercial paper 7,952 — (3 ) 7,949 Corporate debt securities 48,073 — (105 ) 47,968 Asset-backed securities 10,240 — (19 ) 10,221 Total cash, cash equivalents, and marketable securities $ 117,162 $ — $ (133 ) $ 117,029 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Market Value Cash $ 43,604 $ — $ — $ 43,604 Cash equivalents: Money market funds 959 — — 959 Commercial paper and corporate debt securities 2,499 — — 2,499 Marketable securities: U.S. Treasury securities 5,667 — — 5,667 U.S. Government agency securities 11,412 — (7 ) 11,405 Certificates of deposits 23,000 19 — 23,019 Commercial paper 22,402 — — 22,402 Corporate debt securities 14,194 — (6 ) 14,188 Municipal securities 756 — (1 ) 755 Asset-backed securities 5,466 — (3 ) 5,463 Total cash, cash equivalents, and marketable securities $ 129,959 $ 19 $ (17 ) $ 129,961

Financial Statement Components

Financial Statement Components (Tables)	12 Months Ended
	Dec. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Selected financial statement components	The following tables provide details of selected financial statement components as of the following dates (in thousands): At December 30, 2017 December 31, 2016 Inventories: Raw materials and sub-assemblies $ 32,187 $ 23,506 Work in process 13,498 10,347 Finished goods 7,175 4,984 Inventories 52,860 38,837 Inventories-delivered systems 1,534 2,457 Total inventories $ 54,394 $ 41,294 Property, plant and equipment, net: (1) Land $ 15,573 $ 15,568 Building and improvements 20,880 20,532 Machinery and equipment 36,380 35,659 Furniture and fixtures 2,420 2,282 Software 9,558 9,756 Capital in progress 4,418 2,748 Total property, plant and equipment, gross 89,229 86,545 Accumulated depreciation and amortization (44,419 ) (42,319 ) Total property, plant and equipment, net $ 44,810 $ 44,226 (1) Total depreciation and amortization expense for the years ended December 30, 2017, December 31, 2016 and December 26, 2015 was $6.7 million, $6.8 million, and $6.9 million, respectively. Other Current Liabilities: Accrued warranty $ 4,863 $ 3,838 Accrued taxes 813 706 Customer deposits — 581 Accrued professional services 534 424 Accrued royalties — 1,233 Other 1,039 1,265 Total other current liabilities $ 7,249 $ 8,047
Components of accumulated other comprehensive income (loss)	Components of Accumulated Other Comprehensive Income (Loss) Foreign Currency Translations Defined Benefit Pension Plans Unrealized Income (Loss) on Investment Accumulated Other Comprehensive Income Balance as of December 26, 2015 $ (4,948 ) $ (210 ) $ (44 ) $ (5,202 ) Current period change (869 ) (17 ) 42 (844 ) Balance as of December 31, 2016 (5,817 ) (227 ) (2 ) (6,046 ) Current period change 4,170 (160 ) (88 ) 3,922 Balance as of December 30, 2017 $ (1,647 ) $ (387 ) $ (90 ) $ (2,124 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of goodwill	The following table summarizes the activity in the Company’s goodwill during the years ended December 30, 2017 and December 31, 2016, respectively (in thousands): Amounts Balance as of December 26, 2015 $ 9,415 Foreign currency movements (475 ) Balance as of December 31, 2016 8,940 Foreign currency movements 1,292 Balance as of December 30, 2017 $ 10,232
Summary of finite-lived intangible assets	Finite-lived intangible assets are recorded at cost, less accumulated amortization. Finite-lived intangible assets as of December 30, 2017, and December 31, 2016 consisted of the following (in thousands): December 30, 2017 Adjusted cost Accumulated amortization Net carrying amount Developed technology $ 18,887 $ (16,681 ) $ 2,206 Customer relationships 9,438 (9,438 ) — Brand names 1,927 (1,927 ) — Patented technology 2,252 (2,252 ) — Trademark 80 (80 ) — Total $ 32,584 $ (30,378 ) $ 2,206 December 31, 2016 Adjusted cost Accumulated amortization Net carrying amount Developed technology $ 15,726 $ (15,380 ) $ 346 Customer relationships 9,322 (9,322 ) — Brand names 1,927 (1,927 ) — Patented technology 2,252 (2,186 ) 66 Trademark 80 (80 ) — Total $ 29,307 $ (28,895 ) $ 412
Estimated future amortization expense	The estimated future amortization expense of finite intangible assets as of December 30, 2017, is as follows (in thousands): Fiscal Years Amounts 2018 283 2019 352 2020 286 2021 286 2022 286 Thereafter 713 Total future amortization expense 2,206

Warranties (Tables)

Warranties (Tables)	12 Months Ended
	Dec. 30, 2017
Product Warranties Disclosures [Abstract]
Components of the warranty accrual	Components of the warranty accrual, which were included in the accompanying consolidated balance sheets with other current liabilities, were as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 Balance as of beginning of period $ 3,838 $ 4,504 Accruals for warranties issued during period 5,247 4,509 Settlements during the period (4,222 ) (5,175 ) Balance as of end of period $ 4,863 $ 3,838

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Future minimum lease payments under operating leases	Future minimum lease payments under its operating leases are as follows (in thousands): Operating Leases 2018 1,664 2019 935 2020 313 2021 54 2022 2 Thereafter — Total $ 2,968

Net Income Per Share (Tables)

Net Income Per Share (Tables)	12 Months Ended
	Dec. 30, 2017
Earnings Per Share [Abstract]
Reconciliation of the basic and diluted net income (loss) per share computations	A reconciliation of the share denominator of the basic and diluted net income per share computations is as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Weighted average common shares outstanding used in basic net income per share calculation 25,334 24,655 24,059 Potential dilutive common stock equivalents, using treasury stock method 585 498 316 Weighted average shares used in diluted net income per share calculation 25,919 25,153 24,375

Stockholders' Equity and Stoc32

Stockholders' Equity and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share repurchases	Shares repurchased and retired for fiscal year 2017, 2016 and 2015, with the associated cost of repurchase and amount available for repurchase at the end of the respective periods are as follows (in thousands, except number of shares and weighted average price per share): Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Number of shares of common stock repurchased 1,065,848 — 111,050 Weighted average price per share $ 25.33 — $ 15.49 Total cost of repurchase $ 26,999 — $ 1,721 Amount available for repurchase at end of period $ 23,001 — $ 4,397
Option plans	The Nanometrics option plans are as follows: Plan Name Participants Shares Authorized 2005 Equity Incentive Plan Employees, consultants and directors 8,292,594 2000 Employee Stock Option Plan Employees and consultants 2,450,000 2000 Director Stock Option Plan Non-employee directors 250,000 Accent Optical Technologies, Inc. Stock Incentive Plan Employees and consultants 205,003
Employee stock purchase plan assumptions	The weighted-average fair value calculations are based on the following average assumptions: Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Employee Stock Purchase Plan: Expected life 0.5 years 0.5 years 0.5 years Volatility 37.2% 38.7% 36.9% Risk free interest rate 0.91% 0.44% 0.12% Dividends — — —
Stock option plans activity	A summary of activity of stock options is as follows: Number of Shares Outstanding (Options) Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in Thousands) Options Outstanding at December 26, 2015 1,059,471 $ 14.61 2.47 $ 1,920 Exercised (442,339 ) 13.66 Cancelled/Forfeited (176,587 ) 15.83 Outstanding at December 31, 2016 440,545 15.06 2.12 $ 4,405 Exercised (223,364 ) 13.35 Cancelled/Forfeited (855 ) 16.63 Outstanding at December 30, 2017 216,326 $ 16.82 1.76 $ 1,752 Exercisable at December 30, 2017 215,620 $ 16.81 1.76 $ 1,748
Ranges of outstanding and exercisable options	The following table summarizes ranges of outstanding and exercisable options as of December 30, 2017. Options Outstanding Options Exercisable Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $12.98-$15.00 23,383 1.83 $ 14.64 23,383 $ 14.64 $15.08-$15.65 27,697 1.37 15.62 27,697 15.62 $15.74-$15.74 3,333 0.40 15.74 3,333 15.74 $15.85-$15.85 60,000 2.20 15.85 60,000 15.85 $16.00-$17.33 31,700 1.82 17.00 31,700 17.00 $17.70-$18.08 6,613 1.55 17.92 6,588 17.92 $18.22-$18.22 3,600 3.16 18.22 3,449 18.22 $18.51-$18.51 9,000 3.14 18.51 8,583 18.51 $18.79-$18.79 1,000 3.23 18.79 887 18.79 $19.03-$19.03 50,000 1.13 $ 19.03 50,000 $ 19.03 $12.98-$19.03 216,326 215,620
Summary of activity for RSUs	A summary of activity for RSUs is as follows: Summary of activity for RSUs Number of RSUs Weighted Average Fair Value Outstanding RSUs as of December 26, 2015 713,243 $ 15.99 Granted 476,667 17.45 Released (315,872 ) 16.05 Cancelled (54,253 ) 16.29 Outstanding RSUs as of December 31, 2016 819,785 16.79 Granted 454,600 27.12 Released (387,592 ) 16.81 Cancelled (96,494 ) 19.01 Outstanding RSUs as of December 30, 2017 790,299 $ 22.46
Summary of activity for PSUs	A summary of activity for PSUs is as follows: Summary of activity for PSUs Number of PSUs Weighted Average Fair Value Outstanding PSUs as of December 26, 2015 60,000 $ 12.23 Granted 67,500 8.52 Released (13,333 ) 12.03 Cancelled (6,667 ) 12.03 Outstanding PSUs as of December 31, 2016 107,500 9.94 Granted 122,050 20.51 Released (38,500 ) 10.41 Cancelled (61,100 ) 19.41 Outstanding PSUs as of December 30, 2017 129,950 $ 15.60
PSUs valuation assumptions	The assumptions for the valuation of PSUs are summarized as follows: 2017 Award 2016 Award 2015 Award Grant Date Fair Values Per Share $14.57-$26.75 $ 8.52 $ 12.23 Weighted-average assumptions/inputs: Expected Dividend — — — Range of risk-free interest rates 1.74%-1.84% 0.92% 0.25%-1.1% Range of expected volatilities for peer group 22%-66% 22%-93% 23%-65%
Stock-based compensation expense for all share-based payment awards	Stock-based compensation expense for all share-based payment awards made to the Company’s employees and directors pursuant to the employee stock option and employee stock purchase plans by function were as follows (in thousands): Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Cost of products $ 842 $ 403 $ 274 Cost of service 616 509 309 Research and development 1,720 1,408 1,036 Selling 2,323 2,046 1,881 General and administrative 3,318 3,300 2,748 Total stock-based compensation expense related to employee stock options and employee stock purchases $ 8,819 $ 7,666 $ 6,248
Stock Options, RSUs and PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option plans activity including options, RSUs and PSUs	A summary of activity under the Company’s stock option plans including options, RSUs and PSUs during fiscal year 2017, 2016 and 2015 and shares available for grant as of the respective period end dates, is as follows: Fiscal Year 2017 Fiscal Year 2016 Fiscal Year 2015 Shares available for grant at beginning of fiscal year 1,334,581 1,916,589 2,464,082 Additional Shares Authorized 1,000,000 — — Options – cancelled 855 176,587 94,012 Options - expired plan shares (116,192 ) (1,800 ) RSUs – granted (772,820 ) (810,334 ) (860,980 ) RSUs – cancelled 164,040 92,230 202,356 RSUs - shares issued to satisfy tax withholding obligations 251,724 179,117 120,919 PSUs – granted (207,485 ) (114,750 ) (102,000 ) PSUs – cancelled 103,870 11,334 — Shares available for grant at end of fiscal year 1,874,765 1,334,581 1,916,589

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Income (loss) before provision for income taxes	Income (loss) before provision for income taxes consists of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Domestic $ 34,238 $ 25,372 $ 178 Foreign 9,060 3,763 5,390 Income (loss) before income taxes $ 43,298 $ 29,135 $ 5,568
Provision (benefit) for income taxes	The provision (benefit) for income taxes consists of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Current: Federal $ 3,250 $ 697 $ 148 State 9 85 3 Foreign 2,998 2,111 2,266 6,257 2,893 2,417 Deferred: Federal 6,314 (16,641 ) 190 State 53 (320 ) 3 Foreign 472 (832 ) 53 6,839 (17,793 ) 246 Provision (benefit) for income taxes $ 13,096 $ (14,900 ) $ 2,663
Components of deferred tax assets and liabilities	Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands): At December 30, 2017 December 31, 2016 Deferred tax assets: Reserves and accruals $ 5,797 $ 11,043 Deferred revenue 240 349 Shared based compensation 1,483 2,590 Tax credit carry-forwards 9,669 10,112 Net operating losses 9,755 8,434 Depreciation & amortization (1,525 ) (2,898 ) Other 207 (1,252 ) Total deferred tax assets 25,626 28,378 Less: Valuation allowance (13,702 ) (10,980 ) Total deferred tax assets net of valuation allowance 11,924 17,398 Deferred tax liabilities: Depreciation & amortization (12 ) (6 ) Other (167 ) (14 ) Total deferred tax liabilities (179 ) (20 ) Net deferred tax assets $ 11,745 $ 17,378
Income Tax Rate Reconciliation	Differences between income taxes computed by applying the statutory federal income tax rate to income (loss) before income taxes and the provision (benefit) for income taxes consist of the following (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Income taxes computed at U.S. statutory rate $ 15,153 $ 10,197 $ 1,949 State income taxes 227 223 28 Foreign tax rate differential 794 3,502 342 Change in valuation allowance 1,490 (25,738 ) 1,648 Equity compensation (1,803 ) 380 311 Tax credits (2,336 ) (3,191 ) (1,834 ) Domestic production activities deduction (608 ) (354 ) — Liabilities for uncertain tax positions 18 67 74 Other, net 161 14 145 Provision (benefit) for income taxes $ 13,096 $ (14,900 ) $ 2,663
Reconciliation of unrecognized tax benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Rollforward Table (at Gross): As of December 30, 2017 December 31, 2016 December 26, 2015 Unrecognized tax benefits - beginning of the period $ 6,477 $ 6,961 $ 6,442 Gross increases-tax positions in prior period 32 23 127 Gross decreases-tax positions in prior period — (1,193 ) (306 ) Gross increases-current-period tax positions 723 686 698 Lapse of statute of limitations (81 ) — — Unrecognized tax benefits - end of the period $ 7,151 $ 6,477 $ 6,961

Segment, Geographic, Product 34

Segment, Geographic, Product and Significant Customer Information (Tables)	12 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Total net revenue	The following tables summarize total net revenues and long-lived assets (excluding intangible assets) attributed to significant countries (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Total net revenues (1): South Korea $ 94,082 $ 44,735 $ 30,572 China 29,826 43,460 17,373 Singapore 21,810 37,096 17,395 United States 33,983 29,887 36,720 Taiwan 20,147 27,189 46,715 Japan 41,979 26,604 31,140 Other 16,794 12,158 7,452 Total net revenues $ 258,621 $ 221,129 $ 187,367 (1)
Long-lived tangible assets	December 30, 2017 December 31, 2016 Long-lived tangible assets: United States $ 43,427 $ 42,688 Taiwan 510 818 South Korea 576 554 Japan 60 57 All Other 237 109 Total long-lived tangible assets $ 44,810 $ 44,226
Revenues by product type	The Company’s product lines differ primarily based on the environment in which the systems will be used. Automated systems are used primarily in high-volume production environments. Materials characterization products are primarily used to measure the composition, band gap, structure, and other physical and electrical properties of semiconducting materials for discrete electronic industry, high brightness LED and solar/photovoltaic structures in both development and high-volume environments. Integrated systems are installed inside wafer processing equipment to provide near real-time measurements for improving process control and increasing throughput. Revenues by product type were as follows (in thousands): Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Automated Systems $ 151,401 $ 127,378 $ 102,386 Integrated Systems 42,183 43,846 31,579 Materials Characterization Systems 21,293 13,842 12,980 Total product revenues $ 214,877 $ 185,066 $ 146,945
Customers accounted for 10% or more of total accounts receivable	The following customers accounted for 10% or more of total accounts receivable, net: Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Taiwan Semiconductor Manufacturing Company Limited *** 20 % 26 % Samsung Electronics Co. Ltd. 13 % 14 % *** Micron Technology, Inc. 18 % 12 % *** Intel Corporation *** 11 % *** Toshiba Corporation 31 % 10 % 27 % *** The customer accounted for less than 10% of total accounts receivable, net, as of that period end.
Customers accounted for 10% or more of total revenue	The following customers accounted for 10% or more of total net revenue: Years Ended December 30, 2017 December 31, 2016 December 26, 2015 Samsung Electronics Co. Ltd. 26 % *** 13 % SK Hynix 13 % 15 % 11 % Micron Technology, Inc. 12 % 20 % 16 % Intel Corporation 11 % 18 % *** Toshiba Corporation 11 % *** 10 % Taiwan Semiconductor Manufacturing Company Limited *** 10 % 19 % *** The customer accounted for less than 10% of total net revenue during the period.

Nature of Business, Basis of 35

Nature of Business, Basis of Presentation and Significant Accounting Policies - Textual (Details) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017USD ($)Customershares	Dec. 31, 2016USD ($)Customershares	Dec. 26, 2015USD ($)Customershares
Accounting Policies [Line Items]
Fiscal year duration	364 days	371 days	364 days
Products revenues	$ 214,877	$ 185,066	$ 146,945
Cost of products revenues	100,910	85,391	76,224
Service revenues	43,744	36,063	40,422
Cost of service revenues	20,804	20,160	19,450
Foreign currency transaction gain (loss)	$ (600)	(400)	500
Maximum period of delivery to customers	6 months
Maximum period services are provided over the fixed arrangement term	12 months
Product warranty period	12 months
Advertising costs	$ 200	$ 200	$ 300
Potential dilutive common stock equivalents, using treasury stock method | shares	585	498	316
Number of Major Customer | Customer	5	5	5
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member]
Accounting Policies [Line Items]
Concentration of risk percentage	73.00%	73.00%	69.00%
Stock Options [Member]
Accounting Policies [Line Items]
Potential dilutive common stock equivalents, using treasury stock method | shares	600	500	300
Reclassification [Member]
Accounting Policies [Line Items]
Products revenues	$ 12,100	$ 11,000
Cost of products revenues	$ 2,700	$ 2,400
Service revenues			$ 7,900
Cost of service revenues			$ 3,000
Minimum [Member]
Accounting Policies [Line Items]
Fiscal year duration	364 days
Maximum [Member]
Accounting Policies [Line Items]
Fiscal year duration	371 days

Nature of Business, Basis of 36

Nature of Business, Basis of Presentation and Significant Accounting Policies - Estimated Useful Lives of Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 30, 2017
Building and Improvements [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	5 years
Building and Improvements [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	40 years
Machinery and equipment [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	3 years
Machinery and equipment [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	10 years
Furniture and fixtures [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	3 years
Furniture and fixtures [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	10 years
Software [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	3 years
Software [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful lives of depreciable assets	7 years

Nature of Business, Basis of 37

Nature of Business, Basis of Presentation and Significant Accounting Policies - Estimated Useful Lives of Intangible Assets (Details)	12 Months Ended
	Dec. 30, 2017
Minimum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	2 years
Maximum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	10 years
Developed technology [Member] | Minimum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	5 years
Developed technology [Member] | Maximum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	10 years
Customer relationships [Member] | Minimum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	2 years
Customer relationships [Member] | Maximum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	10 years
Brand name [Member] | Minimum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	5 years
Brand name [Member] | Maximum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	10 years
Patented technology [Member] | Minimum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	7 years
Patented technology [Member] | Maximum [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	10 years
Trademark [Member]
Accounting Policies [Line Items]
Finite-lived intangibles estimated lives	5 years

Recent Accounting Pronounceme38

Recent Accounting Pronouncements - Textual (Details) - USD ($) $ in Thousands	Jan. 02, 2017	Apr. 01, 2017	Dec. 30, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Deferred revenue			$ 1,661	$ 816
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase (decrease) in accumulated deficit	$ 100	$ 1,200
Adjustments for New Accounting Pronouncement [Member] | Minimum [Member] | Pro Forma [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings related to new standard accounting			700
Deferred revenue			1,500
Adjustments for New Accounting Pronouncement [Member] | Maximum [Member] | Pro Forma [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings related to new standard accounting			1,200
Deferred revenue			$ 2,500

Fair Value Measurements and D39

Fair Value Measurements and Disclosures - Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Assets:
Total marketable securities	$ 82,130	$ 82,899
Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	256	3,458
Total marketable securities	82,130	82,899
Total	82,386	86,357
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	256	959
Total marketable securities	0	0
Total	256	959
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	2,499
Total marketable securities	82,130	82,899
Total	82,130	85,398
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	0
Total marketable securities	0	0
Total	0	0
Money market funds [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	256	959
Money market funds [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	256	959
Money market funds [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	0
Money market funds [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	0
Commercial paper and corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	2,499
Commercial paper and corporate debt securities [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	0
Commercial paper and corporate debt securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	2,499
Commercial paper and corporate debt securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total cash equivalents	0	0
U.S. Treasury securities and U.S. Government agency debt securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	1,495	17,072
U.S. Treasury securities and U.S. Government agency debt securities [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
U.S. Treasury securities and U.S. Government agency debt securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	1,495	17,072
U.S. Treasury securities and U.S. Government agency debt securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Certificates of deposits [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	14,497	23,019
Certificates of deposits [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Certificates of deposits [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	14,497	23,019
Certificates of deposits [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	7,949	22,402
Commercial paper [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Commercial paper [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	7,949	22,402
Commercial paper [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Municipal securities and corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	47,968	14,943
Municipal securities and corporate debt securities [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Municipal securities and corporate debt securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	47,968	14,943
Municipal securities and corporate debt securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	10,221	5,463
Asset-backed Securities [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	0	0
Asset-backed Securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	10,221	5,463
Asset-backed Securities [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total marketable securities	$ 0	$ 0

Fair Value Measurements and D40

Fair Value Measurements and Disclosures - Measured at Fair Value on Recurring Basis (Parenthetical) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	$ 256	$ 3,458
Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents	$ 34,600	$ 43,600

Fair Value Measurements and D41

Fair Value Measurements and Disclosures - Textual (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Fair Value Measurements and Disclosures (Textual) [Abstract]
Fair value assets among level 1, level 2 and level 3 transfers, amount	$ 0
Forward Foreign Currency Contracts [Member]
Fair Value Measurements and Disclosures (Textual) [Abstract]
Derivative term	30 days
Forward Foreign Currency Contracts [Member] | Other Income (Expense), Net [Member]
Fair Value Measurements and Disclosures (Textual) [Abstract]
Gain (loss) on settlement of derivatives	$ 1,400,000	$ (1,700,000)

Fair Value Measurements and D42

Fair Value Measurements and Disclosures - Outstanding Derivative Instruments (Details) - Forward Foreign Currency Contracts [Member] - Not Designated as Hedging Instrument [Member] - USD ($)	Dec. 30, 2017	Dec. 31, 2016
Purchase [Member]
Derivatives Fair Value [Line Items]
Notional Amount	$ 27,500,000	$ 12,600,000
Fair Value Asset	0	0
Fair Value Liability	100,000	0
Sell [Member]
Derivatives Fair Value [Line Items]
Notional Amount	16,800,000	1,300,000
Fair Value Asset	100,000	0
Fair Value Liability	$ 0	$ 0

Cash and Investments (Details)

Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 117,162	$ 129,959
Gross Unrealized Gains	0	19
Gross Unrealized Losses	(133)	(17)
Estimated Fair Market Value	117,029	129,961
U.S. Government agency securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,500	11,412
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5)	(7)
Estimated Fair Market Value	1,495	11,405
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,952	22,402
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	0
Estimated Fair Market Value	7,949	22,402
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	48,073	14,194
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(105)	(6)
Estimated Fair Market Value	47,968	14,188
Asset-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,240	5,466
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(19)	(3)
Estimated Fair Market Value	10,221	5,463
Cash [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,643	43,604
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	34,643	43,604
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	256	959
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	256	959
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	14,498	23,000
Gross Unrealized Gains	0	19
Gross Unrealized Losses	(1)	0
Estimated Fair Market Value	$ 14,497	23,019
U.S. Treasury securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		5,667
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Market Value		5,667
Commercial paper and corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		2,499
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Market Value		2,499
Municipal securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		756
Gross Unrealized Gains		0
Gross Unrealized Losses		(1)
Estimated Fair Market Value		$ 755

Cash and Investments - Addition

Cash and Investments - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Investments Debt And Equity Securities [Abstract]
Net realized gains and losses on sale of securities	$ 1.3	$ 0.5	$ 0.2
Investment maturity period, less than	2 years	2 years

Accounts Receivable - Textual (

Accounts Receivable - Textual (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Accounts Receivable (Additional Textual) [Abstract]
Sold receivables amount	$ 18,600,000	$ 31,500,000
Due from unrelated third parties	$ 0	$ 0
Minimum [Member]
Accounts Receivable (Textual) [Abstract]
Administrative fees as well as interest percent	0.61%
Maximum [Member]
Accounts Receivable (Textual) [Abstract]
Administrative fees as well as interest percent	1.68%

Financial Statement Component46

Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Inventories:
Raw materials and sub-assemblies	$ 32,187	$ 23,506
Work in process	13,498	10,347
Finished goods	7,175	4,984
Inventories	52,860	38,837
Inventories-delivered systems	1,534	2,457
Total inventories	54,394	41,294
Property, plant and equipment, net:
Total property, plant and equipment, gross	89,229	86,545
Accumulated depreciation and amortization	(44,419)	(42,319)
Total property, plant and equipment, net	44,810	44,226
Other Current Liabilities:
Accrued warranty	4,863	3,838	$ 4,504
Accrued taxes	813	706
Customer deposits		581
Accrued professional services	534	424
Accrued royalties		1,233
Other	1,039	1,265
Total other current liabilities	7,249	8,047
Land [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	15,573	15,568
Building and improvements [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	20,880	20,532
Machinery and equipment [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	36,380	35,659
Furniture and fixtures [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	2,420	2,282
Software [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	9,558	9,756
Capital in progress [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	$ 4,418	$ 2,748

Financial Statement Component47

Financial Statement Components - Selected Financial Statement Components (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Depreciation and amortization expense	$ 6.7	$ 6.8	$ 6.9

Financial Statement Component48

Financial Statement Components - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance Value	$ 243,774	$ 187,328	$ 179,537
Current period change	3,922	(844)	(2,433)
Ending Balance Value	262,383	243,774	187,328
Foreign Currency Translations [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance Value	(5,817)	(4,948)
Current period change	4,170	(869)
Ending Balance Value	(1,647)	(5,817)	(4,948)
Defined Benefit Pension Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance Value	(227)	(210)
Current period change	(160)	(17)
Ending Balance Value	(387)	(227)	(210)
Unrealized Income (Loss) on Investment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance Value	(2)	(44)
Current period change	(88)	42
Ending Balance Value	(90)	(2)	(44)
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance Value	(6,046)	(5,202)	(2,769)
Ending Balance Value	$ (2,124)	$ (6,046)	$ (5,202)

Goodwill and Intangible Asset49

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 8,940	$ 9,415
Foreign currency movements	1,292	(475)
Ending balance	$ 10,232	$ 8,940

Goodwill and Intangible Asset50

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Summary of Finite-lived intangible assets
Adjusted cost	$ 32,584	$ 29,307
Accumulated amortization	(30,378)	(28,895)
Finite lived intangible assets, Net carrying amount	2,206	412
Developed technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	18,887	15,726
Accumulated amortization	(16,681)	(15,380)
Finite lived intangible assets, Net carrying amount	2,206	346
Customer relationships [Member]
Summary of Finite-lived intangible assets
Adjusted cost	9,438	9,322
Accumulated amortization	(9,438)	(9,322)
Finite lived intangible assets, Net carrying amount	0	0
Brand names [Member]
Summary of Finite-lived intangible assets
Adjusted cost	1,927	1,927
Accumulated amortization	(1,927)	(1,927)
Finite lived intangible assets, Net carrying amount	0	0
Patented technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	2,252	2,252
Accumulated amortization	(2,252)	(2,186)
Finite lived intangible assets, Net carrying amount	0	66
Trademark [Member]
Summary of Finite-lived intangible assets
Adjusted cost	80	80
Accumulated amortization	(80)	(80)
Finite lived intangible assets, Net carrying amount	$ 0	$ 0

Goodwill and Intangible Asset51

Goodwill and Intangible Assets - Textual (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 200,000	$ 1,500,000	$ 2,100,000
Impairment charges	$ 0
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangibles estimated lives	2 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangibles estimated lives	10 years

Goodwill and Intangible Asset52

Goodwill and Intangible Assets - Future Amortization (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Estimated future amortization expense
2,018	$ 283
2,019	352
2,020	286
2,021	286
2,022	286
Thereafter	713
Finite lived intangible assets, Net carrying amount	$ 2,206	$ 412

Warranties - Textual (Details)

Warranties - Textual (Details)	12 Months Ended
	Dec. 30, 2017
Product Warranties Disclosures [Abstract]
Product warranty period	12 months

Warranties (Details)

Warranties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Components of the warranty accrual [Roll Forward]
Balance as of beginning of period	$ 3,838	$ 4,504
Accruals for warranties issued during period	5,247	4,509
Settlements during the period	(4,222)	(5,175)
Balance as of end of period	$ 4,863	$ 3,838

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Long Term Purchase Commitment [Line Items]
Liabilities recorded for obligations	$ 0	$ 0
Rent expense	1,800,000	$ 1,800,000	$ 1,700,000
Inventories [Member]
Long Term Purchase Commitment [Line Items]
Purchase commitment	$ 50,700,000

Commitments and Contingencies56

Commitments and Contingencies - Future minimum lease payments (Details) $ in Thousands	Dec. 30, 2017USD ($)
Future minimum lease payments under operating leases
2,018	$ 1,664
2,019	935
2,020	313
2,021	54
2,022	2
Thereafter	0
Total	$ 2,968

Net Income Per Share (Details)

Net Income Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Reconciliation of the basic and diluted net income per share computations
Weighted average common shares outstanding used in basic net income per share calculation	25,334	24,655	24,059
Potential dilutive common stock equivalents, using treasury stock method	585	498	316
Weighted average shares used in diluted net income per share calculation	25,919	25,153	24,375

Net Income Per Share - Textual

Net Income Per Share - Textual (Details) - shares shares in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Earnings Per Share [Abstract]
Weighted average common share equivalents consisting of stock options included in the calculation of diluted net income per share	585	498	316

Stockholders' Equity and Stoc59

Stockholders' Equity and Stock-Based Compensation - Textual (Details) - USD ($)	May 23, 2017	Feb. 28, 2018	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015	Nov. 15, 2017	May 29, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized			47,000,000	47,000,000
Common stock, par value per share			$ 0.001	$ 0.001
Shares of preferred stock authorized			3,000,000	3,000,000
Preferred stock, par value per share			$ 0.001	$ 0.001
Maximum amount of common stock approved to repurchase, Value							$ 20,000,000
Remaining shares available for future repurchase (in shares)			$ 23,001,000	$ 4,400,000	$ 4,397,000
Number of shares of common stock repurchased			1,065,848		111,050
Weighted average price per share			$ 25.33		$ 15.49
Cost of repurchase			$ 26,999,000		$ 1,721,000
Number of options granted			0	0	0
Closing stock price			$ 24.92
Intrinsic value of options exercised			$ 3,100,000	$ 2,700,000	$ 1,600,000
Fair value of options vested			300,000	700,000	1,500,000
Excess tax benefit			0	$ 1,000,000	$ 0
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs			$ 100,000
2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized	1,000,000		8,292,594
Share-based compensation plan, extended throguh	2,027
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of salary withholdings			10.00%
Purchase price of common stock, percent			85.00%
Shares remaining for issuance under the ESPP			500,000
Shares purchased under the ESPP			122,298	212,619	125,504
Weighted average price of shares issued (in dollars per share)			$ 21.19	$ 14.29	$ 13.98
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining amortization period for unrecognized compensation costs			1 month 6 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining amortization period for unrecognized compensation costs			1 year 9 months
Shares per unit granted			1.7
Granted (in shares)			454,600	476,667
Unrecognized compensation costs			$ 12,500,000
Cancelled (in shares)			96,494	54,253
Restricted Stock Units (RSUs) [Member] | Key Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			454,600	476,667
Restricted Stock Units (RSUs) [Member] | Maximum [Member] | Key Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of vesting			3 years
Restricted Stock Units (RSUs) [Member] | 2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			772,820
Cancelled (in shares)			164,040
Performance-Based Restricted Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			122,050	67,500
Percent of granted shares that will vest if target stock price performance is achieved			66.70%
Maximum percent of granted shares that will vest if maximum stock price performance is achieved			100.00%
Cumulative maximum number of shares expected to vest for all measurement period			62,500
Cancelled (in shares)			61,100	6,667
Performance-Based Restricted Stock Units (PSUs) [Member] | Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of vesting			1 year
Performance-Based Restricted Stock Units (PSUs) [Member] | Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of vesting			2 years
Performance-Based Restricted Stock Units (PSUs) [Member] | Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of vesting			3 years
Performance-Based Restricted Stock Units (PSUs) [Member] | 2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			207,485
Cancelled (in shares)			103,870
Share Repurchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum amount of common stock approved to repurchase, Value						$ 50,000,000
Stock repurchase program, effective date			Nov. 20, 2017
Share Repurchase Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program completed month and year		2018-02
Number of shares of common stock repurchased		896,187
Weighted average price per share		$ 25.65
Cost of repurchase		$ 23,000,000

Stockholders' Equity and Stoc60

Stockholders' Equity and Stock-Based Compensation - Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 26, 2015	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares of common stock repurchased	1,065,848	111,050
Weighted average price per share	$ 25.33	$ 15.49
Total cost of repurchase	$ 26,999	$ 1,721
Amount available for repurchase at end of period	$ 23,001	$ 4,397	$ 4,400

Stockholders' Equity and Stoc61

Stockholders' Equity and Stock-Based Compensation - Option Plans (Details) - shares	Dec. 30, 2017	May 23, 2017
2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized	8,292,594	1,000,000
2000 Employee Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized	2,450,000
2000 Director Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized	250,000
Accent Optical Technologies, Inc. Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Authorized	205,003

Stockholders' Equity and Stoc62

Stockholders' Equity and Stock-Based Compensation - Employee Stock Purchase Plan Assumptions (Details) - Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Assumption of stock option's fair value
Expected life	6 months	6 months	6 months
Volatility	37.20%	38.70%	36.90%
Risk free interest rate	0.91%	0.44%	0.12%
Dividends	0.00%	0.00%	0.00%

Stockholders' Equity and Stoc63

Stockholders' Equity and Stock-Based Compensation - Summary of Activity of Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Activity of stock option plans [Roll Forward]
Number of Shares Outstanding (Options), Beginning Balance (in shares)	440,545	1,059,471
Number of Shares Outstanding (Options), Exercised (in shares)	(223,364)	(442,339)
Number of Shares Outstanding (Options), Cancelled/Forfeited (in shares)	(855)	(176,587)	(94,012)
Number of Shares Outstanding (Options), Ending Balance (in shares)	216,326	440,545	1,059,471
Number of Shares Outstanding (Options), Exercisable (in shares)	215,620
Weighted average exercise price for stock option plans [Roll Forward]
Weighted Average Exercise Price, Beginning Balance (in dollars per share)	$ 15.06	$ 14.61
Weighted Average Exercise Price, Exercised (in dollars per share)	13.35	13.66
Weighted Average Exercise Price, Cancelled/Forfeited (in dollars per share)	16.63	15.83
Weighted Average Exercise Price, Ending Balance (in dollars per share)	16.82	$ 15.06	$ 14.61
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 16.81
Weighted Average Remaining Contractual Term, Outstanding	1 year 9 months 3 days	2 years 1 month 13 days	2 years 5 months 19 days
Weighted Average Remaining Contractual Term, Exercisable	1 year 9 months 3 days
Aggregate Intrinsic Value, Outstanding	$ 1,752	$ 4,405	$ 1,920
Aggregate Intrinsic Value, Exercisable	$ 1,748

Stockholders' Equity and Stoc64

Stockholders' Equity and Stock-Based Compensation - Ranges of Outstanding and Exercisable Options (Details) - $ / shares	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding (in shares)	216,326	440,545	1,059,471
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 9 months 3 days	2 years 1 month 13 days	2 years 5 months 19 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 16.82	$ 15.06	$ 14.61
Options Exercisable, Number Exercisable (in shares)	215,620
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 16.81
$12.98-$15.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	12.98
Exercise Price, Upper Range Limit	$ 15
Options Outstanding, Number Outstanding (in shares)	23,383
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 9 months 29 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 14.64
Options Exercisable, Number Exercisable (in shares)	23,383
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 14.64
$15.08-$15.65 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	15.08
Exercise Price, Upper Range Limit	$ 15.65
Options Outstanding, Number Outstanding (in shares)	27,697
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 4 months 13 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 15.62
Options Exercisable, Number Exercisable (in shares)	27,697
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 15.62
$15.74-$15.74 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	15.74
Exercise Price, Upper Range Limit	$ 15.74
Options Outstanding, Number Outstanding (in shares)	3,333
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	4 months 24 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 15.74
Options Exercisable, Number Exercisable (in shares)	3,333
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 15.74
$15.85-$15.85 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	15.85
Exercise Price, Upper Range Limit	$ 15.85
Options Outstanding, Number Outstanding (in shares)	60,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	2 years 2 months 12 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 15.85
Options Exercisable, Number Exercisable (in shares)	60,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 15.85
$16.00-$17.33 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	16
Exercise Price, Upper Range Limit	$ 17.33
Options Outstanding, Number Outstanding (in shares)	31,700
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 9 months 25 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 17
Options Exercisable, Number Exercisable (in shares)	31,700
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 17
$17.70-$18.08 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	17.70
Exercise Price, Upper Range Limit	$ 18.08
Options Outstanding, Number Outstanding (in shares)	6,613
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 6 months 18 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 17.92
Options Exercisable, Number Exercisable (in shares)	6,588
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 17.92
$18.22-$18.22 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	18.22
Exercise Price, Upper Range Limit	$ 18.22
Options Outstanding, Number Outstanding (in shares)	3,600
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 1 month 28 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 18.22
Options Exercisable, Number Exercisable (in shares)	3,449
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 18.22
$18.51-$18.51 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	18.51
Exercise Price, Upper Range Limit	$ 18.51
Options Outstanding, Number Outstanding (in shares)	9,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 1 month 20 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 18.51
Options Exercisable, Number Exercisable (in shares)	8,583
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 18.51
$18.79-$18.79 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	18.79
Exercise Price, Upper Range Limit	$ 18.79
Options Outstanding, Number Outstanding (in shares)	1,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 2 months 23 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 18.79
Options Exercisable, Number Exercisable (in shares)	887
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 18.79
$19.03-$19.03 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	19.03
Exercise Price, Upper Range Limit	$ 19.03
Options Outstanding, Number Outstanding (in shares)	50,000
Options Outstanding, Weighted Average Remaining Contractual Life (Years)	1 year 1 month 17 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 19.03
Options Exercisable, Number Exercisable (in shares)	50,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 19.03
$12.98-$19.03 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower Range Limit	12.98
Exercise Price, Upper Range Limit	$ 19.03
Options Outstanding, Number Outstanding (in shares)	216,326
Options Exercisable, Number Exercisable (in shares)	215,620

Stockholders' Equity and Stoc65

Stockholders' Equity and Stock-Based Compensation - Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Activity for RSUs [Roll Forward]
Number of units Beginning balance (in shares)	819,785	713,243
Number of units, Granted (in shares)	454,600	476,667
Number of units, Released (in shares)	(387,592)	(315,872)
Number of units, Cancelled (in shares)	(96,494)	(54,253)
Number of units, Ending balance (in shares)	790,299	819,785
Weighted Average Fair Value for RSUs [Roll Forward]
Weighted Average Fair Value, Beginning balance (in dollars per share)	$ 16.79	$ 15.99
Weighted Average Fair Value, Granted (in dollars per share)	27.12	17.45
Weighted Average Fair Value, Released (in dollars per share)	16.81	16.05
Weighted Average Fair Value, Cancelled (in dollars per share)	19.01	16.29
Weighted Average Fair Value, Ending balance (in dollars per share)	$ 22.46	$ 16.79

Stockholders' Equity and Stoc66

Stockholders' Equity and Stock-Based Compensation - Performance Stock Units Activity (Details) - Performance-Based Restricted Stock Units (PSUs) [Member] - $ / shares	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Activity for PSUs [Roll Forward]
Number of units Beginning balance (in shares)	107,500	60,000
Number of units, Granted (in shares)	122,050	67,500
Number of units, Released (in shares)	(38,500)	(13,333)
Number of units, Cancelled (in shares)	(61,100)	(6,667)
Number of units, Ending balance (in shares)	129,950	107,500	60,000
Weighted Average Fair Value for PSUs [Roll Forward]
Weighted Average Fair Value, Beginning balance (in dollars per share)	$ 9.94	$ 12.23
Weighted Average Fair Value, Granted (in dollars per share)	20.51	8.52	$ 12.23
Weighted Average Fair Value, Released (in dollars per share)	10.41	12.03
Weighted Average Fair Value, Cancelled (in dollars per share)	19.41	12.03
Weighted Average Fair Value, Ending balance (in dollars per share)	$ 15.60	$ 9.94	$ 12.23

Stockholders' Equity and Stoc67

Stockholders' Equity and Stock-Based Compensation - Performance Stock Units Valuation Assumptions (Details) - Performance-Based Restricted Stock Units (PSUs) [Member] - $ / shares	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Values Per Share (in dollars per share)	$ 20.51	$ 8.52	$ 12.23
Expected Dividend	0.00%	0.00%	0.00%
Risk free interest rate		0.92%
Range of risk-free interest rates, minimum	1.74%		0.25%
Range of risk-free interest rates, maximum	1.84%		1.10%
Range of expected volatilities for peer group, minimum	22.00%	22.00%	23.00%
Range of expected volatilities for peer group, maximum	66.00%	93.00%	65.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Values Per Share (in dollars per share)	$ 14.57
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Values Per Share (in dollars per share)	$ 26.75

Stockholders' Equity and Stoc68

Stockholders' Equity and Stock-Based Compensation - Stock Option Plans Activity Including Options, RSUs and PSUs (Details) - shares	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Activity of stock option plans including options and RSUs [Roll Forward]
Additional Shares Authorized, (in shares)	1,000,000	0	0
Options cancelled (in shares)	855	176,587	94,012
Options - expired plan shares (in shares)	0	(116,192)	(1,800)
Stock Options, RSUs and PSUs [Member]
Activity of stock option plans including options and RSUs [Roll Forward]
Number of Shares Outstanding (Options), Beginning Balance (in shares)	1,334,581	1,916,589	2,464,082
Number of Shares Outstanding (Options), Ending Balance (in shares)	1,874,765	1,334,581	1,916,589
Restricted Stock Units - Equivalent Shares [Member]
Activity of stock option plans including options and RSUs [Roll Forward]
Granted (in shares)	(772,820)	(810,334)	(860,980)
Cancelled (in shares)	164,040	92,230	202,356
RSUs - shares issued to satisfy tax withholding obligations (in shares)	251,724	179,117	120,919
Performance Stock Units - Equivalent Shares [Member]
Activity of stock option plans including options and RSUs [Roll Forward]
Granted (in shares)	(207,485)	(114,750)	(102,000)
Cancelled (in shares)	103,870	11,334	0

Stockholders' Equity and Stoc69

Stockholders' Equity and Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	$ 8,819	$ 7,666	$ 6,248
Cost of products [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	842	403	274
Cost of service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	616	509	309
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	1,720	1,408	1,036
Selling [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	2,323	2,046	1,881
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	$ 3,318	$ 3,300	$ 2,748

Defined Benefit Pension Plan (D

Defined Benefit Pension Plan (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.3	$ 0.2	$ 0.2
Net funding deficiency of the Benefit Plan	$ 0.5	$ 0.4	$ 0.3

Income Taxes - Income (Loss) Be

Income Taxes - Income (Loss) Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 34,238	$ 25,372	$ 178
Foreign	9,060	3,763	5,390
Income before income taxes	$ 43,298	$ 29,135	$ 5,568

Income Taxes - Provision (Benef

Income Taxes - Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Current:
Federal	$ 3,250	$ 697	$ 148
State	9	85	3
Foreign	2,998	2,111	2,266
Total current	6,257	2,893	2,417
Deferred:
Federal	6,314	(16,641)	190
State	53	(320)	3
Foreign	472	(832)	53
Total deferred	6,839	(17,793)	246
Provision (benefit) for income taxes	$ 13,096	$ (14,900)	$ 2,663

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Deferred tax assets:
Reserves and accruals	$ 5,797	$ 11,043
Deferred revenue	240	349
Shared based compensation	1,483	2,590
Tax credit carry-forwards	9,669	10,112
Net operating losses	9,755	8,434
Depreciation & amortization	(1,525)	(2,898)
Other	207	(1,252)
Total deferred tax assets	25,626	28,378
Less: Valuation allowance	(13,702)	(10,980)
Total deferred tax assets net of valuation allowance	11,924	17,398
Deferred tax liabilities:
Depreciation & amortization	(12)	(6)
Other	(167)	(14)
Total deferred tax liabilities	(179)	(20)
Net deferred tax assets	$ 11,745	$ 17,378

Income Taxes - Textual (Details

Income Taxes - Textual (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Operating Loss Carryforwards [Line Items]
Change in amount of operating loss carryforwards valuation allowance		$ 1,500	$ (25,800)
Increase in valuation allowance for deferred tax assets		$ 300
Federal corporate tax rate		35.00%
Provisional estimate for income taxes		$ 600
Maximum amount company recognize from unrecognized tax benefit		7,151	$ 6,477	$ 6,961	$ 6,442
Unrecognized tax benefits that would impact effective tax rate if recognized		4,000
Scenario, Forecast [Member]
Operating Loss Carryforwards [Line Items]
Federal corporate tax rate	21.00%
California [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		25,600
State research and experimental tax credit carryforward		8,900
Other States [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		3,000
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		35,000
Federal [Member]
Operating Loss Carryforwards [Line Items]
State research and experimental tax credit carryforward		$ 7,000

Income Taxes - Income Tax Rate

Income Taxes - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Income taxes computed at U.S. statutory rate	$ 15,153	$ 10,197	$ 1,949
State income taxes	227	223	28
Foreign tax rate differential	794	3,502	342
Change in valuation allowance	1,490	(25,738)	1,648
Equity compensation	(1,803)	380	311
Tax credits	(2,336)	(3,191)	(1,834)
Domestic production activities deduction	(608)	(354)
Liabilities for uncertain tax positions	18	67	74
Other, net	161	14	145
Provision (benefit) for income taxes	$ 13,096	$ (14,900)	$ 2,663

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Unrecognized tax benefits - beginning of the period	$ 6,477	$ 6,961	$ 6,442
Gross increases-tax positions in prior period	32	23	127
Gross decreases-tax positions in prior period		(1,193)	(306)
Gross increases-current-period tax positions	723	686	698
Lapse of statute of limitations	(81)		0
Unrecognized tax benefits - end of the period	$ 7,151	$ 6,477	$ 6,961

Segment, Geographic, Product 77

Segment, Geographic, Product and Significant Customer Information - Textual (Details)	12 Months Ended
	Dec. 30, 2017segment
Segment Reporting [Abstract]
Number of operating segments	1

Segment, Geographic, Product 78

Segment, Geographic, Product and Significant Customer Information - Revenue Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Net revenues:
Total net revenues	$ 258,621	$ 221,129	$ 187,367
South Korea [Member]
Net revenues:
Total net revenues	94,082	44,735	30,572
China [Member]
Net revenues:
Total net revenues	29,826	43,460	17,373
Singapore [Member]
Net revenues:
Total net revenues	21,810	37,096	17,395
United States [Member]
Net revenues:
Total net revenues	33,983	29,887	36,720
Taiwan [Member]
Net revenues:
Total net revenues	20,147	27,189	46,715
Japan [Member]
Net revenues:
Total net revenues	41,979	26,604	31,140
Other [Member]
Net revenues:
Total net revenues	$ 16,794	$ 12,158	$ 7,452

Segment, Geographic, Product 79

Segment, Geographic, Product and Significant Customer Information - Long-lived Tangible Assets (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Long-lived tangible assets:
Total long-lived tangible assets	$ 44,810	$ 44,226
United States [Member]
Long-lived tangible assets:
Total long-lived tangible assets	43,427	42,688
Taiwan [Member]
Long-lived tangible assets:
Total long-lived tangible assets	510	818
South Korea [Member]
Long-lived tangible assets:
Total long-lived tangible assets	576	554
Japan [Member]
Long-lived tangible assets:
Total long-lived tangible assets	60	57
All Other [Member]
Long-lived tangible assets:
Total long-lived tangible assets	$ 237	$ 109

Segment, Geographic, Product 80

Segment, Geographic, Product and Significant Customer Information - Product Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Segment Reporting Information [Line Items]
Products	$ 214,877	$ 185,066	$ 146,945
Automated Systems [Member]
Segment Reporting Information [Line Items]
Products	151,401	127,378	102,386
Integrated Systems [Member]
Segment Reporting Information [Line Items]
Products	42,183	43,846	31,579
Materials Characterization Systems [Member]
Segment Reporting Information [Line Items]
Products	$ 21,293	$ 13,842	$ 12,980

Segment, Geographic, Product 81

Segment, Geographic, Product and Significant Customer Information - Customers More Than 10% of Accounts Receivable (Details) - Accounts Receivable [Member] - Credit Concentration Risk [Member]	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Taiwan Semiconductor Manufacturing Company Limited [Member]
Customers accounted for 10% or more of total accounts receivable
Customers accounted for 10% or more of total accounts receivable		20.00%	26.00%
Samsung Electronics Co. Ltd. [Member]
Customers accounted for 10% or more of total accounts receivable
Customers accounted for 10% or more of total accounts receivable	13.00%	14.00%
Micron Technology, Inc. [Member]
Customers accounted for 10% or more of total accounts receivable
Customers accounted for 10% or more of total accounts receivable	18.00%	12.00%
Intel Corporation [Member]
Customers accounted for 10% or more of total accounts receivable
Customers accounted for 10% or more of total accounts receivable		11.00%
Toshiba Corporation [Member]
Customers accounted for 10% or more of total accounts receivable
Customers accounted for 10% or more of total accounts receivable	31.00%	10.00%	27.00%

Segment, Geographic, Product 82

Segment, Geographic, Product and Significant Customer Information - Customers More Than 10% of Revenues (Details) - Sales Revenue, Net [Member] - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Micron Technology, Inc. [Member]
Net revenues:
Customers accounted for 10% or more of total revenue	12.00%	20.00%	16.00%
Intel Corporation [Member]
Net revenues:
Customers accounted for 10% or more of total revenue	11.00%	18.00%
SK Hynix [Member]
Net revenues:
Customers accounted for 10% or more of total revenue	13.00%	15.00%	11.00%
Taiwan Semiconductor Manufacturing Company Limited [Member]
Net revenues:
Customers accounted for 10% or more of total revenue		10.00%	19.00%
Samsung Electronics Co. Ltd. [Member]
Net revenues:
Customers accounted for 10% or more of total revenue	26.00%		13.00%
Toshiba Corporation [Member]
Net revenues:
Customers accounted for 10% or more of total revenue	11.00%		10.00%

Schedule II - Valuation and Q83

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Allowance for Doubtful Accounts Receivable [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 73	$ 150	$ 253
Additions to Allowance	78		10
Charges Utilized/Write-offs	(25)	(77)	(113)
Balance at end of period	126	73	150
Valuation Allowance for Deferred Tax Assets [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	10,980	36,786	35,835
Additions to Allowance	2,984	1,643	951
Charges Utilized/Write-offs	(262)	(27,449)
Balance at end of period	$ 13,702	$ 10,980	$ 36,786