EXHIBIT 23.1

            CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Annual Report (Form 10-K)
of Cognex Corporation of our report dated February 26, 2007, with respect to the
consolidated financial statements of Cognex Corporation and our report dated
February 26, 2007 with respect to Cognex Corporation management's assessment of
the effectiveness of internal control over financial reporting and the
effectiveness of internal control over financial reporting of Cognex
Corporation, included in the 2006 Annual Report to Shareholders of Cognex
Corporation.

Our audits also included the financial statement schedule of Cognex Corporation
listed in Item 15(a). This schedule is the responsibility of Cognex
Corporation's management. Our responsibility is to express an opinion based on
our audits. In our opinion, as to which the date is February 26, 2007, the
financial statement schedule referred to above, when considered in relation to
the basic financial statements taken as a whole, presents fairly in all material
respects the information set forth therein.

We consent to the incorporation by reference in the Registration Statements on
Form S-8 (File Nos. 33-81150, 333-04621, 333-02151, 333-60807, 33-32815,
333-44824, 333-68158, 333-96961, 333-100709, and 333-126787) of Cognex
Corporation of our report dated February 26, 2007, with respect to the
consolidated financial statements of Cognex Corporation incorporated herein by
reference, our report dated February 26, 2007 with respect to Cognex Corporation
management's assessment of the effectiveness of internal control over financial
reporting and the effectiveness of internal control over financial reporting of
Cognex Corporation incorporated herein by reference, and our report included in
the preceding paragraph with respect to the financial statement schedule of
Cognex Corporation included in this Annual Report (Form 10-K) of Cognex
Corporation.

/s/ Ernst & Young LLP

Boston, Massachusetts
February 26, 2007