UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
--------------------------------------------------------------------------------

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                                (AMENDMENT NO. )*



                               Cognex Corporation
--------------------------------------------------------------------------------
                                (NAME OF ISSUER)



                                  Common Stock
--------------------------------------------------------------------------------
                        (TITLE OF CLASS OF SECURITIES)



                                    192422103
--------------------------------------------------------------------------------
                                 (CUSIP NUMBER)



                                   12/31/2004
--------------------------------------------------------------------------------
              (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

          /X/ Rule 13d-1(b)
          / / Rule 13d-1(c)
          / / Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).






CUSIP NO. 192422103      
-------------------

--------------------------------------------------------------------------------
1         NAME OF REPORTING PERSON
               The Hartford Series Fund, Inc. on behalf of:
               The Hartford Capital Appreciation HLS Fund

          S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS 
          (entities only)    22-2481744

--------------------------------------------------------------------------------
2         CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
          (see instructions)

             (a) [    ]
             (b) [    ]
--------------------------------------------------------------------------------
3         SEC USE ONLY
--------------------------------------------------------------------------------
4         CITIZENSHIP OR PLACE OF ORGANIZATION
                           Maryland

--------------------------------------------------------------------------------

                           5      SOLE VOTING POWER

NUMBER OF                  -----------------------------------------------------
SHARES 
BENEFICIALLY               6      SHARED VOTING POWER
OWNED BY                               2,503,500
EACH                       -----------------------------------------------------
REPORTING                         
PERSON                     7      SOLE DISPOSITIVE POWER
WITH: 
                           -----------------------------------------------------
                                                  
                           8      SHARED DISPOSITIVE POWER
                                       2,503,500
--------------------------------------------------------------------------------
9         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
                          2,503,500

--------------------------------------------------------------------------------
10        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES 
          (see instructions)

--------------------------------------------------------------------------------
11        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
                            5.43%
--------------------------------------------------------------------------------
12        TYPE OF REPORTING PERSON (see instructions)
                            IV
--------------------------------------------------------------------------------


                                  Page 2 of 5

CUSIP NO. 192422103      
-------------------



Item 1(a). Name of Issuer:
                      Cognex Corporation

Item 1(b). Address of Issuer's Principal Executive Offices:
                      One Vision Drive
                      Natick, MA  01760

Item 2(a). Name of Person(s) Filing:
                      The Hartford Series Fund, Inc. on behalf of:
                      The Hartford Capital Appreciation HLS Fund

Item 2(b). Address of Principal Business Office or; if none, residence:
                      200 Hopmeadow Street
                      Simsbury, CT  06089

Item 2(c). Citizenship:
                      Maryland

Item 2(d). Title of Class of Securities:
                      Common Stock

Item 2(e). CUSIP Number:
                      192422103

Item 3. If this statement is filed pursuant toss.ss.240.13d-1(b) or 240.13d-2(b)
        or (c), check whether the person filing is a:
  
        (a)  / / Broker or Dealer registered under Section 15 of the Act 
             (15 U.S.C. 78o).

        (b)  / / Bank as defined in Section 3(a)(6) of the Act 
             (15 U.S.C. 78c).

        (c)  / / Insurance Company as defined in Section 3(a) (19) of the Act
             (15 U.S.C. 78c).

        (d)  /X/ Investment Company registered under Section 8 of the
             Investment Company Act of 1940 (15 U.S.C. 80a-8).


                                  Page 3 of 5

CUSIP NO. 192422103      
-------------------

          (e)  / / An investment adviser in accordance
               with ss.240.13d-1(b)(1)(ii)(E);

          (f)  / / An employee benefit plan or endowment fund in accordance with
               ss.240.13d-1(b)(1)(ii)(F);

          (g)  / / A parent holding company or control person in accordance with
               ss.240.13d-1(b)(1)(ii)(G);

          (h)  / / A savings association as defined in Section 3(b) of the
               Federal Deposit Insurance Act (12 U.S.C. 1813);

          (i)  / / A church plan that is excluded from the definition of an
               investment company under Section 3(c)(14) of the Investment
               Company Act of 1940 (15 U.S.C. 80a-3);

          (j)  / / Group, in accordance withss.240.13d-1(b)(1)(ii)(J).


Item 4.   Ownership:

          Provide the following information regarding the aggregate number and
          percentage of the class of securities of the issuer identified in 
          Item 1.

          (a) Amount Beneficially Owned  2,503,500                 
                                        ---------------------------

          (b) Percent of Class   5.43%           
                              ------------------

          (c)  Number of shares as to which such person has:

               (i)  sole power to vote or to direct the vote
                    
                    ----------------------------------------------------        

               (ii) shared power to vote or to direct the vote 
                                2,503,500
                    ----------------------------------------------------        

               (iii) sole power to dispose or to direct the disposition of
                                                                                
                    ----------------------------------------------------        

               (iv) shared power to dispose or to direct the disposition of
                                2,503,500
                    ----------------------------------------------------        



                                  Page 4 of 5

CUSIP NO. 192422103      
-------------------

Item 5.   Ownership of Five Percent or Less of a Class:

          If this statement is being filed to report the fact that as of the
          date hereof the reporting person has ceased to be the beneficial owner
          of more than five percent of the class of securities, check the
          following: [ ]

Item 6.   Ownership of More than Five Percent on behalf of Another Person: N/A

Item 7.   Identification and Classification of the Subsidiary which Acquired the
          Security being Reported on by the Parent Holding Company: N/A

Item 8.   Identification and Classification of Members of the Group: N/A

Item 9.   Notice of Dissolution of Group: N/A

Item 10.  Certification:

     By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired and are held in the ordinary
course of business and were not acquired and are not held for the purpose of or
with the effect of changing or influencing the control of the issuer of the
securities and were not acquired and are not held in connection with or as a
participant in any transaction having that purpose or effect.


     Signature
    
     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


                                   DATE:  February 10, 2005


                                   The Hartford Series Fund, Inc. on behalf of:
                                   The Hartford Capital Appreciation HLS Fund



                                    BY: /s/George R. Jay
                                       ----------------------
                                        George R. Jay
                                        Vice President, Chief Compliance Officer

                                  Page 5 of 5