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                                                                    EXHIBIT 10.4

                              TRIPATH IMAGING, INC.
                              780 Plantation Drive
                              Burlington, NC 27215

                                 August 3, 2004

[Name of Director]
[Address]
[City, State, Zip Code]

Dear _________________:

      This letter agreement is being entered into by and between you and TriPath
Imaging, Inc. (the "Company"), a Delaware corporation, in connection with that
certain option agreement dated as of _________ (the "Option Agreement") by and
between you and the Company. Capitalized terms not otherwise defined in this
letter agreement shall have the meanings set forth in the Option Agreement.

      The parties hereby agree to amend the Option Agreement as follows:

      1.    The Option Agreement is hereby amended by adding the following
            language immediately after Section 10 of the Option Agreement:

                  "11. Notwithstanding any other provision of the Plan, if a
            Change in Control (as herein defined) occurs on or before August 3,
            2006, and (a) the Optionee's service with the Company as a member of
            the Board has not terminated as of, or immediately prior to, the
            effective time of the Change in Control, and (b) the surviving
            entity in such Change of Control does not provide the Optionee with
            the opportunity to serve as a member of the board of directors of
            the surviving entity for a period of not less than the balance of
            the Optionee's then current term as a member of the Board, then this
            Option, or any substitute option issued herefor, shall (x) become
            immediately vested and exercisable in full notwithstanding the
            original option exercise schedule, and (y) remain exercisable
            following the cessation of the Optionee's service as a director for
            a period equal to the shorter of (I) twelve (12) months, or (II) the
            remaining balance of the original term of this Option.

                  For purposes of this Option, a "Change in Control" means the
            consummation and closing of an event or occurrence set forth in
            either or both of clauses (a) and (b) below (including the
            consummation and closing of an event or occurrence that constitutes
            a Change in Control under one clause but is specifically exempted
            from the other clause):

                  (a) the acquisition by an individual, entity or group (within
            the meaning of Section 13(d)(3) or 14(d)(2) of the Securities
            Exchange Act of 1934, as amended (the

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            "Exchange Act")) (a "Person") of beneficial ownership of any capital
            stock of the Company if, after such acquisition, such Person
            beneficially owns (within the meaning of Rule 13d-3 promulgated
            under the Exchange Act) 50% or more of either (A) the
            then-outstanding shares of common stock of the Company (the
            "Outstanding Company Common Stock") or (B) the combined voting power
            of the then-outstanding securities of the Company entitled to vote
            generally in the election of directors (the "Outstanding Company
            Voting Securities"); provided, however, that for purposes of this
            paragraph (a), the following acquisitions shall not constitute a
            Change in Control: (I) any acquisition directly from the Company
            (excluding an acquisition pursuant to the exercise, conversion of
            exchange of any security exercisable for, convertible into or
            exchangeable for common stock or voting securities of the Company,
            unless the Person exercising, converting or exchanging such security
            acquired such security directly from the Company or an underwriter
            or agent of the Company), (II) any acquisition by the Company, (III)
            any acquisition by any employee benefit plan (or related trust)
            sponsored or maintained by the Company or any corporation controlled
            by the Company, or (IV) any acquisition by any corporation pursuant
            to a transaction which complies with subclause (A) of clause (b) of
            this Section 11; or

                  (b) the consummation of a merger, consolidation,
            reorganization, recapitalization or statutory share exchange
            involving the Company or a sale, lease, exchange or other
            disposition of all or substantially all of the assets of the Company
            (a "Business Combination"), unless, immediately following such
            Business Combination, (A) all or substantially all of the
            individuals and entities who were the beneficial owners of the
            Outstanding Company Common Stock and Outstanding Company Voting
            Securities immediately prior to such Business Combination
            beneficially own, directly or indirectly, more than 50% of the
            then-outstanding shares of common stock and the combined voting
            power of the then outstanding securities entitled to vote generally
            in the election of directors, respectively, of the resulting or
            acquiring corporation in such Business Combination (which shall
            include, without limitation, a corporation which as a result of such
            transaction owns the Company or substantially all of the Company's
            assets either directly or through one or more subsidiaries) (such
            resulting or acquiring corporation is referred to herein as the
            "Acquiring Corporation") in substantially the same proportions as
            their ownership, immediately prior to such Business Combination, of
            the Outstanding Company Stock and Outstanding Company Voting
            Securities, respectively."

      2.    Except as set forth above, the Option Agreement remains unmodified
            and in full force and effect.

      3.    This Agreement may be signed in one of more counterparts, each of
            which shall be deemed an original and all of which, taken together,
            shall be deemed one and the same document.

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      Please sign below where indicated to acknowledge your agreement to the
foregoing.

                                           Sincerely,

                                           TRIPATH IMAGING, INC.

                                           By: _________________________________
                                           Name:  Arthur T. King, Ph.D.
                                           Title: Chairman of the Nominating and
                                                  Governance Committee

AGREED TO AND ACCEPTED BY:

__________________________
[Director's Name]