Exhibit 4.11

                              WAIVER TO CERTAIN OF
                             THE OPERATIVE DOCUMENTS

        This Waiver dated as of April 30, 2002 (this "Waiver") refers to the
Participation Agreement dated as of June 23, 1998, as amended (the
"Participation Agreement"), entered into by and among GSI Lumonics Corporation
(formerly known as Lumonics Corporation), a Michigan corporation, as the Lessee
and Construction Agent (in its capacity as lessee, the "Lessee" and in its
capacity as construction agent, the "Construction Agent"); GSI Lumonics Inc.
(formerly known as Lumonics Inc.), a New Brunswick corporation, as Guarantor
(the "Guarantor"); Bank of Montreal, a Canadian banking organization ("BMO"),
and the other various financial institutions as are or may from time to time
become lenders (the "Lenders") under the Loan Agreement; BMO, as Administrative
Agent (in such capacity, the "Administrative Agent") for the Lenders and
Arranger; and BMO Global Capital Solutions, Inc. (formerly known as BMO Leasing
(U.S.), Inc.), a Delaware corporation, as Agent Lessor and Lessor (in such
capacity as the agent lessor, the "Agent Lessor" and in such capacity as the
arranger, the "Lessor"). Terms defined in the Participation Agreement are,
unless otherwise defined herein or the context otherwise requires, used herein
as defined therein.

        Whereas, the Lessee, the Guarantor, the Agent Lessor, the Lenders, the
Administrative Agent and the Arranger have entered into the Participation
Agreement;

        Whereas, the Lessee and the Guarantor have breached certain financial
covenants set forth in Section 10.2 of the Participation Agreement and have
requested that such defaults be waived; and

        Whereas, the Agent Lessor, the Administrative Agent, the Lessors and the
Lenders are willing to waive the financial covenants subject to the satisfaction
of the conditions set forth in Section 2 hereof;

        Now, Therefore, the parties hereto agree as follows:

        Section 1.  Waiver. Effective on (and subject to the occurrence of) the
Amendment Effective Date (as defined below), the Agent Lessor, Lessors,
Administrative Agent and Lenders waive any and all defaults of Sections 10.2(a),
(b), (c), (d) and (e) of the Participation Agreement which occurred prior to the
date hereof and prospectively through June 22, 2003.

        Section 2.  Representations and Warranties. The Lessee and Guarantor
represent and warrant to the Lenders that, after giving effect hereto, (a) each
representation and warranty set forth in Section 8.2 of the Participation
Agreement is true and correct as of the date of the execution and delivery of
this Amendment by the Lessee and Guarantor with the same effect as if made on
such date (except to the extent such representations and warranties expressly
refer to an earlier date, in which case they were true and correct as of such
earlier date), except if changes to such representations and warranties have
been disclosed pursuant to publicly available documents and (b) no Event of
Default or Unmatured Event of Default exists.



        Section 3.  Effectiveness. The waivers set forth in Section 1 above
shall become effective on the date (the "Amendment Effective Date") when the
Administrative Agent shall have received (a) counterparts of this Amendment
executed by the Lessee, the Guarantor, the Agent Lessor, the Lessors, the Lender
and the Administrative Agent and Arranger, (b) copies of corporate action of the
respective Board of Directors of the Guarantor taken by such respective Board of
Directors relative to the pledge of collateral described in (c) below certified
by a secretary or assistant secretary as of the date hereof to be true and
correct and in full force and effect as of such date and (c) cash collateral in
the amount of U.S. $18,925,000 and an executed Security Agreement re: Deposit
Account regarding the same.

        Section 4.  Reaffirmation of Guaranty. The Guarantor heretofore executed
and delivered to the Agent Lessor, the Lender, the Administrative Agent and the
Lessors, the Guaranty dated June 23, 1998. The Guarantor hereby consents to this
Waiver and confirms that the Guaranty and all of the Guarantor's obligations
thereunder remain in full force and effect with respect to the obligations
guaranteed thereunder as such obligations have been amended and increased by
this Amendment.

        Section 5.  Miscellaneous.

      Section 5.1.  Continuing Effectiveness, etc. The Participation Agreement,
the Loan Agreement and the remaining Operative Documents shall remain in full
force and effect and are hereby ratified and confirmed in all respects.

      Section 5.2.  Counterparts. This Waiver may be executed in any number of
counterparts and by the different parties on separate counterparts, and each
such counterpart shall be deemed to be an original but all such counterparts
shall together constitute one and the same Amendment.

      Section 5.3.  Governing Law. This Waiver shall be a contract made under
and governed by the laws of the State of Illinois applicable to contracts made
and to be performed entirely within such state.

      Section 5.4.  Successors and Assigns. This Waiver shall be binding upon
the Lessee, the Guarantor, the Agent Lessor, the Lessor, the Lender, the
Administrative Agent and the Arranger and their respective successors and
assigns, and shall inure to the benefit of the Lessee, Guarantor, the Agent
Lessor, the Lenders, the Lessor and the Administrative Agent and the respective
successors and assigns of the Agent Lessor, the Lessor, the Lenders and the
Administrative Agent and the Arranger.

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        In Witness Whereof, the parties hereto have caused this Waiver to be
duly executed and delivered by their duly authorized officers as of the day and
year first above written.

                                     GSI Lumonics Corporation (formerly known as
                                         Lumonics Corporation), as Lessee and
                                         Construction Agent


                                     By:  /s/ Victor H. Woolley
                                           Name: Victor H. Woolley
                                           Title: Vice President


                                     GSI Lumonics Inc. (formerly known as
                                        Lumonics Inc.), as Guarantor


                                     By:  /s/  Thomas R. Swain
                                          Name: Thomas R. Swain
                                          Title:  V.P. & CFO


                                     By   /s/  Eileen Casal
                                          Name:  Eileen Casal
                                          Title:  V.P. & General Counsel


                                     BMO Global Capital Solutions, Inc.
                                        (formerly known as BMO Leasing
                                        (U.S.), Inc.), as Agent Lessor and
                                        as a Lessor


                                     By:  /s/  Thomas A. Batterham
                                          Name:  Thomas A. Batterham
                                          Title:  Vice President


                                     Bank of Montreal, as Administrative Agent,
                                        Arranger and as a Lender


                                     By:  /s/  Ben Ciallella
                                          Name:  Ben Ciallella
                                          Title:  Asset Portfolio Management

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