SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                 SCHEDULE 13D/A
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                                (Amendment No. 4)

                              Spectra-Physics, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, par value $0.01 per share
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                   847568 10 2
--------------------------------------------------------------------------------
                                 (CUSIP Number)

                             Seth H. Hoogasian, Esq.
                                 General Counsel
                           Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046
                                 (781) 622-1000

                                    Copy to:

                              Neil H. Aronson, Esq.
                           Mintz, Levin, Cohn, Ferris,
                             Glovsky and Popeo, P.C.
                              One Financial Center
                           Boston, Massachusetts 02111
                                 (617) 542-6000

--------------------------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)

                                November 6, 2001
--------------------------------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the  subject of this  Schedule  13D and is filing this
schedule  because of Rule  13d-1(e),  13d-1(f) or 13d-1(g),  check the following
box [ ].





================================================
CUSIP NO.  847568 10 2                                               13D
================================================

============== =================================================================
           1
                          NAMES OF REPORTING PERSONS
                          I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES
                          ONLY)

                          Thermo Electron Corporation
                          04-2209186
-------------- -----------------------------------------------------------------
           2
                          CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                (a)    _
                                                                (b)    x
-------------- -----------------------------------------------------------------
           3
                          SEC USE ONLY
-------------- -----------------------------------------------------------------
           4
                          SOURCE OF FUNDS

                          WC
-------------- -----------------------------------------------------------------
           5              CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS
                          REQUIRED

                          PURSUANT TO ITEMS 2(d) or 2(e)                [ ]
-------------- -----------------------------------------------------------------
           6
                          CITIZENSHIP OR PLACE OF ORGANIZATION

                          Delaware
================================================================================
NUMBER OF
                                           7       SOLE VOTING POWER
SHARES
                                                                     13,333,000
                                           -------------------------------------
BENEFICIALLY

OWNED BY                                   8       SHARED VOTING POWER
EACH                                                                       0
                                           -------------------------------------

                                           9       SOLE DISPOSITIVE POWER
REPORT REPORTING
PERSON                                                               13,333,000
                                           -------------------------------------
                                           10      SHARED DISPOSITIVE POWER
 WITH
                                                                           0
================================================================================
11                       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING
                          PERSON

                          13,333,000
------------- ------------------------------------------------------------------

12                       CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
                         CERTAIN SHARES                                [  ]
------------- ------------------------------------------------------------------

13                       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                         78.5%
------------- ------------------------------------------------------------------

14                       TYPE OF REPORTING PERSON

     CO
===============================================================================

     Thermo  Electron  Corporation  hereby  amends its statement on Schedule 13D
relating  to the shares  (the  "Shares")  of common  stock,  par value $0.01 per
share, of Spectra-Physics, Inc. (the "Issuer") as set forth below.

Item 2.  Identity and Background

     Item 2 is hereby amended and restated to read as follows:

     This  Amendment  is  being  filed  by  Thermo  Electron   Corporation  (the
"Reporting  Person"),  pursuant to Rule 13d-2, to reflect changes to information
previously reported under Item 4 of Schedule 13D. The Reporting Person holds the
Shares of the Issuer that are the subject of this Amendment directly and through
one or  more  wholly-owned  subsidiaries.  As of the  date  of  this  Amendment,
13,000,000  Shares  were held by  Spectra-Physics  AB,  which is a  wholly-owned
subsidiary of the Reporting Person, and 333,000 Shares were held directly by the
Reporting Person.

     The Reporting  Person develops,  manufactures and markets  technology-based
instruments, components and systems serving multiple markets, including, without
limitation,  life  sciences,  telecommunications  and  food,  drug and  beverage
production.  The  Reporting  Person  also  develops,  manufactures  and  markets
diagnostic and monitoring products serving the healthcare industry.

     The  principal  business  address  and  principal  office  address  of  the
Reporting  Person,  a  Delaware  corporation,   is  81  Wyman  Street,  Waltham,
Massachusetts 02454-9046.

     Appendix  A attached  to this  Amendment  sets  forth with  respect to each
executive  officer and director of the Reporting Person his or her (a) name; (b)
residence or business address;  (c) present  principal  occupation or employment
and the  name,  principal  business  and  address  of any  corporation  or other
organization in which such employment is conducted; and (d) citizenship.  To the
knowledge of the Reporting Person,  there is no person who may be deemed to be a
controlling person of the Reporting Person.

     During  the last five  years,  neither  the  Reporting  Person  nor (to the
knowledge  of the  Reporting  Person) any  executive  officer or director of the
Reporting Person has been convicted in a criminal proceeding  (excluding traffic
violations and similar misdemeanors).

     During  the last five  years,  neither  the  Reporting  Person  nor (to the
knowledge  of the  Reporting  Person) any  executive  officer or director of the
Reporting  Person  has  been a party  to a civil  proceeding  of a  judicial  or
administrative  body of competent  jurisdiction  which  resulted in a judgement,
decree or final order (i) enjoining  future  violations  of, or  prohibiting  or
mandating  activities  subject  to,  federal  or state  securities  laws or (ii)
finding a violation with respect to such laws.






Item 4.  Purpose of Transaction

         The third, fourth and fifth paragraphs of Item 4 are hereby amended and
restated in their entirety as follows:

     On August 21, 2001,  the Reporting  Person  issued a press release  stating
that the  Reporting  Person  planned to make a cash  tender  offer by the end of
September 2001 for any and all of the  outstanding  Shares of the Issuer held by
minority  stockholders  at $20 per Share in cash.  On September  26,  2001,  the
Reporting  Person  announced that it was reevaluating the offer price of $20 per
share in order to analyze  the impact on the  Issuer of the  worsening  economic
conditions  associated with the terrorist  attacks on September 11, 2001.  After
the market closed on November 6, 2001, the Reporting  Person announced a revised
offer price of $17.50 per share in cash. The Reporting  Person currently owns of
record approximately 78.5% of the outstanding Shares.

     The  Reporting  Person is seeking to receive  acceptances  from  holders of
enough Shares so that, when combined with its current  ownership of Shares,  the
Reporting  Person's  ownership  reaches at least 90%.  If the  Reporting  Person
achieves this 90% ownership  threshold,  it will acquire as soon as  practicable
after  February 22, 2002 all remaining  outstanding  Shares through a subsequent
short-form  merger in Delaware.  Stockholders  who do not tender their Shares to
the Reporting Person during the tender offer would also receive $17.50 per Share
in cash for their Shares in the short-form merger.

     The  Reporting  Person has caused in the past and  intends to  continue  to
cause a majority of the members of the Issuer's board of directors to consist of
the Reporting  Person's  designees.  From time to time, the Reporting Person has
loaned,  and may  continue to loan,  money to the Issuer in such a manner and in
such amounts as it and the Issuer determine to be appropriate.

     Except as set forth in this Item 4,  neither the  Reporting  Person nor, to
the Reporting Person's knowledge,  any of the executive officers or directors of
the Reporting Person has any current plans or proposals which relate to or would
result in any of the actions  specified  in clauses (a) through (j) of Item 4 of
Schedule 13D,  although the Reporting  Person and such other persons do not rule
out the  possibility  of  effecting or seeking to effect any such actions in the
future.







                                    SIGNATURE

     After reasonable  inquiry and to the best of its knowledge and belief,  the
Reporting  Person  certifies that the information set forth in this statement is
true, complete and correct.

                                        THERMO ELECTRON CORPORATION



Date: November 21, 2001                 /s/ Kenneth J. Apicerno
                                        ---------------------------------------
                                        By:     Kenneth J. Apicerno
                                        Its:    Treasurer






Appendix A is hereby amended and restated in its entirety as follows:


                                   APPENDIX A

     The following  individuals  are  executive  officers or directors of Thermo
Electron  Corporation  ("Thermo  Electron").  Unless  otherwise  noted, all such
individuals  are citizens of the United  States.  Unless  otherwise  noted,  the
business address of each executive officer and director of Thermo Electron is 81
Wyman Street, Waltham, Massachusetts 02454-9046.


Peter O. Crisp:                         Director, Thermo Electron

         Mr. Crisp is the vice chairman of Rockefeller Financial Services, Inc.

Frank Jungers:                          Director, Thermo Electron

     Mr.  Jungers is a consultant on business and energy  matters.  His business
address is 822 N.W. Murray Boulevard, Suite 242, Portland, Oregon 97229.

Jim P. Manzi:                           Director, Thermo Electron

     Mr. Manzi is the managing director of Stonegate  Capital,  a firm he formed
to manage his investments in technology  start-up ventures  primarily related to
the Internet.

Robert A. McCabe:                       Director, Thermo Electron

     Mr.  McCabe  is  the  Chairman  of  Pilot  Capital   Corporation,   a  firm
specializing  in private  investment  and  acquisition  services.  His  business
address is Pilot Capital Corporation,  444 Madison Avenue, Suite 2103, New York,
New York 10022.

Robert W. O'Leary:                      Director, Thermo Electron

     Mr.  O'Leary is the  Chairman and Chief  Executive  Officer of The Sagamore
Group, a firm specializing in change  management  situations with a focus on the
service sector.

Hutham S. Olayan:                       Director, Thermo Electron

     Ms. Olayan is the President and a director of Olayan America Corporation, a
firm  engaged  in  private  investments,  including  real  estate  and  advisory
services.  Her business  address is Suite 1100,  505 Park Avenue,  New York, New
York 10022.

Michael E. Porter:                      Director, Thermo Electron

     Dr.  Porter is the Bishop  William  Lawrence  University  Professor  at the
Harvard Business  School,  and a leading  authority on competitive  strategy and
international competitiveness.  His business address is Harvard Business School,
Soldiers Field Road, Boston, Massachusetts 02163.



Elaine S. Ullian:                       Director, Thermo Electron

     Ms.  Ullian is  president  and chief  executive  officer of Boston  Medical
Center, a 550-bed academic medical center affiliated with Boston University. Her
business  address is Boston Medical Center,  Talbot 1, One Boston Medical Center
Plaza, Boston, Massachusetts 02118-2393.

Richard F. Syron:                       Director, Chairman of the Board and
                                        Chief Executive Officer, Thermo Electron

Marijn E. Dekkers:                      Director, President and Chief Operating
                                        Officer, Thermo Electron

     Mr. Dekkers is a citizen of The Netherlands.

Guy Broadbent:                          Vice President, Thermo Electron;
                                        President, Optical Technologies

     Mr. Broadbent is a citizen of the United Kingdom.

Barry S. Howe:                          Vice President, Thermo Electron;
                                        President, Measurement and Control

Seth H. Hoogasian:                      Vice President and General Counsel,
                                        Thermo Electron

Theo Melas-Kyriazi:                     Vice President and Chief Financial
                                        Officer, Thermo Electron

     Mr. Melas-Kyriazi is a citizen of Greece.

Peter E. Hornstra:                      Corporate Controller and Chief
                                        Accounting Officer, Thermo Electron