Silicon mirrors having reduced hinge stress from temperature variations

• US 20030206356A1
• Filed: 05/03/2002
• Published: 11/06/2003
• Est. Priority Date: 05/03/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Orcutt, John W.
• Granted Patent: US 7,468,826 B2
• Time in Patent Office: Days
• US Class Current: 359/872
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 7/008 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G02B 7/18 for prisms; for mirrors

Abstract

A device such as a mirror assembly comprises a movable structure (41) having a first movable portion (45) hinged to a frame portion (43) by a first pair of torsional hinges (47A and 47B) spaced apart along a first axis (49). The device may also have a second movable portion (51) and a second pivot axis provided by set of torsional hinge (53A and 53B). The movable structure or mirror assembly (41) having a first coefficient of expansion is attached to a support structure (42) having a different coefficient of expansion at a single attaching or anchor point (63) such as by epoxy or a clamp (101). The single attaching point (63) allows expansion and/or contraction along two dimensions and thereby prevents compression and/or tension forces resulting from different coefficients of expansion between the mirror assembly 41 and the support structure 42 from being applied to the torsional hinges 47A, 47B, 53A and 53B. One embodiment of the invention also includes a biasing member or finger (105) which bears against the frame portion 43 of mirror assembly 41 to prevent vibrations in the third dimension.

Claims

1. A torsional hinge apparatus having minimal hinge stress due to temperature variations comprising:

a support substrate having a first coefficient of expansion;

an integral torsional hinge device formed from a material having a different coefficient of expansion, and having an inside portion attached to a support portion along an axis by at least one pair of torsional hinges; and

an anchor for attaching said support portion of said integral torsional hinge device to said support substrate at a single location to allow substantially unrestricted expansion and retraction along two dimensions of said integral torsional hinge device.

2. The torsional hinge apparatus of claim 1 further comprising a biasing member attached to said support substrate and bearing against said support portion of said integral torsional hinge device at another location spaced from said single location.

3. The torsional hinge apparatus of claim 1, wherein said anchor is a clamp.

4. The torsional hinge apparatus of claim 1, wherein said anchor is an adhesive such as epoxy.

5. The torsional hinge apparatus of claim 1, wherein said support substrate defines a cavity to provide a space for rotation of said inside portion.

6. The torsional hinge apparatus of claim 1, wherein said support portion is substantially rectangular in shape, and said single location is proximate a corner of said support portion.

7. The torsional hinge apparatus of claim 1, wherein said integral torsional hinge device further includes an intermediate portion attached to said inside portion by a first pair of hinges and to said support portion by a second pair of hinges to allow rotation of said intermediate portion and said inside portion with respect to said support portion.

8. The torsional hinge apparatus of claim 6, wherein said anchor is a clamp.

9. The torsional hinge apparatus of claim 6, wherein said anchor is an adhesive such as epoxy.

10. The torsional hinge apparatus of claim 7 further comprising a biasing member attached to said support substrate and bearing against said support portion of said integral torsional hinge device at another location spaced from said single location.

11. The torsional hinge apparatus of claim 1, wherein said inside portion is a reflective surface.

12. The torsional hinge apparatus of claim 6, wherein said inside portion is a reflective surface.

13. The torsional hinge apparatus of claim 7, wherein said second pair of hinges are orthogonal to said first pair of hinges.

14. A method of manufacturing a torsional hinge apparatus for rotation about a pair of hinges having minimal hinge stress due to temperature variations comprising the steps of:

providing a support substrate having a first coefficient of expansion;

providing an integral torsional hinge device formed from a material having a different coefficient of expansion, and having an inside portion attached to a support portion along an axis by at least one pair of torsional hinges; and

attaching said support portion of said integral torsional hinge device to said support substrate at a single location so as to allow substantially unrestricted expansion and retraction along two dimensions of said integral torsional hinge device.

15. The method of claim 14 further comprising the step of restraining said support portion from movement due to vibrations and inertia forces by applying a biasing force at a location on said integral torsional hinge device spaced from said single location.

16. The mirror device of claim 14, wherein said step of providing an integral torsional hinge device comprises the further step of said integral torsional hinge device further including an intermediate portion attached to said inside portion by a first pair of hinges and to said support portion by a second pair of hinges so as to allow rotation of said intermediate portion and said inside portion with respect to said support portion.

17. The method of claim 16 further comprising the step of restraining said support portion from movement due to vibrations and inertia forces by applying a biasing force at a location on said support portion of said integral torsional hinge device spaced from said single location.

18. The method of claim 16, wherein said second pair of hinges are orthogonal to said first pair of hinges.

22. The mirror apparatus of claim 17, wherein said anchor is an adhesive such as epoxy.

19. A mirror apparatus for rotation about a pair of hinges having minimal hinge stress of the mirror due to temperature variations comprising:

a support substrate having a first coefficient of expansion;

an integral mirror device formed from a material having a different coefficient of expansion, and having a mirror portion attached to a support portion along an axis by at least one pair of torsional hinges; and

an anchor for attaching said support portion of said integral mirror device to said support substrate at a single location to allow substantially unrestricted expansion and retraction along two dimensions of said integral mirror device.

20. The mirror apparatus of claim 19 further comprising a biasing member attached to said support substrate and bearing against said mirror support portion of said integral mirror device at another location spaced from said single location.

21. The mirror apparatus of claim 19, wherein said anchor is a clamp.

23. The mirror apparatus of claim 19, wherein said support substrate defines a cavity to provide a space for rotation of said mirror portion.

24. The mirror apparatus of claim 19, wherein said support portion is substantially rectangular in shape, and said single location is proximate a corner of said support portion.

25. The mirror apparatus of claim 19, wherein said integral mirror device further includes an intermediate portion attached to said mirror first pair of hinges and to said support portion by a second pair of hinges to allow rotation of said intermediate portion and said mirror portion with respect to said support portion.

26. The mirror apparatus of claim 25, wherein said second pair of hinges are orthogonal to said first pair of hinges.

27. The mirror apparatus of claim 25, wherein said anchor is a clamp.

28. The mirror apparatus of claim 25, wherein said anchor is an adhesive such as epoxy.

29. A method of manufacturing a mirror for rotation about a pair of hinges having minimal hinge stress due to temperature variations comprising the steps of:

providing a support substrate having a first coefficient of expansion;

providing an integral mirror device formed from a material having a different coefficient of expansion, and having a mirror portion attached to a support portion along an axis by at least one pair of hinges; and

attaching said support portion of said integral mirror device to said support substrate at a single location so as to allow substantially unrestricted expansion and retraction along two dimensions of said integral mirror.

30. The method of claim 29 further comprising the step of restraining said support portion from movement due to vibrations and inertia forces by applying a biasing force at a location on said integral mirror device spaced from said single location.

31. The method of claim 29, wherein said step of providing an integral mirror device comprises the further step of said integral mirror device further including an intermediate portion attached to said mirror portion by a first pair of hinges and to said support portion by a second pair of hinges so as to allow rotation of said intermediate portion and said mirror portion with respect to said support portion.

32. The method of claim 31, wherein said second pair of hinges are orthogonal to said fist pair of hinges.

33. The method of claim 31 further comprising the step of restraining said support portion from movement due to vibrations and inertia forces by applying a biasing force at a location on said support portion of said mirror device spaced from said single location.