Deflectable spatial light modulator having stopping mechanisms

• US 6,396,619 B1
• Filed: 08/11/2000
• Issued: 05/28/2002
• Est. Priority Date: 01/28/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Huibers, Andrew G., Heureux, Peter J.
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): O'NEILL, GARY WILLIAM
• Application Number:
  US09/637,479
• Time in Patent Office: 655 Days
• Field of Search: 359/290,291,846,847,848,214,223,245 345/101 349/84
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A spatial light modulator having one or more deflection limiting mechanisms and process for fabrication therefor. In one embodiment, the mirror support structure has rigid deflection stoppers that limit the tilt angle of the reflective plate. The mirror support structure may also include an attraction electrode that is attached to the back-side of the reflective plate such that the reflective plate may be selectively actuated by electrostatic force. Alternatively, a deflection stopping mechanism can be provided separate from the mirror support structure. The deflection stopping mechanism can be used in conjunction with one or more additional stopping mechanisms such as the abutment of a portion of the reflective plate against the substrate upon which it was constructed. Advantages of the present invention include: (1) increased fill factor as the torsion hinge is hidden behind the reflective plate; (2) increased contrast due to fewer scattering optical surfaces exposed, and due to a greater ability to control their angle and geometry; and (3) increased geometric flexibility to optimize electro-mechanical performance and robustness with respect to manufacturing.

Claims

1. A micro-electromechanical device comprising:

a substrate having a first surface;

a support structure coupled to said first surface of said optically transmissive substrate; and

a reflective element deflectably coupled to said substrate via said support structure, wherein said support structure comprises a stopping mechanism constructed for resisting deflection of said reflective element beyond a pre-determined tilt angle.

2. A micro-electromechanical device as recited in claim 1 wherein said support structure comprises a first end and a second end that are attached to said first surface.

3. A micro-electromechanical device as recited in claim 2 wherein said stopping mechanism of the support structure comprises a first deflection stopper positioned near said first end and a second deflection stopper positioned near said second end.

4. A micro-electromechanical device as recited in claim 1 wherein said reflective element comprises a substantially rigid reflective plate and the substrate is an optically transmissive substrate.

5. A micro-electromechanical device as recited in claim 4 further comprising a second stopping mechanism which comprises a bump positioned along an edge of said reflective plate, wherein said bump is configured for abutting against the optically transmissive substrate and for reducing an area of contact between said second stopping mechanism of the reflective element and said optically transmissive substrate.

6. A micro-electromechanical device as recited in claim 1 further comprising a semiconductor substrate positioned across and spaced apart from said first surface of said substrate, said semiconductor substrate comprising electronic circuitry adapted for causing said reflective element to deflect by means of electrostatic force.

7. A micro-electromechanical device as recited in claim 6 wherein said support structure further comprises an attraction electrode attached to said reflective element, wherein said attraction electrode is electrically coupled to said semiconductor substrate and configured for selective actuation by said electronic circuitry.

8. A micro-electromechanical device as recited in claim 7 wherein said support structure and said attraction electrode are composed of a laminate including a conductive layer.

9. A micro-electromechanical device as recited in claim 1, wherein said stopping mechanism is disposed on a side of the reflective element opposite to that of the substrate.

10. A micro-electromechanical device as recited in claim 1, wherein the support structure comprises a hinge and posts, the posts extending past the reflective element to connect directly or indirectly to the substrate, and the hinge extending from the posts and connecting to the reflective element.

11. A micro-electromechanical device as recited in claim 10, wherein the stopping mechanism comprises a flared end of each post.

12. A micro-electromechanical device as recited in claim 10, wherein the stopping mechanism comprises an edge of the hinge that abuts against the reflective element when deflected.

13. A micro-electromechanical device as recited in claim 1, further comprising a second stopping mechanism that includes an extension or portion of the reflective element that abuts against the substrate when the reflective element is deflected.

14. A spatial light modulator comprising:

a first substrate having a first surface;

a deflectable element deflectably coupled to the first surface of the first substrate;

a second substrate positioned across from and spaced apart from said first surface of said first substrate, said second substrate comprising electronic circuitry adapted for causing said deflectable element to deflect; and

a primary stopping mechanism and a secondary stopping mechanism, each for stopping deflection of the deflectable element when deflected by the electronic circuitry, the primary stopping mechanism and the secondary stopping mechanism each positioned so as to stop deflection of the deflectable element when the deflectable element deflects and then abuts against the primary and secondary stopping mechanisms.

15. The spatial light modulator of claim 14, wherein the primary and secondary stopping mechanisms are constructed to stop movement of the deflectable element at different angles of deflection of the deflectable element.

16. The spatial light modulator of claim 14, wherein the primary and secondary stopping mechanisms are constructed in different planes relative to the deflectable element.

17. The spatial light modulator of claim 14, wherein one of the primary and secondary stopping mechanisms comprises a portion or extension of the deflectable element which abuts against the first substrate during deflection of the deflectable element.

18. The spatial light modulator of claim 17, wherein the other of the primary and secondary stopping mechanisms comprises support structure connected to the first substrate which is disposed on a side of the deflectable element opposite to the side on which the first substrate is disposed, the deflectable element adapted to abut against the support structure when the deflectable element is deflected.

19. The spatial light modulator of claim 14, further comprising a hinge that extends along a side of the deflectable element opposite to the first substrate.

20. The spatial light modulator of claim 19, wherein the secondary stopping mechanism comprises a portion of the hinge, the hinge portion constructed so as to abut against the deflectable element when the deflectable element is deflected.

21. The spatial light modulator of claim 14, wherein a gap is disposed between the first substrate and the deflectable element, and a second gap is disposed between the deflectable element and one of the primary and secondary stopping mechanisms.

22. The spatial light modulator of claim 19, wherein the hinge comprises a flexible portion, the flexible portion being hidden from view by the deflectable element when viewed via the first substrate.

23. The spatial light modulator of claim 19, wherein the hinge is connected to the first substrate via posts that extend from the bottom surface of the first substrate and past the deflectable element.

24. The spatial light modulator of claim 14, wherein the deflectable element is held on a bottom surface of the first substrate, and wherein the deflectable element has first and second portions such that during deflection of the deflectable element, the second portion moves towards the bottom surface as the first portion moves away from the bottom surface.

25. The spatial light modulator of claim 19, wherein the hinge extends across the deflectable element between the second substrate and the deflectable element and connects to the deflectable element towards a center part of the deflectable element.

26. The spatial light modulator of claim 14, wherein one of the primary and secondary stopping mechanisms comprises a post or wall connected at one end to the first substrate and having a second end with a protrusion which is adapted to abut against the deflectable element when the deflectable element pivots up to a predetermined angle.

27. The spatial light modulator of claim 14, wherein the secondary stopping mechanism is constructed to avoid abutment against the deflectable element unless the primary stopping mechanism fails.

28. The spatial light modulator of claim 14, further comprising a hinge which is disposed on a side of the deflectable element opposite to that of the first substrate, the hinge having an end portion which comprises at least part of one of the primary and secondary stopping mechanisms.

29. The spatial light modulator of claim 19, wherein a gap is disposed between the hinge and the deflectable element, and said gap being disposed between one of the primary and secondary stopping mechanisms and the deflectable element.

30. The spatial light modulator of claim 19, wherein the hinge is connected to the first substrate via the secondary stopping mechanism.

31. The spatial light modulator of claim 14, wherein the deflectable element is part of an array of deflectable elements held on the first substrate.

32. The spatial light modulator of claim 31, wherein each deflectable element in the array corresponds to a pixel in a projection display system.

33. The spatial light modulator of claim 32, wherein there are at least 1024×

768 pixels in the array.

34. The spatial light modulator of claim 14, wherein the first substrate is an optically transmissive substrate.

35. The spatial light modulator of claim 14, wherein the deflectable element is a reflective mirror element.

36. The spatial light modulator of claim 14, wherein the first substrate is an optically transmissive substrate and the deflectable element is a reflective mirror element positioned to reflect light incoming through the optically transmissive substrate.

37. A spatial light modulator, comprising:

a first substrate;

a deflectable element held on the first substrate via a hinge and stop assembly, the hinge connected to the deflectable element so as to allow the deflectable element to pivot around an axis, and the stop positioned to arrest the pivoting of the deflectable element.

38. The spatial light modulator of claim 37, further comprising a second substrate positioned on a side of the deflectable element opposite to that of the first substrate.

39. The spatial light modulator of claim 38, further comprising an electrode on the second substrate for electrostatically attracting the deflectable element.

40. The spatial light modulator of claim 38, wherein the first substrate is an optically transmissive substrate, the deflectable element is a reflective and conductive element, and the second substrate comprises addressing circuitry.

41. The spatial light modulator of claim 37, wherein the hinge and stop assembly comprises a post connecting to the first substrate, the deflectable element constructed to abut against a portion of the hinge and/or post when deflected.

42. The spatial light modulator of claim 39, wherein the hinge extends across the deflectable element between the electrode and the deflectable element and connects to the deflectable element towards a center part of the deflectable element.

43. The spatial light modulator of claim 37, wherein the deflectable element is held on a bottom surface of the first substrate, and wherein the deflectable element has first and second portions such that during deflection of the deflectable element, the second portion moves towards the bottom surface as the first portion moves away from the bottom surface.

44. The spatial light modulator of claim 43, wherein part of said first portion abuts against an area of the hinge and stop assembly.

45. The spatial light modulator of claim 44, wherein part of said second portion abuts against an area of the first substrate.

46. The spatial light modulator of claim 37, wherein a plurality of deflectable element are provided in an array on the first substrate.

47. The spatial light modulator of claim 46, wherein at least 1024×

768 deflectable elements are provided in the array as part of a projection display system.

48. A spatial light modulator comprising:

a first substrate;

a deflectable element pivotably held on the first substrate;

a post or wall extending from the first substrate and having a lip or protrusion which extends past a portion of the deflectable element such that when the deflectable element pivots, a portion of the deflectable element abuts against the lip or protrusion so as to stop the movement of the deflectable element.

49. The spatial light modulator of claim 48, wherein the first substrate is an optically transmissive substrate.

50.The spatial light modulator of claim 49, wherein the first substrate is glass, quartz or sapphire.

50. The spatial light modulator of claim 48, wherein the deflectable element is a conductive and substantially rigid mirror element.

51. The spatial light modulator of claim 48, wherein the deflectable element comprises first and second portions such that when the deflectable element pivots, the second portion moves towards the first substrate as the first portion moves away from the first substrate.

54. The spatial light modulator of claim 48, further comprising a hinge that extends across a portion of the deflectable element for allowing pivoting movement of the deflectable element.

57. The spatial light modulator of claim 48, further comprising a second silicon substrate with addressing circuitry and an electrode for electrostatically attracting the deflectable element.

52. The spatial light modulator of claim 52, wherein the first portion concurrently moves away from the first substrate and toward the lip or protrusion of the post or wall and an area of the first portion constructed to abut against the lip or protrusion so as to stop the pivoting movement of the deflectable element.

53. The spatial light modulator of claim 53, wherein the second portion is constructed so as to be capable of abutting against the first substrate.

55. The spatial light modulator of claim 55, wherein the hinge connects to the post or wall.

56. The spatial light modulator of claim 55, wherein the hinge is separated from the post or wall.

58. A spatial light modulator comprising in cross section:

an optically transmissive substrate;

a first gap disposed below the optically transmissive substrate;

a pivotable mirror disposed below the first gap;

a second gap disposed below the mirror; and

a deflection stopper disposed below the second gap.

59. The spatial light modulator of claim 59, further comprising a connector that connects the pivotable mirror with the optically transmissive substrate.

62. The spatial light modulator of claim 59, wherein the deflection stopper is part of a hinge and post assembly for pivotably holding the mirror to the optically transmissive substrate.

63. The spatial light modulator of claim 59, further comprising a hinge and post assembly spaced apart from the deflection stopper with the hinge disposed below the second gap.

64. The spatial light modulator of claim 59, further comprising a third gap below the deflection stopper and a second substrate disposed below the third gap.

66. The spatial light modulator of claim 59, wherein the deflection stopper comprises a protrusion that extends below the second gap and a wall or post which connects to the optically transmissive substrate.

60. The spatial light modulator of claim 60, wherein said connector comprises said deflection stopper.

61. The spatial light modulator of claim 60, wherein said connector comprises a hinge for providing pivotable movement of said mirror.

65. The spatial light modulator of claim 65, wherein said second substrate comprises addressing circuitry and an electrode for electrostatically causing the mirror to pivot.