Micromirror array having reduced gap between adjacent micromirrors of the micromirror array

• US 6,970,281 B2
• Filed: 01/11/2005
• Issued: 11/29/2005
• Est. Priority Date: 07/03/2003
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Huibers, Andrew, Patel, Satyadev
• Primary Examiner(s): Mack, Ricky L.
• Assistant Examiner(s): THOMAS, BRANDI N
• Application Number:
  US11/034,398
• Publication Number:
  US 20050231788A1
• Time in Patent Office: 322 Days
• Field of Search: 359/290, 359/291, 359/292, 359/293, 359/294, 359/295, 359/298
• US Class Current: 359/290
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A spatial light modulator is disclosed, along with a method for making such a modulator that comprises an array of micromirror devices. The center-to-center distance and the gap between adjacent micromirror devices are determined corresponding to the light source being used so as to optimize optical efficiency and performance quality. The micromirror device comprises a hinge support formed on a substrate and a hinge that is held by the hinge support. A mirror plate is connected to the hinge via a contact, and the distance between the mirror plate and the hinge is determined according to desired maximum rotation angle of the mirror plate, the optimum gap and pitch between the adjacent micromirrors.

In a method of fabricating such spatial light modulator, one sacrificial layer is deposited on a substrate followed by forming the mirror plates, and another sacrificial layer is deposited on the mirror plates followed by forming the hinge supports. The two sacrificial layers are removed via the small gap between adjacent mirror devices with spontaneous vapor phase chemical etchant. Also disclosed is a projection system that comprises such a spatial light modulator, as well as a light source, condensing optics, wherein light from the light source is focused onto the array of micromirrors, projection optics for projecting light selectively reflected from the array of micromirrors onto a target, and a controller for selectively actuating the micromirrors in the array.

Claims

1. A spatial light modulator, comprising:

an array of movable mirror plates formed on a substrate for selectively reflecting a light beam incident on the mirror plates, wherein each mirror plate is attached to a deformable hinge that is spaced apart from the mirror plate from 0.15 to 1.5 micrometers in a direction perpendicular to the mirror plate;

wherein adjacent mirror plates of the array have a gap from 0.15 to 0.5 micrometers when the adjacent mirror plates are parallel to the substrate.

2. The spatial light modulator of claim 1, further comprising:

a hinge that is attached to each mirror plate such that the mirror plate can rotate relative to the substrate, wherein the hinge and the mirror plate are spaced apart from 0.5 to 1.5 micrometers.

3. The spatial light modulator of claim 1, wherein the adjacent mirror plates have a center-to-center distance from 4.28 to 10.16 micrometers.

4. The spatial light modulator of claim 1, wherein the array of mirror plates comprises at least 1280 mirror plates along a length of the mirror plate array.

5. The spatial light modulator of claim 1, wherein the array of mirror plates comprises at least 1400 mirror plates along a length of the mirror plate array.

6. The spatial light modulator of claim 1, wherein the array of mirror plates comprises at least 1600 mirror plates along a length of the mirror plate array.

7. The spatial light modulator of claim 1, wherein the array of mirror plates comprises at least 1920 mirror plates along a length of the mirror plate array.

8. The spatial light modulator of claim 1, wherein the adjacent mirror plates has a gap of 0.5 micrometers or less therebetween when the adjacent mirror plates are parallel to the substrate.

9. The spatial light modulator of claim 2, wherein a distance between the hinge and the mirror plate is from 0.5 to 0.8 micrometers.

10. The spatial light modulator of claim 2, wherein a distance between the hinge and the mirror plate is from 0.8 to 1.25 micrometers.

11. The spatial light modulator of claim 2, wherein a distance between the hinge and the mirror plate is from 1.25 to 1.5 micrometers.

12. The spatial light modulator of claim 3, wherein the center-to-center distance of adjacent mirror plates is from 6.23 to 9.34 micrometers.

13. The spatial light modulator of claim 3, wherein the center-to-center distance of adjacent mirror plates is from 4.38 to 6.57 micrometers.

14. The spatial light modulator of claim 3, wherein the center-to-center distance of adjacent mirror plates is from 4.38 to 9.34 micrometers.

15. The spatial light modulator of claim 1, further comprising:

a hinge attached to the mirror plate such that the mirror plate can rotate relative to the substrate along a rotation axis that is parallel to but offset from a diagonal of the mirror plate when viewed from the top of the mirror plate;

wherein the mirror plate can rotate to an angle at least 14 degrees relative to the substrate; and

wherein the adjacent mirror plates has a center-to-center distance from 4.38 to 10.16 micrometers; and

wherein the hinge and the mirror plate is spaced apart from 0.5 to 1.5 micrometers.

16. The spatial light modulator of claim 1, further comprising:

an electrode proximate to each mirror plate for electrostatically deflecting the mirror plate.

17. The spatial light modulator of claim 1, wherein the substrate is glass or quartz that is visible light transmissive.

18. The spatial light modulator of claim 17, wherein the substrate comprises an anti-reflection film on a surface of the substrate.

19. The spatial light modulator of claim 17, wherein the substrate comprises a light absorption frame around an edge of the substrate.

20. The spatial light modulator of claim 1, wherein each mirror plate has an area;

and

wherein a ratio of a summation of all areas of the mirror plates to an area of the substrate is 90 percent or more.

21. The spatial light modulator of claim 1, wherein each mirror plate rotate relative to the substrate in response to an electrostatic field.

22. The spatial light modulator of claim 1, further comprising:

a first electrode that drives the mirror plate rotate in a first rotation direction relative to the substrate; and

a second electrode that drives the mirror plate rotate in a second rotation direction opposite to the first rotation direction relative to the substrate.

23. The spatial light modulator of claim 22, wherein the first electrode and the second electrode are on the same side relative to the rotation axis of the mirror plate.

24. The spatial light modulator of claim 22 wherein the first electrode and the second electrode are on the opposite sides relative to the rotation axis of the mirror plate.

25. The spatial light modulator of claim 1, wherein the substrate is semiconductor.

26. The spatial light modulator of claim 1, wherein the gap between the adjacent mirror plates is from 0.15 to 0.25 micrometers.

27. The spatial light modulator of claim 1, wherein the gap between the adjacent mirror plates is from 0.25 to 0.5 micrometers.

28. The spatial light modulator of claim 1, wherein the gap between the adjacent mirror plates is 0.5 micrometers or less.

29. The spatial light modulator of claim 1, wherein the distance between the hinge and the mirror plate is from 0.15 to 0.25 micrometers.

30. The spatial light modulator of claim 1, wherein the mirror plate is attached to a hinge such that the mirror plate rotates in a first direction to an angle from 15°

degrees to 27°

degrees relative to the substrate.

31. The spatial light modulator of claim 30, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

32. The spatial light modulator of claim 1, wherein the mirror plate is attached to a hinge such that the mirror plate rotates in a first direction to an angle from 17.5°

degrees to 22.5°

degrees relative to the substrate.

33. The spatial light modulator of claim 30, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

34. The spatial light modulator of claim 1, wherein the mirror plate is attached to a hinge such that the mirror plate rotates in a first direction to an angle around 20°

degrees relative to the substrate.

35. The spatial light modulator of claim 34, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

36. The spatial light modulator of claim 1, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle around 30°

degrees relative to the substrate.

37. The spatial light modulator of claim 36, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

38. The spatial light modulator of claim 3, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first rotation direction to an angle from 12°

degrees to 20°

degrees relative to the substrate.

39. The spatial light modulator of claim 38, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

40. The spatial light modulator of claim 2, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first rotation direction to an angle from 12°

degrees to 20°

degrees relative to the substrate.

41. The spatial light modulator of claim 40, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

42. The spatial light modulator of claim 3, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first rotation direction to an angle from 12°

degrees to 20°

degrees relative to the substrate; and

wherein the hinge and the mirror plate is spaced apart from 0.5 to 1.5 micrometers.

43. The spatial light modulator of claim 40, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

44. The spatial light modulator of claim 1, wherein each mirror plate is held on the substrate via a hinge that is separated from the respective mirror plate by a gap.

45. The spatial light modulator of claim 1, wherein the gap between the mirror plate and hinge is from 0.15 to 1.5 micrometers.

46. The spatial light modulator of claim 45, wherein the gap between the mirror plate and hinge is from 0.15 to 0.45 micrometers.

47. The spatial light modulator of claim 46, wherein the gap between the mirror plate and hinge is from 0.5 to 1.5 micrometers.

48. A projection system, comprising:

a light source;

the spatial light modulator of claim 1;

a first lens for directing light from the light source onto the spatial light modulator; and

a second lens for directing light reflected from the spatial light modulator onto a display target.

49. The system of claim 48, wherein the light source is an arc lamp having an effective arc length around 1.0 millimeter.

50. The system of claim 48, wherein the light source is an arc lamp having an effective arc length less than 1.0 millimeter.

51. The system of claim 48, wherein the light source is an arc lamp having an effective arc length around 0.7 millimeter.

52. The system of claim 48, further comprising:

a video signal input that inputs a plurality of video signals, based on which the mirror plates of the spatial light modulator selectively reflects light such that the reflected light from the mirror plates forms a plurality of videos on the display target.