Methods and apparatus for spatial light modulation

• US 20070159679A1
• Filed: 02/28/2007
• Published: 07/12/2007
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Barton, Roger, Payne, Richard, Steyn, Jasper, Hagood, Nesbitt
• Granted Patent: US 7,365,897 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0078 Side-by-side arrangements, e.g. for large area displays

Abstract

Improved apparatus and methods for spatial light modulation are disclosed which utilize optical cavities having both front and rear reflective surfaces. Light-transmissive regions are formed in the front reflective surface for spatially modulating light.

Claims

1. A display apparatus having a front, comprising:

a first reflective surface defining a plurality of light-transmissive regions for reflecting light away from the front of the display apparatus,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the front of the display apparatus, and

an array of light modulators, positioned between the second reflective surface and the front of the display apparatus, for forming a plurality of display pixels by selectively obstructing respective light-transmissive regions defined by the first reflective surface, wherein light modulators in the array of light modulators correspond to respective light-transmissive regions.

2. The display apparatus of claim 1, wherein light modulators in the array of light modulators correspond one-to-one to light-transmissive regions of the plurality of light-transmissive regions.

3. The display apparatus of claim 1, wherein the array is separated from the first reflective surface by a gap, which is less than or equal to about 100 μ

m wide.

4. The display apparatus of claim 1, wherein the array is separated from the first reflective surface by a gap, which is less than or equal to about 10 μ

m wide.

5. The display apparatus of claim 1, wherein the array is separated from the first reflective surface by a gap, which is less than or equal to about 1 μ

m wide.

6. The display apparatus of claim 1, comprising a spacer for keeping the array at about a predetermined distance from the first reflective surface, thereby forming a gap.

7. The display apparatus of claim 1, comprising a fluid at least partially filling a gap maintained between the first reflective surface and the array.

8. The display apparatus of claim 7, wherein the fluid comprises a liquid.

9. The display apparatus of claim 8, wherein the liquid comprises a lubricant.

10. The display apparatus of claim 8, wherein the light modulators comprise MEMS light modulators and the liquid at least partially surrounds the MEMS light modulators

11. The display apparatus of claim 1, wherein light modulators in the array of light modulators comprise liquid crystal components.

12. The display apparatus of claim 1, wherein light modulators in the array of light modulators are independently controllable.

13. The display apparatus of claim 1, wherein light modulators in the array of light modulators are collectively controllable.

14. The display apparatus of claim 1, wherein light modulators in the array of light modulators comprise MEMS light modulators.

15. The display apparatus of claim 1, wherein the array of light modulators comprises a plurality of shutters arranged in a plane, at least one of the shutters having a first position substantially in the plane that does not obstruct light reflected from the second reflective surface and a second position substantially in the plane to obstruct light reflected from the second reflective surface.

16. The display apparatus of claim 1, wherein the array of light modulators comprises a plurality of shutters arranged in a plane, at least one of the shutters having a first position substantially in the plane to obstruct light reflected from the second reflective surface and a second position, in which at least part of the shutter is substantially out of the plane, that does not obstruct light reflected from the second reflective surface.

17. The display apparatus of claim 1, wherein the first and second reflective surfaces have a space therebetween that defines a substantially transparent cavity.

18. The display apparatus of claim 1, wherein the first reflective surface is substantially parallel to and opposes the second reflective surface.

19. The display apparatus of claim 1, wherein the first reflective surface is at least partially transverse with respect to the second reflective surface.

20. The display apparatus of claim 1, comprising a light guide positioned between the first and second reflective surfaces.

21. The display apparatus of claim 20, wherein the first reflective surface is substantially parallel to a front surface of the light guide.

22. The display apparatus of claim 20, wherein the first reflective surface is disposed on the front surface of the light guide.

23. The display apparatus of claim 20, comprising a dielectric layer disposed between the light guide and the first reflective surface.

24. The display apparatus of claim 23, wherein the light guide has a first refractive index and the dielectric layer has a refractive index less than that of the first refractive index.

25. The display apparatus of claim 20, wherein the array is formed on the light guide.

26. The display apparatus of claim 25 comprising a cover plate separated from the light guide by a gap.

27. The display apparatus of claim 20, wherein the second reflective surface is disposed on a side of the light guide which is opposite to a side of the light guide nearest the first reflective surface.

28. The display apparatus of claim 1, comprising a substrate on which the first reflective surface is disposed.

29. The display apparatus of claim 28, wherein the substrate is substantially transparent.

30. The display apparatus of claim 28, comprising a light guide positioned between the first reflective surface and the second reflective surface, and wherein the substrate is in contact with the light guide.

31. The display apparatus of claim 28, comprising a light guide positioned between the first reflective surface and the second reflective surface, and wherein the substrate is separated from the light guide by a gap.

32. The display apparatus of claim 31, wherein the gap between the light guide and the substrate is filled with a fluid.

33. The display apparatus of claim 32, wherein the fluid comprises a gas.

34. The display apparatus of claim 28, wherein the array is formed on the substrate.

35. The display apparatus of claim 34, comprising a cover plate separated from the substrate by a gap.

36. The display apparatus of claim 35, wherein the gap between the substrate and the cover plate is filled with a fluid.

37. The display apparatus of claim 36, wherein the fluid comprises a lubricant.

38. The display apparatus of claim 36, wherein the fluid has a first index of refraction and the substrate has a second index of refraction, and wherein the first index of refraction substantially matches that of the second index of refraction.

39. The display apparatus of claim 1, comprising a substrate on which the array is formed.

40. The display apparatus of claim 39, wherein the substrate is substantially transparent.

41. The display apparatus of claim 39, wherein the array is formed on a side of the substrate facing away from the front of the display apparatus.

42. The display apparatus of claim 39, comprising a second substrate positioned between the array and the second reflective surface and on which the first reflective surface is disposed.

43. The display apparatus of claim 42, wherein the second substrate comprises a light guide

44. The display apparatus of claim 42, wherein the substrate on which the array is formed and the substrate on which the first reflective surface is formed are separated by a gap.

45. The display apparatus of claim 44, wherein the gap is at least partially filled with a fluid.

46. The display apparatus of claim 45, wherein the fluid is a liquid.

47. The display apparatus of claim 46, wherein the fluid comprises a lubricant.

48. The display apparatus of claim 45, wherein the fluid has a first index of refraction and the second substrate has a second index of refraction, and wherein the first index of refraction substantially matches that of the second index of refraction

49. The display apparatus of claim 1, wherein the first reflective surface comprises a metallic film.

50. The display apparatus of claim 1, wherein the first reflective surface comprises a dielectric film

51. The display apparatus of claim 1, wherein the first reflective surface comprises a dielectric mirror.

52. The display apparatus of claim 1, comprising a light source for illuminating pixels on the display apparatus.

53. The display apparatus of claim 1, wherein at least one of the light-transmissive regions has a corresponding filter.

54. The display apparatus of claim 1, wherein the modulators comprise MEMS-based shutter assemblies at least partially coated in a reflective film for reflecting light impinging on the shutters from the second reflective surface, back towards the second reflective surface.

55. The display apparatus of claim 1, wherein the modulators comprise MEMS-based shutter assemblies at least partially coated in a light-absorbing film to absorb ambient light.

56. The display apparatus of claim 1, comprising an active matrix for controlling the light modulators in the array.

57. A spatial light modulator having a front, comprising:

a first reflective surface defining a plurality of light-transmissive regions for reflecting light away from the front of the spatial light modulator,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the front of the spatial light modulator, and

an array of light modulators, positioned between the second reflective surface and the front of the display apparatus, for selectively obstructing light-transmissive regions defined by the first reflective surface, wherein the array of light modulators is separated from the first reflective surface by a gap that is less than about 100 μ

m wide.

58. The spatial light modulator of claim 57, wherein the gap is less than about 10 μ

m wide.

59. The spatial light modulator of claim 57, wherein the gap is less than about 1 μ

m wide.

60. The spatial light modulator of claim 57, comprising a spacer for keeping the array at about a predetermined distance from the first reflective surface, thereby forming a gap.

61. The spatial light modulator of claim 57, wherein light modulators in the array of light modulators correspond to respective light-transmissive regions defined by the first reflective surface.

62. The spatial light modulator of claim 57, wherein the spatial light modulator comprises a portion of a display apparatus and light modulators in the array of light modulators selectively obstruct the light-transmissive regions defined by the first reflective surface to form a plurality of display pixels on the display apparatus.

63. The spatial light modulator of claim 57, wherein light modulators in the array of light modulators comprise MEMS light modulators.