Methods and apparatus for spatial light modulation

• US 7,417,782 B2
• Filed: 09/02/2005
• Issued: 08/26/2008
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Barton, Roger, Hagood, Nesbitt W.
• Primary Examiner(s): Choi; William C
• Application Number:
  US11/218,690
• Publication Number:
  US 20060187528A1
• Time in Patent Office: 1,089 Days
• Field of Search: 359/198, 359/214, 359/224, 359/290, 359/295, 359/230
• US Class Current: 359/290
• 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 comprising:

a first reflective surface defining a plurality of light-transmissive regions,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the plurality of light-transmissive regions,

a light guide for distributing light substantially throughout a cavity formed between the first and second reflective surfaces, and

an array of light modulators for selectively obstructing the plurality of light-transmissive regions thereby forming pixels on the display apparatus, wherein the array of light modulators is separated from the first reflective surface by a gap, wherein the gap is less than about 100 μ

m wide.

2. The display apparatus of claim 1, wherein one of the reflective surfaces is formed from one of a mirror, a dielectric mirror, and a metallic film.

3. The display apparatus of claim 1, wherein at least one of the light-transmissive regions comprises an aperture.

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

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

6. The display apparatus of claim 1, wherein the light modulators in the array of light modulators are one of independently and collectively controllable.

7. The display apparatus of claim 1, wherein the space between the first and second reflective surfaces defines a substantially transparent cavity.

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

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

10. 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 allowing the passage of light through a corresponding one of the plurality of light-transmissive regions and a second position substantially in the plane to obstruct light reflected from second reflective surface.

11. The display apparatus of claim 1, wherein the first reflective surface is disposed on the surface of the light guide.

12. The display apparatus of claim 11, comprising a substrate on which the array of light modulators is disposed.

13. The display apparatus of claim 12, wherein the substrate is substantially transparent.

14. The display apparatus of claim 12, wherein:

the substrate is substantially opaque; and

the substrate defines a plurality of apertures corresponding to the plurality of light-transmissive regions in the first reflective surface.

15. The display apparatus of claim 12, comprising a spacer for maintaining the gap.

16. The display apparatus of claim 15, comprising a fluid filling the gap.

17. The display apparatus of claim 12, wherein the light guide is coupled to the substrate.

18. The display apparatus of claim 1, comprising a substrate upon which the first reflective surface and the array of light modulators are disposed.

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

20. The display apparatus of claim 1, 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.

21. The display apparatus of claim 1, wherein the light guide comprises a plurality of scattering points for redirecting light out of the light guide.

22. The display apparatus of claim 1, comprising a light source for introducing light into the light guide.

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

24. The display apparatus of claim 23, wherein the MEMS light modulators comprise shutters having a roughened surface to absorb ambient light.

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

26. The display apparatus of claim 25, wherein the substrate is substantially transparent.

27. The display apparatus of claim 25, comprising a spacer for keeping the light guide and the substrate a predetermined distance apart from one another, thereby forming a gap.

28. The display apparatus of claim 27, comprising a fluid filling the gap between the substrate and the light guide.

29. The display apparatus of claim 1, wherein the is less than or equal to about 10 μ

m wide.

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

31. The display apparatus of claim 1, wherein the light guide has a first refractive index, the display apparatus further comprising a film having a refractive less than the first refractive index positioned between the light guide and the first reflective surface.

32. A display apparatus comprising:

a first reflective surface defining a plurality of light-transmissive regions,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the plurality of light-transmissive regions,

a light guide for distributing light substantially throughout a cavity formed between the first and second reflective surfaces, and

an array of light modulators for selectively obstructing the plurality of light-transmissive regions thereby forming pixels on the display apparatus, wherein light modulators in the array of light modulators correspond to respective light-transmissive regions of the plurality of light-transmissive regions.

33. The display apparatus of claim 32, wherein one of the reflective surfaces is formed from one of a mirror, a dielectric mirror, and a metallic film.

34. The display apparatus of claim 32, wherein at least one of the light-transmissive regions comprises an aperture.

35. The display apparatus of claim 32, wherein at least one of the light-transmissive regions has a corresponding filter.

36. The display apparatus of claim 32, wherein the light modulators in the array of light modulators comprise liquid crystal components.

37. The display apparatus of claim 32, wherein the light modulators in the array of light modulators are one of independently and collectively controllable.

38. The display apparatus of claim 32, wherein the space between the first and second reflective surfaces defines a substantially transparent cavity.

39. The display apparatus of claim 32, wherein the first reflective surface is substantially parallel to, and opposes the second reflective surface.

40. The display apparatus of claim 32, wherein the first reflective surface is at least partially transverse with respect to the second reflective surface.

41. The display apparatus of claim 32, 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 allowing the passage of light through a corresponding one of the plurality of light-transmissive regions and a second position substantially in the plane to obstruct light reflected from the second reflective surface.

42. The display apparatus of claim 32, 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 to allow the passage of light through the corresponding one of the plurality of light-transmissive regions.

43. The display apparatus of claim 32, wherein the first reflective surface is disposed on the surface of the light guide.

44. The display apparatus of claim 43, comprising a substrate on which the array of light modulators is disposed.

45. The display apparatus of claim 44, wherein the substrate is substantially transparent.

46. The display apparatus of claim 45, wherein:

the substrate is substantially opaque; and

the substrate defines a plurality of apertures corresponding to the plurality of light-transmissive regions in the first reflective surface.

47. The display apparatus of claim 45, comprising a spacer for keeping the light guide and the substrate a predetermined distance apart from one another, thereby forming a gap.

48. The display apparatus of claim 47, comprising a fluid filling the gap between the substrate and the light guide.

49. The display apparatus of claim 45, wherein the light guide is coupled to the substrate.

50. The display apparatus of claim 32, comprising a substrate upon which the first reflective surface and an array of light modulators are disposed.

51. The display apparatus of claim 32, wherein the first reflective surface comprises a reflective film.

52. The display apparatus of claim 32, 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.

53. The display apparatus of claim 32, wherein the light guide comprises a plurality of scattering points for redirecting light out of the light guide.

54. The display apparatus of claim 32, comprising a light source for introducing light into the light guide.

55. The display apparatus of claim 32, wherein the light modulators in the array of light modulators comprise MEMS light modulators.

56. The display apparatus of claim 55, wherein the MEMS light modulators comprise shutters having a roughened surface to absorb ambient light.

57. The display apparatus of claim 32, comprising a substrate upon which the first reflective surface is disposed.

58. The display apparatus of claim 57, wherein the substrate is substantially transparent.

59. The display apparatus of claim 57, comprising a spacer for keeping the light guide and the substrate a predetermined distance apart from one another, thereby forming a gap.

60. The display apparatus of claim 59, comprising a fluid filling the gap between the substrate and the light guide.

61. The display apparatus of claim 32, 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.

62. The display apparatus of claim 32, wherein the first reflective surface comprises a dielectric film.

63. The display apparatus of claim 32, wherein the light guide has a first refractive index, the display apparatus further comprising a film having a refractive less than the first refractive index positioned between the light guide and the first reflective surface.

64. A display apparatus comprising:

a first reflective layer defining a plurality of light-transmissive regions,

a second reflective layer, at least partially facing the first reflective layer, for reflecting light towards the plurality of light-transmissive regions,

a light guide for distributing light substantially throughout a cavity formed between the first and second reflective layers to illuminate pixels of the display apparatus, wherein the first reflective layer is deposited directly on a surface of the light guide.

65. A spatial light modulator comprising:

a first reflective surface defining a plurality of light-transmissive regions,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the plurality of light-transmissive regions, and

an array of liquid crystal light modulators for selectively obstructing the plurality of light-transmissive regions, wherein light modulators in the array of light modulators correspond to respective light-transmissive regions of the plurality of light-transmissive regions.

66. A spatial light modulator comprising:

a first reflective surface defining a plurality of light-transmissive regions,

a second reflective surface, at least partially facing the first reflective surface, for reflecting light towards the plurality of light-transmissive regions, and

an array of liquid crystal light modulators for selectively obstructing the plurality of light-transmissive regions, wherein the first reflective surface is substantially parallel to the array of liquid crystal light modulators.