Methods and apparatus for spatial light modulation

• US 20060187528A1
• Filed: 09/02/2005
• Published: 08/24/2006
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Barton, Roger W., Hagood, Nesbitt W.
• Granted Patent: US 7,417,782 B2
• Time in Patent Office: Days
• US Class Current: 359/298
• 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 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.

2. The spatial light modulator of claim 1, comprising

an array of light modulators for selectively obstructing the plurality of light-transmissive regions.

3. The spatial light modulator of claim 1, wherein one of the reflective surfaces is formed from one of a mirror, a dielectric mirror, and a metallic film.

4. The spatial light modulator of claim 1, wherein at least one of the light-transmissive regions comprises an aperture.

5. The spatial light modulator of claim 1, wherein at least one of the light-transmissive regions comprises a filter.

6. The spatial light modulator of claim 1, wherein at least one of the light-transmissive regions comprises a liquid crystal component.

7. The spatial light modulator of claim 2, wherein the light modulators in the array of light modulators are one of independently and collectively controllable.

8. The spatial light modulator of claim 2, wherein the array of light modulators comprises a plurality of MEMS-based shutters assemblies.

9. The spatial light modulator of claim 8, wherein the MEMS-based shutter assemblies are bi-stable shutter assemblies.

10. The spatial light modulator of claim 8, wherein the MEMS-based shutter assemblies comprise shutters at least partially coated in a reflective film for reflecting light impinging on the shutters, reflected from the second reflective surface, back towards the second reflective surface.

11. The spatial light modulator of claim 8, wherein the MEMS-based shutter assemblies comprise shutters at least partially coated in a light-absorbing film to absorb ambient light or roughened surface.

12. The spatial light modulator of claim 1, wherein the space between the first and second reflective surfaces defines a substantially transparent cavity.

13. The spatial light modulator of claim 1, wherein the first reflective surface is substantially parallel to, and opposes the second reflective surface.

14. The spatial light modulator of claim 1, wherein the first reflective surface is at least partially transverse with respect to the second reflective surface.

15. The spatial light modulator of claim 2, 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.

16. The spatial light modulator of claim 2, 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.

17. The spatial light modulator of claim 1, comprising a light guide for distributing light substantially throughout a cavity formed between the first and second reflective surfaces.

18. The spatial light modulator of claim 17, wherein the first reflective surface is disposed on the surface of the light guide.

19. The spatial light modulator of claim 18, comprising a substrate on which the array of light modulators is disposed.

20. The spatial light modulator of claim 19, wherein the substrate is substantially transparent.

21. The spatial light modulator of claim 19, 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.

22. The spatial light modulator of claim 19, comprising a spacer for keeping the light guide and the substrate a predetermined distance apart from one another, thereby forming a gap.

23. The spatial light modulator of claim 19, wherein the light guide is coupled to the substrate.

24. The spatial light modulator of claim 17, comprising a substrate upon which the first reflective surface and the array of light modulators are disposed.

25. The spatial light modulator of claim 24, wherein the first reflective surface comprises a reflective film.

26. The spatial light modulator of claim 24, comprising an optical diffuser positioned between the light guide and the substrate.

27. The spatial light modulator of claim 24, comprising an optical prism positioned between the light guide and the substrate.

28. The spatial light modulator of claim 17, 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.

29. The spatial light modulator of claim 17, wherein the light guide comprises a plurality of scattering points for redirecting light out of the light guide.

30. The spatial light modulator of claim 2, wherein the array of light modulators comprises liquid crystal component.

31. The spatial light modulator of claim 12, comprising a light source for introducing light into the substantially transparent cavity.

32. The spatial light modulator of claim 31, wherein the light source comprises a light emitting diode.

33. The spatial light modulator of claim 31, comprising an array of light modulators for selectively obstructing light from passing through at least one of the light-transmissive regions.

34. The spatial light modulator of claim 33, wherein the array of light modulators comprises an array of MEMS-based shutter assemblies.

36. The method of claim 33, comprising distributing the introduced light substantially evenly throughout the reflective cavity.

35. A method of forming an image, comprising:

introducing light into a reflective optical cavity including a plurality of light-transmissive regions through which light can escape the reflective optical cavity;

forming an image by allowing the introduced light to escape the reflective optical cavity through at least one of the light-transmissive regions.

37. The method of claim 35, wherein introducing the light comprises alternately illuminating a plurality different colored light sources.

38. The method of claim 35, comprising selectively obstructing at least one light-transmissive region to prevent light from escaping the reflective cavity through the at least one light-transmissive region.

39. The method of claim 38, wherein the selectively obstructing comprises altering a voltage applied to a light modulator.

40. The method of claim 39, wherein the light modulator comprises a MEMS-based shutter assembly.

41. The method of claim 39, wherein the light modulator comprises a liquid crystal component.

42. The method of claim 35, wherein allowing the introduced light to escape the reflective cavity comprises removing at least one obstruction preventing the introduced light from escaping the reflective cavity through corresponding ones of the light-transmissive regions.

43. The method of claim 42, comprising selectively reflecting ambient light impinging on the corresponding ones of the light-transmissive regions through which the introduced light is allowed to escape.

44. The method of claim 35, wherein at least one light-transmissive region comprises an aperture.

45. The method of claim 35, wherein at least one light-transmissive region comprises a filter.

46. The method of claim 35, wherein at least one light-transmissive region comprises a liquid crystal component.

47. The method of claim 35, wherein the reflective cavity comprises a first reflective surface including the plurality of light-transmissive regions and a second reflective surface at least partially facing the first reflective surface.

48. The method of claim 35, comprising introducing the introduced light into a light guide substantially contained within the reflective cavity.

49. A method of forming an image, comprising:

receiving ambient light;

positioning a plurality of shutters on at least one substrate to selectively reflect the received ambient light to form the image.

50. A method of manufacturing a spatial light modulator comprising:

forming a substantially transparent cavity having first and second opposing sides into which light can be introduced;

coupling a first reflective surface to the first side of the transparent cavity such that the first reflective surface faces the interior of the transparent cavity;

forming a plurality of light-transmissive regions in the first reflective surface; and

coupling a second reflective surface to the second side of the transparent cavity such that the second reflective surface faces the interior transparent cavity.