Methods and apparatus for spatial light modulation

• US 20070091038A1
• Filed: 11/06/2006
• Published: 04/26/2007
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Payne, Richard, Hagood, Nesbitt, Stein, Jasper
• Granted Patent: US 7,619,806 B2
• Time in Patent Office: Days
• US Class Current: 345/85
• 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 layer of reflective material;

an array of MEMS-based light modulators positioned proximate the layer of reflective material, wherein each of the MEMS-based light modulators includes a modulation element and an actuator for moving the modulation element relative to the layer of reflective material.

2. The display apparatus of claim 1, comprising a plurality of apertures formed in the layer of reflective material for allowing light to pass through the layer of reflective material.

3. The display apparatus of claim 2, wherein the modulation element comprises a shutter for selectively obstructing at least one of the plurality of apertures.

4. The display apparatus of claim 2, wherein the each aperture of the plurality of apertures corresponds to one of the MEMS-based light modulators.

5. The display apparatus of claim 2, comprising a spacer disposed between the layer of reflective material and the array to keep the modulation elements about a predetermined distance from the layer of reflective material.

6. The display apparatus of claim 1, wherein the modulation elements of the MEMS-based light modulators are maintained less than about 100 microns away from the layer of reflective material.

7. The display apparatus of claim 1, wherein the modulation elements of the MEMS-based light modulators are maintained less than about 10 microns away from the layer of reflective material.

8. The display apparatus of claim 1 the modulation elements of the MEMS-based light modulators are maintained less than about 10 microns away from the layer of reflective material.

9. The display apparatus of claim 1, wherein the layer of reflective material reflects light impinging on a surface of the layer of reflective material facing away from the array of MEMS-based light modulators.

10. The display apparatus of claim 9, wherein the layer of reflective material absorbs light impinging on a surface of the layer of reflective material facing towards from the array of MEMS-based light modulators.

11. The display apparatus of claim 9, comprising a second layer of reflective material positioned on an opposite side of the layer of reflective material from the MEMS-based light modulators, and facing towards the layer of reflective materials.

12. The display apparatus of claim 11, comprising a light guide positioned between the layer of reflective material and the second layer of reflective material.

13. The display apparatus of claim 1, comprising a liquid located at least between the modulation elements and the layer of reflective material.

14. The display apparatus of claim 13, wherein the liquid is a lubricant.

15. The display apparatus of claim 1, wherein the layer of reflective material comprises a dielectric mirror.

16. The display apparatus of claim 1, wherein the layer of reflective material comprises a metal.

17. A display apparatus comprising:

an array of MEMS-based light modulators;

a liquid in which the array of MEMS-based light modulators is at least partially immersed.

18. The display apparatus of claim 17, comprising a transparent substrate on which the array of MEMS-based light modulators are formed.

19. The display apparatus of claim 18, wherein the liquid is sealed into a cavity formed between the substrate and a transparent body.

20. The display apparatus of claim 19, wherein the transparent substrate is spaced away from and opposite to the transparent body and the fluid fills a gap existing between the MEMS-based light modulators and the transparent body.

21. The display apparatus of claim 19, wherein the transparent body comprises a cover plate.

22. The display apparatus of claim 21, wherein the liquid has a first index of refraction, the substrate has a second index of refraction, and wherein the first index of refraction substantially matches the second index of refraction.

23. The display apparatus of claim 19, wherein the liquid has a first index of refraction, the transparent body has a second index of refraction, and wherein the first index of refraction substantially matches the second index of refraction.

24. The display apparatus of claim 23, wherein the transparent body comprises a light guide.

25. This display apparatus of claim 17, wherein the liquid has an index of refraction of less than about 1.5.

26. The display apparatus of claim 17, wherein the liquid has a dielectric constant of above about 2.0.

27. The display apparatus of claim 17, wherein the liquid is a lubricant.

28. The display apparatus of claim 17, wherein the liquid has a viscosity below about 10 centipoise.

29. The display apparatus of claim 17, wherein the liquid has a dielectric breakdown strength above about 104 V/cm.

30. The display apparatus of claim 17, wherein the liquid reduces stiction between surfaces of the MEMS-based light modulators when the surfaces are in contact.

31. The display apparatus of claim 17, wherein the liquid comprises one of de-ionized water, methanol, ethanol, silicone oils, fluorinated silicone oils, dimethylsiloxane, polydimethylsiloxane, hexamethyldisiloxane, and diethylbenzene.

32. The display apparatus of claim 17, wherein the MEMS-based light modulators in the array of MEMS-based light modulators comprises shutters.

33. The display apparatus of claim 32, comprising an aperture layer having a plurality of apertures formed therein positioned proximate the array of MEMS-based light modulators.

34. The display apparatus of claim 33, wherein the aperture layer comprises a reflective material.

35. The display apparatus of claim 33, wherein the aperture layer comprises one of a dielectric mirror and a metal.

36. The display apparatus of claim 33, wherein the shutters are positioned less than about 100 microns from the aperture layer.

37. The display apparatus of claim 33, wherein the shutters are positioned less than about 10 microns from the aperture layer.

38. A display apparatus comprising:

a light guide;

a substrate having a front surface facing an intended viewer and a rear surface facing the light guide, wherein the substrate is separated from the light guide by a gap; and

an array of MEMS-based light modulators formed on the rear substrate of the substrate.

39. The display apparatus of claim 38, comprising an aperture layer having a plurality of apertures formed therein positioned between the light guide and the substrate.

40. The display apparatus of claim 39, wherein the aperture layer comprises one of a dielectric mirror and a metal.

41. The display apparatus of claim 39, wherein the aperture layer is deposited on a front surface of the light guide.

42. The display apparatus of claim 39, wherein a side of the aperture layer facing the light guide is reflective.

43. The display apparatus of claim 42, comprising a second reflective layer facing the light guide positioned on a side of the light guide opposite the aperture layer.

44. The display apparatus of claim 39, comprising a plurality of spacers for keeping the substrate about a predetermined distance from the aperture layer.

45. The display apparatus of claim 44, wherein the spacers keep portions of the MEMS-based light modulators less than about 100 microns from the aperture layer.

46. The display apparatus of claim 44, wherein the spacers keep portions of the MEMS-based light modulators less than about 10 microns from the aperture layer.

47. The display apparatus of claim 39, wherein the array includes one MEMS-based light modulator corresponding to each aperture in the aperture layer.

48. The display apparatus of claim 39, wherein the MEMS-based light modulators comprise shutters and actuators for moving the shutters to selectively obstruct the apertures in the aperture layer.

49. The display apparatus of claim 48, wherein the actuators move the shutters substantially transversely with respect to the apertures.