DEVICES AND METHODS FOR ENHANCING BRIGHTNESS OF DISPLAYS USING ANGLE CONVERSION LAYERS

• US 20090201565A1
• Filed: 02/11/2009
• Published: 08/13/2009
• Est. Priority Date: 02/12/2008
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gruhlke, Russell W., Mienko, Marek, Xu, Gang, Bita, Ion, Wang, Lai
• Granted Patent: US 8,040,589 B2
• Time in Patent Office: Days
• US Class Current: 359/290
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer

Abstract

Various embodiments of the present invention relate to enhancing the brightness of displays that employ illumination systems. In some embodiments, the illumination systems include light guides, diffractive microstructure, and light-turning features. The diffractive microstructure may be configured to receive ambient light at a first angle and produce diffracted light at a second angle greater than the first angle and greater than the critical angle for of light guide. The light is thereby guided within the light guide. The light-turning features may be configured to turn the light guided within the light guide out of a light guide and onto, for example, a spatial light modulator at near normal incidence.

Claims

1. An illumination apparatus comprising:

a light guide that guides light propagating therein at an angle greater than a critical angle for the light guide and ejects light from the light guide to provide illumination;

diffractive microstructure disposed to receive ambient light at a first angle smaller than said critical angle and to diffract said ambient light to produce diffracted light at a second larger angle; and

light-turning features configured to turn the diffracted light and direct the turned light out of the light guide.

2. The illumination apparatus of claim 1, wherein said diffracting comprises reflective diffraction.

3. The illumination apparatus of claim 1, wherein said diffracting comprises transmissive diffraction.

4. The illumination apparatus of claim 1, wherein said light guide comprises a plate, sheet, or film.

5. The illumination apparatus of claim 2, wherein said light guide comprises glass or plastic.

6. The illumination apparatus of claim 1, wherein said diffractive microstructure comprise surface or volume features.

7. The illumination apparatus of claim 1, further comprising a holographic layer comprising said diffractive microstructure.

8. The illumination apparatus of claim 1, further comprising a surface diffractive layer comprising said diffractive microstructure and a planarization layer thereon.

9. The illumination apparatus of claim 8, wherein a refractive index of said planarization layer differs from a refractive index of said diffractive layer.

10. The illumination apparatus of claim 8, wherein a refractive index of said planarization layer is greater than a refractive index of said diffractive layer.

11. The illumination apparatus of claim 1, wherein the second angle is greater than said critical angle of the light guide.

12. The illumination apparatus of claim 1, wherein said light-turning features comprise prismatic or diffractive features.

13. The illumination apparatus of claim 1, wherein said light-turning features are shaped and oriented to turn the diffracted light such that the turned light is directed out of the light guide.

14. The illumination apparatus of claim 1, wherein the ambient light is transmitted through said light-turning features prior to being received by said diffractive microstructure.

15. The illumination apparatus of claim 1, further comprising a light-turning layer comprising said light-turning features, and a diffractive layer comprising said diffractive microstructure.

16. The illumination apparatus of claim 15, wherein the light-turning layer is positioned over the diffractive layer.

17. The illumination apparatus of claim 15, wherein the light-turning layer is physically separated by one or more separation layers from the diffractive layer.

18. The illumination apparatus of claim 15, wherein the refractive index of the light-turning layer is higher than the refractive index of the diffractive layer.

19. The illumination apparatus of claim 15, further comprising an isolation layer positioned below the diffractive layer, wherein the index of refraction the isolation layer is less than the index of refraction of a layer positioned on the isolation layer.

20. The illumination apparatus of claim 1, further comprising a substrate.

21. The illumination apparatus of claim 1, wherein said illumination apparatus comprises a light-turning layer comprising said light-turning features, a diffractive layer comprising said diffractive microstructure, and a substrate.

22. The illumination apparatus of claim 1, wherein the illumination apparatus is disposed with respect to a spatial light modulator such that light ejected therefrom illuminates said spatial light modulator.

23. The illumination apparatus of claim 22, wherein said spatial light modulator comprises a MEMS device.

24. The illumination apparatus of claim 23, wherein said MEMS device comprises interferometric modulators.

25. The illumination apparatus of claim 23, wherein said MEMS comprises first and second reflective surfaces, one of which is movable with respect to the other.

26. The illumination apparatus of claim 22, further comprising:

a processor that is configured to communicate with said spatial light modulator, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

27. The illumination apparatus of claim 26, further comprising a driver circuit configured to send at least one signal to the spatial light modulator.

28. The illumination apparatus of claim 27, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

29. The illumination apparatus of claim 26, further comprising an image source module configured to send said image data to said processor.

30. The illumination apparatus of claim 29, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

31. The illumination apparatus of claim 26, further comprising an input device configured to receive input data and to communicate said input data to said processor.

32. A method of manufacturing an illumination apparatus comprising:

providing a light guide that guides light propagating therein at an angle greater than a critical angle for the light guide and ejects light therefrom to provide illumination;

disposing diffractive microstructure to receive ambient light at a first angle smaller than said critical angle and to diffract said ambient light to produce diffracted light at a second larger angle; and

providing light-turning features configured to turn the diffracted light and direct the turned light out of the light guide.

33. The method of manufacturing of claim 32, wherein the second angle is greater than said critical angle of the light guide.

34. The method of manufacturing of claim 32, wherein disposing diffractive microstructure comprises providing a diffractive layer comprising the diffractive microstructure, and wherein providing light-turning features comprises providing a light-turning layer comprising the light-turning features.

35. The method of manufacturing of claim 34, wherein the diffractive layer comprises a holographic layer.

36. The method of manufacturing of claim 34, further comprising disposing the light-turning layer over the diffractive layer.

37. The method of manufacturing of claim 36, further comprising disposing the diffractive layer over a substrate.

38. The method of manufacturing of claim 34, further comprising disposing one or more separation layers over the diffractive layer;

and disposing the light-turning layer over the one or more separation layers.

39. The method of manufacturing of claim 32, further comprising disposing said illumination apparatus with respect to a spatial light modulator such that light ejected therefrom illuminates said spatial light modulator.

40. The method of manufacturing of claim 39, wherein said spatial light modulator comprises a MEMS device.

41. The method of manufacturing of claim 40, wherein said MEMS device comprises interferometric modulators.

42. The method of manufacturing of claim 39, further comprising forming the spatial light modulator.

43. The method of manufacturing of claim 42, wherein forming the spatial modulator comprises forming a first reflective surface, and forming a second movable reflective surface.

44. A illumination system fabricated by the method of claim 32.

45. An illumination apparatus comprising:

means for guiding light propagating therein at an angle greater than a critical angle for the light guiding means and ejecting light from the light guiding means to provide illumination;

means for diffracting ambient light received at a first angle smaller than said critical angle to produce diffracted light at a second larger angle; and

means for turning the diffracted light and directing the turned light out of said light guiding means.

46. The MEMS device of claim 45, wherein means for guiding light propagating therein at an angle greater than a critical angle for the light guiding means and ejecting light from the light guiding means to provide illumination comprises a light guide.

47. The MEMS device of claim 45, wherein means for diffracting ambient light received at a first angle smaller than said critical angle to produce diffracted light at a second angle larger angle comprises a diffractive microstructure.

48. The MEMS device of claim 45, wherein means for diffracting ambient light received at a first angle smaller than said critical angle to produce diffracted light at a second angle larger angle comprises a holographic layer.

49. The MEMS device of claim 45, wherein means for turning the diffracted light and directing the turned light out of said light guide comprises light-turning features.

50. An illumination apparatus comprising:

a light guide that guides light propagating therein at an angle greater than a critical angle for the light guide and ejects light from the light guide to provide illumination; and

an angle converting structure disposed to receive ambient light at a first angle greater than said critical angle and to diffract said ambient light to produce diffracted light at a second smaller angle,

wherein said angle converting structure comprises at least one of a diffractive and holographic layer.

51. The illumination apparatus of claim 50, wherein said angle converting structure comprises a diffractive layer.

52. The illumination apparatus of claim 50, wherein said angle converting structure comprises diffractive microstructure.