Display apparatus with optical cavities

• US 20070279727A1
• Filed: 09/26/2006
• Published: 12/06/2007
• Est. Priority Date: 06/05/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Gandhi, Jignesh, Hagood, Nesbitt W., Barton, Roger W.
• Granted Patent: US 7,876,489 B2
• Time in Patent Office: Days
• US Class Current: 359/242
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• 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 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer

Abstract

A display includes an array of light modulators that define a display plane, a light guide and front- and rear-facing reflective surfaces. The light guide includes a plurality of geometric light redirectors, and at least 50% of the light guide'"'"'s rear surface is parallel to the display plane. The rear-facing reflective surface is parallel to the display plane and includes a plurality of apertures.

Claims

1. A display comprising:

an array of light modulators defining a display surface;

a light guide having front and rear surfaces and a plurality of geometric light redirectors formed therein;

a rear-facing reflective layer, positioned proximate to the display surface, wherein the rear-facing reflective surface has a plurality of apertures formed therein; and

a front-facing reflective layer positioned proximate the rear surface of the light guide.

2. The display of claim 1, wherein the array of light modulators comprises a plurality of MEMs-based light modulators for selectively allowing light passing through the plurality of apertures in the rear-facing reflective layer to contribute to the formation of an image.

3. The display of claim 1, wherein at least 50% of the rear surface of the light guide is substantially parallel to the display surface.

4. The display of claim 1, wherein at least 70% of the rear surface of the light guide is substantially parallel to the display surface.

5. The display of claim 1, wherein at least 90% of the rear surface of the light guide is substantially parallel to the display surface.

6. The display of claim 1, wherein the rear-facing reflective layer comprises a dielectric mirror.

7. The display of claim 1, wherein the rear-facing reflective layer comprises a metal layer.

8. The display of claim 1, wherein the rear-facing reflective layer is deposited on the front surface of the light guide.

9. The display of claim 1, comprising a refractive layer, having a refractive index less than that of a refractive index of the light guide, disposed between the rear-facing reflective layer and the front surface of the light guide.

10. The display of claim 1, wherein the light guide comprises a composite of at least first and second layers.

11. The display of claim 10, wherein the first layer of the light guide comprises one of glass and plastic.

12. The display of claim 11, wherein the second layer of the light guide comprises one of glass and plastic.

13. The display of claim 1, wherein the plurality of geometric light redirectors comprise substantially smooth reflective surfaces.

14. The display of claim 1, wherein the rear-facing and front-facing reflective layers comprise specular reflective layers.

15. The display of claim 1, wherein at least one of the front-facing and rear-facing reflective layers comprise substantially diffusive reflective material.

16. The display of claim 1, comprising a light injection system including a lamp and a light collimator for introducing a non-random fraction of light output by the lamp into the light guide collimated light within a predetermined range of angles.

17. The display of claim 1, comprising a prismatic turning film positioned between the light guide and the rear-facing reflective layer.

18. The display of claim 1, comprising a brightness enhancement film positioned between the light guide and the rear-facing reflective layer.

19. The display of claim 1, comprising a side-facing reflective layer positioned proximate to a side of the light guide.

20. The display of claim 1, wherein the plurality of geometric light redirectors comprise prismatic light redirectors.

21. The display of claim 20, wherein the prismatic light directors have a first surface facing a lamp and a second surface facing away from the lamp, wherein the area of the footprint of the first surface projected onto the front-facing reflective surface is greater than the area of the footprint of the second surface projected onto the front-facing reflective surface.

22. The display of claim 20, wherein the prismatic light directors have a first surface facing a lamp and a second surface facing away from the lamp, wherein the area of the footprint of the first surface projected onto the front-facing reflective surface is substantially equal to the area of the footprint of the second surface projected onto the front-facing reflective surface.

23. The display of claim 1, wherein the plurality of geometric light redirectors comprise refractive light redirectors.

24. The display of claim 1, wherein at least 50% of light reflecting off of the rear-facing reflective layer within 40 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 40 degrees of the axis.

25. The display of claim 1, wherein at least 50% of light reflecting off of the rear-facing reflective layer within 30 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 30 degrees of the axis.

26. The display of claim 1, wherein at least 50% of light reflecting off of the rear-facing reflective layer within 20 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 20 degrees of the axis.

27. The display of claim 1, wherein at least 70% of light reflecting off of the rear-facing reflective layer within 40 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 40 degrees of the axis.

28. The display of claim 1, wherein at least 70% of light reflecting off of the rear-facing reflective layer within 30 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 30 degrees of the axis.

29. The display of claim 1, wherein at least 70% of light reflecting off of the rear-facing reflective layer within 20 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 20 degrees of the axis.

30. The display of claim 1, wherein at least 90% of light entering the light guide within 40 degrees of an axis perpendicular to the display surface exits the light guide within 40 degrees of the axis.

31. The display of claim 1, wherein at least 90% of light reflecting off of the rear-facing reflective layer within 30 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 30 degrees of the axis.

32. The display of claim 1, wherein at least 90% of light reflecting off of the rear-facing reflective layer within 20 degrees of an axis perpendicular to the display surface is redirected back towards the rear-facing reflective layer within 20 degrees of the axis.

33. The display of claim 1, wherein a density of the plurality of geometric light deflectors in the light guide varies as a function of distance from a lamp.

34. The display of claim 1, wherein a density of the plurality of geometric light deflectors in the light guide varies as a function of angle of the geometric light deflectors with respect to the light.

35. The display of claim 1, wherein the front-facing reflective layer is at an angle of less than about 10 degrees from the display surface.

36. The display of claim 1, wherein the rear-facing reflective surface is positioned within 0.5 mm of the display surface.

37. The display of claim 1, wherein the array of light modulators has a light modulator pitch, and the distance between the rear-facing reflective surface and the display surface is less than the light modulator pitch.

38. The display of claim 1, wherein the array of light modulators is formed on a substrate, and the distance between the rear-facing reflective layer and the display surface is less than the thickness of the substrate.

39. A display comprising:

a plurality of light modulators;

a light guide, coupled to the plurality of light modulators, having front and rear surfaces and a plurality of geometric light redirectors formed therein;

a front-facing reflective layer positioned proximate the rear surface of the light guide; and

a rear-facing reflective layer, positioned between the light guide and the plurality of light modulators, having a plurality of apertures formed therein, wherein each of the respective apertures of the plurality of apertures is associated with at least one respective light modulator in the plurality of light modulators.

40. The display of claim 39, wherein each respective aperture of the plurality of apertures is associated with a single respective light modulator in the plurality of light modulators.

41. The display of claim 39, wherein each respective aperture of the plurality of apertures is associated with multiple respective light modulators in the plurality of light modulators.

42. The display of claim 39, wherein multiple respective apertures of the plurality of apertures are associated with a single respective light modulator.

43. The display of claim 39, wherein each aperture in the plurality of apertures allows a flux of light to pass through the aperture, and wherein the association between a respective aperture and a respective at least one light modulators comprises a relationship in which substantially the entire flux of light allowed to pass through the respective aperture is modulated by the respective at least one light modulator.

44. The display of claim 39, wherein each aperture in the plurality of apertures allows a flux of light to pass through the aperture within a range of angles suitable for contributing to image formation, and wherein the association between a respective aperture and a respective at least one light modulators comprises a relationship in which substantially the entire flux of light allowed to pass through the respective aperture within the range of suitable angles is modulated by the respective at least one light modulator.

45. The display of claim 39, wherein the plurality of light modulators comprises a plurality of MEMs-based light modulators for selectively allowing light passing through the associated ones of the plurality of apertures in the rear-facing reflective layer to contribute to the formation of an image.

46. A method of forming an image comprising:

providing a array of light modulators, which defines a display surface, in proximity to an optical cavity including a rear-facing reflective aperture layer as a front surface of the optical cavity, a rear surface, and a light guide positioned between the front surface and the rear surface;

reflecting light off of the rear-facing reflective aperture layer to within a useful range of angles about a display axis perpendicular to the display surface;

redirecting a portion of the light reflected into the useful range of angles, by the rear surface of the optical cavity, towards the display surface, also within the useful range of angles about the display axis, such that the intensity of the redirected light within the useful range of angles about the display axis is at least 50% of the initial total light intensity.

47. The method of claim 46, wherein the useful range of angles about the display axis is about 40 degrees about the display axis.

48. The method of claim 46, wherein the useful range of angles about the display axis is about 30 degrees about the display axis.

49. The method of claim 46, wherein the intensity of the redirected light within the useful range of angles about the display axis is at least 70% of the initial total light intensity.

50. The method of claim 46, wherein the intensity of the redirected light within the useful range of angles about the display axis is at least 90% of the initial total light intensity.