Backlight for correcting diagonal line distortion

• US 6,256,447 B1
• Filed: 12/31/1998
• Issued: 07/03/2001
• Est. Priority Date: 12/31/1998
• Status: Expired due to Term

• Current Assignee: Luminit LLC
• Original Assignee: Physical Optics Corporation
• Inventors: Laine, Jeffrey A.
• Primary Examiner(s): Healy, Brian
• Application Number:
  US09/223,987
• Time in Patent Office: 915 Days
• Field of Search: 385/36, 385/129, 385/146, 385/147, 385/901, 359/443, 359/449, 362/559, 362/560, 362/561, 349/56, 349/57, 349/58, 349/64, 349/65, 349/67
• US Class Current: 385/146
• 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 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

A backlight apparatus has a collimating waveguide with a light input end, a top surface, a bottom surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle for the material of the waveguide. A plurality of first facets are formed in the bottom surface distributed along the waveguide between the light input end and the far end. Each of the first facets has a first facet bottom surface which converges toward the top surface in a direction away from the far end relative to the top surface. A light scattering and reflective surface is disposed adjacent the far end of the collimating waveguide. The first facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end. The first facet bottom surfaces then cause the light rays reflected from the far end to exit the top surface. The first facet bottom surfaces may be formed either as straight facets or as curved surface facets and may also be alternatively formed having a reflective material layer thereon.

Claims

1. A backlight apparatus comprising:

a collimating waveguide having a light input end, a top surface, a bottom surface opposite the top surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle;

a plurality of first facets in the bottom surface distributed along the collimating waveguide between the light input end and the far end and extending at least part way between the opposing sides;

each of the first facets having a first facet bottom surface converging toward the top surface in a direction away from the far end at an angle γ

relative to the top surface of less than about 10°

;

a light scattering and reflective surface disposed adjacent the far end of the collimating waveguide; and

wherein the first facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide, wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface.

2. The backlight apparatus according to claim 1 wherein the first facet bottom surfaces cause light rays reflected from the far end at an angle near the total internal reflection critical angle to exit the top surface at an angle of about 2γ

relative to the top surface.

3. The backlight apparatus according to claim 1 wherein the first facet bottom surfaces have a density p distributed along the bottom surface of the collimating waveguide that varies as a function of a distance from the far end along the collimating waveguide.

4. The backlight apparatus according to claim 3 wherein the density ρ

increases as the distance from the far end increases.

5. The backlight apparatus according to claim 1 wherein each of the first facet bottom surfaces is a straight facet bottom surface.

6. The backlight apparatus according to claim 3 wherein each of the first facet bottom surfaces is a straight facet bottom surface, wherein the density ρ

of the straight first facet bottom surfaces increases as the distance from the far end increases, and wherein the angle γ

of each successive first straight facet bottom surface increases slightly in a direction away from the far end relative to each previous first straight facet bottom surface.

7. The backlight apparatus according to claim 6 wherein each straight first facet bottom surface is parallel to each other of the straight facet bottom surfaces.

8. The backlight apparatus according to claim 1 further comprising:

a plurality of second facets in the bottom surface each having a second facet bottom surface, the plurality of second facets being distributed along the collimating waveguide between the light input end and the far end interleaved alternately between the plurality of first facets and extending at least part way between the opposing sides.

9. The backlight apparatus according to claim 8 wherein only each of the first facet bottom surfaces includes a reflective layer to prevent light leaking from each of the first facet bottom surfaces.

10. The backlight apparatus according to claim 9 wherein the reflective layer on each first facet bottom surface is a metallized reflective layer.

11. The backlight apparatus according to claim 1 wherein each of the first facets extends entirely across the backlight collimating waveguide between the opposing sides.

13. The backlight apparatus according to claim 1, further comprising:

a diffuser optically coupled to the top surface of the collimating waveguide for homogenizing light exiting the top surface.

14. The backlight apparatus according to claim 1, further comprising:

a non-Lambertian diffuser optically coupled to the light input end of the collimating waveguide for reducing reflection from the light input end.

15. The backlight apparatus according to claim 1, further comprising:

a spatial light modulator optically coupled to the collimating waveguide.

16. The backlight apparatus according to claim 1, further comprising:

a light source optically coupled to the light input end of the collimating waveguide.

17. The backlight apparatus according to claim 1, further comprising:

a liquid crystal display optically coupled to the top surface of the collimating waveguide.

12. The backlight apparatus according to claim I wherein the plurality of first facets are distributed along the bottom surface so that light emitted from the top surface over a length of the collimating waveguide has a substantially uniform intensity.

18. A liquid crystal display apparatus comprising:

a liquid crystal element having a front viewing surface and an opposite rear surface;

a collimating waveguide having a light input end, a top surface facing the rear surface of the liquid crystal display, a bottom surface opposite the top surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle;

a light source disposed adjacent the light input end;

a plurality of first facets in the bottom surface distributed along the collimating waveguide between the light input end and the far end and extending at least part way between the opposing sides;

each of the first facets having a first facet bottom surface converging toward the top surface in a direction away from the far end at an angle γ

relative to the top surface of less than about 10°

;

a light scattering and reflective surface disposed at the far end of the collimating waveguide; and

wherein the first facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide, wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface toward the liquid crystal element.

19. The liquid crystal display according to claim 18, further comprising:

a non-Lambertian first diffuser optically coupled to the liquid crystal element for directing light rays exiting the liquid crystal display;

a second diffuser optically coupled to the top surface of the collimating waveguide for homogenizing light rays exiting the top surface; and

a non-Lambertian third diffuser optically coupled to the light input end of the collimating waveguide for reducing reflection from the light input end.

20. The liquid crystal display according to claim 18, further comprising:

a spatial light modulator optically coupled to the collimating waveguide.

21. The liquid crystal display according to claim 18, further comprising:

a plurality of second facets in the bottom surface each having a second facet bottom surface, the plurality of second facets being distributed along the collimating waveguide between the light input end and the far end interleaved alternately between the plurality of first facets and extending at least part way between the opposing sides, wherein the first facet bottom surfaces and the second facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide whereby the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface at an angle nearly tangential to the top surface.

22. A backlight apparatus comprising:

a collimating waveguide having a light input end, a top surface, a bottom surface opposite the top surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle;

a plurality of first facets in the bottom surface distributed along the collimating waveguide between the light input end and the far end and extending at least part way between the opposing sides;

each of the first facets having a curved first facet bottom surface converging toward the top surface in a direction away from the far end;

a plurality of second facets in the bottom surface each having a second facet bottom surface, the plurality of second facets being distributed along the collimating waveguide between the light input end and the far end interleaved alternately between the plurality of first facets and extending at least part way between the opposing sides;

a light scattering and reflective surface disposed adjacent the far end of the collimating waveguide; and

wherein the first facet and second facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide whereby the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the curved first facet bottom surfaces are arranged to reflect a light ray bundle incident to the curved first facet bottom surface and reflected from the far end to exit the top surface at an angle nearly normal to the top surface.

23. A backlight apparatus comprising:

a collimating waveguide having a light input end, a top surface, a bottom surface opposite the top surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle;

a plurality of first facets in the bottom surface distributed along the collimating waveguide between the light input end and the far end and extending at least part way between the opposing sides, wherein each of the first facets has a first facet bottom surface converging toward the top surface in a direction away from the far end; and

a light scattering and reflective surface disposed adjacent the far end of the collimating waveguide;

wherein the first facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide, wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface.

24. The backlight apparatus according to claim 23, wherein the first facet bottom surfaces have a density value distributed along the bottom surface of the collimating waveguide that varies as a function of a distance from the far end along the collimating waveguide.

25. The backlight apparatus according to claim 24, wherein the density value increases as the distance from the far end increases.

26. The backlight apparatus according to claim 23, wherein each of the first facet bottom surfaces is a straight facet bottom surface.

27. The backlight apparatus according to claim 24, wherein each of the first facet bottom surfaces is a straight facet bottom surface, and wherein the density value of the straight first facet bottom surfaces increases as the distance from the far end increases.

28. The backlight apparatus according to claim 27, wherein each straight first facet bottom surface is parallel to each other of the straight facet bottom surfaces.

29. The backlight apparatus according to claim 23, further comprising:

a plurality of second facets in the bottom surface, wherein each second facet has a second facet bottom surface, wherein the plurality of second facets are distributed along the collimating waveguide between the light input end and the far end interleaved alternately between the plurality of first facets and extending at least part way between the opposing sides.

30. The backlight apparatus according to claim 29, wherein only each of the first facet bottom surfaces includes a reflective layer to prevent light leaking from each of the first facet bottom surfaces.

31. The backlight apparatus according to claim 30, wherein the reflective layer on each first facet bottom surface is a metallized reflective layer.

32. The backlight apparatus according to claim 23, wherein each of the first facets extends entirely across the backlight collimating waveguide between the opposing sides.

33. The backlight apparatus according to claim 23, wherein the plurality of first facets are distributed along the bottom surface so that light emitted from the top surface over a length of the collimating waveguide has a substantially uniform intensity.

34. The backlight apparatus according to claim 23, further comprising:

a diffuser optically coupled to the top surface of the collimating waveguide for homogenizing light exiting the top surface.

35. The backlight apparatus according to claim 23, further comprising:

a non-Lambertian diffuser optically coupled to the light input end of the collimating waveguide for reducing reflection from the light input end.

36. The backlight apparatus according to claim 23, further comprising:

a spatial light modulator optically coupled to the collimating waveguide.

37. The backlight apparatus according to claim 23, further comprising:

a light source optically coupled to the light input end of the collimating waveguide.

38. The backlight apparatus according to claim 23, further comprising:

a liquid crystal display optically coupled to the top surface of the collimating waveguide.

39. A liquid crystal display apparatus comprising:

a liquid crystal element have a front viewing surface and an opposite rear surface;

a collimating waveguide having a light input end, a top surface facing the rear surface of the liquid crystal display, a bottom surface opposite the top surface, opposing sides, a far end opposite the light input end, and a total internal reflection critical angle;

a light source disposed adjacent the light input end;

a plurality of first facets in the bottom surface distributed along the collimating waveguide between the light input end and the far end and extending at least part way between the opposing sides, wherein each of the first facets has a first facet bottom surface converging toward the top surface in a direction away from the far end; and

a light scattering and reflective surface disposed at the far end of the collimating waveguide;

wherein the first facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide, wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface toward the liquid crystal element.

40. The liquid crystal display according to claim 39, further comprising:

a non-Lambertian first diffuser optically coupled to the liquid crystal element for directing light rays exiting the liquid crystal display;

a second diffuser optically coupled to the top surface of the collimating waveguide for homogenizing light rays exiting the top surface; and

a non-Lambertian third diffuser optically coupled to the light input end of the collimating waveguide for reducing reflection from the light input end.

41. The liquid crystal display according to claim 39, further comprising:

a spatial light modulator optically coupled to the collimating waveguide.

42. The liquid crystal display according to claim 39, further comprising:

a plurality of second facets in the bottom surface, wherein each second facet has a second facet bottom surface, wherein the plurality of second facets are distributed along the collimating waveguide between the light input end and the far end interleaved alternately between the plurality of first facets and extending at least part way between the opposing sides, wherein the first facet bottom surfaces and the second facet bottom surfaces cause light rays entering the light input end to be totally internally reflected to the far end of the collimating waveguide, wherein the scattering and reflective surface at the far end reflects and scatters light rays incident thereon back toward the light input end, and wherein the first facet bottom surfaces cause light rays reflected from the far end to exit the top surface at an angle nearly tangential to the top surface.