Ultra-thin backlight

• US 20020172039A1
• Filed: 05/15/2002
• Published: 11/21/2002
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Visus
• Original Assignee: Visus
• Inventors: Inditsky, Ben-Zion
• Granted Patent: US 7,001,058 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• 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 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A backlight for a display device, such as a liquid crystal display device, includes a light guiding plate having a front and a rear surface. The front and rear surfaces may be parallel to one another, or may instead be non-parallel. To the extent that such surfaces are non-parallel, one surface may be inclined at a single, or multiple angles with respect to the other surface. The backlight further includes a light source that is coupled to an edge of the light guiding plate by means of an energy conserving coupling section, and which provides light that is conditioned and transmitted through the light guiding plate. Light extractors are disposed on at least one side of the light guiding plate to assist in the transmission and conditioning of the light that is provided to the light guiding plate by the light source. A reflector may also be provided to assure that all light flux directed into the light guiding plate is ultimately directed in the direction of the display device.

Claims

1. A backlight for a display device comprising:

A light guiding plate having at least a front and a back surface said front surface being disposed proximate to said display device;

a light source couple to an edge portion of said light guiding plate;

a light extraction means disposed along at least one of said front or said back surfaces of said light guiding plate; and

a reflector disposed behind at least said back surface.

2. A backlight as in claim 1, wherein said front and back surfaces are parallel to one another forming a planar light guiding plate.

3. A backlight as in claim 1, wherein said light guiding plate has a first portion wherein the front and back surfaces are parallel and a second portion wherein said front and back surfaces are not parallel.

4. A backlight as in claim 1, wherein said front and back surfaces form a linear wedge.

5. A backlight as in claim 1, wherein said front and back surfaces are not parallel to one another.

6. A backlight as in claim 1, wherein the surface of the light guiding plate proximate to the display device is not parallel to the display device.

7. A backlight as in claim 1, wherein the surface of the light guiding plate proximate to the display device is parallel to the display device.

8. A backlight as in claim 3, wherein at least one of said surfaces is non-planar.

9. A backlight as in claim 3, wherein one of said surfaces has a first area that is inclined with respect to the other surface at a first angle, and a second area that is inclined with respect to the other surface at a second SMALLER angle.

10. A backlight as in claim 9, wherein said display device is disposed adjacent the non-inclined surface and opposite the second area.

11. A backlight as in claim 9, wherein said display device is disposed adjacent the inclined surface.

12. A backlight as in claim 4, wherein said non-parallel portion is planar.

13. A backlight as in claim 4, wherein said non-parallel portion is non-planar.

14. A backlight as in claim 4, wherein said non-parallel portion has a first area that is inclined with respect to the other surface at a first angle, and a second area that is inclined with respect to the other surface at a second angle.

15. A backlight as in claim 14, wherein the angle of inclination of the second area is smaller that the angle of inclination of the first area.

16. A backlight as in claim 4, wherein said display device is disposed adjacent the non-inclined surface, and opposite the non-parallel portion.

17. A backlight as in claim 1, wherein said light source is a monochromatic LED.

18. A backlight as in claim 1, wherein said light source is produces a plurality of colors.

19. A backlight as in claim 1, wherein said light source is a cold cathode fluorescent tube type light.

20. A backlight as in claim 1, wherein said light source is disposed in a recess formed in an edge of said light guiding plate.

21. A backlight as in claim 1, further including a focon disposed between said light source and said light guiding plate.

24. A backlight as in claim 18, wherein the surface proximate to the display device is not parallel to the display device.

22. A backlight for a display device comprising:

A light guiding plate having at least a first surface and a second surface, said first surface being disposed proximate to said display device, and wherein said first and second surfaces are at least partially non-parallel;

a light emitting diode couple to an edge portion of said light guiding plate;

a light extraction means disposed along at least said back surface of said light guiding plate; and

a reflector disposed behind at least said back surface.

23. A backlight as in claim 22, wherein said light guiding plate has a first portion wherein the front and back surfaces are parallel and a second portion wherein said first and second surfaces are not parallel.

25. A backlight as in claim 22, wherein the surface proximate to the display device is parallel to the display device.

26. A backlight as in claim 22, wherein at least one of said surfaces is non-planar.

27. A backlight as in claim 22, wherein one of said surfaces has a first area that is inclined with respect to the other surface at a first angle, and a second area that is inclined with respect to the other surface at a second angle.

28. A backlight as in claim 27, wherein said display device is disposed adjacent the non-inclined surface and opposite the second area.

29. A backlight as in claim 23, wherein said non-parallel portion is planar.

30. A backlight as in claim 23, wherein said non-parallel portion is non-planar.

31. A backlight as in claim 23, wherein said non-parallel portion has a first area that is inclined with respect to the other surface at a first angle, and a second area that is inclined with respect to the other surface at a second angle.

32. A backlight as in claim 23, wherein said display device is disposed adjacent the non-inclined surface, and opposite the non-parallel portion.

33. A backlight as in claim 22, wherein said light emitting diode is disposed in a recess formed in an edge of said light guiding plate.

34. A backlight as in claim 22, further including a focon disposed between said light source and said light guiding plate.

36. A flat illumination device as in claim 35, wherein, a portion of each of said internal flux components is coupled out of said plate, all such portions adding up to an extracted flux.

37. A flat illumination device as in claim 35, wherein there is defined over each illumination window a luminous emittance or luminance, as the fraction of said extracted flux that passes through an elementary area of the respective illumination window.

38. A flat illumination device as in claim 35, wherein a density of said pattern of light extracting regions varies over each of said light extracting faces.

39. A flat illumination device as in claim 38, wherein said density varies so as to effect any specified distribution of luminous emittance over at least one illumination window.

40. A flat illumination device as in claim 35, wherein said device include two illumination windows and said plate is disposed therebetween.

41. A flat illumination device as in claim 35, wherein said variation of the density pattern of extracting regions over any light extracting face is generally a function of both of its coordinate axes.

42. A flat illumination device as in claim 35, wherein said specified distribution of luminous emittance is uniform within a specified value.

43. A flat illumination device as in claim 35, wherein said variation of the density pattern of light extracting surfaces has been arrived at by iterative calculations.

44. A flat illumination device as in claim 35, wherein on each light extracting face all said light extracting regions have a maximal possible extractor density, such that a desired extracted flux emittance is obtained in a first pass of the internally propagating flux and the optical passes of that flux inside the plate before being coupled out are minimal.

45. A flat illumination device as in claim 35, wherein on each light extracting face the variation of the extractor density is maximal.

46. A flat illumination device as in claim 35, wherein the thickness of said flux coupling edge(s) of said LGP is smaller by a factor of between 1-10 than a vertical dimension of the corresponding source of light.

47. A flat illumination device as in claim 35, wherein the input luminous flux of said light sources is coupled to the corresponding edge over only a fraction of the edge'"'"'s length.

48. A flat illumination device as in claim 35, wherein the variation of said pattern of extracting regions is a variation in the ratio of the total area of extracting regions within any area element of the face to the total area of that element.

49. A flat illumination device as in claim 35, wherein said extracting regions are formed as small dots of constant size with varying distances between centers of adjacent dots.

50. A flat illumination device as in claim 35, wherein both faces of said plate are light extracting faces and said distribution of luminous emittance is specified with respect to each of the illumination windows.

51. A flat illumination device as in claim 35, wherein said extracting regions are formed by high resolution silk printing technique with a reduced paint thickness.

35. A flat illumination device (FID), having at least one illumination window defined over at least one plane, comprising:

a light guiding plate, having two mutually parallel faces, and at least one edge said illumination window being outside said light guiding plate;

at least one light source, each said light source disposed so as to couple a respective input luminous flux from the light source into a corresponding edge;

each input luminous flux forming a corresponding internal flux component which propagates through said light guiding plate by total internal reflection;

wherein at least one of said faces is a flux extracting face, which has a pattern of flux extracting elements distributed thereon covering a varying fraction of an elementary area of said flux extracting faces.

52. A flat illumination device (FID), having at least one illumination window defined over at least one plane, comprising:

a light guiding plate, having two faces at least one of which is non-planar and at least one edge;

at least one light source, each operative and disposed so as to couple a respective input luminous flux into any one of said edges;

each input luminous flux forming a corresponding internal flux component, which propagates through said plate mainly by internal reflection;

wherein, for any non-planar face of said plate, the normal distance from any point on the face to a given plane varies over the face so as to effect any specified distribution of luminous emittance over at least one illumination window.

53. A flat illumination device as in claim 52, wherein a dimension is a nonlinear monotonically decreasing function of the distance between the respective point and the corresponding flux-coupling edge, as projected onto said given plane.

54. A flat illumination device as in claim 52, wherein said dimension is a product of two different non-linear monotonically decreasing functions of the distance between the position of the respective point and at least two corresponding flux-coupling edges along any two orthogonal dimensions of said plane, as projected onto said given plane.

55. A flat illumination device as in claim 52, wherein said face forms a smooth concave surface with variable negative tilt and variable curvature which has different values in two principal planes (X,Y) and the flux coupling edges of a constant thickness.

56. A flat illumination device as in claim 52, wherein the outline of each face of said plate may have any geometric shape and said edges are formed correspondingly.

57. A flat illumination device as in claim 52, wherein the input luminous flux of any of said light sources is coupled to the corresponding edge over only a fraction of the edge'"'"'s length.

58. A flat illumination device as in claim 52, wherein both faces of said plate are non-planar.