Ultra-thin backlight

• US 7,001,058 B2
• Filed: 05/15/2002
• Issued: 02/21/2006
• Est. Priority Date: 05/16/2001
• Status: Expired due to Fees

• Current Assignee: Visus
• Original Assignee: Visus
• Inventors: Inditsky, Ben-Zion
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): PAYNE, SHARON E
• Application Number:
  US10/145,078
• Publication Number:
  US 20020172039A1
• Time in Patent Office: 1,378 Days
• Field of Search: 362/31, 362/555, 362/558, 362/560, 362/561, 362/311, 362/330, 362/800, 362/606, 362/610, 362/612, 362/625, 362/616, 362/310
• US Class Current: 362/610
• 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 included 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.

Claims

1. A backlight for a display device comprising:

a light guiding plate having at least one edge and a front major surface and a back major surface said front major surface being disposed proximate to said display device, and wherein said back major surface of said light guiding plate forms a doubly curved wedge light guiding plate;

at least one light source coupled to said edge 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 major 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 front and back surfaces form a linear wedge.

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

5. 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.

6. 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.

7. A backlight as in claim 1, 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.

8. A backlight as in claim 7, wherein said display device is disposed adjacent the non-inclined surface and opposite the second area.

9. A backlight as in claim 7, wherein said display device is disposed adjacent the inclined surface.

10. A backlight as in claim 3, wherein said non-parallel portion is planar.

11. A backlight as in claim 3, wherein said non-parallel portion is non-planar.

12. A backlight as in claim 3, 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.

13. A backlight as in claim 12, wherein the angle of inclination of the second area is smaller that the angle of inclination of the first area.

14. A backlight as in claim 3, wherein said display device is disposed adjacent the non-inclined surface, and opposite the non-parallel portion.

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

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

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

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

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

22. A backlight as in claim 16, wherein the surface proximate to the display device is not parallel to the display device.

40. A backlight as in claim 1, wherein a first portion of the back major surface is parallel to said front major surface and a second portion of said back major surface is not parallel to said first major surface.

20. A backlight for a display device comprising:

a light guiding plate having at least one edge, a first major surface and a second major surface, said first major surface being disposed proximate to said display device, and wherein said second major surface of said light guiding plate forms a doubly curved wedge light guiding plate;

at least one light emitting diode coupled to an edge portion of said light guiding plate;

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

a reflector disposed behind at least said second major surface.

21. A backlight as in claim 20, 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.

23. A backlight as in claim 20, wherein the surface proximate to the display device is parallel to the display device.

24. A backlight as in claim 20, wherein at least one of said surfaces is non-planar.

25. A backlight as in claim 20, 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.

26. A backlight as in claim 25, wherein said display device is disposed adjacent the non-inclined surface and opposite the second area.

27. A backlight as in claim 21, wherein said non-parallel portion is planar.

28. A backlight as in claim 21, wherein said non-parallel portion is non-planar.

29. A backlight as in claim 21, 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.

30. A backlight as in claim 21, wherein said display device is disposed adjacent the non-inclined surface, and opposite the non-parallel portion.

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

32. A backlight as in claim 20, further including a focon disposed between said light source and said light guiding plate.

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

a light guiding plate, having two major faces at least one of which is planar and one of which is non-planar and at least two edges, and wherein one of said major surfaces of said light guiding plate forms a doubly curved wedge light guiding plate;

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 by internal reflection;

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

34. A flat illumination device as in claim 33, wherein a thickness of the light guiding plate is a non-linear monotonically decreasing function of the distance between the respective point and the corresponding flux-coupled edge, as projected onto said given plane.

35. A flat illumination device as in claim 33, 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.

36. A flat illumination device as in claim 33, 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.

37. A flat illumination device as in claim 33, wherein the outline of each face of said plate may have any geometric shape and said edges are formed correspondingly.

38. A flat illumination device as in claim 33, 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.

39. A flat illumination device as in claim 33, wherein both faces of said plate are non-planar.