Thin Displays Having Spatially Variable Backlights

• US 20120032999A1
• Filed: 04/05/2010
• Published: 02/09/2012
• Est. Priority Date: 04/15/2009
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Seetzen, Helge
• Granted Patent: US 8,810,503 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133612 Electrical details
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A display has a light source layer having control inputs for controlling the light source layer to emit light such that the light output varies smoothly with position in a manner determined by the control inputs. An LCD panel or other spatial light modulator modulates light from the light source layer. The light source layer may be thin.

Claims

1. A light source comprising:

a light-emitting layer operative to emit light in response to an electrical potential difference being applied across the light-emitting layer, emitted light having an intensity dependent upon a magnitude of the potential difference;

a first electrode structure comprising a first electrically-conductive electrode on a first face of the light-emitting layer; and

a second electrode structure comprising a layer of a potential-distributing material having an electrical resistance on a second face of the light-emitting layer and an array of control points in electrical contact with the layer of potential-distributing material at locations spaced apart over the second face of the light-emitting layer.

2. A light source according to claim 1 comprising a power supply having a plurality of independently-controllable outputs, the outputs each connected to a corresponding one of the control points.

3. A light source according to claim 1 wherein the light-emitting layer comprises an organic light emitting diode (OLED) layer.

4. A light source according to claim 1 wherein the light-emitting layer comprises a field emissive display (FED) layer.

5. A light source according to claim 1 wherein the light-emitting layer comprises a, phosphor-coated plate.

6. A light source according to claim 1 wherein the light-emitting layer comprises an electrofluorescent material.

7. A light source according to claim 1 wherein the control points are arranged in a triangular grid.

8. A light source according to claim 1 wherein the control points are arranged in a rectangular grid.

9. A light source according to claim 1 wherein the control points have a non-uniform spatial density.

10. A light source according to claim 9 wherein the control points are concentrated more densely in a central region of the light-emitting layer and less densely in a peripheral region of the light-emitting layer.

11. A light source according to claim 1 wherein the first electrode is substantially transparent to the emitted light.

12. A light source according to claim 1 wherein the control points comprise metallic pads in contact with the potential-distributing layer.

13. A light source according to claim 1 wherein the potential-distributing layer comprises a doped semiconductor.

14. A light source according to claim 1 wherein the potential-distributing layer comprises an electrical resistivity that varies with position on the potential-distributing layer.

15. A light source according to claim 1 comprising optically absorbing spots on the first surface of the light emitting layer at locations corresponding to the control points.

16. A light source according to claim 15 wherein the optically absorbing spots have optical densities that drop off with distance from the control points.

17. A light source according to claim 1 wherein the light-emitting layer is operable to emit white light.

18. A light source comprising:

a light-emitting layer operative to emit light in response to an electrical potential difference being applied across the light-emitting layer,

a plurality of control inputs, each of the control inputs connected to control the potential difference at a corresponding location on the light-emitting layer;

control distribution means for applying a smoothly spatially varying potential difference at positions on the light-emitting layer between the locations corresponding to the control inputs.

19. A light source according to claim 18 wherein the control distribution means comprises a layer of a potential-distributing material.

20. A light source according to claim 18 wherein the control distribution means comprises a resistor network.

21. A light source according to claim 18 wherein the control distribution means comprises a plurality of interpolation circuits.

22. A display comprising:

a light source comprising a plurality of control inputs; and

a spatial light modulator illuminated by the light source;

wherein;

the control inputs correspond to spots on the light source,

the spatial light modulator comprises a plurality of pixels, each illuminated by a different area of the light source, and

the illumination provided by each of the different areas of the light source is a function of the position of the area relative to positions of the spots and of signals applied to the control inputs.

23. A display according to claim 22 wherein the spots are arranged in a rectangular array.

24. A display according to claim 23 wherein the rectangular array is a square array.

25. A display according to claim 22 wherein the light source is coextensive with the spatial light modulator.

26. A display according to claim 25 wherein the light source extends parallel to the spatial light modulator.

27. A display according to claim 26 wherein the light source and spatial light modulator are both substantially planar.

28. A display according to claim 26 wherein the light source and spatial light modulator are both curved.

29. A display according to claim 26 wherein the light source is against a rear face of the spatial light modulator.

30. A display according to claim 22 wherein the spatial light modulator comprises a transmission-type spatial light modulator.

31. A display according to claim 30 wherein the spatial light modulator comprises a liquid crystal panel.

32. A display according to claim 22 comprising a controller operative to apply a first set of signals to the control inputs of the light source and a second set of signals to control pixels of the spatial light modulator.

33. A display according to claim 32 wherein the controller is configured to generate each of the first and second sets of signals based upon image data.

34. A display according to claim 33 wherein the controller is configured to generate the first set of signals by an algorithm comprising at least one of low-pass filtering and downsampling the image data.

35. A display according to claim 33 wherein the controller comprises:

means for generating the first set of signals from the image data;

means for estimating a light output of the light source at each of the areas;

means for generating the second set of signals from the image data and estimated light outputs.

36. A display according to claim 33 wherein the controller comprises:

a image processor connected to receive the image data and generate the first set of signals based on the image data;

a light field estimator connected to receive the first set of signals and to generate an estimate of the light field that would be produced by the light source layer in response to the first set of signals; and

a computation unit connected to receive the image data and the estimated light field and to generate the second set of signals based on the image data and the estimated light field.

37. A display according to claim 36 wherein the estimate of the light field comprises a two-dimensional map indicating light intensity as a function of position on the light source.

38. A display according to claim 36 wherein the computation unit performs a calculation which comprises dividing an intensity value represented by the image data for a particular pixel by a value of the estimated light field corresponding to the area of the light source corresponding to the pixel.

39. A display according to claim 36 wherein the light field estimator is operative to:

based on the first set of signals, determine an electrical potential as a function fo position on the light source;

and, based on a function relating light output to applied electrical potential, estimate light outputs for positions on the light source.

40. A display according to claim 36 wherein the illumination provided by the light source varies smoothly in a manner given by the equation:

41. A display according to claim 22 wherein the light source comprises a plurality of light-emitting layers, each coextensive with the spatial light modulator, with a second of the light emitting layers being between a first one of the light emitting layers and the spatial light modulator.

42. A display according to claim 41 wherein the first and second light-emitting layers are operable to emit light having distinct spectral characteristics and the second light-emitting layer is transparent to light of at least some wavelengths included in the spectral characteristics of the first light-emitting layer.

43. A display according to claim 42 wherein the spatial light modulator comprises a color spatial light modulator.

44. A display according to claim 43 wherein the spatial light modulator comprises an RGB LCD panel.

45. A display according to claim 22 wherein a thickness measured between a front face of the spatial light modulator and a rear face of the light source is 2 cm or less.

46. A display according to claim 22 wherein the light source has 50 to 5000 control inputs.

47. A display according to claim 22 wherein a ratio of control spots of the light source to pixels of the spatial light modulator is in the range of 1:

200 to 1;

40,000.

48. A display according to claim 22 wherein the spatial light modulator comprises 1 million or more pixels and the number of control spots is ten thousand or fewer

49. A display comprising:

a light source comprising a layer of a material that emits light in response to applied electrical field, the layer extending in two dimensions, one or more power supplies operable to deliver individually-controllable electrical potentials to a plurality of spaced-apart locations on the light source, and a non-insulating material extending between the locations such that electrical potentials at positions on the light source on a path between two adjacent ones of the spaced apart locations change smoothly with position along the path; and

a spatial light modulator illuminated by the light source, the spatial light modulator comprising a plurality of pixels, each pixel illuminated by a different area of the light source.

50. A display comprising:

a substantially continuous two-dimensionally-extending layer of a material that emits light in response to an applied electrical field;

means for applying an electrical field across the layer, the electrical field having a magnitude that varies smoothly with position on the layer; and

a spatial light modulator comprising an array of pixels

wherein the layer is parallel to and in aligned relationship to the spatial light modulator.

51. A method for displaying an image specified by image data, the method comprising:

based on the image data, generating first control signals to be applied to a plurality of spaced apart control points of a light source;

estimating a light output of the light source at locations at and between the control points;

based on the estimated light output and the image data generating control signals for pixels of a spatial light modulator;

applying the first control signals to the control points of the light source and thereby causing the light source to emit light at and between the control points and applying the second control signals to control the pixels of the spatial light modulator.

52. A method according to claim 51 wherein estimating the light output of the light source comprises modeling an electrical potential distribution over the light source resulting from application of the first control signals and establishing an estimated light output at points of a two-dimensional map of the light source as a function of the electrical potential corresponding to the points.

53. A method for generating illumination that varies smoothly over a two-dimensional surface of a light source, the method comprising:

providing a substantially continuous two-dimensionally-extending layer of a material that emits light in response to an applied electrical field; and

,

applying an electrical field across the layer, the electrical field having a magnitude that varies smoothly with position on the layer.

54. A method for generating light having an intensity that varies smoothly with position, the method comprising:

providing a light emitting material of a type that emits light at a point in response to the application of a control signal at the point;

generating a first plurality of control signals each associated with a corresponding point of a first set of points on the light-emitting material;

applying each of the first plurality of control signals to the corresponding first point on the light-emitting material;

generating a second set of control signals associated with a corresponding second point on the light-emitting material, the second points not including the points of the first set, by connecting the first plurality of control signals as inputs to an analog circuit and applying each of the second plurality of control signals to the corresponding second point on the light-emitting material.

55. A method according to claim 54 wherein the analog circuit comprises a voltage divider.

56. A method according to claim 54 wherein the analog circuit comprises a resistor network.

57. A method according to claim 54 wherein the analog circuit comprises two-dimensional electrically resistive continuum.

58. A method according to claim 54 wherein the analog circuit comprises an array of interpolation circuits.

59. A method according to claim 54 wherein the analog circuit comprises a continuous layer of an electrically resistive material.

60. A method according to claim 59 wherein the electrically-resistive material has a sheet resistance of 10¹² Ω

/square or less.

61. A method according to claim 59 wherein the electrically-resistive material has a sheet resistance in the range of 10² to 10⁷ Ω

/square.

62. A method according to claim 54 wherein the points of the first set of points are arranged in a regular array on the light-emitting material.

63. A method according to claim 54 wherein the second plurality of points form a continuous region that surrounds points of the first plurality of points.

64. A light source for generating light having an intensity that varies smoothly with position, the light source comprising:

a layer of a light-emitting material extending in two dimensions and operative to emit light at a point in response to the application of a control signal at the point;

a plurality of first control inputs each electrically-connected to apply a control signal at a corresponding point of a first set of points on the light-emitting material;

an analog circuit having inputs connected to the first control outputs and outputs electrically connected to deliver control signals at corresponding second points on the light-emitting material, the second points not including the points of the first set.

65. A display comprising:

a source of image data defining one or more images to be displayed;

a logic unit configured to process the image data to obtain first driving signals corresponding to spaced-apart first locations on a two-dimensional light source;

an analog circuit connected to receive the first driving signals as inputs and operative to produce second driving signals corresponding to second locations on the light source outside of the first locations;

the light source connected to be controlled by the first and second driving signals; and

a spatial light modulator comprising an array of pixels and arranged to be illuminated by light emitted by the light source.

66. A display comprising:

a source of image data defining one or more images to be displayed;

a logic unit configured to process the image data to obtain first signals corresponding to desired light intensity at spaced-apart first locations on a two-dimensional light source;

an analog circuit connected to receive the first signals as inputs and operative to produce a plurality of driving signals, wherein a number of the driving signals exceeds a number of the first signals;

the light source connected to be controlled at least in part by the driving signals; and

a spatial light modulator comprising an array of pixels and arranged to be illuminated by light emitted by the light source.

67. Methods comprising any new and inventive, step, act, combination of steps and/or acts or sub-combination of steps and/or acts as described or depicted herein.

68. Apparatus comprising any new and inventive feature, combination of features or sub-combination of features as described or depicted herein.