Liquid crystal display backlight with filtering

• US 8,378,955 B2
• Filed: 10/25/2004
• Issued: 02/19/2013
• Est. Priority Date: 11/09/2001
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J.
• Primary Examiner(s): SHERMAN, STEPHEN G
• Application Number:
  US10/973,157
• Publication Number:
  US 20050083295A1
• Time in Patent Office: 3,039 Days
• Field of Search: 345/82, 345/204, 345 87-104, 345/690, 345/76
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0238 Improving the black level
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A display is backlit by a source having spatially modulated luminance to attenuate illumination of dark areas of images and increase the dynamic range of the display.

Claims

1. A method of illuminating a backlit display, said method comprising:

(a) spatially varying, without manual input and in at least two different directions and among a plurality of non-zero luminance values, the luminance of a light source illuminating a plurality of displayed pixels in response to the automated quantification of spatial variance of luminance data in respective ones of received frames of an input image to be displayed on said backlit display to a user;

(b) varying the transmittance of a light valve of said display in a non-binary manner;

(c) wherein said spatially varying the luminance of said light source is based upon low-pass filtering image data to be displayed on said display.

2. The method of claim 1 wherein said low-pass filtering is based upon the intensity of said image data.

3. The method of claim 1 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the steps of:

(a) determining a luminance of said pixel from an intensity value of said pixel; and

(b) varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source.

4. The method of claim 3 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

5. The method of claim 3 wherein the step of determining a luminance of a pixel from an intensity value comprises the step of filtering an intensity value for a plurality of pixels.

6. The method of claim 5 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

7. The method of claim 5 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

8. The method of claim 7 further comprising the step of rescaling a sample of said filtered intensity value to reflect a nonlinear relationship between said luminance of said light source and said intensity of said displayed pixel.

9. The method of claim 3 wherein the step of varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source comprises the steps of:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

10. The method of claim 9 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source according to a relationship of said luminance of said light source and a mean luminance of said plurality of pixels.

11. The method of claim 10 wherein the step of attenuating a luminance of a light source illuminating a pixel comprises the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames.

12. The method of claim 11 wherein the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames comprises the step of attenuating said luminance of said light sources for a subset of frames of said sequence, said subset including less than all said frames of said sequence.

13. The method of claim 10 wherein said plurality of pixels comprises at least two contiguous pixels.

14. The method of claim 1 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the step of varying a luminance of a plurality of light sources illuminating a plurality of displayed pixels substantially comprising a frame in a sequence of video frames.

15. The method of claim 14 wherein the step of varying a luminance of a plurality of light sources illuminating a plurality of pixels substantially comprising a frame in a sequence of video frames comprises the step of varying said luminance of said light sources for less than all frames of said sequence.

16. A method of illuminating a backlit display, said method comprising:

(a) spatially varying, without manual input and in at least two different directions and among a plurality of non-zero luminance values, the luminance of a light source illuminating a plurality of displayed pixels in response to the spatial variance of received input frame data of an input image having a plurality of individual frames to be displayed on said backlit display to a user, wherein said spatially varying the luminance of a light source is synchronized with the display of the individual frames containing the spatially varied input frame data, in response to which said spatially varying the luminance of a light source is done;

(b) varying the transmittance of a light valve of said display in a non-binary manner;

(c) wherein said spatially varying luminance of said light source is based upon sub-sampling image data to be displayed on said display.

17. The method of claim 16 wherein said sub-sampling image data comprises obtaining a light source illumination signal at spatial coordinates corresponding to said light source.

18. The method of claim 17 wherein said light source illumination signal is used to output a power signal to a light source driver, said light source driver spatially varying luminance of said light source based upon said power signal.

19. The method of claim 16 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the steps of:

(a) determining a luminance of said pixel from an intensity value of said pixel; and

(b) varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source.

20. The method of claim 19 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

21. The method of claim 19 wherein the step of determining a luminance of a pixel from an intensity value comprises the step of filtering an intensity value for a plurality of pixels.

22. The method of claim 21 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

23. The method of claim 21 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

24. The method of claim 23 further comprising the step of resealing a sample of said filtered intensity value to reflect a nonlinear relationship between said luminance of said light source and said intensity of said displayed pixel.

25. The method of claim 19 wherein the step of varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source comprises the steps of:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

26. The method of claim 25 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source according to a relationship of said luminance of said light source and a mean luminance of said plurality of pixels.

27. The method of claim 26 wherein the step of attenuating a luminance of a light source illuminating a pixel comprises the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames.

28. The method of claim 27 wherein the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames comprises the step of attenuating said luminance of said light sources for a subset of frames of said sequence, said subset including less than all said frames of said sequence.

29. The method of claim 26 wherein said plurality of pixels comprises at least two contiguous pixels.

30. The method of claim 16 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the step of varying a luminance of a plurality of light sources illuminating a plurality of displayed pixels substantially comprising a frame in a sequence of video frames.

31. The method of claim 30 wherein the step of varying a luminance of a plurality of light sources illuminating a plurality of pixels substantially comprising a frame in a sequence of video frames comprises the step of varying said luminance of said light sources for less than all frames of said sequence.

32. A method of illuminating a backlit display, said method comprising:

(a) spatially varying, without manual input and in at least two different directions and among a plurality of non-zero luminance values, the luminance of a light source illuminating a plurality of displayed pixels in response to an automatically measured spatial variance in a quantifiable property of received frame data of an input image to be displayed on said backlit display to a user;

(b) varying the transmittance of a light valve of said display in a non-binary manner;

(c) wherein spatially varying luminance of said light source is based upon non-linear resealing image data to be displayed on said display.

33. The method of claim 32 wherein said non-linear rescaling image data to be displayed on said display comprises simulating performance of a non-backlit display.

34. The method of claim 33 wherein said non-backlit display is a CRT, the output of said CRT expressed by the equation:

35. The method of claim 32 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the steps of:

(a) determining a luminance of said pixel from an intensity value of said pixel; and

(b) varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source.

36. The method of claim 35 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

37. The method of claim 35 wherein the step of determining a luminance of a pixel from an intensity value comprises the step of filtering an intensity value for a plurality of pixels.

38. The method of claim 37 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

39. The method of claim 37 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

40. The method of claim 39 further comprising the step of resealing a sample of said filtered intensity value to reflect a nonlinear relationship between said luminance of said light source and said intensity of said displayed pixel.

41. The method of claim 35 wherein the step of varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source comprises the steps of:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

42. The method of claim 41 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source according to a relationship of said luminance of said light source and a mean luminance of said plurality of pixels.

43. The method of claim 42 wherein the step of attenuating a luminance of a light source illuminating a pixel comprises the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames.

44. The method of claim 43 wherein the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames comprises the step of attenuating said luminance of said light sources for a subset of frames of said sequence, said subset including less than all said frames of said sequence.

45. The method of claim 42 wherein said plurality of pixels comprises at least two contiguous pixels.

46. The method of claim 32 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the step of varying a luminance of a plurality of light sources illuminating a plurality of displayed pixels substantially comprising a frame in a sequence of video frames.

47. The method of claim 46 wherein the step of varying a luminance of a plurality of light sources illuminating a plurality of pixels substantially comprising a frame in a sequence of video frames comprises the step of varying said luminance of said light sources for less than all frames of said sequence.

48. A method of illuminating a backlit display, said method comprising:

(a) spatially varying, without a precondition of manual input and in at least two different directions and among a plurality of non-zero luminance values, the luminance of a light source illuminating a plurality of displayed pixels in response to the spatial variance of received frame data of an input image to be displayed on said backlit display to a user;

(b) varying the transmittance of a light valve of said display in a non-binary manner;

(c) wherein spatially varying luminance of said light source is based upon rescaling sub-sampled image data to be displayed on said display.

49. The method of claim 48 wherein said rescaling sub-sampled image data is relative to image data to be displayed on said display.

50. The method of claim 49 wherein said resealing sub-sampled image data relative to image data to be displayed on said display is used to achieve a desirable gray scale at said plurality of displayed pixels.

52. The method of claim 48 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the steps of:

(a) determining a luminance of said pixel from an intensity value of said pixel; and

(b) varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source.

53. The method of claim 52 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

54. The method of claim 52 wherein the step of determining a luminance of a pixel from an intensity value comprises the step of filtering an intensity value for a plurality of pixels.

55. The method of claim 54 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

56. The method of claim 54 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

57. The method of claim 56 further comprising the step of rescaling a sample of said filtered intensity value to reflect a nonlinear relationship between said luminance of said light source and said intensity of said displayed pixel.

58. The method of claim 52 wherein the step of varying a luminance of said light source according to a relationship of said luminance of said pixel and said luminance of said light source comprises the steps of:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

59. The method of claim 58 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source according to a relationship of said luminance of said light source and a mean luminance of said plurality of pixels.

60. The method of claim 59 wherein the step of attenuating a luminance of a light source illuminating a pixel comprises the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames.

61. The method of claim 60 wherein the step of attenuating a luminance of a plurality of light sources illuminating a plurality of pixels comprising a frame in a sequence of video frames comprises the step of attenuating said luminance of said light sources for a subset of frames of said sequence, said subset including less than all said frames of said sequence.

62. The method of claim 59 wherein said plurality of pixels comprises at least two contiguous pixels.

63. The method of claim 48 wherein the step of varying a luminance of a light source illuminating a displayed pixel comprises the step of varying a luminance of a plurality of light sources illuminating a plurality of displayed pixels substantially comprising a frame in a sequence of video frames.

64. The method of claim 63 wherein the step of varying a luminance of a plurality of light sources illuminating a plurality of pixels substantially comprising a frame in a sequence of video frames comprises the step of varying said luminance of said light sources for less than all frames of said sequence.

51. The method of 49 wherein said rescaling sub-sampled image data relative to image data to be displayed on said display is used to achieve a constant slope gray scale to avoid excess contrast at said plurality of displayed pixels.

65. A method of illuminating a backlit display, said method comprising the steps of:

(a) spatially varying without manual input and, in at least two different directions, the luminance of a light source illuminating a plurality of displayed pixels based on the automatically measured spatial variance of a plurality of pixel values of a received input image to be displayed on said display, wherein said light source is spatially displaced at a location at least partially directly beneath said plurality of pixels, wherein a first region of said light source provides a different non-zero luminance value than a non-zero luminance value of a second region of said light source;

(b) modifying the illumination from said display based upon a filter that is determined at least in part by a non-uniform illumination profile of said light source; and

(c) varying the transmittance of a light valve of said display in a non-binary manner.

66. The method of claim 65 wherein a relationship of said pixel values and said luminance of said light source is a nonlinear relationship.

67. The method of claim 65 further comprising the step of filtering pixel value for a plurality of pixels.

68. The method of claim 67 further comprising the step of sampling said filtered intensity value for a spatial location of said light source.

69. The method of claim 68 further comprising the step of resealing a sample of said filtered intensity value to reflect a nonlinear relationship between said intensity of said light source and said intensity of said displayed pixel.

70. The method of claim 65 further comprising:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

71. The method of claim 70 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source based upon of said luminance of said light source and a mean luminance of said plurality of pixels.

72. The method of claim 65 wherein said spatially varying the luminance is based upon low pass filtered pixel values.

73. The method of claim 65 further comprising variably reducing luminance of a portion of said light source based upon a dark local spatial area of said pixel data.

74. The method of claim 65 further comprising non-linear modification of said pixel values in a manner that simulates a CRT display.

75. A display apparatus comprising:

(a) a display having a plurality of pixels;

(b) a light source element;

(c) a controller to modulate, without manually inputted data, a luminance output of said light source between a plurality of non-zero values based on the spatial variance of frame data of an input image; and

(d) said controller adjusts said luminance output according to a data which is produced based on a luminance data of said pixels being compared to a threshold.

76. A display apparatus of claim 75 wherein said data is produced using a statistical measure.

77. A backlit display comprising:

(a) a plurality of light source elements arrayed along at least two different directions, each said light source element having a variable luminance between at least two non-zero luminance values;

(b) a light valve arranged for locally modulated transmittance of light from said light source elements;

(c) a light source controller to independently modulate, without manually inputted data, a luminance output of each of said light source elements in response to the spatial variance of pixel data of a corresponding input image to be displayed on said display;

(d) said light source controller modifies said luminance output based on said image having a dark area which includes a small bright portion.

78. A backlit display comprising:

(a) a plurality of light source elements arrayed along at least two different directions, each said light source element having a variable luminance between at least two non-zero luminance values;

(b) a light valve arranged for locally modulated transmittance of light from said light source elements;

(c) a light source controller to independently modulate, without manually inputted data a luminance output of each of said light source elements in response to the spatial variance of pixel data of a corresponding input image to be displayed on said display;

(d) said light source controller modifies said luminance output based on a dark area included in said image being small.

79. A backlit display comprising:

(a) a plurality of light source elements arrayed along at least two different directions, each said light source element having a variable luminance between at least two non-zero luminance values;

(b) a light valve arranged for locally modulated transmittance of light from said light source elements;

(c) a light source controller to independently modulate, without manually inputted data, a luminance output of each of said light source elements in response to the spatial variance of pixel data of a corresponding input image to be displayed on said display;

(d) said light source controller modifies said luminance output based on a maximum luminance exceeding a threshold luminance.