Liquid crystal display backlight with level change

• US 20050088401A1
• Filed: 10/30/2004
• Published: 04/28/2005
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J.
• Granted Patent: US 7,714,830 B2
• Time in Patent Office: Days
• 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

1-22. -22. (canceled)

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

(a) spatially varying the luminance of a light source illuminating a plurality of displayed pixels;

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

(c) variably reducing luminance of said light source illuminating said plurality of displayed pixels based upon a local spatial area of image data to be displayed on said display.

24. The method of claim 23 wherein said local spatial area of image data to be displayed on said display is a darkened image to be displayed on said display.

25. The method of claim 23 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.

26. The method of claim 25 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

27. The method of claim 25 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.

28. The method of claim 27 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

29. The method of claim 27 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

30. The method of claim 29 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.

31. The method of claim 25 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.

32. The method of claim 31 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.

33. The method of claim 32 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.

34. The method of claim 33 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.

35. The method of claim 32 wherein said plurality of pixels comprises at least two contiguous pixels.

36. The method of claim 23 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.

37. The method of claim 36 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.

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

(a) spatially varying the luminance of a light source illuminating a plurality of displayed pixels;

(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 the content of the image to be displayed on said display.

39. The method of claim 38 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.

40. The method of claim 39 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

41. The method of claim 39 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.

42. The method of claim 41 wherein said relationship of said luminance of said pixel and said luminance of said light source is a nonlinear relationship.

43. The method of claim 41 further comprising the step of sampling a filtered intensity value at a spatial coordinate corresponding to said light source.

44. The method of claim 43 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.

45. The method of claim 39 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.

46. The method of claim 45 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.

47. The method of claim 46 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.

48. The method of claim 47 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.

49. The method of claim 46 wherein said plurality of pixels comprises at least two contiguous pixels.

50. The method of claim 38 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.

51. The method of claim 50 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.