High dynamic range display devices

• US 7,403,332 B2
• Filed: 03/13/2003
• Issued: 07/22/2008
• Est. Priority Date: 03/13/2002
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Whitehead, Lorne A., Seetzen, Helge, Graham, Don, Ward, Greg, Stuerzlinger, Wolfgang
• Primary Examiner(s): MAHONEY, CHRISTOPHER E
• Application Number:
  US10/507,460
• Publication Number:
  US 20050162737A1
• Time in Patent Office: 1,958 Days
• Field of Search: 359/443, 359/449, 349/51, 349/61, 345/51
• US Class Current: 359/443
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133613 characterized by the sequence of light sources
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• 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 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• 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 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/34 by control of light from an independent source
• CPC Class Codes: G09G 3/3426 : the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3611 : Control of matrices with row and column drivers
• CPC Class Codes: H01J 63/06 : Lamps with luminescent screen excited by the ray or stream
• CPC Class Codes: H04N 9/3102 : using two-dimensional electronic spatial light modulators micromechanical modulators as such G02B26/0833; liquid crystal modulators as such G02F1/13
• CPC Class Codes: H04N 9/3126 : for spatial light modulators in series
• CPC Class Codes: H04N 9/3155 : for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3194 : including sensor feedback
• CPC Class Codes: H04N 9/3197 : using light modulating optical valves
• CPC Class Codes: H05B 45/20 : Controlling the colour of the light

Abstract

A display has a screen which incorporates a light modulator. The screen may be a front projection screen or a rear-projection screen. The screen is illuminated with light from a light source comprising an array of controllable light-emitters. The controllable-emitters and elements of the light modulator may be controlled to adjust the intensity of light emanating from corresponding areas on the screen. The display may provide a high dynamic range.

Claims

1. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output; and

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements than the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator; and

the display comprises a grid of reflective walled channels located intermediate the light source and the spatial light modulator.

2. The display of claim 1 wherein the reflective walled channels are hexagonal and arranged in a honeycomb structure.

3. The display of claim 1 wherein each of the light-emitting elements emits light into one of the reflective-walled channels.

4. The display of claim 1 wherein each of the controllable elements of the spatial light modulator is illuminated by light from only one of the reflective-walled channels.

5. A display according to claim 1 wherein the light-emitting elements comprise light emitting diodes which emit white light.

8. The display of claim 4 wherein each light-emitting element of the light source corresponds to 145 or fewer corresponding controllable elements of the spatial light modulator.

6. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output; and

,

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements than the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator; and

at the spatial light modulator, a distribution of light incident from each of a plurality of the light-emitting elements of the light source comprises a convolution of a rectangular distribution and a spread function wherein the spread function has a full width at half maximum in the range of 0.3×

d₂ to 3×

d₂, where d₂ is a center-to-center spacing on the spatial light modulator of distributions of light modulated by adjacent light-emitting elements of the light source.

7. The display of claim 6 wherein each of the light-emitting elements of the light source corresponds to eight or more corresponding controllable elements of the spatial light modulator.

9. The display of claim 6 comprising a diffuser located intermediate the light source and the spatial light modulator.

10. The display of claim 6 comprising a diffuser located between the spatial light modulator and a viewing position.

11. The display of claim 6 wherein, a ratio of luminance of a first point, for which a corresponding light-emitting element is at a maximum light output and a corresponding element of the spatial light modulator is set to provide maximum illumination, and a second point, for which the corresponding light-emitting element is at minimum light output and the corresponding element of the spatial light modulator is set to provide minimum illumination, exceeds 1000:

1.

12. The display of claim 6 wherein, a ratio of luminance of a first point, for which a corresponding light-emitting element is at a maximum light output and a corresponding element of the spatial light modulator is set to provide maximum illumination, and a second point, for which the corresponding light-emitting element is at minimum light output and the corresponding element of the spatial light modulator is set to provide minimum illumination, exceeds 1500:

1.

13. The display of claim 6 wherein each of the light-emitting elements comprises a solid state light emitting element.

14. The display of claim 13 wherein the solid state light emitting elements comprise light emitting diodes.

15. The display of claim 13 wherein a color of light emitted by the solid state light emitting elements is controllable.

16. The display of claim 6 wherein the controllable elements of the spatial light modulator comprise liquid crystal display elements.

17. A display according to claim 6 wherein the light-emitting elements comprise light emitting diodes which emit white light.

18. The display according to claim 6, wherein:

the light-emitting elements comprise white light emitting Light Emitting Diodes (LEDs); and

the display further comprises a video control circuit configured to receive an image signal, and, based on the image signal, provide a backlight control signal configured to locally dim portions of the LED array.

19. The display according to claim 18, wherein:

the spatial light modulator comprises an LCD panel; and

the video control circuit further configured to, based on the image signal, provide an LCD control signal configured to adjust the LCD panel to modulate the locally dimmed light from the LED array so that a resulting image viewed on the LCD panel approaches a desired image carried by the image signal.

20. The display according to claim 6, wherein:

the spatial light modulator comprises an LCD panel; and

the display further comprises a video control circuit configured to receive an image signal, and, based on the image signal, provide an LCD control signal configured to adjust the LCD panel to modulate light from the light emitting elements so that a resulting image viewed on the LCD panel approaches a desired image carried by the image signal.

21. The display according to claim 6, wherein:

the spatial light modulator comprises an LCD panel, and the light source comprises a two-dimensional array of Light Emitting Diode (LED) based white light-emitting sources; and

the display further comprises a video control circuit configured to receive an image signal, and, based on the image signal, provide a backlight control signal configured to locally dim portions of the LED based white light-emitting sources when applied to the LED based white light-emitting sources, and an LCD control signal configured to set a transmissivity in each pixel of the LCD panel when applied to the LCD panel, said transmissivity of each pixel of the LCD panel being an amount to modulate each pixel at the LCD panel being such that a low resolution image provided by the LED based white light-emitting sources is transformed by modulation according to the LCD panel so that an image viewed on the LCD panel approaches a desired image.

22. The display according to claim 21, wherein pixels of the light source are common to a plurality of pixels of the spatial light modulator, and the LCD control signal is configured to control the higher-resolution spatial light modulator to reduce artefacts which result from the fact that each pixel of the lower-resolution light source is common to a plurality of pixels of the higher-resolution spatial light modulator.

23. The display according to claim 21, wherein pixels of the light source are of a lower resolution than pixels of the spatial light modulator, and the LCD control signal is configured to control the higher-resolution spatial light modulator to reduce artefacts which result from the fact that the spatial light modulator has more controllable elements than the light source has light-emitting elements.

24. The display according to claim 21, wherein the backlight control signal is configured to adjust intensity of the light emitting elements over a predetermined intensity range in a predetermined number of steps and the LCD control signal is configured to adjust intensity of the controllable elements of the spatial light modulator over a similar intensity range in a number of steps greater than the predetermined number of steps.

25. The display according to claim 6, wherein the light emitting elements adjust light intensity in coarser steps than the controllable elements of the spatial light modulator.

26. The display according to claim 6, wherein the light emitting elements are configured to be adjusted over an intensity range in a predetermined number of steps and the controllable elements of the spatial light modulator are configured to be adjusted over a similar range of intensity in a number of steps greater than the predetermined number of steps.

27. The display according to claim 26, wherein the controllable elements of the spatial light modulator are configured to be adjusted over the intensity range in 512 steps.

28. The display according to claim 6, wherein the illumination of the controllable light elements on the spatial light modulator comprises an approximation of a desired image.

29. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output; and

,

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements than the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator; and

,

the light-emitting elements of the light source each have a number N of discrete selectable brightness levels, and the controllable elements of the spatial light modulator have a number M of discrete selectable brightness levels and N>

M.

30. A display according to claim 29 wherein the light-emitting elements comprise light emitting diodes which emit white light.

31. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output;

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements than the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator;

each of the light-emitting elements comprises a solid state light emitting element;

the solid state light emitting elements comprise light emitting diodes; and

,

the light emitting diodes emit white light.

32. The display of claim 31 wherein the spatial light modulator comprises a color spatial light modulator.

33. The display of claim 32 wherein each controllable element of the spatial light modulator comprises a plurality of color sub pixels.

34. The display of claim 31 comprising a controller connected to deliver image data to both the light source and the spatial light modulator.

35. The display of claim 34 wherein the controller is configured to periodically refresh the controllable elements and to dim or turn off the corresponding light emitting element while a controllable element is being refreshed.

36. The display of claim 34 comprising a light detector coupled to receive stray light from at least one of the light-emitting elements and to generate a stray light intensity signal indicative of an intensity of the stray light wherein the controller is configured to:

receive the stray light intensity signal;

determine a current correction for the at least one of the light-emitting elements based at least in part on the intensity of the stray light from the at least one of the light-emitting elements and a reference value; and

, use the current correction in controlling the at least one of the light-emitting elements.

37. A display according to claim 36 wherein the light detector is coupled to receive the stray light by a planar waveguide.

38. A display according to claim 37 wherein the light-emitting elements are received in apertures of the planar waveguide and the waveguide captures light emitted by the light-emitting elements in a sideways direction.

39. A display according to claim 38 wherein the planar waveguide is located behind the light-emitting elements.

40. The display of claim 34 wherein upon determining that a defective one of the light-emitting elements is not operating, the controller is configured to increase intensities of other light-emitting elements adjacent to the defective one of the light-emitting elements.

41. The display of claim 34 wherein upon determining that a defective one of the light-emitting elements is not operating, the controller is configured to increase a transmissivity of those of the controllable elements which correspond to the defective light-emitting element.

42. A display according to claim 34 comprising a planar waveguide located in front of the light-emitting elements and a light sensor coupled to the planar waveguide to detect light emitted by the light-emitting elements.

43. A display according to claim 42 wherein one surface of the planar waveguide is roughened sufficiently to direct a fraction of light emitted by the light-emitting elements into the planar waveguide.

44. The display of claim 31 wherein the light-emitting elements are arranged in a regular array.

45. A display according to claim 31 comprising a control circuit for individually varying the controllable light outputs of the light-emitting elements by varying duty cycles of the light-emitting elements.

46. A display according to claim 31 comprising a control circuit for individually varying the controllable light outputs of the light-emitting elements by varying electrical driving currents delivered to the light-emitting elements.

47. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output;

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements than the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator;

the light-emitting elements are arranged in a regular array; and

,

the display comprises light barriers disposed between adjacent ones of the light-emitting elements.

48. The display of claim 47 wherein the array is a rectangular array.

49. The display of claim 47 wherein the array is a hexagonal array.

50. A display according to claim 47 wherein the light-emitting elements comprise light emitting diodes which emit white light.

51. A display comprising:

a light source comprising a two-dimensional array of light-emitting elements each having a controllable light output; and

a spatial light modulator comprising a plurality of controllable elements located to modulate light from the light source;

wherein;

the spatial light modulator has more controllable elements that the light source has light-emitting elements;

each of the light-emitting elements of the light source is located to illuminate a plurality of corresponding controllable elements of the spatial light modulator;

at the spatial light modulator , a distribution of light incident from each of a plurality of the light emitting elements of the light source comprises a convolution of a rectangular distribution and a spread function wherein the spread function has a full width at half maximum in the range of 0.3×

d₂ to 3×

d₂, where d₂ is a center-to-center spacing on the spatial light modulator of distributions of light modulated by adjacent light-emitting elements of the light-source;

the light source comprises a two-dimensional array of Light Emitting Diode (LED) based white light-emitting sources;

the display further comprising a video control circuit configured to receive an image signal, and, based on the image signal, provide a backlight control signal configured to locally dim portions of the LED array;

the spatial light modulator comprises an LCD panel;

the video control circuit further configured to, based on the image signal, provide an LCD control signal configured to adjust the LCD panel to modulate the locally dimmed light from the LED array so that a resulting image viewed on the LCD panel approaches a desired image carried by the image signal;

the backlight control signal further configured to adjust light intensity of the light-emitting elements in coarser steps than the LCD control signal is configured to adjust light intensity of the controllable elements of the spatial light modulator;

the backlight control signal configured to adjust intensity of the light emitting elements in a predetermined number of steps and the LCD control signal configured to adjust intensity of the controllable elements of the spatial light modulator in a number of steps greater than the predetermined number of steps; and

the illumination of the controllable light elements on the spatial light modulator comprises an approximation of a desired image.

52. The display according to claim 51, wherein the predetermined number of steps of the backlight control signal control intensity over a similar range of intensity as the greater number of steps configured in the LCD control signal.

53. The display according to claim 51, wherein the LCD control signal is configured to control the controllable elements of the spatial light modulator in 512 steps of intensity.

54. The display according to claim 51, wherein each pixel of the light source is common to a plurality of pixels of the spatial light modulator, and the LCD control signal is configured to control the spatial light modulator to reduce artifacts which result from the fact that each pixel of the light source is common to a plurality of pixels of the spatial light modulator.

55. The display according to claim 51, wherein the light control signals are based on an averaging function of the desired image.

56. The display according to claim 55, wherein the averaging function is a weighted average.

57. The display according to claim 51, wherein the distribution is based on a rectangular profile having a width d₁ equal to an active width of the pixel and d₁ is approximately equal to d₂.

58. The display according to claim 51, wherein the display comprises a locally-dimmed flat-panel LCD high dynamic range display having a dynamic range of 800:

1 or greater.