LOCALLY DIMMED DISPLAY

• US 20120188296A1
• Filed: 04/05/2012
• Published: 07/26/2012
• Est. Priority Date: 02/27/2001
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Whitehead, Lorne, Ward, Greg, Stuerzlinger, Wolfgang, Seetzen, Helge
• Granted Patent: US 8,277,056 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• 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: G03B 21/14 Details
• CPC Class Codes: G03B 21/2053 Intensity control of illuminating light controlled by video signal processing H04N5/74 or H04N9/31
• CPC Class Codes: G03B 21/26 Projecting separately subsidiary matter simultaneously with main image
• CPC Class Codes: G03B 21/56 Projection screens
• CPC Class Codes: G03B 21/567 for colour projection G03B21/58, G03B21/60 take precedence
• CPC Class Codes: G03B 21/60 characterised by the nature of the surface
• CPC Class Codes: G03B 21/625 Lenticular translucent screens
• 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 2320/0633 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 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 5/7416 : involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• CPC Class Codes: H04N 9/31 : Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3126 : for spatial light modulators in series
• CPC Class Codes: H04N 9/3138 : using arrays of modulated light sources electroluminescent display devices G09G3/30
• CPC Class Codes: H04N 9/3188 : Scale or resolution adjustment scaling in general G06T3/40; resolution modifying circuits for displays in general G09G5/391

Abstract

A locally dimmed display has a spatial light modulator illuminated by a light source. The spatial light modulator is illuminated with a low resolution version of a desired image. The illumination may comprise a series of lighting elements that vary smoothly from one element to another at the spatial light modulator.

Claims

1. A display comprising:

a controller configured to receive image data and to control elements of a low-resolution light source and elements of a light-modulating panel having a spatial resolution higher than that of the light source, the image data specifying a desired image, the desired image having a desired luminance corresponding to each of the pixels of the light-modulating panel;

the light source connected to receive from the controller first signals for separately controlling light output of a plurality of separately-controllable elements of the light source and configured such that light from the elements of the light source illuminates a face of the light modulating panel, wherein light from the elements of the light source spreads and mixes with light from adjacent ones of the elements of the light source such that output light varies smoothly;

the light-modulating panel connected to receive from the controller second signals for controlling light transmissivity of pixels of the light-modulating panel;

the controller configured to determine from the image data driving values for the separately-controllable elements of the light source and to provide the driving values in the first signals such that application of the first signals to control the separately-controllable elements of the light source results in illumination of the light modulating panel with light that provides an approximation of the desired image having a variation in light intensity with position on the light-modulating panel according to the image data, the controller further configured to set the second signals for controlling light transmissivity of the pixels of the light-modulating panel such that the resulting displayed image approaches the desired image specified by the image data.

2. A display according to claim 1 wherein the controller is configured to determine the light intensities of the approximation at the pixels of the light-modulating panel by estimating intensities of light emitted from the light source layer at the pixels of the light-modulating panel.

3. A display according to claim 2 wherein the controller is configured to determine the driving values for the separately-controllable elements of the light source layer by determining averages or weighted averages of the desired luminance values for image areas corresponding to each of the elements of the light source layer.

4. A display according to claim 1 wherein the controller is configured to set the pixels of the light-modulating panel based on elements of the light source having a spread function with a full width at half-maximum in the range of 0.3×

d2 to 3×

d2, where d2 is a center-to-center spacing of the separately-controllable elements of the light source.

5. A display according to claim 4 wherein the spread function has a full width at half-maximum approximately equal to d2.

6. A display according to claim 1 wherein the controller is configured to estimate an approximate intensity of light from the elements of the light source and to use the estimate to set the pixels of the light-modulating panel.

7. A display according to claim 1 wherein the light from the elements of the light source spreads substantially to the center of the adjacent pixels.

8. A display according to claim 1 wherein the display has a dynamic range of 800:

1 or greater.

9. A display according to claim 1 wherein all elements of the light source have a variable light intensity controlled by the controller.

10. A display according to claim 1 wherein the light source is configured to emit white light.

11. A display according to claim 1 wherein the light-modulating panel comprises a color LCD panel wherein the pixels of the light-modulating panel comprise color sub-pixels.

12. A display according to claim 1 wherein a maximum luminance of the display is at least 10⁵ cd/m².

13. A display according to claim 1 wherein the elements or the light source are rectangular.

14. A display according to claim 1 wherein the elements of the light source are configured to emit light which is somewhat diffuse.

15. A display according to claim 1 wherein an intensity profile of light from an element of the light source has a peak and falls off smoothly from the peak.

16. A display according to claim 15 wherein the intensity profile comprises a Gaussian spread function.

18. A controller according to claim 1 wherein the controller is configured to determine the light intensities of the approximation at the pixels of the light-modulating panel by estimating intensities of light emitted from the light source layer at the pixels of the light-modulating panel.

19. A controller according to claim 18 wherein the controller is configured to determine the driving values for the separately-controllable elements of the light source layer by determining averages or weighted averages of the desired luminance values for image areas corresponding to each of the elements of the light source layer.

17. A display controller for controlling a display having a controllable light source and a light-modulating panel illuminated by the light source the light-modulating panel having a spatial resolution higher than that of the light source,

the controller configured to receive image data specifying a desired image and to generate first signals for separately controlling light output of a plurality of separately-controllable elements of the light source and second signals for controlling light transmissivity of the pixels of the light-modulating panel, the desired image having a desired luminance corresponding to each of the pixels of the light-modulating panel;

the controller configured to determine from the image data driving values for the separately-controllable elements of the light source such that application of the driving values to drive the separately-controllable elements of the light source results in light from the elements of the light source illuminating a face of the light modulating panel, wherein the light from the elements of the light source spreads and mixes with light from adjacent ones of the elements of the light source such that emitted light varies smoothly to provide an approximation of the desired image having a variation in light intensity with position on the light-modulating panel according to the image data;

the controller further configured to set the signals for controlling light transmissivity of the pixels of the light-modulating panel based on a known intensity of light from the light source on the pixels such that the resulting displayed image approaches the desired image specified by the image data.

20. A controller according to claim 17 wherein the controller is configured to set the pixels of the light-modulating panel based on elements of the light source having a spread function with a full width at half-maximum in the range of 0.3×

d2 to 3×

d2, where d2 is a center-to-center spacing of the separately-controllable elements of the light source.

21. A controller according to claim 20 wherein the spread function has a full width at half-maximum approximately equal to d2.

22. A controller according to claim 17 wherein the controller is configured to estimate an approximate intensity of light from the elements of the light source and to use the estimate to set the pixels of the light-modulating panel.