Calibration of displays having spatially-variable backlight

• US 20070097321A1
• Filed: 08/18/2006
• Published: 05/03/2007
• Est. Priority Date: 03/13/2002
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: University of British Columbia
• Inventors: Seetzen, Helge, Stuerzlinger, Wolfgang, Whitehead, Lorne, Ward, Gregory
• Granted Patent: US 7,370,979 B2
• Time in Patent Office: Days
• US Class Current: 353/30
• 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 method for calibrating a display backlit by an array of individually-controllable light sources, the method comprising:

providing a waveguide disposed to collect a portion of light emitted by a plurality of the light sources; and

,

calibrating one light source of the plurality of light sources by;

operating the one light source with current at a calibration level;

at one or more light detectors coupled to the waveguide, measuring a portion of light emitted by the one light source; and

,

comparing a result of the measuring to a stored reference value.

2. A method according to claim 1 wherein comparing the result of the measuring to the stored reference value comprises retrieving the stored reference value from a data structure comprising stored reference values associated with each one of the plurality of light sources.

3. A method according to claim 1 comprising determining that a brightness of the one light source has changed and, in response thereto, adjusting a driving current supplied to the one light source.

4. A method according to claim 1 comprising determining that the one light source is not emitting light and, in response thereto, configuring a controller to operate one or more other ones of the light sources that are neighbors of the one light source to operate at increased brightness.

5. A method according to claim 4 wherein the display comprises a spatial light modulator comprising a plurality of elements and the method comprises, in response to determining that the one light source is not emitting light, configuring the controller to adjust one or more of the elements of the spatial light modulator corresponding to the one light source to provide increased light transmission.

6. A method according to claim 4 wherein the display comprises a spatial light modulator comprising a plurality of elements and operating the one or more other ones of the light sources that are neighbors of the one light source to operate at increased brightness comprises determining an amount to increase the brightness based at least in part upon an image content of an area of the spatial light modulator corresponding to the one light source.

7. A method according to claim 1 wherein the display comprises a spatial light modulator comprising a plurality of elements and the method comprises determining that the one light source is not emitting light and, in response thereto, configuring a controller to adjust one or more of the elements of the spatial light modulator corresponding to the one light source to provide increased light transmission.

8. A method according to claim 1 wherein operating the light source with current at a calibration level is performed in an interval between displaying image frames on the display.

9. A method according to claim 1 comprising, over time, calibrating each one of the plurality of light sources.

10. A method according to claim 1 comprising adjusting a drive current for the one light source until the result of the measuring matches the stored reference value.

11. An electronic display comprising:

a spatial light modulator;

a backlight comprising an array of individually-controllable light sources each disposed to illuminate a portion of the spatial light modulator;

a waveguide disposed to collect a portion of light emitted by a plurality of the light sources;

one or more light detectors coupled to the waveguide; and

,

a controller configured to perform a calibration routine comprising;

turning on one of the light sources;

measuring an amount of light detected based at least in part on a signal from the one or more light detectors; and

,

comparing the amount of light detected to a stored reference value.

12. An electronic display according to claim 11 wherein the light sources comprise light-emitting diodes.

13. An electronic display according to claim 12 wherein the waveguide is disposed to collect stray light from the plurality of light sources.

14. An electronic display according to claim 12 wherein the waveguide comprises a planar waveguide.

15. An electronic display according to claim 14 wherein the light emitting diodes are each inserted in a hole in the waveguide.

16. An electronic display according to claim 14 wherein the waveguide is located behind the light-emitting diodes and the portion of light is made up of light emitted by the light-emitting diodes in a rearward direction.

17. An electronic display according to claim 14 wherein the waveguide is located between the light-emitting diodes and the spatial light modulator.

18. An electronic display according to claim 17 wherein the waveguide is located between a grid and the spatial light modulator.

19. An electronic display according to claim 14 wherein the one or more light detectors are located at edges of the array.

20. An electronic display according to claim 11 comprising a memory storing the reference value wherein the memory stores a reference value for each one of the plurality of light sources.

21. An electronic display according to claim 11 wherein the controller is configured to:

receive image data;

control the plurality of the light sources and the spatial light modulator to display frames according to the image data; and

perform the turning on the one of the light sources and the measuring in an interval between displaying successive ones of the frames.

22. An electronic display according to claim 21 wherein the controller is configured to, over time, calibrate each one of the plurality of light sources.