METHODS AND APPARATUS FOR COLOR UNIFORMITY

• US 20100060911A1
• Filed: 09/11/2008
• Published: 03/11/2010
• Est. Priority Date: 09/11/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: MARCU, Gabriel Gheorghe, Chen, Wei
• Granted Patent: US 8,289,344 B2
• Time in Patent Office: Days
• US Class Current: 358/1.900
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 1/6055 using test pattern analysis

Abstract

Methods and apparatus for achieving color and luminance uniformity in color output devices. In one embodiment, measurements of luminance and chrominance are taken at various regions of the display surface for a range of color inputs. Using the collected data, a color volume is formed for each of the measured regions. This color volume comprises a set of all colors producible at the measured region. The color volumes for each of the measured regions are then used to generate a common color gamut, i.e., a volume of colors that are producible in each of the measured regions. A gamut mapping can then be performed for all or a portion of the positions on the display surface to a target color gamut. Input data for the gamut mapping process may be determined by conventional interpolative techniques.

Claims

1. A method for achieving color uniformity in a color output device, the method comprising:

measuring luminance and chrominance values at each position of a first set of positions of a display surface for a plurality of input signals;

generating a color gamut for each of the positions of the first set based at least in part upon the luminance and chrominance values;

creating a common color gamut based at least in part upon the generated color gamuts;

determining a color gamut at a second set of positions on the display surface for the plurality of input signals; and

mapping at least a portion of the color gamut of one or more positions of the second set into the common color gamut so as to enable at least two positions on the display surface to produce a uniform color output.

2. The method of claim 1, wherein the first set of positions is determined by arranging a set of points on the display surface into a two-dimensional lattice.

3. The method of claim 2, wherein the two-dimensional lattice comprises a position at the center of the display surface.

4. The method of claim 1, wherein the first set of positions is determined by arranging a set of points on the display surface into a triangular area.

5. The method of claim 4, wherein said arranging a set of points on the display surface into a triangular area comprises performing Delaunay triangulation on the display surface.

6. The method of claim 1, wherein said measuring is performed by a calorimeter.

7. The method of claim 1, wherein said measuring is performed by a spectroradiometer.

8. The method of claim 1, wherein said measuring is performed by a color calibrated camera.

9. The method of claim 1, wherein said generating a color gamut for each of the positions of the first set comprises converting a native color space to an independent color space.

10. The method of claim 9, wherein the independent color space comprises the CIELAB color space.

11. The method of claim 9, wherein the independent color space comprises the CIELUV color space.

12. The method of claim 1, wherein the common color gamut comprises an intersection of each of the generated color gamuts.

13. The method of claim 1, wherein determining a color gamut at a second set of positions comprises performing bi-linear interpolation for each position of the second set.

14. The method of claim 13, wherein input the bi-linear interpolation for each position is based at least in part upon a minimum rectangle comprising a respective one of said positions, wherein the first set of positions comprises the vertices of said minimum rectangle.

15. The method of claim 1, wherein said determining a color gamut at a second set of positions comprises performing triangular interpolation for each position of the second set.

16. The method of claim 1, wherein said mapping at least a portion of the color gamut of one or more positions of the second set into the common color gamut comprises mapping at least a portion of the color gamut of each position of the second set into the common color gamut.

17. An apparatus for achieving color uniformity in a color output device, the apparatus comprising:

a first module adapted to record luminance and chrominance values for a plurality of positions on a display surface;

a second module adapted to construct a color gamut for each of said positions, wherein each color gamut is based at least in part upon said luminance and chrominance values;

a third module adapted to construct a common color gamut based at least in part upon the color gamuts constructed by the second module; and

a fourth module adapted to receive a source color gamut and map at least a portion of the source color gamut into the common color gamut.

18. The apparatus of claim 17, wherein the plurality of positions is adapted to form a two-dimensional lattice on the display surface.

19. The apparatus of claim 18, wherein the two-dimensional lattice comprises a position at the center of the display surface.

20. The apparatus of claim 17, wherein the plurality of positions is adapted to form a triangular region on the display surface.

21. The apparatus of claim 17, wherein the plurality of positions is determined by Delaunay triangulation.

22. The apparatus of claim 17, wherein the third module is adapted to construct a common color gamut by intersecting each of the color gamuts constructed by the second module.

23. The apparatus of claim 17, wherein the source color gamut is determined by bi-linear interpolation.

24. The apparatus of claim 23, wherein the bi-linear interpolation is based at least in part upon the luminance and chrominance values for four positions of the plurality of positions.

25. The apparatus of claim 24, wherein the four positions form vertices of a rectangle comprising a position on the display surface that is associated with the source color gamut.

26. The apparatus of claim 17, wherein the source color gamut is determined by triangular interpolation.

27. The apparatus of claim 17, wherein the apparatus is disposed within a computing device.

28. A method of mapping a color set producible by a set of positions associated with a first display surface to a color set producible by a target position associated with a second display surface, the method comprising:

generating a first color gamut for the first set of positions;

generating a second color gamut for the target position;

generating a common color gamut based at least in part upon the first and second color gamuts; and

mapping the first color gamut to the common color gamut.

29. The method of claim 28, wherein the first color gamut is based at least in part upon a measurement of luminance and chrominance values taken for a plurality of color inputs.

30. The method of claim 28, wherein the first color gamut is based at least in part upon interpolated luminance and chrominance values.

31. The method of claim 28, wherein the second color gamut is based at least in part upon a measurement of luminance and chrominance values taken for a plurality of color inputs.

32. The method of claim 28, wherein the second color gamut is based at least in part upon interpolated luminance and chrominance values.

33. The method of claim 28, wherein the common color gamut comprises the intersection of the first and second color gamuts.