System and method for computing color correction coefficients

• US 20080100639A1
• Filed: 10/27/2006
• Published: 05/01/2008
• Est. Priority Date: 10/27/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Pettitt, Gregory S., Ramanath, Rajeev
• Granted Patent: US 7,737,989 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/506 measuring the colour produced by screens, monitors, displays or CRTs
• CPC Class Codes: G01J 3/524 Calibration of colorimeters
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 5/06 using colour palettes, e.g. look-up tables

Abstract

System and method for computing coefficients for color correcting rendered colors used in displaying images. A preferred embodiment comprises measuring color values of light output for a display system, receiving color values of desired colors, and computing a color correction matrix based on the measured color values and the input color values. The color correction matrix may be used to modify color commands to a light engine of the display system. The modifications to the color commands permit the storage and use of a set of color commands designed for a reference display system, simplifying display system design and manufacture.

Claims

1. A method for color-correcting colors in a display system, the method comprising:

measuring output color values of light output for the display system;

receiving desired color values of desired colors;

computing a color correction matrix based on the measured output color values and the desired color values; and

modifying color commands to a light engine of the display system using the color correction matrix.

2. The method of claim 1, wherein the computing comprises:

computing intermediate values based on nominal color values of a reference display system; and

computing color correction values based on the measured color values, the desired color values, and the intermediate values.

3. The method of claim 2, wherein the computing of the intermediate values comprises:

creating a first look-up table for a calibrated color sequence;

generating a color conversion matrix to convert color values from a first color space to a second color space, wherein the color conversion matrix is based on the measured color values;

generating an indexing matrix to convert color values in the second color space to indexed color values;

for each location (ix, iy) in a two-dimensional look-up table,

selecting a first set of color values in a first color space that is closest in chromatic characteristics to a second set of color values in a second color space, wherein the second set of color values is an unindexed version of (ix, iy); and

storing the second set of color values at location (ix, iy) in the two-dimensional look-up table.

4. The method of claim 3, wherein the selecting further comprises interpolating the first set of color values between two or more sets of color values around the second set of color values.

5. The method of claim 3, wherein the first look-up table comprises a three-dimensional look-up table stored as a two-dimensional memory array with each memory location corresponding to a location on a face of the three-dimensional look-up table and containing a color value in the second color space.

6. The method of claim 3, wherein the first color space comprises the RGB color space and the second color space comprises the xy color space.

7. The method of claim 2, wherein the computing of the color correction values comprises:

generating a color transformation matrix for a selected color based on the measured color values;

converting the desired color values into an indexed color space of the reference display system;

selecting gain values in the first color space based on the indexed color space; and

storing the gain values in the color correction matrix.

8. The method of claim 7, wherein there are multiple colors used in creating the color correction matrix, and wherein the converting, the selecting, and the storing are repeated for each remaining color.

9. The method of claim 7, wherein the storing is based on the selected color.

10. The method of claim 7, wherein the gain values are converted into floating point numbers prior to the storing.

11. The method of claim 7, wherein the converting comprises:

converting the desired color values into a nominal color space; and

converting the color values in the nominal color space into the indexed color space of the reference display system.

12. A method of manufacturing a display system, the method comprising:

installing a light engine configured to generate multiple colors of light;

installing a spatial light modulator in a light path of the multiple colors of light;

installing a controller configured to control the light engine and the spatial light modulator;

measuring output color values of a light output of the display system;

receiving desired color values of desired colors;

computing a color correction matrix based on the measured output color values and the desired color values; and

storing the color correction matrix in a memory in the display system.

13. The method of claim 12 further comprising, prior to the measuring, placing the display system into a test mode.

14. The method of claim 12 further comprising, prior to the measuring, instructing the light engine to generate the light output.

15. The method of claim 12, wherein the computing of the color correction matrix is further based on chromatic properties of a reference display system.

16. A display system comprising:

a light source to produce light responsive to received light commands;

an array of light modulators configured to produce images on a display plane by modulating the light from the light source based on image data;

a controller coupled to the array of light modulators and to the light source, the controller configured to process color information and to correct color values based on a reference color space; and

an optoelectric sensor coupled to the controller, the optoelectric sensor configured to provide to the controller chromatic information associated with the light from the light source.

17. The display system of claim 16, wherein the controller comprises:

a color correction unit coupled to the optoelectric sensor, the color correction unit configured to compute color correction values based on the chromatic information provided by the optoelectric sensor; and

an enhance color unit coupled to the color correction unit, the enhance color unit configured to boost color values of input color information to increase image brightness.

18. The display system of claim 17, wherein the color correction unit also computes color correction values based on chromatic information of a reference display system and chromatic information of desired colors.

19. The display system of claim 18, wherein the color correction unit modifies the light commands received by the light source using the computed color correction values to cause the display system produce light that is substantially chromatically equivalent to light produced by the reference display system.

20. The display system of claim 16, wherein the array of light modulators is a digital micromirror device.