Color gamut and luminance matching techniques for image display systems

• US 6,388,648 B1
• Filed: 09/08/1999
• Issued: 05/14/2002
• Est. Priority Date: 11/05/1996
• Status: Expired due to Fees

• Current Assignee: A Division Of Planar Systems Clarity
• Original Assignee: Clarity Visual Systems, Inc. (Leyard Optoelectronic Co., Ltd.)
• Inventors: Gulick, Paul E., Fogarty, John P., Sorenson, Greg A., Clifton, Benjamin R.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): ZAMANI, ALI A
• Application Number:
  US09/391,551
• Time in Patent Office: 979 Days
• Field of Search: 345/88, 345/147, 345/149, 345/1, 345/90, 345/89, 345/199
• US Class Current: 345/88
• CPC Class Codes: H04N 9/3147 Multi-projection systems displays in general H04N9/12; video walls G06F3/1446, G09G2300/026
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607

Abstract

An LCD projection unit employs a luminance and color balance system employing an LCD array characterization lookup table storing multiple sets of luminance and gamma correction values that are user selectable to control luminance and color balance. The lookup table values are determined by measuring the transfer function of the LCD array in the projection unit for each of a set of red (“R”), green (“G”), and blue (“B”) input data values, converting the resulting S-curve responses to corresponding sets of gamma responses and scaling the gamma responses to generate multiple R, G, and B families of luminance and gamma corrected values. Color balance is adjusted by selecting the particular R, G, and B families of luminance and gamma corrected values that cause the LCD projection unit to match a predetermined ratio of R, G, and B luminance values. Luminance is adjusted by selecting sets of families of R, G, and B, luminance values that maintain the color balance ratio while causing the LCD to transmit the desired overall luminance.

The primary colors are adjusted by a method of color mixing implemented by a mathematical matrix algorithm that generates color modification coefficients for a color space conversion circuit. The primary color matching algorithm involves measuring the intrinsic colors coordinates of the primaries, determining a set of predetermined target coordinates, and performing matrix operations to calculate the coefficients used in the color space conversion circuit to convert the measured to the target coordinates, thereby matching the primary colors. When the primary color are matched, the above-described color balance and luminance matching system adjusts the white and gray balance to result in a well-matched multiscreen display system.

Claims

1. A display apparatus that receives color input information and provides a spectral output having predetermined primary color coordinates, a predetermined luminance, and a predetermined color balance ratio, comprising:

a display device having a transfer function and providing the spectral output having intrinsic primary color coordinates;

a color processor receiving the intrinsic primary color coordinates and the predetermined primary color coordinates and calculating a set of matrix coefficients relating the intrinsic and predetermined color coordinates;

a color space converter receiving the matrix coefficients and the color input information and generating primary color-corrected input information;

a gain controller that receives the primary color-corrected input information and provides gain-adjusted amounts of the primary color-corrected input information to establish the predetermined color balance ratio and the predetermined luminance; and

a display device transfer function converter receiving the primary color-corrected input information and providing display device driving signals in amounts that compensate for the transfer function while maintaining in the spectral output the predetermined primary color coordinates and the predetermined color balance ratio.

2. The apparatus of claim 1 in which the transfer function is nonlinear and the gain controller and the display device transfer function converter are embodied in at least one lookup table.

3. The apparatus of claim 1 in which the predetermined luminance and the predetermined color balance ratio are independently adjustable without substantial interaction.

4. The apparatus of claim 1 in which the display device includes a liquid crystal light transmission device.

5. The apparatus of claim 1 in which the display apparatus comprises a projection display.

6. The apparatus of claim 1 in which the predetermined primary color coordinates include red, blue, and green primary color coordinates.

7. The apparatus of claim 1 in which the display device comprises a liquid crystal display and the display device transfer function converter includes a lookup table storing addressable values for compensating for an S-curve nonlinear transfer function of the liquid crystal display device.

8. In a multiscreen display system that receives color input information, a method of providing a spectral output having predetermined primary color coordinates, and a predetermined color balance ratio, comprising:

providing an array of substantially similar display devices, each display device contributing to the spectral output and including;

a transfer function, intrinsic primary color coordinates, and an intrinsic color gamut, the predetermined primary color coordinates being within the intrinsic color gamut of each of the display devices;

storing the intrinsic primary color coordinates and the predetermined primary color coordinates;

calculating a set of matrix coefficients relating the intrinsic and predetermined color coordinates;

receiving the matrix coefficients and the color input information and generating primary color-corrected input information; and

receiving the primary color-corrected input information and providing display device driving signals in amounts that compensate for the transfer function while maintaining in the spectral output the predetermined primary color coordinates and the predetermined color balance ratio.

9. The method of claim 8 in which the spectral output further has a predetermined luminance and the method further includes receiving the primary color-corrected input information and providing in each display device gain-adjusted amounts of the primary color-corrected input information to establish the predetermined color balance ratio and the predetermined luminance.

10. The method of claim 8 in which each display device includes a liquid crystal light transmission device.

11. The method of claim 8 in which the multiscreen display system comprises a projection display.

12. The method of claim 8 in which the predetermined primary color coordinates include red, blue, and green primary color coordinates.

13. The method of claim 8 in which the providing step includes measuring the spectral output to determine a set of intrinsic red (“

R”

), green (“

G”

), and blue (“

B”

) brightness and color coordinates for each display device.

14. The method of claim 13 in which the storing and calculating steps include:

entering the set of intrinsic coordinates into a matrix;

defining a set of target R, G, B, and white color coordinates corresponding to the predetermined primary color coordinates;

calculating a ratio of R, G, and B values that provide a predetermined white coordinate;

calculate a set of X and Z components for the intrinsic and target R, G, and B color coordinates; and

determining the primary color-corrected input information by solving a color space transformation matrix having three coefficients for each primary color.

15. A multiscreen display apparatus that receives color input information and provides a spectral output having predetermined primary color coordinates, and a predetermined color balance ratio, comprising:

an array of substantially similar display devices, each display device contributing to the spectral output and including;

a transfer function, intrinsic primary color coordinates, and an intrinsic color gamut, the predetermined primary color coordinates being within the intrinsic color gamut of each of the display devices;

a color processor receiving the intrinsic primary color coordinates and the predetermined primary color coordinates and calculating a set of matrix coefficients relating the intrinsic and predetermined color coordinates;

a color space converter receiving the matrix coefficients and the color input information and generating primary color-corrected input information; and

a display device transfer function converter receiving the primary color-corrected input information and providing display device driving signals in amounts that compensate for the transfer function while maintaining in the spectral output the predetermined primary color coordinates and the predetermined color balance ratio.