System and method to generate multiprimary signals

• US 20080122861A1
• Filed: 11/27/2006
• Published: 05/29/2008
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ramanath, Rajeev, Kempf, Jeffrey Matthew
• Granted Patent: US 8,305,391 B2
• Time in Patent Office: Days
• US Class Current: 345/604
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/2044 using dithering
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables

Abstract

System and method for generating multiprimary signals with optimization for bit depth for use in display devices. A preferred embodiment comprises converting an input color signal into an output color signal, wherein the number of colors in the output color signal is less than a number of colors used in a display system, when a weighting of the input color signal is less than a specified threshold, and converting the input color signal into an output color signal, wherein the number of colors in the output color signal is equal to the number of colors used in the display system, when the weighting of the input color signal is greater than the specified threshold. The use of fewer colors eliminates low bit depth colors, allowing increased dither quality in dimmer images.

Claims

1. A method for generating an output color signal from an input color signal, the method comprising:

first converting the input color signal into an output color signal in response to a determination that a weighting of the input color signal is less than a specified threshold, wherein a number of colors in the output color signal is less than a number of colors used in a display system; and

second converting the input color signal into an output color signal in response to a determination that a weighting of the input color signal is greater than a specified threshold, wherein a number of colors in the output color signal is equal to the number of colors used in the display system.

2. The method of claim 1, wherein the first converting and the second converting comprises:

converting the input color signal into an intermediate color space representation of the input color signal;

converting one of a set of output color signals that is a representation of the input color signal into an intermediate color space representation of the respective output color signal, wherein the number of colors in the output color signal used to represent the input color signal is based on a weighting of the input color signal;

computing a quality measure of the intermediate color space representation of the input color signal and the intermediate color space representation of the output color signal;

repeating the converting of an output color signal and the computing for other output color signals of the set of output color signals; and

selecting the output color signal that optimizes the quality measure.

3. The method of claim 2, wherein the set of output color signals comprises at least one output color signal that renders a color that is substantially equal in chromatic characteristics to the input color signal.

4. The method of claim 2, wherein the output color signal representing the input color signal uses (N-K) colors if the weight of the input color signal is less than a specified threshold, where N is the number of colors used in a display system and K is the number of colors out of the N colors that are not used to represent the input color signal.

5. The method of claim 4, wherein the K colors not used to represent the input color signal have lower perceived bit depth than the (N-K) colors used to represent the input color signal.

6. The method of claim 4, wherein (N-K) is greater than or equal to a number of colors in the input color signal.

7. The method of claim 2, wherein the quality measure comprises computing a distance between the intermediate color space representation of the input color signal and the intermediate color space representation of the output color signal.

8. The method of claim 2, wherein the quality measure comprises computing an energy change between the intermediate color space representation of the output color signal and the intermediate color space representation of its neighboring signals.

9. The method of claim 2, wherein the quality measure comprises computing a phase difference between the intermediate color space representation of the output color signal and the intermediate color space representation of its neighboring signals.

10. A method for displaying an image, wherein the image is comprised of multiple color signals, the method comprising:

receiving an input color signal;

retrieving an output color signal corresponding to the input color signal, wherein the retrieving is based on a weighting of the input color signal, wherein the output color signal is stored in a memory of a system used to display the image; and

displaying the output color signal.

11. The method of claim 10, wherein the output color signals are generated prior to use in the system, and wherein the generating of the output color signals comprises:

(a) converting an input color signal from a set of input color signals into an intermediate color space representation of the input color signal;

(b) converting one of a set of output color signals that is a representation of the input color signal into an intermediate color space representation of the respective output color signal, wherein a dimension of the output color signal is based on the weighting of the input color signal;

(c) computing a quality measure of the intermediate color space representation of the input color signal and the intermediate color space representation of the output color signal;

(d) repeating the converting of an output color signal and the computing for other output color signals in the set of output color signals;

(e) selecting an output color signal that optimizes the quality measure;

(f) storing the selected output color signal in a memory; and

(g) repeating the (a), (b), (c), (d), (e), and (f) for each remaining input color signal in a set of input color signals.

12. The method of claim 11, wherein the set of color signals contains color signals that are distributed throughout a displayable chromatic range of the system, and the method further comprising after the retrieving, correcting the output color signal based on a difference between the input color signal and an input color signal used to create the output color signal.

13. The method of claim 10, wherein multiple sets of output color signals are stored in the memory, wherein the output color signal is chosen from a set of output color signals, and wherein a set is chosen based on one or more of the following criterion:

an operating environment of the system, chromatic characteristics of a light source used in the system, and chromatic settings of the system.

14. A display system comprising:

a light source;

an array of light modulators optically coupled to the light source, the array of light modulators configured to modulate light from the light source based upon image data to produce images on a display plane;

a controller coupled to the array of light modulators and the light source, the controller comprising,

a weight calculating unit to calculate a weight of an input color vector;

a selecting unit coupled to the weight calculating unit, the selecting unit configured to select an output color vector based on the input color vector and the weight of the input color vector;

a light control unit coupled to the selecting unit, the light control unit configured to provide light commands to the light source, wherein the light commands are specified by the output color vector; and

a memory coupled to the controller, the memory to store a set of output color vectors that are representative of expected input color vectors.

15. The display system of claim 14, wherein the selecting unit comprises:

a weight compare unit to compare the weight of the input color vector with a specified threshold; and

a second selecting unit coupled to the weight compare unit, the second selecting unit configured to select an output color vector from the memory based on an output produced by the weight compare unit.

16. The display system of claim 14, wherein the display system utilizes N colors to display the image data, wherein the output color vector uses fewer than N colors to render the input color vector if the weight of the input color vector is less than a specified threshold, and wherein the light modulators in the array of light modulators are placed in an off state when the light source is producing a color not used in the output color vector.

17. The display system of claim 14, wherein the display system utilizes N colors to display the image data, wherein the output color vector uses fewer than N colors to render the input color vector if the weight of the input color vector is less than a specified threshold, and wherein the means for commanding reassigns a display time associated with the colors not used by the output color vector to render the input color vector to a display time associated with the colors used by the output color vector to render the input color vector.

18. The display system of claim 14, wherein the display system utilizes N colors to display the image data, wherein the output color vector uses fewer than N colors to render the input color vector if the weight of the input color vector is less than a specified threshold, and wherein the means for commanding switches off the light source during a display time associated with the colors not used by the output color vector to render the input color vector.

19. The display system of claim 14, wherein the array of light modulators is a spatial light modulator.

20. The display system of claim 19, wherein the array of light modulators is a digital micromirror device (DMD).