Secondary color boost in sequential color systems

• US 6,567,134 B1
• Filed: 06/08/2000
• Issued: 05/20/2003
• Est. Priority Date: 06/08/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Morgan, Daniel J.
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): DESIR, JEAN WICEL
• Application Number:
  US09/590,473
• Time in Patent Office: 1,076 Days
• Field of Search: 348/771, 348/742, 348/743, 348/750, 348/758, 348/759, 348/70, 348/744, 348/268, 348/269, 348/270, 348/271, 353/31, 345/84, 359/618, 358/512, 382/162
• US Class Current: 348/743
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/3123 using pulse width modulation

Abstract

A method and system of increasing the intensity of secondary colors in sequential color display systems. The method utilizes light during a transition period between two primary color periods to form a secondary color. The light generated during this transition is generally not used since it does not represent a pure primary color, but instead typically starts as light of a first pure primary and ends as light of a second pure primary. A display controller determines which secondary color is needed, and the amount of the secondary color needed, and enables the transition or spoke light to contribute to the image during a time period appropriate to desired secondary color intensity given the intensity and switching characteristics of the light during the transition period. For example, light (210) filtered by a color wheel (200) during the transitional period (212 to 214) between a red (102) and green (106) filter is used to increase the yellow component of the image. Several optional methods are used to minimize the artifacts created by the spoke light and to adapt the secondary color boost to white-boosting spoke light recapture methods. In general, the spoke periods are used to boost the white level of de-saturated images and to boost the secondary colors of saturated images.

Claims

1. A method of producing secondary colors in a primary color display system, the method comprising:

receiving a color data word for an image pixel;

determining a secondary color value of said color data word; and

enabling a spatial light modulator during a transition period for a period dependent on said secondary color value.

2. The method of claim 1, further comprising the step of:

reducing at least one primary color value to offset partially said period dependent on said secondary color value.

3. The method of claim 1, further comprising the step of:

determining a second secondary color value of said color data word; and

enabling a spatial light modulator during a transition period for a period dependent on said second secondary color value.

4. The method of claim 1, further comprising the step of:

reducing at least one primary color value to offset partially said period dependent on said second secondary color value.

5. The method of claim 1, said enabling step comprising:

enabling said spatial light modulator during sequential transition periods for at least two periods, a sum of said at least two periods dependent on said secondary color value.

6. The method of claim 1, said step of determining a secondary color value of said color data word further comprising the steps of:

determining a white component of said color data word;

setting said secondary color value equal to zero when said white component exceeds a pre-determined threshold.

7. The method of claim 1, said step of determining a secondary color value of said color data word further comprising the steps of:

determining a white component of said color data word;

scaling said secondary color value based on said white component.

8. The method of claim 1, said step of determining a secondary color value of said color data word further comprising the steps of:

determining a primary color component of said color data word;

scaling said secondary color value based on said primary component.

9. The method of claim 1, said step of receiving a color data word for an image pixel comprising the step of:

receiving three primary color data words for said image pixel, each primary color data word representing the intensity of a corresponding primary color component of said image pixel.

10. The method of claim 1, said enabling step further comprising the step of:

applying a mask pattern to said spatial light modulator during said transition period.

11. The method of claim 10, wherein said mask pattern has a 25% density pattern.

12. The method of claim 10, wherein said mask pattern has a 50% density pattern.

13. The method of claim 10, wherein said mask pattern is temporally dithered.

14. The method of claim 10, wherein said mask pattern is temporally dithered from frame to frame.

15. The method of claim 10, wherein said mask pattern is temporally dithered from one revolution of a color wheel to the next revolution of said color wheel.

16. A display system comprising:

a modulated sequential color light source; and

a controller, said controller for receiving a color data word corresponding to each pixel in a desired image, determining a secondary color value of said color data word, and enabling said modulated sequential color light source during a transition period for a period dependent on said secondary color value.

17. The display system of claim 16, said modulated sequential color light source comprised of:

a sequential color light source; and

a spatial light modulator to receive a sequential color light beam from said sequential color light source and to modulate said light beam based on image data received from said controller.

18. The display system of claim 16, said modulated sequential color light source comprised of:

a white light source for generating a beam of white light;

a sequential color filter for temporally filtering said white light beam to create a sequential color light beam; and

a spatial light modulator to receive said sequential color light beam and to modulate said light beam based on image data received from said controller.

19. The display system of claim 18, said sequential color filter comprised of at least two color filters forming a rotating color wheel.

20. The display system of claim 18, said sequential color filter comprised of at least six color filters, three primary color filters and three secondary color filters disposed between said primary color filters.

21. The display system of claim 18, said sequential color filter comprised of at least two primary color filters having a secondary color filter disposed therebetween.

22. The display system of claim 21, said secondary color filter expanding the color gamut of images produced by said primary color filters.

23. The display system of claim 18, said sequential color filter comprised of at least two color filters forming a rotating color drum.