Multi-Color Primary Light Generation in a Projection System Using LEDs

• US 20080143970A1
• Filed: 12/13/2006
• Published: 06/19/2008
• Est. Priority Date: 12/13/2006
• Status: Active Grant

• Current Assignee: Signify North America Corporation (Signify N.V.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Harbers, Gerard, Bierhuizen, Serge
• Granted Patent: US 7,766,490 B2
• Time in Patent Office: Days
• US Class Current: 353/31
• CPC Class Codes: G03B 21/2013 Plural light sources
• CPC Class Codes: G03B 33/10 Simultaneous recording or projection G03B33/02, G03B33/04 G03B33/06 take precedence
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406

Abstract

Amber light LEDs have a higher luminance than red light LEDs. A vast majority of images displayed on television consists of colors that can be created using amber, green and blue components, with only a small percentage of red. In one embodiment of the present invention, the typically red primary light source in a projection display system is augmented with an amber light source. Green and blue primary light sources are also provided. All the light sources are high power LEDs. The particular mixture of the red and amber light is accomplished by varying the duty cycles of the red LEDs and the amber LEDs. If the RGB image to be displayed can be created using a higher percentage of amber light and a lower percentage of red light, the duty cycle of the amber LEDs is increased while the duty cycle of the red LEDs is decreased. Light/pixel modulators for creating the full color image from the three primary light sources are controlled to compensate for the variable amber/red mixture. This technique improves the efficiency of the projection system and generates less heat. A further increase in luminance can be achieved by controlling the light mixture from green and cyan LEDs as a primary light source and/or by controlling the light mixture from blue and blue-cyan LEDs as a primary light source.

Claims

1. A projection system for displaying a full color image comprising:

at least one light modulator for modulating light from a first primary light source, a second primary light source, and a third primary light source to provide modulated light at pixel locations in a display;

the first primary light source comprising at least one red light emitting diode (LED) and at least one non-red LED that emits light at a wavelength shorter than red and longer than green, light from the at least one red LED and light from the at least one non-red LED being combined into a single beam;

the second primary light source comprising at least one green LED;

the third primary light source comprising at least one blue LED;

at least one driver for energizing the at least one red LED, the at least one non-red LED, the at least one green LED, and the at least one blue LED;

at least one processor adapted to receive image signals and, in response, control the at least one light modulator to create a projected image, and control the at least one driver to vary relative brightness levels of the at least one red LED and the at least one non-red LED over a period of time to change a light mixture emitted from the first primary light source, wherein the mixture is based on colors in a particular image to be displayed.

2. The system of claim 1 wherein the at least one non-red LED comprises at least one amber LED.

3. The system of claim 1 wherein the at least one non-red LED comprises at least one yellow LED.

4. The system of claim 1 wherein the at least one processor controls the at least one driver to vary duty cycles of the at least one red LED and the at least one non-red LED.

5. The system of claim 1 wherein the image signals define a series of still images, each image being conveyed in an image frame, wherein the at least one processor controls the at least one driver to vary duty cycles of the at least one red LED and the at least one non-red LED based on an image in a single image frame.

6. The system of claim 1 wherein the image signals define a series of still images, each image being conveyed in an image frame, and wherein the at least one processor controls the at least one driver to vary duty cycles of the at least one red LED and the at least one non-red LED, wherein the duty cycle of the at least one red LED and the duty cycle of the at least one non-red LED add up to approximately 100% for a single image frame.

7. The system of claim 1 wherein the at least one processor controls the at least one light modulator to change modulation of the second primary light source and third primary light source to compensate for changes in the light mixture emitted from the primary light source.

8. The system of claim 1 wherein the at least one light modulator comprises a separate light modulator for the first primary light source, the second primary light source, and the third primary light source.

9. The system of claim 8 wherein the at least one light modulator comprises a liquid crystal panel with controllable pixel locations.

10. The system of claim 1 wherein the at least one light modulator comprises an array of controllable micro-mirrors.

11. The system of claim 1 wherein the second primary light source comprises at least one green light emitting diode (LED) and at least one non-green LED that emits light at a wavelength shorter than green and longer than blue, light from the at least one green light emitting diode (LED) and light from the at least one non-green LED being combined into a single beam, and wherein the at least one processor is adapted to control the at least one driver to vary relative brightness levels of the at least one green LED and the at least one non-green LED over a period of time to change a light mixture emitted from the second primary light source, wherein the mixture is based on colors in a particular image to be displayed.

12. The system of claim 1 wherein the third primary light source comprises at least one blue light emitting diode (LED) and at least one non-blue LED that emits light at a wavelength longer than blue and shorter than green, light from the at least one blue light emitting diode (LED) and light from the at least one non-blue LED being combined into a single beam, and wherein the at least one processor is adapted to control the at least one driver to vary relative brightness levels of the at least one blue LED and the at least one non-blue LED over a period of time to change a light mixture emitted from the third primary light source, wherein the mixture is based on colors in a particular image to be displayed.

13. The system of claim 1 wherein the at least one red LED comprises an array of red LEDs, and the at least one non-red LED comprises a separate array of non-red LEDs.

14. The system of claim 1 wherein the at least one red LED and the at least one non-red LED comprise a single array of interspersed red and non-red LEDs.

15. A method of operating a projection system for displaying a full color image comprising:

modulating, by at least one light modulator, light from a first primary light source, a second primary light source, and a third primary light source to provide modulated light at pixel locations in a display,

the first primary light source comprising at least one red light emitting diode (LED) and at least one non-red LED that emits light at a wavelength shorter than red and longer than green, light from the at least one red LED and light from the at least one non-red LED being combined into a single beam,

the second primary light source comprising at least one green LED,

the third primary light source comprising at least one blue LED;

energizing, by at least one driver, the at least one red LED, the at least one non-red LED, the at least one green LED, and the at least one blue LED;

receiving image signals and, in response, controlling the at least one light modulator to create a projected image, and controlling the at least one driver to vary relative brightness levels of the at least one red LED and the at least one non-red LED over a period of time to change a light mixture emitted from the first primary light source, wherein the mixture is based on colors in a particular image to be displayed.

16. The method of claim 15 wherein the image signals define a series of still images, each image being conveyed in an image frame, wherein controlling the at least one driver comprises controlling the at least one driver to vary duty cycles of the at least one red LED and the at least one non-red LED, wherein the duty cycle of the at least one red LED and the duty cycle of the at least one non-red LED add up to approximately 100% for a single image frame.

17. The method of claim 15 wherein the at least one non-red LED comprises at least one amber LED.

18. The method of claim 15 wherein the at least one non-red LED comprises at least one yellow LED.

19. The method of claim 15 wherein the at least one red LED comprises an array of red LEDs, and the at least one non-red LED comprises a separate array of non-red LEDs.

20. The method of claim 15 wherein the at least one red LED and the at least one non-red LED comprise a single array of interspersed red and non-red LEDs.

21. A projection system for displaying a full color image comprising:

at least one light modulator for modulating light from a first primary light source, a second primary light source, and a third primary light source to provide modulated light at pixel locations in a display;

the first primary light source comprising at least one red light emitting diode (LED);

the second primary light source comprising at least one green LED and at least one non-green LED that emits light at a wavelength shorter than green and longer than blue, light from the at least one green LED and light from the at least one non-green LED being combined into a single beam;

the third primary light source comprising at least one blue LED;

at least one driver for energizing the at least one red LED, the at least one green LED, the at least one non-green LED, and the at least one blue LED;

at least one processor adapted to receive image signals and, in response, control the at least one light modulator to create a projected image, and control the at least one driver to vary relative brightness levels of the at least one green LED and the at least one non-green LED over a period of time to change a light mixture emitted from the second primary light source, wherein the mixture is based on colors in a particular image to be displayed.

22. The system of claim 21 wherein the image signals define a series of still images, each image being conveyed in an image frame, and wherein the at least one processor controls the at least one driver to vary duty cycles of the at least one green LED and the at least one non-green LED, wherein the duty cycle of the at least one green LED and the duty cycle of the at least one non-green LED add up to approximately 100% for a single image frame.

23. The system of claim 21 wherein the at least one green LED comprises an array of green LEDs, and the at least one non-green LED comprises a separate array of non-green LEDs.

24. The system of claim 21 wherein the at least one green LED and the at least one non-green LED comprise a single array of interspersed green and non-green LEDs.

25. A projection system for displaying a full color image comprising:

at least one light modulator for modulating light from a first primary light source, a second primary light source, and a third primary light source to provide modulated light at pixel locations in a display;

the first primary light source comprising at least one red light emitting diode (LED);

the second primary light source comprising at least one green LED;

the third primary light source comprising at least one blue LED and at least one non-blue LED that emits light at a wavelength shorter than green and longer than blue, light from the at least one blue LED and light from the at least one non-blue LED being combined into a single beam;

at least one driver for energizing the at least one red LED, the at least one green LED, the at least one non-blue LED, and the at least one blue LED;

at least one processor adapted to receive image signals and, in response, control the at least one light modulator to create a projected image, and control the at least one driver to vary relative brightness levels of the at least one blue LED and the at least one non-blue LED over a period of time to change a light mixture emitted from the third primary light source, wherein the mixture is based on colors in a particular image to be displayed.

26. The system of claim 25 wherein the image signals define a series of still images, each image being conveyed in an image frame, and wherein the at least one processor controls the at least one driver to vary duty cycles of the at least one blue LED and the at least one non-blue LED, wherein the duty cycle of the at least one blue LED and the duty cycle of the at least one non-blue LED add up to approximately 100% for a single image frame.

27. The system of claim 25 wherein the at least one blue LED comprises an array of blue LEDs, and the at least one non-blue LED comprises a separate array of non-blue LEDs.

28. The system of claim 25 wherein the at least one blue LED and the at least one non-blue LED comprise a single array of interspersed blue and non-blue LEDs.