Method and apparatus for increasing effective contrast ratio and brightness yields for digital light valve image projectors

• US 7,220,006 B2
• Filed: 08/06/2004
• Issued: 05/22/2007
• Est. Priority Date: 08/08/2003
• Status: Expired due to Fees

• Current Assignee: RPX Corporation
• Original Assignee: Eddie E. Allen
• Inventors: Allen, Eddie E., Strade, Thomas D., Coley, Christopher
• Primary Examiner(s): KOVAL, MELISSA J
• Application Number:
  US10/913,744
• Publication Number:
  US 20050052621A1
• Time in Patent Office: 1,019 Days
• Field of Search: 353/31, 353/69, 353/85, 353/97, 353/121, 353/88, 348/744, 348/760, 345/600, 352/198, 352/204, 359/227, 359/738, 369/118, 362/295
• US Class Current: 353/85
• CPC Class Codes: G03B 21/2053 Intensity control of illuminating light controlled by video signal processing H04N5/74 or H04N9/31
• CPC Class Codes: H04N 5/7416 involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• 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
• 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
• CPC Class Codes: H04N 9/3197 using light modulating optical valves

Abstract

The present invention is a method and apparatus for increasing the effective contrast ratio and brightness yields for digital light valve image projectors using a variable luminance control mechanism (VLCM), associated with the projector optics, for modifying the light output and providing a correction thereto. Also included is an adaptive luminance control module (ALCM) for receiving signals from the video input board, the adaptive luminance control module producing a signal on a VLCM bus connecting the variable luminance control mechanism and the adaptive luminance control module, wherein the signal causes the variable luminance control mechanism to change the luminance of the light output and provide a corrected video signal for the projector.

Claims

1. An apparatus for improving the operation of a digital image projector, comprising:

a video input board of the projector;

a light engine of the projector, said light engine receiving video signals and generating a light output for at least one primary color there from;

optics for transforming the light output from said light engine to a focused image for projection to a display screen;

a variable luminance control mechanism, associated with the optics, for receiving the light output and provide a correction thereto; and

an adaptive luminance control module, for receiving signals from said video input board, said adaptive luminance control module producing a control signal, wherein said variable luminance control mechanism operates in response to the control signal to change the luminance of the light output and provide a corrected video signal for the projector, and wherein the adaptive luminance control module comprises;

a video receiver for receiving video signals and buffering the signals;

a luminance level processor for deriving a characteristic of the buffered video signals and producing a luminance content signal; and

an adaptive gamma processor, receiving the luminance content signal from the luminance level processor, for looking-up a modified video signal in response to the buffered video signal and the luminance content signal.

2. The apparatus of claim 1, wherein the adaptive luminance control module further comprises a variable luminance controller for receiving the luminance content signal and producing, in response, a control signal including a current, voltage and buffering drive signal to the variable luminance control mechanism that is in proportion to the luminance content signal.

3. The apparatus of claim 2, wherein the variable luminance controller produces an illumination control signal to control a level of illumination provided by a light source.

4. The apparatus of claim 1, wherein the variable luminance control mechanism comprises an electronically controllable iris system.

5. The apparatus of claim 4, wherein the electronically controllable iris system is temperature resistant so as to provide consistent operation over a range of temperatures.

6. The apparatus of claim 4, wherein the electronically controllable iris system is a single iris located at a focal convergence point to vary the general scene illumination level.

7. The apparatus of claim 4, wherein the variable luminance control mechanism further comprises a sensor to produce a signal indicating a characteristic of the variable luminance control mechanism.

8. The apparatus of claim 7, wherein the characteristic of the variable luminance control mechanism is a representation of the size of an opening of a variable iris.

9. The apparatus of claim 4, wherein the electronically controllable iris system is responsive to the control signal and operates to alter the position of at least one component therein.

10. The apparatus of claim 1, wherein the variable luminance control mechanism comprises:

a primary iris system operating in response to the control signal to change the luminance of the light output; and

a secondary luminance modulation mechanism that also operates in response to the control signal to change the luminance of the light output.

11. The apparatus of claim 10, wherein the secondary luminance modulation mechanism is an iris system.

12. The apparatus of claim 10, wherein the secondary luminance modulation mechanism is an electrochromic device.

13. The apparatus of claim 12, wherein the electrochromic device is a display including a nanocrystalline film.

14. A method for improving the operation of a digital image projector, comprising the steps of:

receiving video signals from a video input board in the projector;

producing a first signal, using an adaptive luminance control module, to provide control information for a variable luminance control mechanism located within the optical path of the projector and a second signal which is a modified video signal, whereby the variable luminance control mechanism operates to produce a modified light output from said digital image projector;

receiving video signals and buffering the signals;

deriving a characteristic of the buffered video signals and producing a luminance content signal; and

receiving the luminance content signal and looking-up a modified video signal in response to the buffered video signal and the luminance content signal.

15. The method of claim 14, further comprising the step of receiving the luminance content signal and producing, in response thereto, a control signal including a current, voltage and buffering drive signal in proportion to the luminance content signal.

16. The method of claim 14, wherein the variable luminance control mechanism includes an electronically controllable iris and wherein the method further comprises the step of altering the position of at least one component in the iris in response to the control signal.

17. The method of claim 14, wherein the variable luminance control mechanism includes an electrochromic device and wherein the method further comprises the step of altering the transmittance of at least a portion of the electrochromic device in response to the control signal.

18. An apparatus for improving the operation of a digital image projector, comprising:

a video input board of the projector;

a light engine of the projector, said light engine receiving video signals and generating a light output for at least one primary color there from;

optics for transforming the light output from said light engine to a focused image for projection to a display screen;

a variable luminance control mechanism, associated with the optics, for receiving the light output and provide a correction thereto; and

an adaptive luminance control module, for receiving signals from said video input board, said adaptive luminance control module producing a control signal, wherein said variable luminance control mechanism operates in response to the control signal to change the luminance of the light output and provide a corrected video signal for the projector, wherein the variable luminance control mechanism comprises;

a primary iris system operating in response to the control signal to change the luminance of the light output; and

a secondary luminance modulation mechanism that also operates in response to the control signal to change the luminance of the light output.

19. The apparatus of claim 18, wherein the adaptive luminance control module comprises:

a video receiver for receiving video signals and buffering the signals;

a luminance level processor for deriving a characteristic of the buffered video signals and producing a luminance content signal; and

an adaptive gamma processor, receiving the luminance content signal from the luminance level processor, for looking-up a modified video signal in response to the buffered video signal and the luminance content signal.

20. The apparatus of claim 18, wherein the adaptive luminance control module further comprises a variable luminance controller for receiving the luminance content signal and producing, in response, a control signal including a current, voltage and buffering drive signal to the variable luminance control mechanism that is in proportion to the luminance content signal.

21. The apparatus of claim 20, wherein the variable luminance controller produces an illumination control signal to control a level of illumination provided by a light source.

22. The apparatus of claim 18, wherein the variable luminance control mechanism comprises an electronically controllable iris system.

23. The apparatus of claim 22, wherein the electronically controllable iris system is temperature resistant so as to provide consistent operation over a range of temperatures.

24. The apparatus of claim 22, wherein the electronically controllable iris system is a single iris located at a focal convergence point to vary the general scene illumination level.

25. The apparatus of claim 22, wherein the variable luminance control mechanism further comprises a sensor to produce a signal indicating a characteristic of the variable luminance control mechanism.

26. The apparatus of claim 25, wherein the characteristic of the variable luminance control mechanism is a representation of the size of an opening of a variable iris.

27. The apparatus of claim 22, wherein the electronically controllable iris system is responsive to the control signal and operates to alter the position of at least one component therein.

28. The apparatus of claim 18, wherein the secondary luminance modulation mechanism is an iris system.

29. The apparatus of claim 18, wherein the secondary luminance modulation mechanism is an electrochromic device.

30. The apparatus of claim 29, wherein the electrochromic device is a display including a nanocrystalline film.

31. A method for improving the operation of a digital image projector, comprising the steps of:

receiving video signals from a video input board in the projector;

producing a first signal, using an adaptive luminance control module, to provide control information for a variable luminance control mechanism located within the optical path of the projector and a second signal which is a modified video signal, whereby the variable luminance control mechanism operates to produce a modified light output from said digital image projector;

wherein the variable luminance control mechanism includes an electronically controllable iris and wherein the method further comprises the step of altering the position of at least one component in the iris in response to the control signal; and

wherein the variable luminance control mechanism includes an electrochromic device and wherein the method further comprises the step of altering the transmittance of at least a portion of the electrochromic device in response to the control signal.