DMD-based image display systems

• US 7,224,335 B2
• Filed: 03/15/2001
• Issued: 05/29/2007
• Est. Priority Date: 03/15/2000
• Status: Expired due to Fees

• Current Assignee: IMAX Corporation
• Original Assignee: IMAX Corporation
• Inventors: Read, Steven, Zhou, Samuel Ziheng, Gibbon, Michael A., Adkins, Sean
• Primary Examiner(s): Awad; Amr A.
• Assistant Examiner(s): HOLTON, STEVEN E
• Application Number:
  US10/220,626
• Publication Number:
  US 20030142274A1
• Time in Patent Office: 2,266 Days
• Field of Search: 353 29- 31, 353/34, 353/37, 353/48, 353/49, 353/64, 345690-694, 345 84- 86, 348/758, 348/771, 359/618
• US Class Current: 345/84
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: G03B 21/26 Projecting separately subsidiary matter simultaneously with main image
• CPC Class Codes: G09G 1/06 using single beam tubes G09G1/26, G09G1/28 take precedence, e.g. three-dimensional or perspective representation, rotation or translation of display pattern, hidden lines, shadows G09G1/28 takes precedence; stereoscopic TV-systems, details thereof H04N13/00; oscilloscopes for three-dimensional representation G01R13/206; vectorscopes G01R13/208
• CPC Class Codes: G09G 2300/02 Composition of display devices
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• 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: 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 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• 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 9/3123 using pulse width modulation
• CPC Class Codes: H04N 9/3126 for spatial light modulators in series

Abstract

A projection system having a controller and a plurality of reflective SLMs operatively coupled to the controller to receive image data from the controller. The reflective SLMs arc aligned in series to receive light form a light source and to reflect imaging light correlated to the image data.

Claims

1. A projection system comprising:

(a) a first spatial light modulator (SLM) having a first array of separately addressable pixels, the first SLM adapted to receive light from a light source and to modulate light into a subsequent SLM;

(b) a second SLM having a second array of separately addressable pixels, the second SLM positioned in series with the first SLM to receive modulated light from the first SLM and to direct that light for producing an output; and

(c) a controller coupled to the first SLM for delivering first image data comprising first pulse width modulation data to the first SLM, and coupled to the second SLM, for delivering second image data comprising second pulse width modulation data to the second SLM, wherein the first pulse width modulation data is synchronized with the second pulse width modulation data and each bit duration and split bit duration of the second SLM corresponds to an available bit duration and split bit duration of the first SLM in order to produce a multiplicative effect of a bit time duration for all image intensities to provide a viewable image at said output.

2. The projection system as claimed in claim 1, wherein the first SLM is a digital micro mirror device and wherein the first array is an array of addressable micro mirrors and wherein the second SLM is a digital micro mirror device and wherein the second array is an array of addressable micro mirrors.

3. The projection system as claimed in claim 1 wherein the first SLM is a reflective liquid crystal device and the second SLM is a reflective liquid crystal device.

4. The projection system as claimed in claim 1 wherein each pixel in the second array corresponds to a pixel in the first array.

5. The projection system as claimed in claim 1 wherein the first image data comprises first intensity data for each pixel in the first array.

6. The projection system as claimed in claim 5, wherein the second image data comprises second intensity data for each pixel in the second array.

7. The projection system as claimed in claim 5, wherein the first intensity data comprises the first pulse width modulation data.

8. The projection system as claimed in claim 6, wherein the second intensity data comprises the second pulse width modulation data.

9. The projection system as claimed in claim 1, further comprising a color wheel operatively coupled to the controller for providing color to the viewable image.

10. The projection system as claimed in claim 1, further comprising a relay for aligning the light onto the second SLM.

11. The projection system as claimed in claim 1, further comprising a projection lens.

12. A projection system as claimed in claim 1, wherein a multiplicative product of a first output by the first SLM determined by the first image signal and a second output by a second SLM determined by the second image signal achieves a light output enhancement.

13. The projection system as claimed in claim 1 wherein the first SLM is a first type of reflective SLM device and the second SLM is a second type of reflective SLM device.

14. The projection system as claimed in claim 13 wherein the first SLM is a reflective liquid crystal device and the second SLM is a digital mirror device.

15. A projection system comprising:

(a) a first spatial light modulator (SLM) having a first array of separately addressable pixels, the first SLM adapted to receive light from a light source and to modulate light into a subsequent SLM;

(b) a second SLM having a second array of separately addressable pixels, the second SLM positioned in series with the first SLM to receive modulated light from the first SLM and to direct that light for producing an output; and

(c) a controller coupled to the first SLM, for delivering first image data comprising first pulse width modulation data to the first SLM, and coupled to the second SLM for delivering second image data comprising second pulse width modulation data to the second SLM, wherein the first pulse width modulation data is synchronized with the second pulse width modulation data and each bit duration and split bit duration of the second SLM corresponds to an available bit duration and split bit duration of the first SLM to provide a viewable image at said output, wherein the controller is capable of splitting image data of a higher bit-depth into at least the first image data and the second image data in accordance with a coding scheme, the first and second image data having a lower bit depth than the image data, and wherein the controller is capable of delivering the first image data to the first SLM and the second image data to the second SLM to produce an overall output dynamic range that exceeds a dynamic range limitation of each the first and second SLM.

16. The projection system as claimed in claim 15, wherein the controller limits the first image data to simple pulse width modulation schemes and uses more complex bit splitting schemes for the second image data.

17. The projection system as claimed in claim 15, wherein the coding scheme used by the controller splits higher bit-depth image data such that each higher bit-depth pixel code of the image data is represented by a lower bit-depth first codeword and a lower bit-depth second codeword, and a combined result from the first and second codewords is equivalent to a higher bit-depth pixel code.

18. The projection system as claimed in claim 17, wherein a first bit-depth of the first codeword matches a first dynamic range of the first SLM and a second bit-depth of the second codeword matches a second dynamic range of the second SLM.

19. The projection system as claimed in claim 17, wherein the higher bit-depth pixel code is selected based on error minimization.

20. The projection system as claimed in claim 17, wherein a result of the first codeword and the second codeword produces nonlinear brightness levels in accordance with human visual ability to detect variations in light intensity levels.

21. The projection system as claimed in claim 18, wherein a combination of first codewords of all pixels of the first image data form a first image for the first SLM and the combination of second codewords of all pixels of the second image data form a second image for the second SLM to form the viewable image.

22. The projection system as claimed in claim 21, wherein the first codeword for the first SLM produces approximately equally spaced brightness levels.

23. A method of increasing the contrast ratio of a projection system that comprises a first spatial light modulator (SLM), a second SLM, a light source, a controller, and a projection lens, wherein the first and second SLM each have array of addressable pixels, the meted comprising:

receiving image data;

splitting image data of a higher bit depth into at least first image data and second image data in accordance with a coding scheme, the first and second image data having a lower bit depth than the image data; and

delivering the first image data to the first SLM and the second image data to the second SLM to produce an overall output dynamic range that exceeds a dynamic range limitation of each the first and second SLM.

24. The method of claim 23, wherein the first image data comprises first pulse width modulation data and the second image data comprises second pulse width modulation data.

25. The method of claim 24, further comprising synchronizing first pulse width modulation data with the second pulse width modulation data.

26. The method of claim 24, wherein the controller limits the first image data to simple pulse width modulation schemes and uses more complex bit splitting schemes for the second image data.

27. The method of claim 23 wherein each bit duration and split bit duration of the second SLM corresponds to an available bit duration and split bit duration of the first SLM.

28. The method of claim 23, wherein the coding scheme used splits higher bit-depth image data such that each higher bit-depth pixel code of the image data is represented by a lower bit-depth first codeword and a lower bit-depth second codeword, and a combined result from the first and second codewords is equivalent to a higher bit-depth pixel code.

29. The method of claim 28, wherein a first bit-depth of the first codeword matches a first dynamic range of the first SLM and a second bit-depth of the second codeword matches a second dynamic range of the second SLM.

30. A projection system comprising:

(a) a first spatial light modulator (SLM) having a first array of separately addressable pixels, the first SLM adapted to receive light from a light source and to modulate light into a subsequent SLM;

(b) a second SLM having a second array of separately addressable pixels, the second SLM positioned in series with the first SLM to receive modulated light from the first SLM and to direct that light for producing an output; and

(c) a controller coupled to the first SLM for delivering first image data having first intensity data for each pixel in the first array to the first SLM, and coupled to the second SLM for delivering second image data having the second image data comprises second intensity data for each pixel in the second array to the second SLM, wherein the first intensity data and the second intensity data are determined in accordance with a bitmap code such that adjacent products of correlated first intensity data and second intensity data differ in quantity approximately in accordance with human ability to detect variations in light intensity levels and the bitmap code correlates first intensity data with second intensity data, the first and second image data being correlated to provide a viewable image at said output.

31. The projection system as claimed in claim 30, wherein the bitmap code is formatted by providing approximately equally spaced brightness levels for the first SLM and selecting code words based on error minimization resulting in a plurality of new code words with a performance equivalent to higher bit depth code words.