Multiple modulator displays and related methods

1. A method for generating control values for pixels of a first plurality of pixels in a dual modulator display in displaying a desired image specified by image data, wherein the first plurality of pixels is configured to emit light which illuminates a second plurality of pixels in response to control values applied to the first plurality of pixels and the second plurality of pixels is configured to modulate light from the first plurality of pixels, the method comprising:

from the image data defining the desired image, generating a target light pattern to be emitted by the first plurality of pixels onto the second plurality of pixels and initializing a set of control values capable of being applied to drive the first plurality of pixels to cause the first plurality of pixels to emit light to produce an approximation of the desired image;

generating an estimated light pattern that would result from applying the set of control values to drive the pixels of the first plurality of pixels; and,

refining the set of control values by determining for a location corresponding to a pixel of the first plurality of pixels a change in one or more control values of the set of control values and a corresponding change in the estimated light pattern at the location corresponding to the pixel, and applying the change to the set of control values if the change reduces a difference between the estimated light pattern and the target light pattern.

2. A method according to claim 1 wherein refining the set of control values comprises performing sequentially, for a set of pixels of the first plurality of pixels:

treating the pixel by determining for the pixel the change that tends to reduce a difference between the estimated light pattern and the target light pattern at the location corresponding to the pixel.

3. A method according to claim 2 wherein treating the pixels is performed in scan line order.

4. A method according to claim 3 wherein the change is a solution to:

I

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Δ

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d

j

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W

j

W

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d

=

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or a mathematical equivalent thereof for Δd j where I is the luminance of the desired image; Wd is the light pattern estimated to be produced in response to the set of control values; α is a constant; and W j is the convolution of a point spread function for the pixel of the first plurality of pixels identified by the index j with a Dirac delta function located at the location of the pixel of the first plurality of pixels.

5. A method according to claim 4 wherein α has a value equal to a midpoint of an optimal range of a set of control values p for pixels of a second plurality of pixels illuminated by the first plurality of pixels.

6. A method according to claim 4 wherein α is 0.5.

7. A method according to claim 4

wherein α has a value chosen based at least in part on the target light pattern in a local neighborhood of the pixel of the first plurality of pixels.

8. A method according to claim 3 wherein the change is determined by the equation:

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or a mathematical equivalent thereof for Δd j where S j is a texture splat for a point spread image of the pixel; I is the luminance of the desired image, M j is a masking function which has a value 1 in a region surrounding the location of the pixel and 0 otherwise; α is a constant; and B( j ) is the value of the estimated light pattern at the pixel.

9. A method according to claim 2 wherein determining the change comprises applying a filter that distinguishes between pixels that have already been treated and pixels that have not yet been treated.

10. A method according to claim 9 wherein applying the filter comprises multiplying by a filter function having one sign for pixels that have already been treated and an opposite sign for pixels that have not yet been treated.

11. A method according to claim 2 comprising determining the estimated light pattern at a resolution that is lower than a resolution of the image data.

12. A method according to claim 2 comprising determining the estimated light pattern by convolving intensities of the pixels when provided with the set of control values by point spread functions of the pixels.

13. A method according to claim 12 comprising truncating a point spread function of at least one of the pixels and, for each pixel having a truncated point spread function, adding a value u to the estimated light pattern for pixels outside of a truncation boundary.

14. A method according to claim 1 wherein refining the set of control values is performed in two or more iterations.

15. A method according to claim 1 wherein the image data comprises video data and the method is performed in real time.

16. A method according to claim 1 comprising generating the target light pattern and the set of control values such that an intensity of the light pattern estimated to be produced at a pixel of a second plurality of pixels illuminated by the first plurality of pixels exceeds an intensity of a corresponding location of the desired image by an amount within a modulation range of the pixel of the second plurality of pixels.

17. A system for generating control values for pixels of a first plurality of pixels in a dual modulator display in displaying a desired image specified by image data wherein the first plurality of pixels is arranged to emit light which illuminates a second plurality of pixels in response to control values applied to the first plurality of pixels and the second plurality of pixels is arranged to modulate the light from the first plurality of pixels, the system comprising:

an initial control values generator for generating a set of control values based on the desired image, the set of control values capable of being applied to drive the first plurality of pixels to cause the first plurality of pixels to emit light to produce an approximation of the desired image;

a light pattern simulator for generating an estimated light pattern expected to be produced if the first plurality of pixels were controlled using the set of control values; and,

a control value adjustment generator for generating for a location corresponding to a pixel of the first plurality of pixels an adjustment of one or more control values of the set of control values that alters the estimated light pattern so as to reduce a difference between the estimated light pattern and the target light pattern at the location corresponding to the pixel.

18. A system according to claim 17 wherein the initial control values generator generates a target light pattern prior to generating the set of control values.

19. A system according to claim 17 wherein the control value adjustment generator generates a set of adjustments for a set of pixels of the first plurality of pixels.

20. A system according to claim 19 wherein the control value adjustment generator generates the set of adjustments sequentially.

21. A system according to claim 17 wherein the adjustment is a solution to:

I

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Δ

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d

j

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W

j

Wd

=

α

or a mathematical equivalent thereof for Δd j where I is the luminance of the desired image; Wd is the simulated light pattern; α is a constant; and W j is the convolution of a point spread function for the pixel of the first plurality of pixels with a Dirac delta function located at the pixel of the first plurality of pixels.

22. A system according to claim 17 wherein the initial control values generator is configured to generate the set of control values such that an intensity of the estimated light pattern at a pixel of the second plurality of pixels illuminated by the first plurality of pixels exceeds an intensity of a corresponding location of the desired image by an amount within a modulation range of the pixel of the second plurality of pixels.