Image modulation apparatus

1. A projector, comprising:

a first spatial light modulator comprising a plurality of first pixels, each first pixel having an ON state and an OFF state;

a second spatial light modulator optically coupled to the first spatial light modulator to receive light from the first spatial light modulator, the second spatial light modulator comprising a plurality of second pixels, each second pixel having an ON state and an OFF state, each second pixel corresponding to at least one first pixel; and

a processing circuit configured to:

determine whether to control the pixels of the spatial light modulators in a high-end mode or a low-end mode based on a video demand indicating greyscale levels for light output by the projector;

in the high-end mode, drive the at least one first pixel in the ON state for at least all of a fraction of a frame time that the corresponding second pixel is in the ON state, the fraction of frame time determined based on the greyscale level for the projector; and

in the low-end mode, drive the at least one first pixel in the OFF state while driving the corresponding second pixel between the ON and OFF states, wherein the fraction of the frame time for which the second pixel is in the ON state is increased to compensate for the at least one first pixel being in the OFF state.

2. The projector of claim 1 , wherein the processing circuit is configured to determine to control the pixels of the spatial light modulators in the high-end mode based on the greyscale level for the light output by the projector being greater than a threshold value.

3. The projector of claim 2 , wherein the processing circuit is configured to determine to control the pixels of the spatial light modulators in the high-end mode further based on greyscale levels for light output by the pixels adjacent to the second pixel.

4. The projector of claim 1 , wherein the processing circuit is configured to determine whether to control the pixels of the spatial light modulators in the high-end mode or the low-end mode further based on at least one of a minimum ON time of the spatial light modulators, or an amount of dither used.

5. The projector of claim 1 , wherein the processing circuit is further configured to decrease the fraction of the frame time for which the second pixel is in the ON state based on an adjacent second pixel being driven in the high-end mode.

6. The projector of claim 1 , further comprising:

a light source; and

relay optics configured to image light from the first pixels onto the second pixels;

wherein the first spatial light modulator is configured to modulate light from the light source, and the second spatial light modulator is configured to modulate light from the relay optics to generate an image indicated by the video demand.

7. The projector of claim 1 , wherein the spatial light modulators are reflective spatial light modulators.

8. The projector of claim 1 , wherein the spatial light modulators are transmissive spatial light modulators.

9. A system, comprising:

a generator module configured to generate a first modulator control signal indicating a first fraction of a frame time for driving at least one first pixel of a first spatial light modulator in an ON state, a second modulator control signal indicating a second fraction of a frame time for driving a second pixel of a second spatial light modulator in an ON state, the second pixel corresponding to the at least one first pixel, and a mode signal indicating a high-end mode or a low-end mode;

a first control module configured to control operation of a first spatial light modulator based on the first modulator control signal and the mode signal, wherein in the high-end mode, the first control module is configured to output the first modulator control signal to the first spatial light modulator, and in the low-end mode, the first control module is configured to drive the at least one first pixel in an OFF state; and

a second control module configured to control operation of a second spatial light modulator based on the second modulator control signal and the mode signal, wherein in the high-end mode, the second control module is configured to output the second modulator control signal to the second spatial light modulator, and in the low-end mode, the second control module increases the second fraction when outputting the second modulator control signal to the second spatial light modulator to compensate for the OFF state of the first spatial light modulator.

10. The system of claim 9 , wherein the generator module is configured to generate the first modulator control signal and the second modulator control signal based on a video demand, the video demand indicating at least one of a perceived intensity of light or a greyscale level.

11. The system of claim 9 , wherein the generator module is configured to generate the mode signal based on a video demand, the video demand indicating at least one of a perceived intensity of light or a greyscale level, the mode signal indicating instructions to operate in the first mode if the at least one of the perceived intensity of light or the greyscale level is greater than a threshold value.

12. The system of claim 9 , further comprising an area filter module configured to modify the first modulator control signal by increasing the first fraction based on video demand information for pixels adjacent to the second pixel.

13. The system of claim 9 , further comprising at least one delay module configured to at least one of the first modulator control signal or the second modulator control signal such that the first modulator control signal and the second modulator control signal are coincident in time.

14. The system of claim 9 , wherein the first fraction is greater than or equal to the second fraction.

15. The system of claim 9 , wherein the second control module is configured to increase the second fraction based on ON/OFF times defined in a lookup table.

16. The system of claim 9 , wherein the second control module is further configured to decrease the second fraction based on an adjacent second pixel being driven in the first mode.

17. A method, comprising:

generating a mode signal indicating whether to drive a first pixel of a first spatial light modulator and a second pixel of a second spatial light modulator according to a high-end mode or a low-end mode based on a video demand signal, the second pixel corresponding to the first pixel, each pixel configured to be in an ON state for a fraction of a frame time;

in the high-end mode, driving the first pixel and the second pixel synchronously based on the video demand signal; and

in the low-end mode, driving the first pixel in the OFF state while driving the second pixel with an increased fraction of the frame time relative to the high-end mode to compensate for the first pixel being driven in the OFF state.

18. The method of claim 17 , wherein generating the mode signal further comprises comparing a light intensity indicated by the video demand signal to a threshold light intensity, the threshold light intensity selected based on a point at which the low-end mode more accurately represents a greyscale range than the high-end mode.

19. The method of claim 17 , further comprising identifying a third pixel of the second spatial light modulator nearby the second pixel and driven in the high-end mode, and decreasing the fraction of the frame time that the second pixel is driven in the ON state based on the identified third pixel.

20. The method of claim 17 , further comprising dithering the first pixel and the second pixel based on the video demand signal.