Projector with local dimming

1. A projection system, comprising:

a housing;

a controller configured to receive a video signal and, in response to the video signal, produce a light-emitting diode (LED) array-controlling signal and a modulation panel-controlling signal;

an LED array disposed in the housing and including LEDs that are configured to produce LED light having corresponding time-varying intensities in response to the LED array-controlling signal;

a modulation panel disposed in the housing and having a plurality of pixels that are configured to modulate corresponding portions of the LED light in response to the modulation panel-controlling signal to form intensity-modulated light; and

a lens disposed in or on the housing, the lens configured to project the intensity-modulated light from the housing to form a video image that corresponds to the video signal,

wherein:

a number of pixels in the plurality of pixels is greater than a number of LEDs in the LED array;

each LED in the LED array corresponds to a subset of pixels of the plurality of pixels; and

the subsets are mutually exclusive.

2. The projection system of claim 1 , wherein the modulation panel comprises:

a first polarizer disposed in the housing and configured to pass a single polarization component of the LED light to form polarized light;

a liquid crystal panel disposed in the housing and having a plurality of pixels that are configured to controllably alter corresponding states of polarization of corresponding portions of the polarized light in response to the modulation panel-controlling signal to form polarization-modulated light; and

a second polarizer disposed in the housing and configured to pass a single polarization component of the polarization-modulated light to form the intensity-modulated light.

3. The projection system of claim 1 , wherein the modulation panel comprises an array of micromirrors.

4. The projection system of claim 1 , wherein adjacent subsets overlap at edges of the adjacent subsets.

5. The projection system of claim 1 , wherein the LED array-controlling signal is configured to average the video signal over the subset of pixels.

6. The projection system of claim 1 , wherein the LED array-controlling signal of each LED is configured to have an intensity value that corresponds to a maximum intensity value of the modulation panel-controlling signal for the corresponding subset of pixels.

7. The projection system of claim 1 , further comprising a diffuser disposed between the LED array and the modulation panel, the diffuser configured to increase a spatial uniformity of the LED light.

8. The projection system of claim 1 , wherein the LEDs of the LED array are disposed on a single substrate.

9. The projection system of claim 1 , further comprising a lens array configured to at least partially focus the LED light, the lens array including lenses in a one-to-one correspondence with the LEDs of the LED array.

10. The projection system of claim 9 , wherein the LEDs of the LED array are disposed on separate substrates.

11. The projection system of claim 1 , wherein the lens includes a first lens element and a second lens element, the second lens element being spaced apart from the first lens element by a user-adjustable spacing to bring the video image into focus at a specified target.

12. The projection system of claim 1 , wherein:

the LED array-controlling signal is a first LED array-controlling signal;

the modulation panel-controlling signal is a first modulation panel-controlling signal;

the controller is further configured to produce a second LED array-controlling signal and a second modulation panel-controlling signal in response to the video signal;

the intensity-modulated light is first intensity-modulated light;

the LED array is a first LED array including LEDs configured to emit first LED light at a first wavelength;

the modulation panel is a first modulation panel;

the projection system further comprises:

a second LED array disposed in the housing and including LEDs that are configured to produce second LED light having corresponding time-varying intensities in response to the second LED array-controlling signal, the second LED array configured to produce light at a different wavelength than the first LED array;

a second modulation panel having a plurality of pixels that are configured to modulate corresponding portions of the second LED light in response to the second modulation panel-controlling signal to form second intensity-modulated light; and

a beam combiner configured to combine the first intensity-modulated light and the second intensity-modulated light to produce wavelength-combined intensity-modulated light; and

the lens is configured to project the wavelength-combined intensity-modulated light out of the housing to form the video image.

13. A method for projecting a video image, the method comprising:

receiving a video signal with a controller disposed in a housing;

producing, with the controller, in response to the video signal, a light-emitting diode (LED) array-controlling signal and a modulation panel-controlling signal;

producing, with LEDs of an LED array disposed in the housing, LED light having corresponding time-varying intensities in response to the LED array-controlling signal;

modulating, with a plurality of pixels of a modulation panel disposed in the housing, corresponding portions of the LED light in response to the modulation panel-controlling signal to form intensity-modulated light; and

projecting, with a lens disposed in or on the housing, the intensity-modulated light from the housing to form a video image that corresponds to the video signal,

wherein:

a number of pixels in the plurality of pixels is greater than a number of LEDs in the LED array;

each LED in the LED array corresponds to a subset of pixels of the plurality of pixels; and

the subsets are mutually exclusive.

14. The method of claim 13 , further comprising:

increasing a spatial uniformity of the LED light with a diffuser disposed between the LED array and the modulation panel.

15. The method of claim 13 , further comprising:

at least partially focusing the LED light with a lens array, the lens array including lenses in a one-to-one correspondence with the LEDs of the LED array.

16. A projection system, comprising:

a housing;

a controller configured to receive a video signal and, in response to the video signal, produce a light-emitting diode (LED) array-controlling signal and a modulation panel-controlling signal;

an LED array disposed in the housing and including LEDs that are configured to produce LED light having corresponding time-varying intensities in response to the LED array-controlling signal;

a diffuser disposed in the housing and configured to increase a spatial uniformity of the LED light to produce diffuse LED light;

a first polarizer disposed in the housing and configured to pass a single polarization component of the diffuse LED light to form polarized light;

a liquid crystal panel disposed in the housing and having a plurality of pixels that are configured to controllably alter corresponding states of polarization of corresponding portions of the polarized light in response to the modulation panel-controlling signal to form polarization-modulated light;

a second polarizer disposed in the housing and configured to pass a single polarization component of the polarization-modulated light to form intensity-modulated light; and

a lens disposed in or on the housing, the lens configured to project the intensity-modulated light out of the housing to form a video image that corresponds to the video signal, the video image being located away from the housing, the lens including a first lens element and a second lens element, the second lens element being spaced apart from the first lens element by a user-adjustable spacing to bring the video image into focus at a specified target.

17. The projection system of claim 16 , further comprising a lens array configured to at least partially focus the LED light, the lens array including lenses in a one-to-one correspondence with the LEDs of the LED array.