Illumination system and projection system incorporating same
An illumination system and a projection system incorporating same are disclosed. The illumination system includes a two-dimensional array of independently operable light sources. Each light source illuminates substantially the entire active area of a pixelated optical light modulator. Each light source emits light in different emission directions. Each emission direction is directed to a respective location in the active area. Each pixel in the active area is illuminated by an incident cone of light from the two-dimensional array of independently operable light sources. The cone has a cone angle and includes at least one light ray from each light source. The cone angle of at least one such cone of light can be controlled by adjusting the intensity of one or more of the independently operable light sources.
1. An illumination system for a projection display comprising:
a plurality of discrete light sources, an output light intensity of each discrete light source being individually controllable;
an aperture stop positioned in a conjugate plane of the plurality of discrete light sources, the aperture stop having an opening, light from the plurality of discrete light sources filling at least a portion of the opening and forming a first optical field at the aperture stop; and
a pixelated light modulator having an active area capable of displaying a projectable image, the first optical field illuminating the active area and forming a second optical field at the active area, the first and second optical fields forming a Fourier transform pair, a contrast ratio of the projectable image being adjustable by selectively controlling the output intensity of one or more of the discrete light sources.
2. The illumination system of claim 1 , wherein the plurality of discrete light sources form a circular array of discrete light sources.
3. The illumination system of claim 1 , wherein at least one of the plurality of discrete light sources is an LED.
4. The illumination system of claim 1 , further comprising electronic circuitry for operating each discrete light source individually.
5. The illumination system of claim 1 , wherein the opening of the aperture stop is a circle.
6. The illumination system of claim 1 , wherein the light from the plurality of discrete light sources substantially fills the entire opening of the aperture stop.
7. The illumination system of claim 1 , wherein each of the plurality of discrete light sources is imaged within the opening of the aperture stop.
8. The illumination system of claim 1 , wherein the pixelated light modulator comprises a liquid crystal modulator.
9. The illumination system of claim 1 , wherein the pixelated light modulator comprises a digital micro-mirror device.
10. The illumination system of claim 1 , wherein the contrast of the projectable image is made greater by reducing the output intensity of one or more of the outermost discrete light sources of the plurality of discrete light sources.
11. A projection display comprising one or more of the illumination system of claim 1 .
12. The projection display of claim 11 being a front projection display.
13. The projection display of claim 11 being a rear projection display.
14. The projection display of claim 11 , wherein an image formed by the projection display is a virtual image.