Illumination device and method for laser projector
View Patent ↗Systems and methods for providing illumination suitable for imaging devices such as laser projection systems. In one embodiment, a highly collimated (e.g., laser light) beam is passed through a holographic diffuser to create a well defined cone angle for the light emanating from each point on the diffuser. This light is focused into an illumination image that is controlled by the prescription of the diffuser. In one embodiment, the image is a uniformly intense rectangle having a 4:3 aspect ratio to match an imager for a projection display. The diffuser prescription and resulting illumination image can be selected to match any desired imager. The present systems and methods may provide the advantages of high level of light efficiency, reduction or elimination of speckle and “worminess” and reduction or elimination of cosine 4 and gaussian intensity falloff, all of which are common in prior art designs.
1. A system comprising:
a light source configured to emit highly collimated light rays;
a controlled angle diffuser configured to receive the highly collimated light rays and to transform each of the light rays into a corresponding light cone having a predetermined profile; and
a field lens configured to focus the light cones into an illumination pattern.
2. The system of claim 1 further comprising an additional light source configured to emit additional highly collimated light rays, wherein the controlled angle diffuser is configured to receive the additional highly collimated light rays and to transform each of the additional light rays into a corresponding light cone having the predetermined profile, and wherein the field lens is configured to focus the light cones of the additional highly collimated light rays into an additional illumination pattern which is identical to and superimposed on the illumination pattern.
3. The system of claim 1 wherein the light source comprises one of the group consisting of: a laser; a light emitting diode; and an arc lamp.
4. The system of claim 1 further comprising a beam expander positioned between the light source and the controlled angle diffuser, wherein the beam expander is configured to expand the diameter of a collimated light beam formed by the highly collimated light rays and to maintain the collimation of the light beam.
5. The system of claim 4 wherein the beam expander is configured to expand the light beam asymmetrically.
6. The system of claim 1 wherein the controlled angle diffuser comprises a holographic diffuser.
7. The system of claim 6 wherein the holographic diffuser has a prescription which corresponds to an illumination pattern which is uniformly intense.
8. The system of claim 6 wherein the holographic diffuser has a prescription which corresponds to an illumination pattern which is rectangular.
9. The system of claim 1 wherein substantially all of the light rays emitted by the light source are focused into the illumination pattern.
10. The system of claim 1 further comprising a beam expander positioned between the light source and the controlled angle diffuser and configured to expand the diameter of a light beam formed by the highly collimated light rays, wherein the numerical aperture of light at the illumination pattern is controlled by the diameter of the expanded light beam.
11. The system of claim 1 wherein the controlled angle diffuser has a prescription which corresponds to an illumination pattern which is rectangular and uniformly intense.
12. A method comprising:
providing highly collimated rays of light;
transforming each of the rays of light into a light cone having a predetermined profile using a controlled angle diffuser;
focusing the light cones into an illumination pattern; and
illuminating a spatial light modulator with the illumination pattern.
13. The method of claim 12 wherein transforming the rays of light using a controlled angle diffuser comprises transforming the rays of light using a holographic diffuser.
14. The method of claim 12 wherein providing the highly collimated rays of light comprises providing a laser light beam.
15. The method of claim 12 wherein focusing the light cones into an illumination pattern and illuminating the spatial light modulator with the illumination pattern comprises focusing the light cones into the illumination pattern at a plane which lies on the spatial light modulator.
16. An illumination system for a display device comprising:
a laser light source configured to emit a highly collimated light beam;
a holographic diffuser configured to receive the highly collimated light beam and to generate a light cone from each ray of the highly collimated light beam, wherein each light cone has a predetermined profile; and
a field lens configured to focus the light cones into an illumination pattern, wherein the illumination pattern has shape and intensity characteristics which match a spatial light modulator of the display device.
17. The illumination system of claim 16 wherein substantially all of the light beam emitted by the laser light source is focused into the illumination pattern.
18. The illumination system of claim 16 wherein the illumination system is configured to generate an identical illumination sub-pattern from each portion of the light beam and to superimpose the identical illumination sub-patterns to form the illumination pattern.
19. The system of claim 1 further comprising a spatial light modulator, wherein the spatial light modulator is positioned at a plane at which the light cones are focused into the illumination pattern.