Laser illumination device
An internal device having a lightguide which cooperates with an internal light source. A first light coupling element couples an external light source to the lightguide and a second light coupling element extracts the total internal reflection (TIR) from the lightguide. Between the first and second lightguides, an angular grating device and phase grating device are imposed. The angular grating device applies angular diversity to the rays of the TIR light, while the phase grating device applies phase diversity to the rays of the TIR light. Each of the grating devices has a plurality of electrically switchable grating pixels having a unique first and second diffracting state which varies based on the applied voltage.
1. An illumination device comprising:
a lightguide;
a first light coupling element for coupling light from an external light source into a total internal reflection (TIR) light path within said lightguide;
at least one first grating device disposed in said lightguide for applying angular diversity to rays of said TIR light;
at least one second grating device disposed in said lightguide for applying phase diversity to rays of said TIR light; and
a second light coupling element for extracting said TIR light from said lightguide,
wherein each of said first or second grating devices comprises a multiplicity of electrically switchable grating pixels, each said grating pixel having a first unique diffracting state under a first applied voltage and a second unique diffracting state under a second applied voltage.
2. The apparatus of claim 1 wherein said grating devices are electrically switchable Bragg gratings sandwiched between transparent substrates, wherein transparent conductive coatings are applied to said substrates and at least one of said coatings is patterned into independently addressable elements overlapping said grating pixels, wherein an electrical control circuit operative to apply said voltages across each said pixel is provided.
3. The apparatus of claim 1 wherein said first and second diffracting states occur during the integration time of the human eye.
4. The apparatus of claim 1 wherein a first set of diffracting states of said grating pixels corresponds to a first unique speckle pattern and a second set of diffracting states of said grating pixels corresponds to a second unique speckle pattern.
5. The apparatus of claim 1 wherein said first and second voltages are points on a temporally-varying voltage characteristic.
6. The apparatus of claim 1 wherein each said pixel has a unique grating vector.
7. The apparatus of claim 1 wherein said grating pixels of said phase diversity grating device each have a first phase retarding characteristic under said first voltage and a second phase retarding characteristic under said second voltage.
8. The apparatus of claim 1 wherein said grating pixels of said angular diversity grating device each have a first light diffusing characteristic under said first voltage and a second light diffusing characteristic under said second voltage.
9. The apparatus of claim 1 wherein said grating devices have at least one of optical power or light diffusing properties.
10. The apparatus of claim 1 wherein at least one of said grating devices comprises identical first and second gratings and the electrical waveforms applied to overlapping pixels of said first and second gratings along said TIR path are anti-phase.
11. The apparatus of claim 1 wherein at least one of said grating devices comprises identical first and second gratings having grating pixels at least partially overlapping along said TIR path.
12. The apparatus of claim 1 wherein said source provides first and second wavelength light and at least one of said grating devices comprises gratings for diffracting said first and second wavelength light.
13. The apparatus of claim 1 disposed within an optical train comprising a laser, a display panel and a projection lens.
14. The apparatus of claim 1 disposed within an optical train comprising a laser, a display panel, a projection lens and an image viewing surface.
15. The apparatus of claim 1 wherein at least one of said first and second light coupling elements is one of a grating or a prism.
16. The apparatus of claim 1 wherein light from said source is scanned.
17. The apparatus of claim 1 wherein at least one said grating device performs spatio-temporal modulation of said light.
18. The apparatus of claim 1 further comprising a diffractive optical element for changing at least one of illumination profile or beam cross section geometry.
19. The apparatus of claim 1 wherein said source comprises at least one laser die of at least one color.
20. The apparatus of claim 1 wherein said source comprises an array of laser die.