Laser illumination device
An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.
1. An optical device comprising:
at least one ESBG element sandwiched between transparent substrates, said ESBG element comprising a multiplicity of ESBG pixels disposed in a layer;
transparent conductive coatings applied to each said substrate, at least one of said coatings being patterned into independently addressable elements overlapping said pixels;
an electrical control circuit operative to apply voltages across each said pixel; and
a light coupling element disposed adjacent to one of said substrates for diverting input light from an external light source into a total internal reflection path within said substrates,
wherein each said pixel is characterized by one of a predefined set of grating vectors,
wherein each said pixel has one non-diffracting state and at least one diffracting state,
wherein each said ESBG pixel when in its diffracting state diffracts light out of said total internal reflection path through one of said substrates into one of a predefined set of output light paths.
2. The apparatus of claim 1 wherein said output optical paths are angularly separated.
3. The apparatus of claim 1 wherein said output optical paths are substantially normal to said substrates.
4. The apparatus of claim 1 wherein said pixel contains a planar grating.
5. The apparatus of claim 1 wherein said input light is collimated.
6. The apparatus of claim 1 wherein said multiplicity of pixels comprises a two dimensional array.
7. The apparatus of claim 1 wherein said input light is modulated with image information.
8. The apparatus of claim 1 wherein each said ESBG element is recorded in a Holographic Polymer Dispersed Liquid Crystal.
9. The apparatus of claim 1 wherein said first and second voltages are points on a time varying voltage characteristic.
10. The apparatus of claim 1 wherein each said pixel has optical power.
11. The apparatus of claim 1 wherein each said pixel converts incident light into diffuse light.
12. The apparatus of claim 1 wherein said ESBG elements comprise overlapping first and second ESBG elements and pixels from said first and second ESBG elements at least partially overlap.
13. The apparatus of claim 1 wherein each said pixel has phase retarding characteristics characterised in that the amount of retardation is proportional to said voltage.
14. The apparatus of claim 1 wherein each said pixel has light diffusing characteristics characterised in that the amount of diffusion is proportional to said voltage.
15. The apparatus of claim 1 wherein each said pixel encodes the optical characteristics of an axicon.
16. The apparatus device of claim 1 wherein each said pixel encodes the optical characteristics of a sub wavelength grating phase retarder.
17. The apparatus of claim 1 wherein said light coupling element is a grating device.
18. The apparatus of claim 1 wherein more than one of the pixels in an ESBG element is in its diffracting state at any time.
19. The apparatus of claim 1 wherein the spatio-temporal addressing of pixels by said electrical control circuit addresses said pixels is characterized by a cyclic process.
20. The apparatus of claim 1 wherein the spatio-temporal addressing of pixels by said electrical control circuit addresses said pixels is characterized by a random process.