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:
a light guiding structure;
a source of light optically coupled to said light guiding structure and configured to emit at least first and second wavelength collimated light color sequentially;
a first ESBG element comprising a first multiplicity of ESBG pixels for diffracting said first wavelength light out of said light guiding structure into a first set of output paths; and
a second ESBG element comprising a second multiplicity ESBG pixels for diffracting said second wavelength light out of said light guiding structure into a second set of output paths substantially overlapping said first set of output paths,
wherein said first and second multiplicity of ESBG pixels are formed in at least one layer disposed within said light guiding structure,
wherein pixels of said first multiplicity are configured to switch into a diffracting state when said source emits said first wavelength light and pixels of said second multiplicity are configured to switch into a diffracting state when said source emits said second wavelength light.
2. The apparatus of claim 1 , wherein said at least one layer is formed between transparent substrates with transparent conductive coatings applied to each said substrate, at least one of said coatings being patterned into independently addressable elements overlapping said first multiplicity and second multiplicity of pixels, wherein an electrical control circuit operative to selectively apply voltages across each said first multiplicity and second multiplicity of pixels is provided.
3. The apparatus of claim 1 , wherein said first and second output paths are angularly separated.
4. The apparatus of claim 1 , wherein said first and second output paths are substantially normal to a total internal reflection surface of said light guiding structure.
5. The apparatus of claim 1 , wherein each said first and second multiplicity of pixels is characterized by one of a predefined set of grating vectors.
6. The apparatus of claim 1 , wherein each said first and second multiplicity of pixels comprises at least one selected from the group of a planar grating, a grating with optical power, a grating providing optical retardation and a grating with diffusing properties.
7. The apparatus of claim 1 , wherein each said first and second multiplicity of pixels have spatially varying diffraction efficiencies.
8. The apparatus of claim 1 , wherein each said first and second multiplicity of pixels have diffraction efficiencies proportional to voltages applied across said electrodes.
9. The apparatus of claim 1 , wherein each said first and second multiplicity of pixels have phase retardations proportional to voltages applied across said electrodes.
10. The apparatus of claim 1 , wherein light diffracted into said first and second output paths is collimated.
11. The apparatus of claim 1 , wherein said first multiplicity of pixels comprises a two-dimensional array.
12. The apparatus of claim 1 , wherein said first multiplicity of pixels comprises a one-dimensional array of elongate elements.
13. The apparatus of claim 1 , wherein each said first and second ESBG element is recorded in a Holographic Polymer Dispersed Liquid Crystal.
14. The apparatus of claim 1 , further comprising a light coupling element, wherein the light coupling element is a grating or prism.
15. The apparatus of claim 2 , wherein the addressing of pixels by said electrical control circuit addresses said pixels is characterized by a cyclic process.
16. The apparatus of claim 2 , wherein the addressing of pixels by said electrical control circuit is characterized by a random process.
17. The apparatus of claim 1 , wherein said light source is laser or LED.
18. The apparatus of claim 1 , further comprising a beam deflector, a dichroic filter, a microlens array, beam shaper, light integrator, polarization rotator.
19. The apparatus of claim 1 , wherein said source further emits third wavelength collimated light further comprising a third multiplicity of ESBG pixels for diffracting said third wavelength light in a third set of output paths substantially overlapping said first set of output paths, wherein said first, second and third multiplicity of ESBG pixels are formed in at least one layer disposed within said light guiding structure, wherein pixels of said third multiplicity are switched into a diffracting state when said source emits said third wavelength light.
20. The apparatus of claim 19 , wherein said first, second and third wavelengths comprises light in red, green and blue spectral bands respectively.