Waveguide laser illuminator incorporating a Despeckler
There is provided an illumination device comprising: a laser; a waveguide comprising at least first and second transparent lamina; a first grating device for coupling light from the laser into a TIR path in the waveguide; a second grating device for coupling light from the TIR path out of the waveguide; and a third grating device for applying a variation of at least one of beam deflection, phase retardation or polarization rotation across the wavefronts of the TIR light. The first second and third grating devices are each sandwiched by transparent lamina.
1. An image projection device comprising:
a light source;
a reflective microdisplay;
a waveguide comprising:
an input grating for coupling light from said light source into a total internal reflection (TIR) path in said waveguide; and
an output grating for coupling light from said TIR path out of said waveguide and towards said reflective microdisplay,
wherein said waveguide is formed from transparent lamina sandwiching said input grating and said output grating,
wherein said output grating is configured to transmit light reflected from said reflective microdisplay; and
a lens for projecting image modulated light reflected from said microdisplay over a field of view.
2. The image projection device of claim 1 , wherein said light source is configured to emit light in at least first and second wavelength bands; and wherein said input grating and said output grating have high diffraction efficiency for light in said first and second wavelength bands.
3. The image projection device of claim 1 , wherein said output grating has at least one characteristic for providing uniform illumination onto said microdisplay selected from the group of optical power, diffusion, spatially varying light cone tilt, spatially varying light cone angle and spatially varying refractive index modulation.
4. The image projection device of claim 1 , further comprising a grating device for applying a variation of at least one of beam deflection or phase retardation across wavefronts of said light coupled into the TIR path, wherein said grating device is sandwiched by said transparent lamina.
5. The image projection device of claim 4 , further comprising transparent electrodes applied to said transparent lamina.
6. The image projection device of claim 4 , wherein said grating device has an optical prescription that varies along said waveguide.
7. The image projection device of claim 4 , wherein said grating device comprises more than one grating lamina adjacently disposed along said waveguide.
8. The image projection device of claim 4 , wherein said grating device comprises a two-dimensional array of switchable grating elements, wherein electrodes are applied to overlapping portions of the transparent lamina sandwiching said switchable grating elements, at least one of said electrodes being pixelated into elements substantially overlapping said switchable grating elements.
9. The image projection device of claim 4 ,
wherein said grating device is disposed along the TIR path between said input grating and said output grating.
10. The illumination device of claim 1 , wherein said grating device diffuses light into the direction of said TIR path.
11. The image projection device of claim 1 , further comprising a second grating device for applying variation of at least one of beam deflection or phase retardation across the wavefronts of said light couple into the TIR path, wherein said grating devices overlap, have identical prescriptions, and are reciprocally configured.
12. The image projection device of claim 1 , wherein said grating device is configured as a Hadamard array.
13. The image projection device of claim 4 , wherein said grating device provides a laser despeckler.
14. The image projection device of claim 1 , wherein said light source comprises at least one laser emitter providing at least one wavelength.
15. The image projection device of claim 4 , wherein at least one said transparent lamina is fabricated from plastic.
16. The image projection device of claim 1 , wherein said lens collimates said image modulated light.
17. The image projection device of claim 1 , wherein said output grating incorporates an optical prescription of at least one selected from the group of a microlens and a diffuser.
18. The image projection device of claim 1 , wherein said waveguide supports at least one selected from the group of a randomly scattering surface structure, a mirror, a reflection grating, a transmission grating, a blazed surface relief grating, a polarization rotation layer and a reflector overlapping said grating device.
19. The image projection device of claim 1 , wherein said waveguide is terminated at an end thereof by at least one selected from the group of a reflector and a quarter wavelength retarder.