Diffractive waveguide providing structured illumination for object detection
There is provided a diffractive waveguide device comprising: a light source, at least one light detector, an SBG device comprising a multiplicity of separately switchable SBG elements sandwiched between transparent substrate to which transparent electrodes have been applied. The substrates function as a light guide. Each SBG element encodes image information to be projected on an image surface. Each SBG element when in a diffracting state diffracts light out of the light guide to form an image region on an image surface. The light detector detects light scattered from an object disposed in proximity to the image surface and illuminated by said image region.
1. A diffractive waveguide device, comprising:
a first light source emitting light of a first wavelength;
at least one switchable SBG elements;
transparent substrates sandwiching said SBG elements, said substrates together functioning as a first light guide;
at least one light detector; and
a means for coupling said first wavelength light into a total internal reflection path in said first light guide,
wherein each said SBG element has a diffracting state and a non diffracting state, each said SBG element when in its diffracting state diffracts said first wavelength light to form a focused image region of predefined geometry and luminance distribution on an image surface,
wherein each said SBG element encodes wavefront and phase information corresponding to said geometry and said luminance distribution,
wherein said light detector is operative to detect light scattered from an object disposed in proximity to said image surface and illuminated by said image region.
2. The apparatus of claim 1 wherein transparent electrodes applied to opposing faces of said substrates, at least one of said transparent electrodes comprising a plurality of independently switchable transparent electrode elements, each of said independently switchable electrode elements substantially overlaying a unique SBG element.
3. The apparatus of claim 1 wherein said diffracting state exists when no electric field is a applied across said SBG element via said transparent electrodes and said non diffracting state exists when an electric field is applied across said SBG element via said transparent electrodes.
4. The apparatus of claim 1 wherein the image surface is disposed in proximity to said display.
5. The apparatus of claim 1 wherein said image region is an image pixel.
6. The apparatus of claim 1 wherein said SBG elements pre-distort the shape of said image region.
7. The apparatus of claim 1 wherein image surface is a diffusing material.
8. The apparatus of claim 1 wherein image surface is the retina of an eye.
9. The apparatus of claim 1 wherein said image surface is curved.
10. The apparatus of claim 1 wherein said first wavelength is in the infrared band.
11. The apparatus of claim 1 wherein said source is a laser or a Light Emitting Diode.
12. The apparatus of claim 1 wherein said sensor comprises an array of photodetectors.
13. The apparatus of claim 1 wherein a multiplicity of image regions each comprising a pixel are formed in rows of pixels.
14. The apparatus of claim 1 wherein first and second image regions are formed simultaneously by first and second SBG elements.
15. The apparatus of claim 1 wherein first and second image regions are formed sequentially to by first and second SBG elements.
16. The apparatus of claim 1 wherein first and second image regions formed by first and second SBG elements abut.
17. The apparatus of claim 1 wherein a multiplicity of image regions each comprising a pixel is formed as row of pixels.
18. The apparatus of claim 1 wherein said image region comprises one of a grid of parallel lines or concentric circles.
19. The apparatus of claim 1 wherein the light diffracted into said image region is temporally modulated.
20. The apparatus of claim 1 wherein two or more SBG elements spatially configured within said light guide for the purpose of determining object range by triangulation are provided.