Diffractive waveguide providing structured illumination for object detection

Patent metadata

Field	Value
Publication number	US-11747719-B2
Application number	US-202117645249-A
Country	US
Kind code	B2
Filing date	Dec 20, 2021
Priority date	Oct 9, 2009
Publication date	Sep 5, 2023
Grant date	Sep 5, 2023

Abstract

A projection display device comprising a light source and an SBG device having a multiplicity of separate SBG elements sandwiched between transparent substrates to which transparent electrodes have been applied. The substrates function as a light guide. A least one transparent electrode comprises a plurality of independently switchable transparent electrode elements, each electrode element substantially overlaying a unique SBG element. Each SBG element encodes image information to be projected on an image surface. Light coupled into the light guide undergoes total internal reflection until diffracted out to the light guide by an activated SBG element. The SBG diffracts light out of the light guide to form an image region on an image surface when subjected to an applied voltage via said transparent electrodes.

First claim

What is claimed is:

1. A diffractive sensor comprising:
a first light source emitting light of a first wavelength;
at least one switchable Bragg grating (SBG) element;
transparent substrates sandwiching said at least one SBG element, said substrates together functioning as a first light guide;
at least one light detector;
a data processor configured to receive output signal from said light detector; and
an input coupler 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 at least one light detector is configured to record sequential image frames of light scattered from an object disposed in proximity to said image surface and illuminated by said image region, and
wherein said data processor is configured to determine at least one of the range or the shape of said object by analyzing changes in said sequential image frames recorded by said at least one light detector.

2. The diffractive sensor of claim 1 , further comprising 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 diffractive sensor of claim 1 , wherein said diffracting state exists when no electric field is 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 diffractive sensor of claim 1 , wherein the image surface is disposed in proximity to said first light guide.

5. The diffractive sensor of claim 1 , wherein said image region is an image pixel.

6. The diffractive sensor of claim 1 , wherein said at least one SBG element pre-distorts the shape of said image region.

7. The diffractive sensor of claim 1 , wherein said image surface is a diffusing material.

8. The diffractive sensor of claim 1 , wherein said image surface is a retina of an eye.

9. The diffractive sensor of claim 1 , wherein said image surface is curved.

10. The diffractive sensor of claim 1 , wherein said first wavelength is in an infrared band.

11. The diffractive sensor of claim 1 , wherein said source is a laser or a light emitting diode.

12. The diffractive sensor of claim 1 , wherein said diffractive sensor comprises an array of photodetectors.

13. The diffractive sensor of claim 1 , wherein the image region comprises a pixel formed in rows of pixels.

14. The diffractive sensor of claim 1 , wherein the image region comprises a first image region and a second image region formed simultaneously by a first SBG element and a second SBG element.

15. The diffractive sensor of claim 1 , wherein the image region comprises a first image region and a second image region formed sequentially by a first SBG element and a second SBG element.

16. The diffractive sensor of claim 1 , wherein the image region comprises an abutting first image region and second image region formed by a first SBG element and a second SBG element.

17. The diffractive sensor of claim 1 , wherein said image region comprises one of a grid of parallel lines or concentric circles.

18. The diffractive sensor of claim 1 , wherein the light diffracted into said image region is temporally modulated.

19. The diffractive sensor of claim 1 , wherein at least one SBG element comprises two or more SBG elements spatially configured within said light guide configured to determine object range by triangulation.

Assignees

• Digilens Inc

Inventors

• Popovich Milan Momcilo
• Waldern Jonathan David

Classifications

• H10H20/814

  having reflecting means, e.g. semiconductor Bragg reflectors · CPC title

• G03B21/005 Primary

  Projectors using an electronic spatial light modulator but not peculiar thereto · CPC title

• G01J3/1895

  using fiber Bragg gratings or gratings integrated in a waveguide · CPC title

• G02B5/1828 Primary

  having means for producing variable diffraction (controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955) · CPC title

• G02B5/1842

  Gratings for image generation (G02B5/1847 takes precedence) · CPC title