Waveguide grating device

Patent metadata

Field	Value
Publication number	US-12379547-B2
Application number	US-202318317864-A
Country	US
Kind code	B2
Filing date	May 15, 2023
Priority date	Feb 12, 2015
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

An optical waveguide comprises at least two TIR surface and contains a grating. Input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions at the grating. Each diffraction directs light into a unique TIR angular range along a second propagation direction.

First claim

What is claimed is:

1. An optical waveguide display comprising:
a waveguide;
a source of light modulated with temporally-varying angularly-distributed information;
a fold grating of a first prescription configured as an evanescently coupled layer in proximity to the waveguide;
an input coupler for directing the light into total internal reflection (TIR) paths in a first propagation direction in the waveguide; and
an output grating for extracting the light from the waveguide,
wherein the fold grating provides a first beam expansion and diffracts light in the first propagation direction into a second propagation direction,
wherein the output grating provides a second beam expansion,
wherein light in a first TIR angular range in the first propagation direction undergoes at least two diffractions within the fold grating,
wherein each ray from the first angular range and its corresponding diffracted rays lie on a diffraction cone of the fold grating,
wherein each diffraction provides a unique TIR angular range along the second propagation direction.

2. The optical waveguide display of claim 1 , wherein a ray from the first angular range and its corresponding diffracted ray are each offset from the diffraction cone by an angle not exceeding half the diffraction angular bandwidth of the fold grating.

3. The optical waveguide display of claim 1 , wherein each unique TIR angular range provides a unique diffraction efficiency versus angle characteristic.

4. The optical waveguide display of claim 3 , wherein the diffraction efficiency versus angle characteristics do not overlap.

5. The optical waveguide display of claim 3 , wherein the diffraction efficiency versus angle characteristics overlap.

6. The optical waveguide display of claim 1 , wherein the angular separation of the diffracted ray vectors produced in the two diffractions is equal to the diffraction cone angle.

7. The optical waveguide display of claim 1 , wherein the fold grating is a leaky grating providing a multiplicity of diffractions, and wherein only two diffractions are characterized by a unique pair of incident and diffracted ray vectors on the diffraction cone.

8. The optical waveguide display of claim 1 , wherein at least one of the diffracted light or the non-diffracted light has a polarization state produced by aligning the average relative permittivity tensor of said fold grating, said polarization state being one of linearly, elliptically or randomly polarized.

9. The optical waveguide display of claim 1 , wherein said input coupler is a grating disposed in a common layer with at least one of the output grating and the fold grating.

10. The optical waveguide display of claim 1 , wherein the fold grating is one of a multiplexed set of gratings.

11. The optical waveguide display of claim 1 , wherein the fold grating has at least one of spatially varying thickness, spatially-varying diffraction efficiency or spatially-varying k-vector directions.

12. The optical waveguide display of claim 1 , wherein the fold grating comprises an array of selectively switchable elements.

13. The optical waveguide display of claim 1 , wherein the input coupler is a grating or a prism.

14. The optical waveguide display of claim 1 , wherein the waveguide has first and second parallel TIR surfaces, the fold grating characterized in that a portion of light reflected from the first TIR surface is diffracted into TIR along the second propagation direction in a first TIR angular range and a portion of light reflected from the second TIR surface is diffracted into TIR along the second propagation direction in a second TIR angular range.

15. The optical waveguide display of claim 14 , wherein the first and second propagation directions are orthogonally disposed in the plane of the waveguide.

16. The optical waveguide display of claim 1 , further comprising a second fold grating of a second prescription, wherein said second fold grating is in at least partial overlap with the first fold grating.

17. The optical waveguide display of claim 16 , wherein the second fold grating is configured as at least one selected from the group of an evanescently coupled layer in proximity to the waveguide, a Bragg grating, a switchable Bragg grating, a grating recorded in cell comprising two substrates, a grating recorded in a HPDLC material, a uniform modulation grating, a grating recorded in a reverse mode HPDLC material or a surface relief grating.

18. The optical waveguide display of claim 16 , wherein the second fold grating deflects light in the first propagation direction into the second propagation direction within the waveguide, the second fold grating characterized in that a portion of light reflected from the first TIR surface is diffracted into TIR along the second propagation direction in a third TIR angular range and a portion of light reflected from the second TIR surface is diffracted into TIR along the second propagation direction in a fourth TIR angular range.

19. The optical waveguide display of claim 16 , wherein the first and second fold gratings are multiplexed.

20. The optical waveguide display of claim 16 , wherein the third and fourth TIR angular ranges correspond to unique diffraction efficiency versus angle characteristics.

21. The optical waveguide display of claim 1 , wherein each diffraction provides a unique diffraction efficiency versus angle characteristic along the second propagation direction, wherein one of the diffractive efficiency versus angle characteristics corresponds to rays that do not meet the condition for TIR at the TIR surfaces.

22. An optical waveguide display comprising:
a waveguide;
a source of light modulated with temporally-varying angularly-distributed information;
a fold grating of a first prescription configured as an evanescently coupled layer in proximity to the waveguide;
an input coupler for directing the light into total internal reflection (TIR) paths in a first propagation direction in the waveguide; and
an output grating for extracting the light from the waveguide,
wherein the fold grating provides a first beam expansion and diffracts light in the first propagation direction into a second propagation direction,
wherein the output grating provides a second beam expansion,
wherein light in a first TIR angular range in the first propagation direction undergoes at least two diffractions within the fold grating,
wherein each ray from the first angular range and its corresponding diffracted rays lie on a diffraction cone of the fold grating,
wherein each diffraction provides a unique TIR angular range along the second propagation direction,
wherein the fold grating is slanted with respect to a plane of the waveguide.

Assignees

• Digilens Inc
• Rockwell Collins Inc

Inventors

• Waldern Jonathan David
• Grant Alastair John
• Popovich Milan Momcilo
• Stanley James H
• Brown Robert D

Classifications

• G02B2027/0125

  Field-of-view increase by wavefront division · CPC title

• G02B27/4261

  having a diffractive element with major polarization dependent properties · CPC title

• G02B6/0016

  Grooves, prisms, gratings, scattering particles or rough surfaces · CPC title

• G02B6/124 Primary

  Geodesic lenses or integrated gratings · CPC title

• G02B5/32

  Holograms used as optical elements · CPC title