WAVEGUIDE GRATING DEVICE

• US 20180074265A1
• Filed: 11/08/2017
• Published: 03/15/2018
• Est. Priority Date: 02/12/2015
• Status: Active Grant

• Current Assignee: DigiLens Inc, Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: DigiLens Inc, Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: WALDERN, Jonathan David, GRANT, Alastair John, POPOVICH, Milan Momcilo, STANLEY, James H., BROWN, Robert D.
• Granted Patent: US 10,156,681 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: G02B 27/4261 having a diffractive element with major polarization dependent properties
• CPC Class Codes: G02B 5/1819 Plural gratings positioned on the same surface, e.g. array of gratings plural diffractive elements positioned sequentially along the optical path G02B27/4272
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals

Abstract

An optical waveguide display comprises: a waveguide; a source of light modulated with temporally-varying angularly-distributed information; a fold grating providing a first beam expansion; an input coupler for directing light into total internal reflection paths in a first propagation direction: and an output grating for providing a second beam expansion and extracting light from the waveguide. The input light undergoes at least two diffractions within the fold grating, each diffraction directing light into a unique total internal reflection angular range along a second propagation direction.

Claims

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 disposed in said waveguide;

an input coupler for directing said light into total internal reflection (TIR) paths in a first propagation direction in said waveguide; and

an output grating for extracting said light from said waveguide,

said fold grating providing a first beam expansion, said output grating providing a second beam expansion, wherein said fold grating diffracts light in said first propagation direction into a second propagation direction, wherein light in a first TIR angular range in said first propagation direction undergoes at least two diffractions within said fold grating, wherein each ray from said first angular range and its corresponding diffracted rays lie on a diffraction cone of said fold grating, wherein each diffraction provides a unique TIR angular range along said second propagation direction.

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

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

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

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

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

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

8. The optical waveguide of claim 1, wherein said fold grating is a Bragg grating or a SBG and is recorded in one of a HPDLC grating, uniform modulation grating or reverse mode HPDLC grating or a surface relief grating.

9. The optical waveguide of claim 1, wherein at least one of said diffracted light or said 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.

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

11. The optical waveguide of claim 1, wherein said fold grating is one of a multiplexed set of gratings.

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

13. The optical waveguide of claim 1, wherein said fold grating comprises an array of selectively switchable elements.

14. The optical waveguide of claim 1, wherein said input coupler is a grating or a prism.

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

16. The optical waveguide of claim 15, wherein said first and second propagation direction are orthogonally disposed in the plane of the waveguide.

17. The optical waveguide of claim 15, further comprising a second fold grating overlaying said first fold grating, wherein said second fold grating deflects light in said first propagation direction into a second propagation direction within said waveguide, said second fold grating characterized in that a portion of light reflected from said first TIR surface is diffracted into TIR along said second propagation direction in a third TIR angular range and a portion of light reflected from said second TIR surface is diffracted into TIR along said second propagation direction in a fourth TIR angular range.

18. The optical waveguide of claim 17, wherein first and second fold gratings are multiplexed.

19. The optical waveguide of claim 17, wherein each said third and fourth TIR angular ranges correspond to unique diffraction efficiency versus angle characteristics.

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