WAVEGUIDE GRATING DEVICE

• US 20160238772A1
• Filed: 02/12/2015
• Published: 08/18/2016
• 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: STANLEY, James H., BROWN, Robert D., WALDERN, Jonathan David, GRANT, Alastair John, POPOVICH, Milan Momcilo
• Granted Patent: US 9,632,226 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 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.

Claims

1. An optical waveguide comprising:

at least two TIR surfaces and containing a grating, wherein input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions, wherein each ray from said first angular range and its corresponding diffracted ray lie on the diffraction cone of said grating, wherein each diffraction provides a unique TIR angular range along a second propagation direction.

2. The apparatus of claim 1 wherein each ray from said first angular range and its corresponding diffracted ray are offset from the k-vector of said grating by an angle less than an angle at which the diffraction efficiency is a predefined fraction of the peak diffraction efficiency.

3. The apparatus of claim 1 wherein each said unique TIR angular range provides a unique diffraction efficiency versus angle characteristic.

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

5. The apparatus of claim 3 wherein said diffraction efficiency versus angle characteristics overlap.

6. The apparatus 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 apparatus of claim 1 wherein said 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 apparatus of claim 1 wherein said 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.

9. The apparatus of claim 1 wherein said diffracted light has a polarization state produced by aligning the average relative permittivity tensor of said grating, said polarization state being one of linearly, elliptically or randomly polarized.

10. The apparatus of claim 1 wherein non-diffracted has a polarization state produced by aligning the average relative permittivity tensor of said grating, said polarization state being one of linearly, elliptically or randomly polarized.

11. The apparatus of claim 1 wherein said grating is one of a multiplexed set of gratings.

12. The apparatus of claim 1 wherein said grating has a spatially varying thickness.

13. The apparatus of claim 1 wherein said grating has spatially-varying diffraction efficiency.

14. The apparatus of claim 1 wherein said grating has spatially-varying k-vector directions.

15. The apparatus of claim 1 wherein said grating comprise an array of selectively switchable elements.

16. The apparatus of claim 1 wherein said diffracted light is transmitted through a TIR face of said waveguide.

17. The apparatus of claim 1 further comprising at least one of a waveguide input coupler for inputting light through a face of said waveguide and directing it into said first propagation path, and a waveguide output coupler for outputting said diffracted light through a face of said waveguide, wherein each of said input and output couplers is one of a grating or prism.

18. The apparatus of claim 17 wherein at least one of said waveguide input coupler and said waveguide output coupler is a grating configured such that grating reciprocity is satisfied within said waveguide.

19. The apparatus of claim 1 wherein said input light is modulated with temporally-varying angularly-distributed information content.

20. The apparatus of claim 1 wherein said waveguide has first and second parallel TIR surfaces, said grating diffracting light out of said first propagation direction into a second propagation direction, said 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.

21. The apparatus of claim 20 wherein said first and second propagation direction are orthogonally disposed in the plane of the waveguide.

22. The apparatus of claim 20 further comprising a second grating overlaying said first grating. Said second grating deflecting light in said first propagation direction into a second propagation direction within said waveguide, said second 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.

23. The apparatus of claim 22 wherein first and second gratings are multiplexed.

24. The apparatus of claim 22 wherein each said third and fourth TIR angular ranges correspond to unique diffraction efficiency versus angle characteristics.

25. The apparatus of claim 1 wherein input TIR light with an angular range in a third propagation direction undergoes at least one diffraction along a unique vector on the diffraction cone of said grating.

26. The apparatus of claim 25 wherein said first and said third propagation direction are in opposing directions.

27. The apparatus of claim 25 wherein said TIR angular range of said input TIR light in said third propagation direction does not overlap with the diffraction efficiency versus angle characteristics of the light in said second propagation direction.

28. The apparatus of claim 25 wherein said input TIR light in said first propagation direction and said input TIR light in third second propagation direction have different wavelengths.

29. The apparatus of claim 25 further comprising a second grating, wherein said input TIR light in said third propagation direction is diffracted by said second grating.

30. The apparatus of claim 25 wherein said grating multiplexes first and second gratings, wherein said input TIR light in said first propagation direction is diffracted by said first multiplexed grating and said input TIR light in said third propagation direction is diffracted by said second multiplexed grating.