Waveguide structure
AssigneeBAE SYSTEMS plc
InventorIAN MARSHALL
Life of this patent
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Abstract
An optical waveguide device for use in a head up display. The waveguide device provides pupil expansion in two dimensions. The waveguide device comprise a primary waveguide and a secondary waveguide, the secondary waveguide being positioned on a face of the primary waveguide. The secondary waveguide has a diffraction grating on a face opposite to the face which contacts the primary waveguide. The diffraction grating diffracts light into more than diffraction order. Rays diffracted into a non-zero order are trapped in the secondary waveguide by total internal reflection.
Claims31
An optical waveguide for a head up display, the optical waveguide being configured to provide pupil expansion in two dimensions, the waveguide comprising:
- a primary waveguide having an input end and an output end;
- a secondary waveguide positioned on a face of the primary waveguide between the input end and the output end, there being an interface between the primary waveguide and secondary waveguide, the refractive index of the primary waveguide being lower than the refractive index of the secondary waveguide;
- and
- a main diffraction grating on a face of the secondary waveguide, which face is parallel and opposite to the interface with the primary waveguide.
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An optical waveguide for a head up display, the optical waveguide being configured to provide pupil expansion in two dimensions, the waveguide comprising:
- a primary waveguide having an input end and an output end;
- a secondary waveguide positioned on a face of the primary waveguide between the input end and the output end, there being an interface between the primary waveguide and secondary waveguide, the refractive index of the primary waveguide being lower than the refractive index of the secondary waveguide;
- a main diffraction grating on a face of the secondary waveguide, which face is parallel and opposite to the interface with the primary waveguide;
- an input section, wherein the input section is configured to couple light into the primary waveguide such that the light is guided by total internal reflection at waveguide/air interfaces of the primary waveguide and of the secondary waveguide;
- and
- an output section at the output end of the primary waveguide, wherein the output section is configured to direct light propagating in the primary waveguide out of that waveguide to an output pupil of the optical waveguide.
Dependencies are inferred from the claim text.