Phase-compensated pupil-replicating lightguide
AssigneeFacebook Technologies, LLC
InventorsJilin Yang, Hee Yoon Lee
Life of this patent
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Abstract
A pupil-replicating lightguide includes an in-coupling grating structure, an out-coupling grating structure, and a phase compensation layer. The out-coupling grating structure has a spatially varying parameter such as grating duty cycle or grating thickness for evening out out-coupled distribution of light. The spatially varying out-coupling grating parameter disturbs the phase of the propagating image light. The phase compensation layer has a spatially varying optical thickness that compensates that disturbed phase to planarize an optical phase profile of out-coupled light, thereby improving a modulation transfer function of the pupil-replicating lightguide.
Claims20
A pupil-replicating lightguide comprising:
- a slab of transparent material;
- an in-coupling grating structure coupled to the slab for in-coupling image light into the slab within an entrance pupil of the pupil-replicating lightguide, for propagating the image light in the slab by a series of internal reflections;
- an out-coupling grating structure coupled to the slab for replicating the entrance pupil by out-coupling a plurality of laterally offset portions of the image light from the slab, each out-coupled image light portion having a corresponding replicated pupil, the replicated pupils of the out-coupled image light portions forming an exit pupil of the pupil-replicating lightguide;
- and
- a phase compensation layer supported by at least one of the in-coupling grating structure, the out-coupling grating structure, or the slab, the phase compensation layer having a laterally variant optical thickness for planarizing an optical phase profile of at least one image light portion across its corresponding replicated pupil.
A display apparatus comprising:
- a projector for providing image light carrying an image in angular domain, the projector having an exit pupil;
- and
- a pupil-replicating lightguide comprising:
- a slab of transparent material;
- an in-coupling grating structure coupled to the slab for in-coupling the image light into the slab for propagation in the slab by a series of internal reflections;
- an out-coupling grating structure coupled to the slab for replicating the projector's exit pupil by out-coupling a plurality of laterally offset portions of the image light from the slab, each out-coupled image light portion having a corresponding replicated pupil, the replicated pupils of the out-coupled image light portions forming an exit pupil of the pupil-replicating lightguide;
- and
- a phase compensation layer having a laterally variant optical thickness for planarizing an optical phase profile of at least one image light portion across its corresponding replicated pupil.
A method of manufacturing a pupil-replicating lightguide, the method comprising:
- providing a slab of transparent material;
- forming an in-coupling grating structure on or in the slab for in-coupling image light into the slab within an entrance pupil of the pupil-replicating lightguide, for propagating the image light in the slab by a series of internal reflections;
- forming an out-coupling grating structure on or in the slab for replicating the entrance pupil by out-coupling a plurality of laterally offset portions of the image light from the slab, each out-coupled image light portion having a corresponding replicated pupil, the replicated pupils of the out-coupled image light portions forming an exit pupil of the pupil-replicating lightguide;
- and
- forming a phase compensation layer on at least one of the in-coupling grating structure, the out-coupling grating structure, or the slab, the phase compensation layer having a laterally variant optical thickness for planarizing an optical phase profile of at least one image light portion across its corresponding replicated pupil.
Dependencies are inferred from the claim text.