SYSTEMS, DEVICES, AND METHODS FOR WAVEGUIDE-BASED EYEBOX EXPANSION IN WEARABLE HEADS-UP DISPLAYS
Systems, devices, and methods for eyebox expansion in wearable heads-up displays (“WHUDs”) are described. The WHUDs described herein each include a projector and an optical waveguide positioned in an optical path between the projector and an eye of the user. For any given light signal from the projector, the optical waveguide receives the light signal at an input coupler and outputs multiple instances or copies of the light signal from multiple discrete, spatially-separated output couplers. The multiple instances or copies of the light signal may be converged by the optical waveguide directly to respective exit pupils at the user's eye or may be routed by the optical waveguide to a holographic combiner in the user's field of view from which the light signals may be converged to respective exit pupils at the user's eye. The optical waveguide employs exit pupil replication to expand the eyebox of the WHUD.
1 . An optical waveguide comprising:
a volume of optically transparent material;
a first input coupler carried by the volume of optically transparent material and positioned and oriented to couple light from a light source into the volume of optically transparent material;
a first output coupler carried by the volume of optically transparent material, the first output coupler positioned and oriented to couple a first portion of light from the light source out of the volume of optically transparent material and direct the first portion of light to a first exit pupil; and
a second output coupler carried by the volume of optically transparent material and spatially-separated from the first output coupler, the second output coupler positioned and oriented to couple a second portion of light from the light source out of the volume of optically transparent material and direct the second portion of light to a second exit pupil, the second exit pupil spatially-separated from the first exit pupil.
2 . The optical waveguide of claim 1 wherein the volume of optically transparent material is positioned and oriented to guide both the first portion of light and the second portion of light towards the first output coupler, and wherein the first output coupler is oriented to redirect the second portion of light towards the second output coupler through the volume of optically transparent material.
3 . The optical waveguide of claim 2 wherein the first output coupler is at least partially reflective of the first portion of light and at least partially transmissive of the second portion of light.
4 . The optical waveguide of claim 1 wherein the volume of optically transparent material is positioned and oriented to guide the first portion of light directly towards the first output coupler without impinging on the second output coupler and to guide the second portion of light directly towards the second output coupler without impinging on the first output coupler.
5 . The optical waveguide of claim 1 wherein at least one of the first input coupler, the first output coupler, and the second output coupler is selected from a group consisting of: an optical grating, a diffraction grating, a hologram, and a holographic optical element comprising at least two holograms.
6 . The optical waveguide of claim 1 , further comprising an eyeglass lens, wherein the volume of optically transparent material is integrated with the eyeglass lens.
7 . The optical waveguide of claim 1 wherein the volume of optically transparent material includes a single optical channel through which the first portion of light and the second portion of light are both guided.
8 . The optical waveguide of claim 1 wherein the volume of optically transparent material includes a first optical channel through which the first portion of light is guided towards the first output coupler and a second optical channel through which the second portion of light is guided towards the second output coupler, and wherein the first portion of light is not guided through the second optical channel and the second portion of light is not guided through the first optical channel.
9 . The optical waveguide of claim 1 , further comprising:
N output couplers carried by the volume of optically transparent material, wherein N is an integer greater than 2, and wherein each respective one of the N output couplers is oriented to couple a respective portion of light from the light source out of the volume of optically transparent material and direct the respective portion of light to a respective one of N exit pupils.
10 . The optical waveguide of claim 9 wherein the N output couplers are arranged in a single row across a length of the volume of optically transparent material, and wherein each of the N output couplers is at least partially reflective to couple a respective portion of light from the light source out of the volume of optically transparent material and direct the respective portion of light to a respective one of the N exit pupils, and each of at least N−1 of the output couplers is partially transmissive to transmit a respective portion of light from the light source through the volume of optically transparent material towards at least one other one of the N output couplers.
11 . The optical waveguide of claim 9 wherein:
the N output couplers are arranged in an array having P>1 rows and Q>1 columns;
the volume of optically transparent material is positioned and oriented to guide a respective portion of light from the light source to each respective one of the N output couplers;
the Q output couplers in each respective one of the P rows are arranged in a row;
each of the Q output couplers in each of the P rows is at least partially reflective to couple a respective portion of light from the light source out of the volume of optically transparent material and direct the respective portion of light to a respective one of the N exit pupils; and
each of at least Q−1 of the Q output couplers in each of the P rows is partially transmissive to transmit a respective portion of light from the light source through the volume of optically transparent material towards at least one other one of the Q output couplers in the row.
12 . The optical waveguide of claim 11 wherein the volume of optically transparent material includes P optical channels and each of the P rows corresponds to a respective one of the P channels.
13 . The optical waveguide of claim 1 , further comprising a second input coupler oriented to couple light from the light source into the volume of optically transparent material, wherein the first input coupler is positioned and oriented to couple the first portion of light from the light source into the volume of optically transparent material and direct the first portion of light from the light source towards the first output coupler and the second input coupler is positioned and oriented to couple the second portion of light from the light source into the volume of optically transparent material and direct the second portion of light from the light source towards the second output coupler.