Systems, devices, and methods for optical waveguides
Systems, devices, and methods for optical waveguides that are well-suited for use in wearable heads-up displays (WHUDs) are described. An optical waveguide includes a volume of optically transparent material, a first holographic optical element (HOE) and a second holographic optical element, wherein the first HOE and the second HOE are carried by the volume of optically transparent material, and the first HOE is positioned across a width of the volume of optically transparent material from the second HOE. Light enters the optical waveguide and is propagated down a length of the waveguide by reflection between the first HOE and the second HOE. Propagation of the light within the optical waveguide does not require total internal reflection. The optical waveguide may include means to in-couple the light into the waveguide and means to out-couple the light from the waveguide. WHUDs that employ such optical waveguides are also described.
1. A wearable heads-up display (WHUD) comprising:
a support structure that in use is worn on a head of a user, the support structure having a shape and appearance of an eyeglass frame;
a projector to generate light signals, the projector comprising at least one light source; and
an optical waveguide comprising:
a volume of optically transparent material;
a first holographic optical element (“HOE”) carried by the volume of optically transparent material;
a second HOE carried by the volume of optically transparent material and positioned opposite the first HOE across a width of the volume of optically transparent material, wherein light signals from the projector that enter the volume of optically transparent material are sequentially reflected at least twice by and between the first HOE and the second HOE to propagate along a length of the optical waveguide;
an in-coupling region; and
an out-coupling region.
2. The WHUD of claim 1 wherein the first HOE and the second HOE both span the length of the volume of optically transparent material.
3. The WHUD of claim 1 wherein the first HOE and the second HOE both span an active region of the volume of optically transparent material.
4. The WHUD of claim 1 wherein the volume of optically transparent material is curved.
5. The WHUD of claim 4 wherein the first HOE and the second HOE are both curved.
6. The WHUD of claim 1 further including an eyeglass lens carried by the support structure.
7. The WHUD of claim 6 wherein the optical waveguide is carried by the eyeglass lens.
8. The WHUD of claim 6 wherein the eyeglass lens is a curved prescription eyeglass lens.
9. The WHUD of claim 8 wherein the optical waveguide is carried by the curved prescription eyeglass lens and wherein a curvature of the optical waveguide corresponds to a prescription curvature of the curved prescription eyeglass lens.
10. The WHUD of claim 1 wherein the volume of optically transparent material has a shape and appearance of an eyeglass lens and is carried by the support structure.
11. The WHUD of claim 1 wherein the in-coupling region includes at least a portion of an element selected from a group consisting of: the first HOE, the second HOE, and a dedicated in-coupling element.
12. The WHUD of claim 11 wherein the in-coupling region includes a dedicated in-coupling element selected from a group consisting of: a hologram, a holographic optical element, a volume diffraction grating, a surface relief diffraction grating, a transmission grating, and a reflection grating.
13. The WHUD of claim 11 wherein light signals are in-coupled according to at least one property selected from a group consisting of: a wavelength of a light signal, an angle of incidence of a light signal on the in-coupling region, and a location of incidence of a light signal on the in-coupling region.
14. The WHUD of claim 11 wherein the projector further includes a controllable mirror to controllably direct the light signals towards the optical waveguide.
15. The WHUD of claim 1 wherein the out-coupling region includes at least a portion of an element selected from a group consisting of: the first HOE, the second HOE, and a dedicated out-coupling element.
16. The WHUD of claim 15 wherein the out-coupling region includes a dedicated out-coupling element selected from a group consisting of: a hologram, a holographic optical element, a volume diffraction grating, a surface relief diffraction grating, a transmission grating, and a reflection grating.
17. The WHUD of claim 15 wherein light signals are out-coupled according to at least one property selected from a group consisting of: a wavelength of a light signal, an angle of incidence of a light signal on the out-coupling region, and a location of incidence of a light signal on the out-coupling region.
18. The WHUD of claim 1 wherein the light source includes at least one laser diode.
19. A wearable heads-up display (WHUD) comprising:
a support structure that in use is worn on a head of a user, the support structure having a shape and appearance of an eyeglass frame;
a projector to generate light signals, the projector comprising at least one light source; and
an optical waveguide comprising:
a volume of optically transparent material;
a first holographic optical element (“HOE”) carried by the volume of optically transparent material;
a second HOE carried by the volume of optically transparent material and positioned opposite the first HOE across a width of the volume of optically transparent material, wherein light signals from the projector that enter the volume of optically transparent material are sequentially reflected at least twice by and between the first HOE and the second HOE to propagate along a length of the optical waveguide;
an in-coupling region; and
an out-coupling region;
wherein the first HOE comprises N holograms, where N is an integer greater than 1 and wherein each of the N holograms in the first HOE is responsive to light in a respective one of N distinct wavebands; and
wherein the second HOE comprises N holograms, wherein each of the N holograms in the second HOE is responsive to light in a respective one of the N distinct wavebands.
20. A wearable heads-up display (WHUD) comprising:
a support structure that in use is worn on a head of a user, the support structure having a shape and appearance of an eyeglass frame;
a projector to generate light signals, the projector comprising at least one light source; and
an optical waveguide comprising:
a volume of optically transparent material;
a first holographic optical element (“HOE”) carried by the volume of optically transparent material;
a second HOE carried by the volume of optically transparent material and positioned opposite the first HOE across a width of the volume of optically transparent material, wherein light signals from the projector that enter the volume of optically transparent material are sequentially reflected at least twice by and between the first HOE and the second HOE to propagate along a length of the optical waveguide;
an in-coupling region; and
an out-coupling region;
wherein the first HOE comprises:
a first hologram responsive to light in a first waveband and unresponsive to light outside the first waveband;
a second hologram responsive to light in a second waveband and unresponsive to light outside the second waveband; and
a third hologram responsive to light in a third waveband and unresponsive to light outside the third waveband, wherein the first waveband, the second waveband, and the third waveband are all distinct and non-overlapping; and
wherein the second HOE comprises:
a fourth hologram responsive to light in the first waveband and unresponsive to light outside the first waveband;
a fifth hologram responsive to light in the second waveband and unresponsive to light outside the second waveband; and
a sixth hologram responsive to light in the third waveband and unresponsive to light outside the third waveband.