Skew mirror auxiliary imaging
Optical systems for performing gaze tracking and imaging an external scene are disclosed. An example optical system may include light sources for emitting visible and non-visible light. The optical system may include a waveguide that is operatively coupled to the light sources. A volume holographic light coupling element may be disposed between the surfaces of the waveguide. The volume holographic light coupling element may include a grating medium and a first volume holographic grating structure within the grating medium. In some examples, the first volume holographic grating structure may be configured to reflect non-visible light of a first wavelength about a first reflective axis offset from a surface normal of the grating medium at a first incidence angle. The optical system may also include an optical filter. Another example optical system may include an imaging device that is configured to receive the light external to the optical system.
1. An electronic device comprising:
a light source configured to output first light at a first wavelength greater than 700 nm;
a display configured to output second light at a second wavelength less than 700 nm;
a waveguide having a first lateral surface and a second lateral surface opposite and parallel to the first lateral surface, the waveguide being configured to propagate the first light and the second light via total internal reflection between the first and second lateral surfaces;
a medium layer on the waveguide and extending parallel to the first and second lateral surfaces;
a first set of volume holograms in the medium layer and configured to reflect the first light about a first reflective axis offset from a surface normal of the medium layer; and
a second set of volume holograms superimposed with the first set of volume holograms in the medium layer, the second set of volume holograms being configured to reflect the second light about a second reflective axis offset from the surface normal of the medium layer.
2. The electronic device of claim 1 , wherein the waveguide has a first substrate, the medium layer contacts the first substrate, and the first substrate has the first lateral surface.
3. The electronic device of claim 2 , wherein the waveguide has a second substrate, the second substrate having the second lateral surface.
4. The electronic device of claim 3 , wherein the medium layer contacts the second substrate.
5. The electronic device of claim 1 , wherein the first set of volume holograms is configured to diffract the first light out of the waveguide.
6. The electronic device of claim 5 , wherein the second set of volume holograms is configured to diffract the second light out of the waveguide.
7. The electronic device of claim 6 , further comprising:
a third set of volume holograms superimposed with the first and second sets of volume holograms in the medium layer, the third set of volume holograms being configured to diffract external light into the waveguide.
8. The electronic device of claim 7 , wherein the waveguide is configured to propagate the external light via total internal reflection between the first and second lateral surfaces.
9. The electronic device of claim 1 , further comprising:
a third set of volume holograms superimposed with the first and second sets of volume holograms in the medium layer, the third set of volume holograms being configured to diffract external light into the waveguide, wherein the waveguide is configured to propagate the external light via total internal reflection between the first and second lateral surfaces.
10. An electronic device comprising:
a light source configured to output first light at a first wavelength greater than 700 nm;
a display configured to output second light at a second wavelength less than 700 nm;
a waveguide configured to propagate the first light and the second light via total internal reflection;
a grating medium on the waveguide;
a first set of volume holograms in the grating medium, the first set of volume holograms being configured to diffract the first light and being configured to expand the first light in at least one dimension; and
a second set of volume holograms superimposed with the first set of volume holograms in the grating medium, the second set of volume holograms being configured to diffract the second light out of the waveguide.
11. The electronic device of claim 10 , wherein the first set of volume holograms is configured to diffract the first light about a reflective axis that is offset from a surface normal of the waveguide.
12. The electronic device of claim 10 , wherein the second set of volume holograms is configured to diffract the first light about a reflective axis that is offset from a surface normal of the waveguide.
13. The electronic device of claim 10 , wherein the second set of volume holograms is configured to expand the second light in at least two dimensions.
14. The electronic device of claim 10 , wherein the first set of volume holograms is configured to diffract the first light out of the waveguide.
15. The electronic device of claim 10 , further comprising:
a third set of volume holograms superimposed with the first and second sets of volume holograms in the grating medium, the third set of volume holograms being configured to diffract external light into the waveguide.
16. The electronic device of claim 15 , wherein the waveguide is configured to propagate the external light via total internal reflection.
17. An electronic device comprising:
a light source configured to output first light at a first wavelength greater than 700 nm;
a waveguide configured to propagate the first light via total internal reflection;
a grating medium on the waveguide;
a first set of volume holograms in the grating medium, the first set of volume holograms being configured to diffract the first light out of the waveguide;
a second set of volume holograms superimposed with the first set of volume holograms in the grating medium, the second set of volume holograms being configured to diffract second light into the waveguide, the second light being at a second wavelength less than 700 nm; and
a camera configured to receive the second light after diffraction by the second set of volume holograms.
18. The electronic device of claim 17 , wherein the waveguide is configured to propagate the second light via total internal reflection.
19. The electronic device of claim 17 , wherein the second light comprises environmental light.
20. The electronic device of claim 17 , further comprising:
a display configured to output third light at a third wavelength less than 700 nm, the waveguide being configured to propagate the third light via total internal reflection; and
a third set of volume holograms superimposed with the first and second sets of volume holograms in the grating medium, the third set of volume holograms being configured to diffract the third light out of the waveguide.