Optical systems with reflective prism input couplers
An electronic device may include a display module that generates light and an optical system that redirects the light towards an eye box. The system may include an input coupler on a waveguide and a lens that directs the light towards the input coupler. The input coupler may include a prism having a reflective surface that reflects the light into the waveguide. The reflective surface may be curved to provide the light with an optical power. The prism may be configured to expand a field of view of the light. A birefringent beam displacer may expand the effective pupil size of the light. The lens may include lens elements that converge the light at a location between the lens elements and the waveguide. A switchable panel may be placed at the location and toggled between first and second orientations to increase the effective resolution of the light.
1. An electronic device comprising:
a projector configured to output light;
a waveguide;
an input coupler comprising a prism configured to couple the light into the waveguide, the waveguide being configured to propagate the light via total internal reflection; and
an optical wedge optically coupled between the projector and the waveguide, wherein the optical wedge is configured to direct the light from the projector towards the input coupler.
2. The electronic device of claim 1 , wherein the optical wedge has a first surface configured to transmit the light and a second surface opposite the first surface and configured to transmit the light, the second surface being non-parallel with respect to the first surface.
3. The electronic device of claim 2 , wherein the first surface faces the waveguide and is parallel to a first lateral surface of the waveguide.
4. The electronic device of claim 3 , wherein the waveguide has a second lateral surface opposite the first lateral surface, wherein the prism is mounted to the second lateral surface, and wherein the first lateral surface is parallel to the second lateral surface.
5. The electronic device of claim 1 , further comprising:
an output coupler configured to couple the light out of the waveguide.
6. The electronic device of claim 1 , wherein the optical wedge comprises a dispersion compensation wedge configured to compensate for dispersion of the light by the input coupler.
7. The electronic device of claim 1 , wherein the prism is a reflective prism with a reflective surface configured to reflect the light into the waveguide.
8. The electronic device of claim 7 , further comprising:
a reflective layer that covers a portion of the reflective surface that overlaps a pupil of the light that has been focused onto the reflective surface; and
an optical absorber that covers a remainder of the reflective surface.
9. A display comprising:
a projector configured to generate light;
a waveguide;
an input coupler, wherein the input coupler is configured to couple the light into the waveguide; and
a birefringent beam displacer configured to receive a pupil of the light from the projector, wherein the birefringent beam displacer is configured to transmit a first polarization of the pupil towards the input coupler within a first beam, wherein the birefringent beam displacer is configured to transmit a second polarization of the pupil towards the input coupler in a second beam that is offset from the first beam, and wherein the second polarization is different from the first polarization.
10. The display of claim 9 , wherein the birefringent beam displacer is optically interposed between the waveguide and the projector.
11. The display of claim 10 , wherein the birefringent beam displacer is mounted to a surface of the waveguide.
12. The display of claim 9 , wherein the waveguide is interposed between the birefringent beam displacer and the input coupler.
13. The display of claim 9 , wherein the birefringent beam displacer is configured to split the pupil of the light from the projector into the first beam and the second beam.
14. The display of claim 9 , wherein the first beam and the second beam collectively exhibit an expanded pupil of light that is larger than the pupil of light.
15. A display comprising:
a projector that produces light;
a waveguide having opposing first and second surfaces, wherein the waveguide is configured to propagate the light via total internal reflection; and
an input coupling prism configured to receive the light, wherein the input coupling prism comprises:
a first wedge mounted to the first surface of the waveguide, wherein the first wedge is configured to couple the light into the waveguide in a first direction, and
a second wedge mounted to a surface of the first wedge, wherein the second wedge is configured to couple the light into the first wedge in a second direction that is non-parallel to the first direction.
16. The display of claim 15 , further comprising:
a polarizing beam splitter or a switchable reflective layer interposed between the first and second wedges.
17. The display of claim 15 , further comprising collimating optics that direct the light towards the second surface of the waveguide, wherein the input coupling prism is configured to receive the light from the collimating optics.
18. The display of claim 15 , wherein the surface of the first wedge is oriented at a first angle with respect to the first surface of the waveguide, the second wedge has an additional surface oriented at a second angle with respect to the first surface of the waveguide, and the second angle is greater than the first angle.
19. The display of claim 15 , wherein the surface of the first wedge is curved and wherein an additional surface of the second wedge is curved.
20. A display comprising:
a projector that produces light;
a waveguide having opposing first and second surfaces; and
an input coupling prism configured to receive the light, wherein the input coupling prism comprises:
a first wedge with a first refractive index and mounted to the first surface of the waveguide, wherein the first wedge is configured to couple the light into the waveguide in a first direction, and
a second wedge with a second refractive index different from the first refractive index and mounted to a surface of the first wedge, wherein the second wedge is configured to couple the light into the first wedge in a second direction that is non-parallel to the first direction.