Optical systems with artifact blocking structures
An electronic device may include a display with a waveguide and a surface relief grating (SRG) on the waveguide. The SRG may direct image light towards an eye box. An optical blocker may at least partially overlap the SRG. The blocker may include a first optical wedge having a curved surface and a second optical wedge separated from the curved surface by an air gap or a low refractive index material. The curved surface may have a freeform shape that configures the first optical wedge to propagate world light incident upon the blocker within a selected range of incident angles away from the SRG via total internal reflection. The blocker may transmit world light at other incident angles to the eye box through the waveguide. This may allow the blocker to block high incident angle world light from reaching the SRG and producing unsightly rainbow artifacts at the eye box.
1. An electronic device comprising:
a waveguide configured to propagate light via total internal reflection;
a surface relief grating on the waveguide and configured to diffract the light; and
an optical blocker at least partially overlapping the surface relief grating wherein:
the optical blocker is configured to transmit, to an eye box through the waveguide, a first portion of world light that is incident upon the optical blocker within a first range of incident angles,
the optical blocker is configured to block, from reaching the surface relief grating, a second portion of the world light that is incident upon the optical blocker within a second range of incident angles different from the first range of incident angles,
the optical blocker includes a first optical wedge having a first surface and having a first curved surface opposite the first surface,
the optical blocker includes a second optical wedge having a second surface and having a second curved surface opposite the second surface,
the first curved surface and the second surface face the waveguide,
the first optical wedge is configured to transmit the first portion of the world light to the waveguide through the second optical wedge, and
the first optical wedge is configured to propagate the second portion of the world light away from the second optical wedge via total internal reflection between the first surface and the first curved surface.
2. The electronic device of claim 1 , wherein the optical blocker comprises an air gap between the first curved surface and the second curved surface.
3. The display system electronic device of claim 2 , wherein the second range of incident angles are at higher angles with respect to an optical axis of the optical blocker than the first range of incident angles.
4. The electronic device of claim 1 , wherein the first curved surface extends parallel to the second curved surface.
5. The electronic device of claim 4 , wherein the first curved surface comprises a freeform curved surface.
6. The electronic device of claim 4 , wherein the second surface is separated from the waveguide by an air gap.
7. The electronic device of claim 1 , further comprising:
an output coupler on the waveguide and configured to couple the light out of the waveguide and towards an eye box, wherein the output coupler includes the surface relief grating.
8. The electronic device of claim 1 , wherein the first surface is configured to transmit the first and second portions of the world light into the first optical wedge, the first surface being curved to is impart a non-zero optical power to the first and second portions of the world light upon transmission of the first and second portions of the world light into the first optical wedge.
9. The electronic device of claim 8 , further comprising:
a lens optically interposed between the waveguide and the eye box, wherein the lens is configured to transmit the first portion of the world light and wherein the lens is configured to at least partially reverse the non-zero optical power imparted to the first portion of the world light by the first surface.
10. The electronic device of claim 8 , wherein the second surface is curved.
11. The electronic device of claim 1 , wherein the first surface is curved.
12. The electronic device of claim 11 , wherein the second surface is curved.
13. The electronic device of claim 1 , wherein the second surface is curved.
14. An optical system configured to display light, the optical system comprising:
a waveguide;
a first optical wedge having a first surface facing the waveguide and a second surface opposite the first surface, wherein the first surface is curved and the waveguide is optically interposed between the first optical wedge and a location at which the light is to be displayed;
a second optical wedge having a third surface facing the waveguide and a fourth surface opposite the third surface, wherein the fourth surface is curved and faces the second surface; and
a surface relief grating structure on the waveguide, wherein
the first and second optical wedges at least partially overlap the surface relief grating structure,
the first optical wedge is configured to transmit, to the location through the second optical wedge and the waveguide, a first portion of world light that is incident upon the second surface within a first range of incident angles, and
the first optical wedge is configured to propagate, away from the second optical wedge via total internal reflection between the first and second surfaces, a second portion of the world light that is incident upon the second surface within a second range of incident angles different from the first range of incident angles.
15. The optical system of claim 14 , wherein the fourth surface is separated from the first surface by an air gap.
16. The optical system of claim 15 , wherein the first surface extends parallel to the fourth surface.
17. The optical system of claim 15 , wherein the second surface is curved and non-parallel with respect to the first, third, and fourth surfaces and wherein the third surface is curved and non-parallel with respect to the first, second, and fourth surfaces.
18. An electronic device comprising:
a waveguide;
a surface relief grating on the waveguide and configured to propagate light via total internal reflection;
a first optical wedge having a first surface and having a first curved surface opposite the first surface, wherein the first curved surface faces the waveguide; and
a second optical wedge having a second surface and having a second curved surface opposite the second surface, wherein the second curved surface faces the first curved surface and extends parallel to the first curved surface, wherein:
the waveguide is optically interposed between the second optical wedge and a location at which the light is to be displayed;
the first and second optical wedges at least partially overlap the surface relief grating,
the second curved surface is separated from the first curved surface by a first gap,
the second optical wedge is separated from the waveguide by a second gap,
the first optical wedge is configured to transmit, to the location through the second optical wedge and the waveguide, a first portion of world light that is incident upon the first optical wedge within a range of incident angles, and
the first optical wedge is configured to propagate, away from the second optical wedge via total internal reflection between the first surface and the first curved surface, a second portion of the world light that is incident upon the first optical wedge from outside of the range of incident angles.
19. The electronic device of claim 18 , wherein the first gap comprises air.
20. The electronic device of claim 18 , wherein the first gap comprises a non-air material having a refractive index different from that of the first optical wedge.
21. The electronic device of claim 18 , wherein:
the first surface is convex,
the second surface is convex,
the first portion of the world light passes from the first optical wedge to the second optical wedge through the first gap,
the first gap is a first air gap,
the first portion of the world light passes from the first gap to the second gap through the second optical wedge, the second gap is a second air gap,
the first portion of the world light passes from the second gap to the waveguide,
the first portion of the world light passes from the waveguide to the location,
the location is within an eye box,
the second portion of the world light does not enter the second optical wedge, and
the electronic device includes a spacer that attaches the first curved surface to the second curved surface at a periphery of the first air gap.