Holographic stray light suppression
An electronic device may include a camera, a lens, and gratings overlapping the lens. The gratings may diffract a first portion of light incident from a first range of incident angles while transmitting a second portion of the light incident from a second range of incident angles. The lens may direct the second portion of the light to the camera. The gratings may diffract the first portion of the light away from the optics. The gratings may be homogenous or spatially varying. If desired, the gratings may diffract the first portion of the light into a waveguide that propagates the first portion of the light away from the optics. The first range of incident angles and/or the location of the gratings may be selected to remove stray light that would otherwise produce artifacts in the image data. The camera may be replaced with an eye box in augmented reality implementations.
1 . An electronic device comprising:
an optical sensor configured to generate sensor data in response to light;
optics configured to transmit the light to the optical sensor;
a medium overlapping the optics; and
a set of holograms in the medium, the set of holograms being configured to
transmit, to the optics, a first portion of the light incident upon the medium from a first range of incident angles, and
diffract, away from the optics, a second portion of the light incident upon the medium from a second range of incident angles that is different from the first range of incident angles, wherein the set of holograms is rotationally symmetric about an optical axis of the optics.
2 . The electronic device of claim 1 , wherein the optics comprise a lens and the medium is layered onto a surface of the lens.
3 . The electronic device of claim 1 , further comprising:
a baffle, wherein the set of holograms is configured to diffract the second portion of the light towards the baffle.
4 . The electronic device of claim 1 , wherein the optics comprise a beam-translating prism, the medium being layered onto a surface of the beam-translating prism.
5 . The electronic device of claim 1 , wherein the second range of incident angles are greater than the first range of incident angles relative to an optical axis of the optics.
6 . The electronic device of claim 1 , further comprising:
a display configured to emit the light.
7 . The electronic device of claim 1 , wherein the set of holograms comprises reflective volume holograms.
8 . The electronic device of claim 7 , wherein the set of holograms further comprises transmissive volume holograms.
9 . The electronic device of claim 8 , wherein the transmissive volume holograms are confined to a first portion of a lateral area of the medium and the reflective volume holograms are confined to a second portion of the lateral area of the medium that is different from the first portion of the lateral area of the medium.
10 . The electronic device of claim 1 , wherein the set of holograms comprises transmissive volume holograms.
11 . The electronic device of claim 1 , wherein the set of holograms has a diffraction efficiency that varies across a lateral area of the medium.
12 . The electronic device of claim 11 , wherein the set of holograms is confined to a subset of the lateral area of the medium.
13 . The electronic device of claim 1 , wherein a first subset of the set of holograms is confined to a first region of a lateral area of the medium, a second subset of the set of holograms is confined to a second region of the lateral area of the medium that is different from the first region of the lateral area, the first subset of the set of holograms is configured to diffract light from a first subset of the second range of incident angles, and the second subset of the set of holograms is configured to diffract light from a second subset of the second range of incident angles that is different from the first subset of the second range of incident angles.
14 . The electronic device of claim 13 , wherein the first subset of the set of holograms is configured to diffract the light from the first subset of the second range of incident angles in a first direction within a total internal reflection (TIR) range of the medium and wherein the second subset of the set of holograms is configured to diffract the light from the second subset of the second range of incident angles in a second direction within the TIR range of the medium, the second direction being opposite the first direction.
15 . The electronic device of claim 1 , wherein the set of holograms is configured to diffract the second portion of the light onto an output angle within a total internal reflection (TIR) range of the medium, the medium being configured to propagate, via TIR, the second portion of the light diffracted by the set of holograms.
16 . A camera comprising:
an array of image sensor pixels;
a waveguide overlapping the array of image sensor pixels;
holograms on the waveguide, wherein
the holograms are configured to diffract, onto output angles within a total internal reflection (TIR) range of the waveguide, a first portion of light incident upon the medium layer from a first range of angles, and
the holograms are configured to transmit a second portion of the light incident upon the medium layer from a second range of angles; and
a lens configured to direct the second portion of the light onto the array of image sensor pixels, the first range of angles being greater than the second range of angles relative to an optical axis of lens, and the array of image sensor pixels being configured to capture images of the second portion of the light.
17 . The camera of claim 16 , wherein the holograms comprise volume holograms and are configured to transmit the second portion of the light without diffracting the second portion of the light.
18 . An electronic device comprising:
a projector configured to output image light;
a waveguide configured to propagate the image light;
an optical coupler on the waveguide configured to couple the image light out of the waveguide and towards an eye box, the optical coupler being configured to transmit external light towards the eye box and overlaid with the image light;
a medium overlapping the waveguide; and
a set of one or more overlapping holograms in the medium, the set of one or more overlapping holograms being configured to
transmit, to the waveguide, a first portion of the external light incident upon the medium from a range of incident angles, and
diffract, onto a range of multiple different output angles oriented away from the waveguide, a single incident angle of the external light, the single incident angle being outside the range of incident angles.
19 . The electronic device of claim 18 , further comprising:
a folded prism configured to couple the image light into the waveguide, the folded prism being configured to reflect the image light at least three times; and
a diffractive optical element layered onto a surface of the folded prism, the diffractive optical element being configured to diffract, away from the waveguide, a range of incident angles of the image light exceeding a threshold incident angle.