Optical systems having optical couplers for sensing light
A display may include an emitter that emits infrared light and a coupler that couples the light into a waveguide and couples reflected infrared light coaxial with the light out of the waveguide. The optical coupler may include a polarizing beam splitter (PBS) mounted to a lateral surface of the waveguide. A linear polarizer may transmit the light to the PBS, which reflects the light towards a prism or a set of diffractive gratings that couple the light into the waveguide and that couple the reflected light out of the waveguide and towards the PBS. The PBS may transmit the reflected light towards a sensor for gaze tracking. The light and reflected light may be coupled through opposing surfaces of the waveguide if desired. These structures may serve to prevent reflected stray light from reaching the sensor and interfering with gaze tracking.
1 . A display comprising:
a waveguide;
an optical emitter configured to emit light;
a polarizing beam splitter (PBS) mounted to the waveguide;
a linear polarizer configured to transmit the light towards the PBS, wherein the PBS is configured to reflect the light into the waveguide, the waveguide is configured to propagate the light via total internal reflection (TIR) towards an object, the waveguide is configured to propagate reflected light from the object via TIR, and the reflected light is configured to be coupled out of the waveguide; and
an optical sensor configured to receive, through the PBS, the reflected light coupled out of the waveguide.
2 . The display of claim 1 , wherein the waveguide has a lateral surface and the PBS is oriented orthogonal to the lateral surface.
3 . The display of claim 2 , further comprising:
a first prism mounted to the lateral surface; and
a second prism, wherein the PBS is sandwiched between the first prism and the second prism, the second prism is configured to transmit the reflected light towards the optical sensor, the first prism is configured to transmit, into the waveguide, the light reflected off the PBS, and the first prism is configured to transmit, to the PBS, the reflected light coupled out of the waveguide.
4 . The display of claim 2 , wherein the PBS comprises a PBS plate.
5 . The display of claim 4 , further comprising:
a prism mounted to the lateral surface, wherein the prism has a surface that is angularly separated from the PBS plate by an air gap, the prism being configured to transmit, into the waveguide, the light reflected off the PBS and being configured to transmit, to the PBS plate, the reflected light coupled out of the waveguide.
6 . The display of claim 4 , further comprising:
a set of diffractive gratings layered on the lateral surface, wherein the set of diffractive gratings is configured to diffract, into the waveguide, the light reflected by the PBS, and is configured to diffract, towards the PBS plate, the reflected light.
7 . The display of claim 6 , wherein the set of diffractive gratings comprises a surface relief grating (SRG) or a set of volume holograms.
8 . The display of claim 4 , wherein the PBS plate comprises a wire grid polarizer.
9 . The display of claim 1 , wherein the PBS comprises a wire grid polarizer.
10 . The display of claim 1 , wherein the light comprises infrared light and the reflected light comprises reflected infrared light.
11 . The display of claim 10 , further comprising:
a projector configured to generate visible light containing an image, wherein the waveguide is configured to propagate the visible light via TIR;
a first optical coupler on the waveguide and configured to couple the visible light out of the waveguide and towards the object; and
a second optical coupler on the waveguide and at least partially overlapping the first optical coupler, wherein the second optical coupler is configured to couple, out of the waveguide and towards the object, the infrared light, and wherein the second optical coupler is configured to couple, from the object and into the waveguide, the reflected infrared light.
12 . The display of claim 11 , further comprising:
a quarter waveplate on the waveguide and at least partially overlapping the second optical coupler.
13 . A display comprising:
an optical emitter configured to emit first light;
a linear polarizer;
an optical sensor;
a waveguide; and
an optical coupler on the waveguide, wherein
the optical coupler comprises a polarizing beam splitter (PBS),
the linear polarizer is optically coupled between the optical emitter and the PBS,
the PBS is configured to reflect the first light,
the optical coupler is configured to couple, into the waveguide, the first light reflected by the PBS,
the optical coupler is configured to receive, from within the waveguide, second light that is co-axial with the first light, and
the optical coupler is configured to couple, out of the waveguide and towards the optical sensor through the PBS, the second light.
14 . The display of claim 13 , wherein the second light comprises a reflected version of the first light.
15 . The display of claim 14 , wherein the first light and the second light comprise infrared light.
16 . The display of claim 13 , wherein the PBS is mounted to a lateral surface of the waveguide and the optical coupler comprises a prism mounted to the lateral surface of the waveguide, the prism being configured to transmit the first light and the second light.
17 . The display of claim 13 , wherein the PBS is mounted to a lateral surface of the waveguide and the optical coupler comprises a set of diffractive gratings layered on the lateral surface of the waveguide, the set of diffractive gratings being configured to diffract, into the waveguide, the first light reflected by the PBS, and the set of diffractive gratings being configured to diffract, towards the PBS, the second light.
18 . A display comprising:
an optical emitter configured to emit first light;
an optical sensor;
a waveguide configured to propagate the first light in a first direction via total internal reflection (TIR) and configured to propagate, via TIR and in a second direction opposite the first direction, second light that is coaxial with the first light;
a first polarizer on the waveguide and configured to transmit light with a first polarization;
a first prism on the first linear polarizer and configured to transmit the first light into the waveguide through the first polarizer;
a second polarizer overlapping the waveguide and configured to transmit light with a second polarization different from the first polarization out of the waveguide and towards the optical sensor, wherein the first polarizer is offset from the second polarizer.
19 . The display of claim 18 , further comprising:
an optical coupler configured to couple the first light out of the waveguide and towards an object external to the waveguide, wherein the optical coupler is configured to couple the second light into the waveguide, and wherein the second light comprises a version of the first light that has reflected off the object.