Optical tracking including imaging-based angle sensitive detectors
The present disclosure is directed to systems and methods of object tracking for use in various applications, such as eye tracking in virtual reality or augmented reality applications that include head-mounted display devices. An eye tracking system may be provided that includes a plurality of assemblies that each include a light detector, such as a quadrant photodetector, and an imaging lens configured to generate an image of the eye on the quadrant photodetector. Machine learning or other techniques may be used to track or otherwise determine a user's gaze direction, which may be used by one or more components of an HMD device to improve its functionality in various ways.
1. An eye tracking system, comprising:
a support structure positionable on the head of a user; and
a plurality of optical detectors carried by the support structure, each of the plurality of optical detectors comprising:
a quadrant photodetector comprising four optically active areas;
an opaque screen spaced apart from and positioned in front of the quadrant photodetector, the opaque screen comprising an aperture therein; and
an imaging lens positioned within the aperture of the opaque screen such that the imaging lens and the aperture are structurally integrated with each other, the imaging lens configured to form a direct optical image of a pupil of an eye of the user onto the quadrant photodetector.
2. The eye tracking system of claim 1 , further comprising:
control circuitry configured to:
receive detector data from each of the plurality of optical detectors;
process the detector data received from the plurality of optical detectors; and
track the position of the eye of the user based at least in part on the processing of the received detector data.
3. The eye tracking system of claim 1 , further comprising:
a light source carried by the support structure, the light source comprising a light emitting diode that emits light having a wavelength that is between 780 nm and 1000 nm.
4. The eye tracking system of claim 3 , further comprising:
control circuitry configured to:
cause the light source to emit light;
receive detector data from each of the plurality of optical detectors;
process the detector data received from the plurality of optical detectors; and
track the position of the eye of the user based at least in part on the processing of the received detector data.
5. The eye tracking system of claim 1 wherein, for each of the plurality of optical detectors, the imaging lens is designed to have:
an object plane that is substantially coplanar with an expected position of the pupil of the eye of the user relative to the imaging lens; and
an image plane that is substantially coplanar with the quadrant photodetector.
6. The eye tracking system of claim 1 wherein the imaging lens comprises at least two lenses.
7. A head-mounted display system, comprising:
a support structure positionable on the head of a user;
a display carried by the support structure;
a light source carried by the support structure, the light source configured to emit light toward an eye of the user;
a plurality of optical detectors carried by the support structure, each of the plurality of optical detectors comprising:
a quadrant photodetector comprising four optically active areas;
an opaque screen spaced apart from and positioned in front of the quadrant photodetector, the opaque screen comprising an aperture therein; and
an imaging lens positioned within the aperture of the opaque screen such that the imaging lens and the aperture are structurally integrated with each other, the imaging lens configured to form a direct optical image of a pupil of the eye of the user onto the quadrant photodetector; and
control circuitry configured to:
cause the light source to emit light;
receive detector data from each of the plurality of optical detectors;
process the detector data received from the plurality of optical detectors; and
track the position of the eye of the user based at least in part on the processing of the received detector data.
8. The head-mounted display system of claim 7 wherein the light source comprises a light emitting diode that emits light having a wavelength that is between 780 nm and 1000 nm.
9. The head-mounted display system of claim 7 wherein, for each of the plurality of optical detectors, the imaging lens is designed to have:
an object plane that is substantially coplanar with an expected position of the pupil of the eye of the user relative to the imaging lens; and
an image plane that is substantially coplanar with the quadrant photodetector.
10. The head-mounted display system of claim 7 wherein the imaging lens comprises at least two lenses.
11. An optical detector, comprising:
a quadrant photodetector comprising four optically active areas;
an opaque screen spaced apart from and positioned in front of the quadrant photodetector, the opaque screen comprising an aperture therein; and
an imaging lens positioned within the aperture of the opaque screen such that the imaging lens and the aperture are structurally integrated with each other, the imaging lens configured to form a direct optical image of an object to be tracked onto the quadrant photodetector.
12. The optical detector of claim 11 wherein the imaging lens comprises at least two lenses.
13. A method of tracking an object, the method comprising:
providing a plurality of optical detectors, each of the plurality of optical detectors comprising:
a quadrant photodetector comprising four optically active areas;
an opaque screen spaced apart from and positioned in front of the quadrant photodetector, the opaque screen comprising an aperture therein; and
an imaging lens positioned within the aperture of the opaque screen such that the imaging lens and the aperture are structurally integrated with each other, the imaging lens configured to form a direct optical image of an object to be tracked onto the quadrant photodetector;
receiving detector data from each of the plurality of optical detectors;
processing the detector data received from the plurality of optical detectors; and
tracking the position of the object based at least in part on the processing of the received detector data.
14. The method of claim 13 , further comprising:
causing a light source to emit light having a wavelength that is between 780 nm and 1000 nm.
15. The method of claim 13 wherein, for each of the plurality of optical detectors, the imaging lens is designed to have:
an object plane that is substantially coplanar with an expected position of the object relative to the imaging lens; and
an image plane that is substantially coplanar with the quadrant photodetector.
16. The method of claim 13 wherein the imaging lens comprises at least two lenses.
17. The method of claim 13 wherein the object comprises an eye of a human.