BINARY-ENCODED ILLUMINATION FOR CORNEAL GLINT DETECTION
An apparatus, system, and method for detecting glints includes a pair of light sources positioned on a head-mounted frame and driven to illuminate a corneal surface of an eye with binary-encoded differential light signals. An image sensor is positioned on the head-mounted frame to receive reflections of the differential light signals from the corneal surface. An orientation of a cornea (e.g., corneal sphere) of the eye may be determined at least partially based on the reflections of the binary-encoded differential light signals.
1 . A glint detection system comprising:
a plurality of pairs of light sources positioned on a head-mounted frame to illuminate a corneal surface of an eye with differential light signals;
an image sensor positioned on the head-mounted frame to receive reflections of the differential light signals from the eye;
processing logic coupled to the plurality of pairs of light sources and to the image sensor; and
one or more memories coupled to the processing logic, the one or more memories storing instructions that, when executed by the processing logic, cause the glint detection system to perform operations comprising:
encode the differential light signals with binary identifiers that are unique to each pair of the plurality of pairs of lights;
receive, from the image sensor, image data that is representative of reflections of the differential light signals; and
identify each of the plurality of pairs of light sources within the image data at least partially based on the binary identifiers.
2 . The glint detection system of claim 1 , wherein the one or more memories store further instructions that when executed by the processing logic, cause the glint detection system to perform further operations comprising:
identify locations, within the image data, of the reflections of the differential light signals; and
determine a location of a corneal sphere of the eye at least partially based on the locations.
3 . The glint detection system of claim 1 , wherein the binary identifiers are binary numbers having at least 2 bits.
4 . The glint detection system of claim 1 , wherein the image sensor is responsive to changes in brightness in a field of view of the image sensor, wherein the image data is representative of the changes in brightness in the field of view of the image sensor.
5 . The glint detection system of claim 1 , wherein the image sensor is an event camera that is responsive to changes in brightness in a field of view of the image sensor.
6 . The glint detection system of claim 1 , wherein the differential light signals from each pair of the plurality of pairs of light sources represent binary-encoded square-wave patterns of opposite polarity.
7 . The glint detection system of claim 1 , wherein the plurality of pairs of light sources emit infrared light.
8 . The glint detection system of claim 1 , wherein the plurality of pairs of light sources emit the binary identifiers at an illumination frequency of at least 1 kHz.
9 . The glint detection system of claim 1 , wherein an intra-light source angle between each light source in each pair of the pairs of light sources is at least 2.5 degrees.
10 . The glint detection system of claim 1 , wherein the plurality of pairs of light sources are light emitting diodes (LEDs), vertical external-cavity surface-emitting lasers (VCSELs), fiber optics, or out-coupling gratings.
11 . The glint detection system of claim 1 , wherein the one or more memories store further instructions that when executed by the processing logic, cause the glint detection system to perform further operations comprising:
identify first bits of the binary identifiers of glints detected at first locations;
confirm second bits of binary identifiers of the detected glints around the first locations; and
associate detected glints with corresponding ones of plurality of pairs of light sources based on the binary identifiers.
12 . The glint detection system of claim 11 , wherein the one or more memories store further instructions that when executed by the processing logic, cause the glint detection system to perform further operations comprising:
update a location of a cornea sphere after first bits and second bits of binary identifiers have been confirmed and associated with corresponding ones of the plurality of pairs of light sources.
13 . A head-mounted display comprising:
a frame;
a display positioned on the frame to provide display light;
a lens assembly positioned on the frame to transmit the display light from the display to an eyebox; and
a glint detection system comprising:
a plurality of pairs of light sources positioned on the frame to illuminate a corneal surface of an eye with differential light signals;
an image sensor positioned on the frame to receive reflections of the differential light signals from the eye;
processing logic coupled to the plurality of pairs of light sources and to the image sensor; and
one or more memories coupled to the processing logic, the one or more memories storing instructions that, when executed by the processing logic, cause the glint detection system to perform operations comprising:
encode the differential light signals with binary identifiers that are unique to each pair of the plurality of pairs of lights;
receive, from the image sensor, image data that is representative of reflections of the differential light signals; and
identify each of the plurality of pairs of light sources within the image data at least partially based on the binary identifiers.
14 . The head-mounted display of claim 13 , wherein the image sensor is an event camera that is responsive to changes in brightness in a field of view of the image sensor.
15 . The head-mounted display of claim 13 , wherein the differential light signals from each pair of the plurality of pairs of light sources represent binary-encoded square-wave patterns of opposite polarity.
16 . The head mounted display of claim 13 , wherein the differential light signals include square wave patterns that repeat at a frequency of at least 1 kHz.
17 . A method of corneal glint detection using binary-encoded illumination comprising:
driving a plurality of pairs of light sources to emit differential light signals towards an eye of a user;
encoding the differential light signals with binary identifiers, wherein each of the binary identifiers is unique to a corresponding pair of the plurality of pairs of light sources;
receiving image data from an image sensor, wherein the image data is representative of reflections of the differential light signals off of the eye of the user; and
identifying each of the plurality of pairs of light sources within the image data at least partially based on the binary identifiers.
18 . The method of claim 17 further comprising:
identifying locations, within the image data, of the reflections of the differential light signals; and
determining an orientation of a cornea of the eye at least partially based on the locations.
19 . The method of claim 18 , wherein the differential signals for each pair of the plurality of pairs of lights sources include square-wave patterns having opposite polarities.
20 . The method of claim 17 , wherein the binary identifiers are binary numbers having at least 2 bits.