Method and system for eye tracking using speckle patterns
A method of tracking movement of an eye of a user includes directing a light beam at the eye. The eye may reflect a portion of the light beam. The method further includes detecting a plurality of speckle patterns formed at a detector by the portion of the light beam reflected by the eye. The plurality of speckle patterns may be detected at a predetermined frame rate. The method further includes tracking movement of the eye by tracking the plurality of speckle patterns from frame to frame.
1. A method of tracking movement of an eye gaze of a user, the method comprising:
recording a video image of an eye of the user using a camera, the video image showing movement of a pupil of the eye;
determining a starting eye gaze based on the video image of the eye, the starting eye gaze characterized by coordinates of a center of the pupil relative to a pre-calibrated origin;
in response to determining the starting eye gaze:
propagating a light beam directly from a light source onto the eye;
detecting a speckle pattern formed on a detector by a portion of the light beam reflected by the eye, the speckle pattern being detected at a predetermined frame rate; and
tracking movement of the eye gaze relative to the starting eye gaze by tracking the speckle pattern from frame to frame;
determining that the eye has blinked;
determining a new starting eye gaze by:
recording a second video image of the eye using the camera; and
determining the new starting eye gaze based on the second video image of the eye; and
tracking movement of the eye gaze relative to the new starting eye gaze by:
detecting a second speckle pattern formed at the detector; and
tracking the second speckle pattern from frame to frame.
2. The method of claim 1 wherein the portion of the light beam reflected by the eye is diffusely reflected or specular reflected by the eye.
3. The method of claim 1 wherein the predetermined frame rate is greater than about 5,000 frames per second and less than about 15,000 frames per second.
4. The method of claim 3 wherein the predetermined frame rate is about 10,000 frames per second.
5. The method of claim 1 wherein the predetermined frame rate is greater than about 50 frames per second and less than about 15,000 frames per second.
6. The method of claim 1 wherein tracking the speckle pattern is performed using an optical flow algorithm.
7. The method of claim 6 wherein the optical flow algorithm comprises a phase correlation algorithm.
8. The method of claim 1 wherein the light beam comprises infrared radiation.
9. The method of claim 1 wherein the portion of the light beam reflected by the eye propagates directly from the eye to the detector.
10. The method of claim 1 wherein the light beam propagates to the eye at a slanted angle relative to the eye.
11. The method of claim 1 wherein:
the light source is mounted to a temple of an eyeglass worn by the user; and
the detector is mounted to the temple adjacent to the light source.
12. A method of tracking a gaze of an eye of a user, the method comprising:
recording a first video image of the eye using a camera at a first frame rate, the first video image showing movement of a pupil of the eye;
determining a starting gaze of the eye based on the first video image of the eye, the starting gaze characterized by coordinates of a center of the pupil relative to a pre-calibrated origin;
in response to determining the starting gaze of the eye:
propagating a light beam directly from a light source onto the eye;
detecting a first speckle pattern formed at a detector by a portion of the light beam reflected by the eye, the first speckle pattern being detected at a second frame rate greater than the first frame rate; and
tracking movement of the gaze of the eye relative to the starting gaze of the eye by tracking the first speckle pattern from frame to frame;
determining that the eye has blinked;
determining a new starting gaze of the eye by:
recording a second video image of the eye using the camera; and
determining the new starting gaze of the eye based on the second video image of the eye; and
tracking movement of the gaze of the eye relative to the new starting gaze of the eye by:
detecting a second speckle pattern formed at the detector at the second frame rate; and
tracking the second speckle pattern from frame to frame.
13. The method of claim 12 wherein the portion of the light beam reflected by the eye is diffusely reflected or specular reflected by the eye.
14. The method of claim 12 wherein tracking the first speckle pattern is performed using an optical flow algorithm.
15. The method of claim 14 wherein the optical flow algorithm comprises a phase correlation algorithm.
16. The method of claim 12 wherein the first frame rate is less than about 10 frames per second, and the second frame rate is greater than about 50 frames per second and less than about 15,000 frames per second.
17. A method of tracking movement of an eye gaze of a user, the method comprising:
recording a video image of an eye of the user using a camera, the video image showing movement of a pupil of the eye;
determining a starting eye gaze based on the video image of the eye, the starting eye gaze characterized by coordinates of a center of the pupil relative to a pre-calibrated origin;
in response to determining the starting eye gaze:
illuminating an eye with coherent light at a slanted angle relative to the eye;
propagating a portion of the coherent light scattered by the eye from the eye to an image sensor;
detecting a speckle pattern formed on the image sensor by the portion of the coherent light scattered by the eye, the speckle pattern being detected at a predetermined frame rate; and
tracking movement of the eye gaze relative to the staring eye gaze by tracking the speckle pattern from frame to frame;
determining that the eye has blinked;
determining a new starting eye gaze by:
recording a second video image of the eye using the camera; and
determining the new starting eye gaze based on the second video image of the eye; and
tracking movement of the eye gaze relative to the new starting eye gaze by:
detecting a second speckle pattern formed at image sensor; and
tracking the second speckle pattern from frame to frame.
18. The method of claim 17 , wherein the portion of the coherent light reflected by the eye propagates directly from the eye to the image sensor.
19. The method of claim 17 , wherein:
the coherent light is generated by a light source mounted on a temple of an eyeglass worn by the user; and
the image sensor is mounted on the temple adjacent to the light source.