Method and system for performing eye tracking using an off-axis camera

1. A method of estimating a gaze vector for a user of an optical device, the method comprising:

receiving, from a camera mounted to the optical device, an input image of an eye of the user;

providing the input image of the eye of the user to a neural network having a plurality of layers, the neural network having been previously trained using a plurality of training input images;

generating, using the neural network, network output data that includes two-dimensional (2D) pupil data and cornea center data, wherein a first subset of the plurality of layers are used to generate the 2D pupil data and a second subset of the plurality of layers are used to generate the cornea center data, wherein the first subset and the second subset share at least one common layer, and wherein each of the first subset and the second subset includes at least one unique layer; and

computing, based on the network output data, the gaze vector corresponding to the eye of the user.

2. The method of claim 1 , wherein the network output data further includes:

eye segmentation data.

3. The method of claim 1 , wherein the 2D pupil data includes a 2D pupil center.

4. The method of claim 2 , wherein the eye segmentation data includes a segmentation of the eye of the user into a plurality of regions including one or more of a background region, a sclera region, a pupil region, or an iris region.

5. The method of claim 1 , wherein the cornea center data includes a 2D or 3D cornea center.

6. The method of claim 2 , further comprising:

computing, based on the 2D pupil data and the eye segmentation data, a three-dimensional (3D) pupil center.

7. The method of claim 6 , further comprising:

computing, based on the 3D pupil center and the cornea center data, an optical axis associated with the eye of the user.

8. The method of claim 7 , further comprising:

computing, based on the optical axis and a calibration angle corresponding to a user, a gaze vector associated with the eye of the user.

9. The method of claim 1 , wherein the neural network was previously trained by:

for each training input image of the plurality of training input images:

providing the training input image to the neural network;

generating, using the neural network, training network output data;

receiving ground-truth (GT) data;

computing error data based on a difference between the training network output data and the GT data; and

modifying the neural network based on the error data.

10. The method of claim 9 , wherein the training network output data includes one or more of:

training 2D pupil center data;

training eye segmentation data;

training glint detection data; or

training cornea center data.

11. The method of claim 10 , wherein the GT data includes one or more of:

2D pupil center GT data;

eye segmentation GT data; or

glint detection GT data.

12. The method of claim 11 , wherein the eye segmentation GT data includes a manually created segmentation of the eye of the user into a plurality of training regions including one or more of a training background region, a training sclera region, a training pupil region, and a training iris region.

13. The method of claim 11 , wherein the glint detection GT data includes a manually created identification of glint locations.

14. The method of claim 11 , wherein the error data includes one or more of:

a difference between the training 2D pupil center data and the 2D pupil center GT data;

a difference between the training eye segmentation data and the eye segmentation GT data;

a difference between the training glint detection data and the glint detection GT data; or

an error based on the training cornea center data and one or more geometric constraints.

15. An optical device comprising:

a camera; and

a processor communicatively coupled to the camera and configured to perform operations including:

receiving, from the camera, an input image of an eye of a user;

providing the input image of the eye of the user to a neural network having a plurality of layers, the neural network having been previously trained using a plurality of training input images;

generating, using the neural network, network output data that includes two-dimensional (2D) pupil data and cornea center data, wherein a first subset of the plurality of layers are used to generate the 2D pupil data and a second subset of the plurality of layers are used to generate the cornea center data, wherein the first subset and the second subset share at least one common layer, and wherein each of the first subset and the second subset includes at least one unique layer; and

computing, based on the network output data, a gaze vector corresponding to the eye of the user.

16. The optical device of claim 15 , further comprising:

a plurality of infrared (IR) light-emitting diodes (LED).

17. The optical device of claim 15 , wherein the network output data further includes:

eye segmentation data.

18. The optical device of claim 15 , wherein the 2D pupil data includes a 2D pupil center.

19. The optical device of claim 17 , wherein the eye segmentation data includes a segmentation of the eye of the user into a plurality of regions including one or more of a background region, a sclera region, a pupil region, or an iris region.

20. The optical device of claim 15 , wherein the neural network was previously trained by:

for each training input image of a plurality of training input images:

providing the training input image to the neural network;

generating, using the neural network, training network output data;

receiving ground-truth (GT) data;

computing error data based on a difference between the training network output data and the GT data; and

modifying the neural network based on the error data.