Eye tracking
Examples are disclosed herein that relate to eye tracking based on two-dimensional image data. One example provides, on a computing device, a method of tracking an eye. The method includes receiving image data from an image sensor, detecting a face of the user in the image data, locating the eye in a region of the face in the image data to obtain an eye image, normalizing one or more of a scale and an illumination of the eye image, fitting an ellipse to an iris of the eye in the eye image, and outputting a determination of an eye gaze direction based upon the ellipse fitted.
1. On a computing device, a method of tracking an eye, the method comprising:
receiving image data from an image sensor;
detecting a face of the user in the image data;
locating the eye in a region of the face in the image data to obtain an eye image;
normalizing one or more of a scale and an illumination of the eye image;
fitting an ellipse to an iris of the eye in the eye image by applying a plurality of ellipse hypotheses to the image data, and determining for each ellipse hypothesis a voting map corresponding to the eye image, wherein fitting the ellipse comprises, for each pixel of the eye image, determining a gradient vector for the pixel, and updating a value of a corresponding pixel of the voting map with a magnitude of the gradient vector; and
outputting a determination of an eye gaze direction based upon the ellipse fitted.
2. The method of claim 1 , wherein normalizing the scale of the eye image comprises scaling the eye image to normalize a distance between features in the eye image.
3. The method of claim 1 , wherein normalizing the illumination of the eye image comprises forming a gray scale image from the eye image and normalizing intensity of the grayscale image.
4. The method of claim 1 , further comprising performing segmentation on the image data to mask out one or more of a non-eye area and a non-iris area of the eye image prior to fitting the ellipse.
5. The method of claim 1 , wherein fitting the ellipse comprises determining a center of the iris based upon the value of each pixel of the voting map.
6. The method of claim 1 , wherein each of the plurality of ellipse hypotheses comprises one or more of a rotation angle, a radius, and a long-short axis ratio.
7. An eye-tracking system comprising:
an image sensor configured to acquire image data;
a logic subsystem; and
a storage subsystem comprising instructions stored thereon that are executable by the logic subsystem to:
detect a face of a user in the image data;
locate the eye in a region of the face in the image data to obtain an eye image;
normalize one or more of a scale and an illumination of the eye image, determine a voting map for each of a plurality of ellipse hypotheses;
fit an ellipse to an iris of the eye in the eye image by applying a plurality of ellipse hypotheses to the image data, and determine for each ellipse hypothesis a voting map corresponding to the eye image, wherein the instructions are executable to fit the ellipse by, for each pixel of the eye image, determining a gradient vector for the pixel, and updating a value of a corresponding pixel of the voting map with a magnitude of the gradient vector; and
output a determination of a gaze direction based upon the ellipse fitted.
8. The eye-tracking system of claim 7 , wherein the instructions are executable to normalize the scale of the eye image by scaling the eye image to normalize a distance between features in the eye image.
9. The eye-tracking system of claim 7 , wherein the instructions are executable to normalize the illumination of the eye image by forming a gray scale image from the eye image and normalizing intensity of the grayscale image.
10. The eye-tracking system of claim 7 , wherein the instructions are further executable to perform segmentation on the image data to mask out one or more of a non-eye area and a non-iris area of the eye image prior to fitting the ellipse.
11. The eye-tracking system of claim 7 , wherein the instructions are executable to fit the ellipse by determining a center of the iris based upon the value of each pixel of the voting map.
12. An eye-tracking system comprising:
an image sensor configured to acquire image data;
a logic subsystem; and
a storage subsystem comprising instructions stored thereon that are executable by the logic subsystem to:
detect a face of a user from the image data;
locate the eye in a region of the face from the image data to obtain an eye image;
normalize one or more of a scale and an illumination of the eye image, perform segmentation on the image data to mask out one or more of non-eye areas and non-iris areas of the eye image;
fit an ellipse to an iris of the eye in the eye image by applying a plurality of ellipse hypotheses to the image data, and determine for each ellipse hypothesis a voting map corresponding to the eye image, wherein the instructions are executable to fit the ellipse by, for each pixel of the eye image, determining a gradient vector for the pixel, and updating a value of a corresponding pixel of the voting map with a magnitude of the gradient vector; and
output a determination of a gaze direction based upon the ellipse fitted.
13. The eye-tracking system of claim 12 , wherein the instructions are executable to normalize the scale of the eye image by scaling the eye image to normalize a distance between features in the eye image.
14. The eye-tracking system of claim 12 , wherein the instructions are executable to normalize the illumination of the eye image by forming a gray scale image from the eye image and normalizing intensity of the grayscale image.
15. The eye-tracking system of claim 12 , wherein the instructions are executable to fit the ellipse by determining a center of the iris based upon the value of each pixel of the voting map.