RE: System 100 Eye Gaze Trackin Patent25 May 2019 16:55
[0004] In one video-based technique, eye gaze direction is calculated by detecting the position of corneal reflections of the light source (known as 'glints') in conjunction with detecting the pupil location in the images. Glints (also known as "first Purkinje images") are virtual images of light sources that illuminate the eye and are created by a reflection from the front surface of the cornea. The optical properties of the cornea mean that it is at least partially reflective at infrared and near-infrared wavelengths, operating as a convex mirror. With knowledge of the positions of the camera and light source, these detected points can be projected onto a geometric model of the eyeball to derive an estimate of eye gaze direction and optionally a point of gaze if eye gaze vectors can be calculated for both eyes. However, when glints are not present (such as when the subject is looking distant from the camera or is squinting) or difficult to discern, this technique can break down or become inaccurate. [0005] In another video-based technique, the pupil position can be combined with an estimate of pose of the subject's head to derive the eye gaze direction. US Patent 7,043,056 to Edwards et al., assigned to Seeing Machines Pty Ltd and entitled "Facial Image Processing System" (hereinafter "Edwards et al.") discloses such a gaze tracking technique. The head pose estimate is obtained by extracting facial feature points from the captured images and fitting these points to a three dimensional model of a human head. However, this technique is very sensitive to the accuracy of the estimated head pose (including the approximated head size in the model) and the technique becomes very inaccurate when the estimated head pose is slightly incorrect.
[0006] US Patent Application Publication 2012/0147328 to Yahav assigned to Microsoft Corporation and entitled "3D Gaze Tracker" (hereinafter "Yahav") relates to a three- dimensional (3D) glint detection-based gaze tracking system that takes into account head orientation to improve accuracy. The technique necessarily requires both conventional two dimensional digital camera and a three dimensional camera. Due to its reliance on glints, this system still breaks down under the relatively common occurrence where glints are not present or difficult to discern.
[0007] Therefore, the inventors have identified a desire for more robust eye gaze tracking techniques which operate effectively under varying operating conditions.
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