Geometry Issues of Gaze Estimation
Arantxa Villanueva, Jan Daryl M. San Juan, Rafael Cabez · InTech eBooks · 2008
A geometry-based model for gaze estimation has been constructed and evaluated. Alternative models have been proposed based on different image features. The results show that a hybrid model is needed for LoS estimation in a free head pose scenario, since glints and pupil separately do not provide sufficient information for optical axis estimation. Glints have been shown to be connected to the corneal centre position. Once the cornea centre has been determined, pupil shape can be used to estimate the pupil centre. The line connecting the pupil centre and the cornea centre is determined as the optical axis of the eye. Thus, the LoS is deduced using Listing's and Donder's Laws. Cornea centre estimation is significantly sensitive to glint position inaccuracies. Hence, the number of light sources has been increased to obtain an averaged cornea centre and to compensate for the error. The obtained results show a better performance as the number of light sources is increased from two to four. The proposed model requires the system hardware, such as the camera, light sources, and screen, to be calibrated beforehand. In addition, individual parameters such as, rc, h, and are required for gaze estimation. Theoretically, one calibration point is sufficient to obtain the aforementioned subject's parameters.