User-calibration-free gaze tracking with estimation of the horizontal angles between the visual and the optical axes of both eyes

This paper presents a user-calibration-free method for estimating the point of gaze (POG) on a display accurately with estimation of the horizontal angles between the visual and the optical axes of both eyes. By using one pair of cameras and two light sources, the optical axis of the eye can be estimated. This estimation is carried out by using a spherical model of the cornea. The point of intersection of the optical axis of the eye with the display is termed POA. By detecting the POAs of both the eyes, the POG is approximately estimated as the midpoint of the line joining the POAs of both the eyes on the basis of the binocular eye model; therefore, we can estimate the horizontal angles between the visual and the optical axes of both the eyes without requiring user calibration. We have developed a prototype system based on this method using a 19" display with two pairs of stereo cameras. We evaluated the system experimentally with 20 subjects who were at a distance of 600 mm from the display. The result shows that the average of the root-mean-square error (RMSE) of measurement of POG in the display screen coordinate system is 16.55 mm (equivalent to less than 1.58°).