Adaptive regulation of CCD camera for real time eye tracking

Abstract

In this paper, an eye tracking method and an automatic focusing technique, which combine the regulation of the aperture with the adjustment of the focus of the camera lens, are proposed to acquire clear eye images in the eye-gaze tracking system. Firstly, the aperture of the CCD lens is controlled to adapt the system to external lighting circumstances with the average brightness value of the processed images as the basic value. Secondly, a sum-modulus-difference (SMD) operator is used for rough and quick focusing in a large scale to obtain the eye glints, and for the control of a pan-tilt unit to track and aim at the eye, and for regulation of the lens focus. Finally, a frequency selective weighted median (FSWM) operator is applied in the determined window to focus automatically and acquire clear eye images. If the pupil contour can be extracted from the eye image, then the average gradient value of the pupil's edge points can be used for real-time focusing. Experimental results show that this system can adapt to external lighting changes and to the user's head movements. It can track the eye and acquire clear eye images in real-time.