We present a fast, robust, and low cost pupil detection technique that uses two near-infrared time multiplexed light sources synchronized with the camera frame rate. The two light sources generate bright and dark pupil images, which are used for pupil segmentation. To reduce artifacts caused mostly by head motion, a larger temporal support is used. This method can be applied to detect and track several pupils (or several people). Experimental results from a real-time implementation of the system show that this technique is very robust, and able to detect pupils using wide field of view low cost cameras under different illumination conditions, even for people with glasses, from considerable long distances.