US Patent 7401920 Head mounted eye tracking and display system

A system for eye tracking that determines the line of sight of a user according to the relative position between the center of the pupil and a reference point, the system including an image detector that captures an image of the eye, a pupil-illuminating light source that illuminates the pupil of the user, a reference light source that illuminates a different portion of the face of the user as a reference point and an imaging processor that analyzes the captured eye image to determine the line of sight.