Eye Tracking Methodology

Abstract

Since the writing of the first edition, several important advancements in the field of eye tracking have occurred in the span of just a few short years. Most important, eye tracking technology has improved dramatically. Due to the increased speed of computer processors and improved computer vision techniques, eye tracking manufacturers have developed devices falling within the fourth generation of the following technological taxonomy. 1. First generation: eye-in-head measurement of the eye consisting of techniques such as scleral contact lens/search coil, electro-oculography 2. Second generation: photo- and video-oculography 3. Third generation: analog video-based combined pupil/corneal reflection 4. Fourth generation: digital video-based combined pupil/corneal reflection, augmented by computer vision techniques and Digital Signal Processors (DSPs) Often the most desired type of eye tracking output (e.g., for human–computer interaction usability studies) is estimation of the projected Point Of Regard (POR) of the viewer, i.e., the ðx; yÞ coordinates of the user’s gaze on the computer display. First- and second-generation eye trackers generally do not provide this type of data. (For second-generation systems, eye movement analysis relies on off-line, frame-by-frame visual inspection of photographs or video frames and does not allow easy POR calculation.) Combined video-based pupil/corneal reflection eye trackers easily provide POR coordinates following calibration, and are today de rigeur. Due to the availability of fast analog-to-digital video processors, these third-generation eye trackers are capable of delivering the calculated POR in real-time. Fourth-generation eye trackers, having recently appeared on the market, make use of digital optics. Coupled with on-chip Digital Signal Processors (DSPs), eye tracking technology has significantly increased in its usability, accuracy, and speed while decreasing in cost.