Thermographic eye tracking

Far infrared thermography, which can be used to detect thermal radiation emitted by humans, has been used to detect physical disease, physiological changes relating to emotion, and polygraph testing, but has not been used for eye tracking. However, because the surface temperature of the cornea is colder than the limbus, it is theoretically possible to track corneal movements through thermal imaging. To explore the feasibility of thermal eye tracking, we invited 10 adults and tracked their corneal movements with passive thermal imaging at 60 Hz. We combined shape models of eyes with intensity threshold to segment the cornea from other parts of the eye in thermal images. We used an animation sequence as a calibration target for 5 point calibration/validation 5 times. Our results were compared to simultaneously collected data using an SR EyeLink eye tracker at 500 Hz, demonstrating the feasibility of eye tracking with thermal images. Blinking and breathing frequencies, which reflect the psychophysical status of the participants, were also robustly detected during thermal eye tracking.