In this section we will discuss the calibration procedure of Tobii Eye Trackers.
Before an eye tracking recording is started, the user is taken through a calibration procedure. During this procedure, the eye tracker measures characteristics of the user’s eyes and uses them together with an internal, physiological 3D eye model to calculate the gaze data. This model includes information about shapes, light refraction and reflection properties of the different parts of the eyes (e.g. cornea, placement of the fovea, etc.). During the calibration the user is asked to look at specific points on the screen, also known as calibration dots. During this period several images of the eyes are collected and analyzed. The resulting information is then integrated in the eye model and the gaze point for each image sample is calculated. When the procedure is