How are the eye movements tracked?
Eye tracking has long been known and used as a method to study the visual attention of individuals. There are several different techniques to detect and track the movements of the eyes. However, when it comes to remote, non‐intrusive, eye tracking the most commonly used technique is Pupil Centre Corneal Reflection (PCCR). The basic concept is to use a light source to illuminate the eye causing highly visible reflections, and a camera to capture an image of the eye showing these reflections. The image captured by the camera is then used to identify the reflection of the light source on the cornea (glint) and in the pupil. We are then able to calculate a vector formed by the angle between the cornea and pupil reflections – the direction of this vector, combined with other geometrical features of the reflections, will then be used to calculate the gaze direction. The Tobii Eye Trackers are an improved version of the traditional PCCR remote eye tracking technology (US Patent US7,572,008).
