During an eye tracking session, the movement of the head is one of the factors that may have an impact on the gaze data accuracy. In this page we will discuss how robust Tobii Eye Trackers are to head movement.
The optical sensor of the Tobii Eye Trackers is composed of two cameras that capture an image of the eyes at a given frequency (30, 60, 120 and 300 Hz). The two cameras produce two images of the eyes and the respective pupil and corneal reflections providing the eye tracker with two different sources of information regarding the eye position. This type of “stereo data processing” offers a robust calculation of the position of the eye in space and the point of gaze even if the position of the head changes. Additionally these two cameras increase the horizontal field of view of the sensor i.e. the horizontal size of the trackbox, increase the freedom of movement of the user.
Nevertheless head movement will still have an impact on the data if the subject moves to fast, turns his head to the side or moves to the edges of the trackbox.