Comparison of eye tracking devices used on printed images

Abstract

Eye tracking as a quantitative method for collecting eye movement data, requires the accurate knowledge of the eye position, where eye movements can provide indirect evidence about what the subject sees. In this study two eye tracking devices have been compared, a Head-mounted Eye Tracking Device (HED) and a Remote Eye Tracking Device (RED). The precision of both devices has been evaluated, in terms of gaze position accuracy and stability of the calibration. For the HED it has been investigated how to register data to real-world coordinates. This is needed since coordinates collected by the HED eye tracker are relative to the position of the subject¿s head and not relative to the actual stimuli as it is the case for the RED device. Results show that the precision gets worse with time for both eye tracking devices. The precision of RED is better than the HED and the difference between them is around 10 - 16 pixels (5.584 mm). The distribution of gaze positions for HED and RED devices was expressed by a percentage representation of the point of regard in areas defined by the viewing angle. For both eye tracking devices the gaze position accuracy has been 95-99% at 1.5-2° viewing angle. The stability of the calibration was investigated at the end of the experiment and the obtained result was not statistically significant. But the distribution of the gaze position is larger at the end of the experiment than at the beginning.