Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research

Abstract

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.

The effect of sampling rate and lowpass filters on saccades – A modeling approach

“…This non-linearity is even worse within studies comparing saccades of different amplitudes, as the acquired main sequences will be significantly distorted. What might reasonably look like the velocity profile of a 10°-saccade at a sampling rate of 55 Hz (Gibaldi, Vanegas, Bex, & Maiello, 2016) might not be true for other amplitudes. Finally, the reduction in peak velocities reported here is a best-case estimate as we made sure that the actual time of the peak velocity coincides with a sample.…”

Saliency in VR: How Do People Explore Virtual Environments?

“…Users sat 0.45 meters away from a 17.3" monitor with a resolution of 1920 × 1080 px, covering a field of view of 23 × 13 • . We used a Tobii EyeX eye tracker with an accuracy of 0.6 • at a sampling frequency of 55 Hz [16]. The image viewer displayed a rectilinear projection of a 97 × 65 • viewport of the panorama.…”

Cloud Gaming with Foveated Video Encoding

“…Characterizing the latency of the Tobii Eye Tracker 4C is beyond the scope of this work. However, the latency of Tobii EyeX, the predecessor to Eye Tracker 4C has been found to be about 50 ms [Gibaldi et al 2017]. Tobii Eye Tracker 4C has a higher sampling rate than Tobii EyeX and uses purportedly improved hardware and algorithms, it may be assumed that the latency of the Tobii eye tracker is less than 50ms as well.…”