Validation of a prototype hybrid eye-tracker against the DPI and the Tobii Spectrum

We benchmark a new hybrid eye-tracker system against the DPI (Dual Purkinje Imaging) tracker and the Tobii Spectrum in a series of three experiments. In a first within-subjects battery of tests, we show that the precision of the new eye-tracker is much better than that of both the DPI and the Spectrum, but that accuracy is not better. We also show that the new eye-tracker is insensitive to effects of pupil contraction on gaze direction (in contrast to both the DPI and the Spectrum), that it detects microsaccades on par with the DPI and better than the Spectrum, and that it can possibly record tremor. In the second experiment, sensors of the novel eye-tracker were integrated into the optical path of the DPI bench. Simultaneous recordings show that saccade dynamics, post-saccadic oscillations and measurements of translational movements are comparable to those of the DPI. In the third experiment, we show that the DPI and the new eye-tracker are capable of detecting 2 arcmin artificial-eye rotations while the Spectrum cannot. Results suggest that the new eye-tracker, in contrast to video-based P-CR systems [Holmqvist and Blignaut 2020], is suitable for studies that record small eye-movements under varying ambient light levels.