Contact lens with moiré labels for precise eye tracking

In this work, we propose an eye-tracking mechanism that exploits specially designed labels integrated into the body of a contact lens. The labels consist of two overlapped gratings with a gap between them. The overlapped gratings produce a moiré pattern, while the gap introduces parallax such that the moiré pattern changes with the observation angle. By combining several moiré labels, we can achieve unambiguous association of the produced pattern with the observation angle. This technique does not require calibration, reference marks, and is independent of illumination conditions and linear geometrical distortions. In our experiments, we achieved lens position and rotational degree of freedom precision higher than 0.3°. Even higher accuracy—better than 0.2°—was observed in a narrow range of angles ~10° around the central direction that is suitable for most AR/VR applications.