Battery-Free Eye Tracker on Glasses

We propose the design of a battery-free wearable eye tracker that achieves sub-millimeter tracking accuracy at high tracking rates. It tracks pupil's 2D position based on pupil's light absorption effect. With a few near-infrared (NIR) lights and photodiodes around the eye, NIR lights sequentially illuminate the eye from various directions while photodiodes sense spatial patterns of reflected light, which are used to infer pupil positions on the fly through a lightweight inference algorithm. The system also exploits characteristics of different eye movement stages and adjusts its sensing and computation accordingly for further energy savings. We have built a prototype with off-the-shelf hardware components and integrated it into a regular pair of glasses. Experiments with ten participants show that the system achieves 0.9-mm mean tracking accuracy (2.4 mm at the 95th percentile) at 120-Hz output frame rate, consuming 395 mu W mean power supplied by two small, thin solar cells on glasses side arms.