A holographic waveguide based eye tracking device

We demonstrated the feasibility of using holographic waveguide for eye tracking. A custom-built holographic waveguide, a 20 mm × 60 mm × 3 mm flat glass substrate with integrated in- and out-couplers, was used for the prototype development. The in- and out-couplers, photopolymer films with holographic fringes, induced total internal reflection in the glass substrate. Diffractive optical elements were integrated into the in-coupler to serve as an optical collimator. The waveguide captured images of the anterior segment of the eye right in front of it and guided the images to a processing unit distant from the eye. The vector connecting the pupil center (PC) and the corneal reflex (CR) of the eye was used to compute eye position in the socket. A 3D printed model eye, which has a similar corneal curvature of human eye and laser pointer tube holder at the tail for simulation of eye gaze on a screen, was used for prototype validation. The benchtop prototype demonstrated a linear relationship between the angular eye position and the PC/CR vector over a range of 60 horizontal degrees and 40 vertical degrees. This prototype eye tracker has a tracking accuracy of 0.72 degree and tracking precision of 0.50 degree over the whole tracking range. These results confirmed that the holographic waveguide technology could be a feasible platform for developing a wearable eye tracker. Further development can lead to a compact, see-through eye tracker, which allows continuous monitoring of eye movement during real life tasks, and thus benefits diagnosis of oculomotor disorders.