Rotational symmetric HMD with eye-Tracking capability

As an important auxiliary function of head-mounted displays (HMDs), eye tracking has an important role in the field of intelligent human-machine interaction. In this paper, an eye-Tracking HMD system (ET-HMD) is designed based on the rotational symmetric system. The tracking principle in this paper is based on pupil-corneal reflection. The ET-HMD system comprises three optical paths for virtual display, infrared illumination, and eye tracking. The display optics is shared by three optical paths and consists of four spherical lenses. For the eye-Tracking path, an extra imaging lens is added to match the image sensor and achieve eye tracking. The display optics provides users a 40° diagonal FOV with a × 0.61 OLED, the 19 mm eye clearance, and 10 mm exit pupil diameter. The eye-Tracking path can capture 15 mm × 15 mm of the users' eyes. The average MTF is above 0.1 at 26 lp/mm for the display path, and exceeds 0.2 at 46 lp/mm for the eye-Tracking path. Eye illumination is simulated using LightTools with an eye model and an 850 nm near-infrared LED (NIR-LED). The results of the simulation show that the illumination of the NIR-LED can cover the area of the eye model with the display optics that is sufficient for eye tracking. The integrated optical system HMDs with eye-Tracking feature can help improve the HMD experience of users.