Safety assessment of virtual reality eye tracking modules

Rendering of the virtual environment in VR devices is computationally expensive. Foveated rendering uses eye tracking to reduce this by only rendering the portion of virtual environment where the user is looking at. The eye tracking module has multiple near-infrared (NIR) LEDs to illuminate the eye homogenously and a camera to track the direction of gaze and eye movement. However, NIR illumination is potentially harmful to the human eye and skin. On the other hand, the safety assessment of eye tracking systems is not straight forward because it is not clear what standard and measurement recommendations to use. The international photobiological safety standard IEC 62471 provides guidelines for evaluating the photobiological hazards of incoherent broadband light sources for illumination purposes. The technical report CIE 245 is tailored for eye tracking systems, but provides only advisory information which is not mandatory. We have evaluated the hazards of a VR eye tracking module according to IEC 62471 and CIE 245. A measurement set up was designed and the classification scheme was used to classify the module. The number of LEDs, their geometrical orientation, optical power and duration of the exposure and the proximity to the eye are among the important parameters that could increase the damage to the cornea, lens and retina. Furthermore, since these modules have multiple IR sources in close proximity to the eye and are meant for prolonged use, the long-term hazard assessment must be thoroughly investigated. Our safety assessment was done on a VR module and opens up possibilities to extend this safety assessment for other eye tracking modules used in AR, VR and MR.