Eye tracking: Pupil orientation geometrical modeling

Lately eye tracking system development and applications are becoming increasingly interesting. Efforts in eye tracking research cover a broad spectrum of fields, being mathematical modeling an important aspect and probably one of the least explored topics. In order to build up a robust and efficient model a deep mathematical review of the geometry and the intrinsic nature of eye tracking systems is needed. Video-oculography represents one of the most popular eye tracking methods due to its non-intrusive nature. The images acquired from user eye are analyzed in order to identify some selected features, and through a calibration process the parameters of a model are adjusted for each user. This paper tries to accomplish the first step of a more extensive model and presents a simple expression for pupil orientation based on framework physical parameters. The proposed model requires alternative calibration strategies depending on the number of parameters employed to obtain an efficient behavior. It exhibits lower errors than other generic mathematical expressions, which normally need more calibration points to construct a competent model. The paper starts modeling a whole video-oculographic system and once the model is derived, the work addresses different simplification ways in order to obtain a simpler and more efficient form. Lastly an experimental validation is provided.