SPEye: A Calibration-Free Gaze-Driven Text Entry Technique Based on Smooth Pursuit

Gaze-based text entry is undoubtedly one of the most useful applications of eye-tracking technology for human-machine interaction, both in the assistive context (users with severe motor disabilities can exploit such writing modalities to communicate with the world) and as a way to allow touchless text input in everyday life. Different eye-driven text entry methods have been developed to date, and almost all of them require preliminary calibration procedures to work correctly. When a short text, such as a password or a PIN, needs to be entered without using hands or voice, calibration may be perceived as an unnecessary nuisance (and may not be properly maintained in public places due to “ambient noise,” caused, for example, by nearby people). Inadequate calibration may also be a problem in case of assistive uses. In this article we present SPEye, a calibration-free eye-controlled writing technique based on smooth pursuit. Although its writing speed is significantly lower than that of ordinary calibrated methods, the absence of an initial calibration makes it suitable for short text entry. The technique has been tested through several experiments, obtaining good performances in terms of key strokes per character and total error rate metrics, and receiving positive feedback from the participants in the tests.