In this paper we present  DigiTap ---a wrist-worn device specially designed for symbolic input in virtual and augmented reality (VR/AR) environments. DigiTap is able to robustly sense thumb-to-finger taps on the four fingertips and the eight minor knuckles. These taps are detected by an accelerometer, which triggers capturing of an image sequence with a small wrist-mounted camera. The tap position is then extracted with low computational effort from the images by an image processing pipeline. Thus, the device is very energy efficient and may potentially be integrated in a smartwatch-like device, allowing an unobtrusive, always available, eyes-free input. To demonstrate the feasibility of our approach an initial user study with our prototype device was conducted. In this study the suitability of the twelve tapping locations was evaluated, and the most prominent sources of error were identified. Our prototype system was able to correctly classify 92% of the input locations.
['Manuel Prätorius', 'Dimitar Valkov', 'Ulrich Burgbacher', 'Klaus H. Hinrichs']
DigiTap: an eyes-free VR/AR symbolic input device