Improving FTIR based multi-touch sensors with IR shadow tracking

Frustrated Total Internal Reflection (FTIR) is a key technology for the design of multi-touch systems. With respect to other solutions, such as Diffused Illumination (DI) and Diffused Surface Illumination (DSI), FTIR based sensors suffer less from ambient IR noise, and is, thus, more robust to variable lighting conditions. However, FTIR does not provide (or is weak on) some desirable features, such as finger proximity and tracking quick gestures. This paper presents an improvement for FTIR based multi-touch sensing that partly addresses the above issues exploiting the shadows projected on the surface by the hands to improve the quality of the tracking system. The proposed solution exploits natural uncontrolled light to improve the tracking algorithm: it takes advantage of the natural IR noise to aid tracking, thus turning one of the main issues of MT sensors into a useful quality, making it possible to implement pre-contact feedback and enhance tracking precision.