F. Echtler, M. Huber, G. Klinker Hand tracking for enhanced gesture recognition on interactive multi-touch surfaces Technical Report TUM-I0721, Nov. 1, 2007. (bib)
	Recently, interactive surfaces with multi-touch sensors based on frustrated total internal reflection (FTIR) have seen increased attention in research and commerce. In this paper, we present a new method of gathering data about the users’ gestures on an interactive table beyond simple binary touch information. In addition to the infrared light emitters at the rim of the interaction surface, a second infrared light source is placed above an interactive table to create shadows of hands and arms. By tracking these shadows with the same rear-mounted camera, several consecutive and disjoint surface contacts can be traced back to the same user, thereby enabling new interaction techniques. We demonstrate this approach at the example of a virtual whiteboard with persistent color assignments for each participant.
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