F. Echtler, T. Sielhorst, M. Huber, G. Klinker A Short Guide to Modulated Light TEI 2009, February 16 - 18, Cambridge, United Kingdom, pp. 393-396. (bib)
	Many types of tangible interaction systems, such as interactive surfaces and gesture-based interfaces, are based on various kinds of optical tracking, using infrared illuminators and cameras. One drawback of these setups is that they suffer from problems common to optical trackers, such as sensitivity to stray environment light from artificial and natural sources. In this paper, we present a method to significantly enhance tracking robustness for those systems which employ active illumination. Through addition of a small electronic circuit which modulates the LEDs used to illuminate the scene, contrast can be significantly increased.
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