PUCs: detecting transparent, passive untouched capacitive widgets on unmodified multi-touch displays

Abstract

Capacitive multi-touch displays are not typically designed to detect passive objects placed on them. In fact, these systems usually contain filters to actively reject such input data. We present a technical analysis of this problem and introduce Passive Untouched Capacitive Widgets (PUCs). Unlike previous approaches, PUCs do not require power, they can be made entirely transparent, and they do not require internal electrical or software modifications. Most importantly they are detected reliably even when no user is touching them.