A recurrence reflection sheet is provided to the outside of at least three sides of a quadrilateral display screen, two light send/receive units, which includes a light scanning element for scanning a light angularly in a plane which is substantially parallel with the display screen, and a light receiving...http://www.google.fr/patents/US6480187?utm_source=gb-gplus-shareBrevet US6480187 - Optical scanning-type touch panel
