The data input device comprises a tablet portion made of a two-dimensional position-sensitive photodetector and a planar display element laid one on the other, and a light emitting pen forming a light spot on a light-receiving surface of the position-sensitive photodetector. The locus of the movement...http://www.google.fr/patents/US4794634?utm_source=gb-gplus-shareBrevet US4794634 - Position-sensitive photodetector and light transmissive tablet and light-emitting pen
Position-sensitive photodetector and light transmissive tablet and light ...
