An optical position detecting unit which includes: an image pickup device having a pixel array region, an imaging lens for forming an image of a light-emitting point, a converging lens for converging light come from the light-emitting point image formed by the imaging lens onto the pixel array region,...http://www.google.com/patents/US5572251?utm_source=gb-gplus-sharePatent US5572251 - Optical position detecting unit and optical coordinate input unit
