Patent ID: 6844539

Claim:
An optical position detecting device comprising: a light retro-reflector provided outside a predetermined region, wherein the predetermined region further comprises a display screen and a non-screen area bordering the display screen; at least two optical transceivers, each including an optical scanning unit for angularly scanning light in a plane substantially parallel to the predetermined region and a light receiving unit for receiving reflected light from a portion of said light retro-reflector irradiated with the scanning light; a detector for detecting a position of a light blocking object present in the predetermined region optically scanned by said optical scanning units, based on scanning angles of said optical scanning units and results of receiving light by said light receiving units; a storing unit for storing size information and positional information about the display screen; and a judging unit for judging whether the light blocking object is present within the display screen or with the non-screen area, based on the position of the light blocking object detected by the detector and size information and positional information stored in the storing unit.