A coordinate input/detection device compares a waveform of a signal corresponding to intensity distribution of rays received from a coordinate input area by a light-receiving unit and a standard waveform at fixed timing. If the waveform is not equal to the standard waveform, the coordinate input/detection...http://www.google.ca/patents/US20010019325?utm_source=gb-gplus-sharePatent US20010019325 - Optical coordinate input/detection device with optical-unit positioning error correcting function
