A coordinate input/detection device (3) compares a waveform of a signal corresponding to intensity distribution of rays received from a coordinate input area (3a) by a light-receiving unit (39) and a standard waveform at fixed timing. If the waveform is not equal to the standard waveform, the coordinate input/detection device (3) determines that an installation position of the light-receiving unit (39) is off a correct position because of shock or vibration, and obtains a new standard waveform and stores the new standard waveform in a storage unit (47), thereby setting the waveform of the signal corresponding to the intensity distribution of rays received by the light-receiving unit (39) located at an incorrect position as the standard waveform. Accordingly, there is no error in relative positions of a peak point corresponding to a standard mark (M1-M4), that is, a standard for detecting coordinates of a pointing instrument (P) in the coordinate input area (3a), and a peak point corresponding to the pointing instrument (P) in the intensity distribution, thereby preventing misdetection of the coordinates. <IMAGE>
Optical coordinate input/detection device with optical-unit positioning error correcting function