Coordinate input apparatus and method

摘要

This invention aims to provide a coordinate input apparatus having high detection reliability and high efficiency and, to control the influence of the ambient light using a simple structure. The coordinate input apparatus detects a light spot (5) flashing on and off in a predetermined cycle and incident at a desired position on a coordinate input screen (10), and comprises a detection means (6), consisting of a plurality of photoelectric conversion elements corresponding to N pixels for detecting a coordinate of a light spot. The difference between signals from photoelectric elements in light emission state and in light non-emission state at each N pixel is found and the smaller of the difference signals of the m-th pixels in each direction forward and backward from the pixel having the maximum difference signal is set as a threshold value. Effective pixels are identified based on the threshold value, and the coordinate is calculated by using the difference data of the selected effective pixels.