This invention provides a high-resolving-power, compact, lightweight, low-cost coordinate input apparatus which suppresses the influence of disturbance light. Signals in light emission and non-light emission states of a light spot flashed by a designation unit in a predetermined cycle are detected by sensors of a coordinate detection unit, and separately integrated by an integration means to obtain a difference signal. The difference signal is input to a coordinate arithmetic means and digitized at a data width of n bits or more to perform coordinate calculation, thereby outputting a coordinate value having a resolving power about the nth power of 2 of the number of sensor pixels.
Coordinate input apparatus and method, and storage medium