US Patent 7375720 Coordinate input apparatus and coordinate input method

In a coordinate input apparatus including the detection unit of a sensor unit (1R, 1L) arranged at a corner of a coordinate input region (4), a retroreflecting member (3) arranged at the peripheral portion of the coordinate input region (4) to retroreflect incident light, the light projecting unit of the sensor unit (1R, 1L) which projects light to the coordinate input region (4), and a control/arithmetic unit (2) which executes a coordinate acquisition operation for obtaining the coordinate position of a pointer (6) having a light-emitting function in the coordinate input region (4) on the basis of a light amount distribution obtained from the detection unit of the sensor unit (1R, 1L), a light-receiving IC (5) detects a light emission signal from the pointer (6), and the control/arithmetic unit 2 controls the coordinate acquisition operation on the basis of the detection result.