PURPOSE: To obtain a coordinate input device with a display device not to be affected with an electromagnetic wave noise generated from a display unit by using a position indicator to generate ultrasonic oscillations.
CONSTITUTION: The title device consists of a position indicator 110, which generates the ultrasonic oscillations are prescribed frequencies based on a timing signal, a display unit 120, which is equipped with a plate having ultrasonic oscillation propagating ability on a display surface, microphones 131 and 132 to detect the ultrasonic oscillations, timing signal generating circuit 140 to generate the timing signal, a time difference detecting circuit 150, which detects the time difference between the time when the timing signal is generated and the time when the ultrasonic oscillations are detected, and a coordinate calculating circuit 170 to calculate the coordinate value of a designated position by the position indicator 110 based on the time difference detection result. That is, the designated position of the position indicator 110 is detected by the ultrasonic oscillations. Thus, without a malfunction due to the effect of the electromagnetic wave noise generated from the display unit 120, the coordinate value at the designated position can be obtained.
AKAMATSU NORIO
AOKI KAZUO
FUKUZAKI YASUHIRO
