Coordinate input apparatus

Abstract

A coordinate input apparatus comprises: a vibration pen to generate a vibration; a vibration propagating plate to propagate the vibration generated by the pen by touching the pen to the plate; vibration sensors to detect the vibration propagated to the plate; a supporting member which supports the plate and whose vibration propagating velocity is slower than the plate; a position coordinate calculating circuit to calculate the position coordinates of the pen on the plate on the basis of the detection signals from the sensors; and a display which is provided below the supporting member and displays the calculated coordinates. The plate is made of metal or transparent glass and the supporting membrr is made of a transparent synthetic resin. The supporting member is directly in contact with the plate at a rough surface, its acoustic impedance value is different from the plate, and its vibration attenuation ratio is larger than that of the plate. Since the vibration wave component propagated to the sensors is not influenced by the interference of the vibration propagated in the support member, the coordinates can be accurately detected on the basis of the vibration detection waveforms without distortion.