COORDINATE INPUT SYSTEM WITH INPUT PEN

摘要

A coordinate input system has a tablet (10) composed of an X-direction loop coil assembly and a Y-direction loop coil assembly, and an input pen (20) having a tuning circuit (29) the tuning frequency of which is variable about a predetermined frequency. The system has a coordinate detecting function for detecting the X- and Y-coordinate values of position input by the input pen,and a phase detecting function for detecting the change in the tuning frequency of the tuning circuit as a change in the phase with respect to the phase of the predetermined tuning frequency. Information concerning the detected coordinate point, e.g., spread of the coordinate point proportional to the pressure at which the pen is pressed onto the tablet, is computed in accordance with the amount of change in the phase detected by the phase detecting function.