Coordinate detection device capable of detecting coordinates using display panel provided specially for display

A coordinate detection device performing a coordinate detection operation by an electromagnetic induction method, the coordinate detection device comprising:

• a flat display panel in which a material having an electro-optical effect characteristic is sealedly filled in a space between two substrates, and a plurality of x-axis electrodes and a plurality of y-axis electrodes which are intersecting each other on the substrates;
• x-axis drive circuit and y-axis drive circuit which are provided for image display use and electrically drive the x-axis electrodes and the y-axis electrodes of the flat display panel respectively;
• a wireless coordinate pointing device including alternating current magnetic field generating means having therein an alternating current power source and an electrode connected to an output terminal of the alternating current magnetic field generating means;
• a coordinate detection circuit including a differential amplifier, a connection switching circuit which selects two adjoining x-axis electrodes or a pair of x-axis electrodes constituted by two adjoining electrode groups of the x-axis electrodes as well as two adjoining y-axis electrodes or a pair of y-axis electrodes constituted by two adjoining electrode groups of the y-axis electrodes, connects the selected electrodes to the differential amplifier, and shifts the selected electrodes one by one in a direction in which the selected electrodes are arranged, peak detection means which obtains a signal which is supplied from the wireless coordinate pointing device to the electrodes by shifting the selected electrodes as a single-humped signal from the differential amplifier and detects a peak portion of the single-humped signal, and position coordinate specifying means for specifying coordinates based on a time at which the peak portion detecting means detects the peak portion and a timing at which the electrodes are selected;
• wherein one end of each of the plurality of x-axis electrodes and one end of each of the plurality of y-axis electrodes are always open, including during a time when the coordinate detection circuitry is being operated;
• and
• a display-coordinate detection changeover circuit which time-sharingly complementarily operates the x-axis drive circuit, the y-axis drive circuit, and the coordinate detection circuit.