Fujitsu Corporation

Toru Asano

Hisashi Yamaguchi

Kazuo Yoshikawa

Shizuo Andoh

Hideaki Takizawa

Kazuhiro Takahara

Keizo Kurahashi

A coordinate detecting apparatus for determining the coordinate data of a point on a plane by indicating the point with a touch of a fingertip or other load to the point. The apparatus comprises a transparent resistive film forming the plane (touch panel) and a buffer circuit operating as a voltage follower circuit having substantially infinate input impedance. The buffer amplifier is operatively connected between each selected pair of facing ends of a substantially rectangular region of the resistive film, and equalizes the potentials at the ends. The change of the impedance between one of the ends and the ground is detected in accordance with the touch of the fingertip to the touch panel and is used as an original coordinate data. Further modifications concerning the avoidance of degradation in the detection quality due to fluctuations of the impedance provided by the touch of a fingertip, for example, and the methods to perform 2-dimensional coordinate detection are described.

Coordinate detecting apparatus

A touch sensing device employing a new sensing method of the present invention is composed of the sensing portion which senses capacitance change of the touch sensing electrodes forming the touch panel, plurality of capacitance compensating capacitors which are used in common for the sensing electrodes in order to compensate fluctuation of touch sensing electrodes of the touch panel, and the ROM which is storing the data for selecting the capacitance compensating capacitors. The ON-OFF output voltage levels in the touch/non-touch conditions to the touch sensing electrodes can be equalized for each electrode and thereby the touch sensing with high accuracy can be realized by selecting the capacitance compensating capacitor by means of the ROM at the time of retrieving each touch sensing electrode.

Touch sensing device

A transparent finger touch sensing device having a sensing circuit including a resonator for sensing a touch an oscillator for supplying an AC signal to the resonator, a buffer circuit for isolating an output of the oscillator from each selected touch electrodes and for supplying the oscillator output to the remaining non-selected touch electrodes when the sensing circuit is sequentially connected to the touch sensing electrodes, is disclosed. Thereby, the selected touch electrodes and non-selected touch electrodes are maintained at a voltage having the same phase and the same level and the inter-electrode impedance is substantially negligible.

A new type touch sensing device comprises a touch panel with a plurality of transparent touch electrodes, a LC parallel resonant circuit connected to the touch electrode and an oscillation circuit. The LC resonant circuit has a resonant point on a same frequency with the oscillation frequency of the oscillation circuit. The touch/non-touch condition to the touch electrode is detected as a change of voltage value at the connecting point of the LC resonant circuit and touch electrode with an increased ON-OFF ratio.

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Kawasaki, Japan

Toru Asano