Importance

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Abstract

A fingerprint sensing device comprises an array of sense elements (12) each of which includes a sense electrode (14) which together with an overlying fingerprint portion forms a capacitor (35). The capacitor is charged by operation of a first switching device (16) via a first address conductor (18). A second switching device (17) is then operated to transfer the charge on the sense electrode to a second address conductor (20) where it is sensed (24) and an output indicative of capacitance provided accordingly. Fast, reliable, scanning is achieved. A row and column array of sense elements is conveniently addressed using sets of row and column conductors (18, 20) and the device can readily be implemented using thin film devices, e.g. TFTs, as the switching devices on an insulating support and with integrated drive circuits.

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First Claim