Fingerprint sensing devices and systems incorporating such
First Claim
1. A fingerprint sensing device comprising:
- an array of sense elements, each sense element including a sense electrode and a first switching device coupled to each sense electrode;
a first address conductor controlled by a control signal generated by a drive circuit, said first address conductor effective to provide a charge to said sense electrodes through said first switching device;
a sensing surface, spaced from said sense electrode, and operable to receive a finger having a fingerprint placed upon said sensing surface;
said sensing surface, a portion of said finger, and said sense electrodes, forming a plurality of capacitors each having a capacitance;
a second address conductor coupled to said sense electrodes with a second switching device disposed therebetween; and
said second switching device being controlled by said drive circuit, following operation of said first switching device, to discharge a charge produced on said sense electrode and to transfer said charge to said second address conductor.
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Accused Products
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.
54 Citations
13 Claims
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1. A fingerprint sensing device comprising:
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an array of sense elements, each sense element including a sense electrode and a first switching device coupled to each sense electrode; a first address conductor controlled by a control signal generated by a drive circuit, said first address conductor effective to provide a charge to said sense electrodes through said first switching device; a sensing surface, spaced from said sense electrode, and operable to receive a finger having a fingerprint placed upon said sensing surface; said sensing surface, a portion of said finger, and said sense electrodes, forming a plurality of capacitors each having a capacitance; a second address conductor coupled to said sense electrodes with a second switching device disposed therebetween; and said second switching device being controlled by said drive circuit, following operation of said first switching device, to discharge a charge produced on said sense electrode and to transfer said charge to said second address conductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of sensing a fingerprint, said method comprising:
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providing an array of sense elements, each sense element including a sense electrode and a first and second switching device coupled to the sense electrodes; providing a first and second address conductor coupled to said sense electrodes through said first and second switching devices respectively; providing a sensing surface, spaced from said sense electrodes, and operable to receive a finger having a fingerprint placed upon said sensing surface, wherein said sensing surface, a portion of said finger, and said sense electrodes, form a plurality of capacitors each having a capacitance; placing said finger on said sensing surface; activating said first switching device thereby charging said capacitors; activating said second switching device, after deactivating said first switching device, said second switching device thereby causing said capacitors to discharge; and measuring said discharge to sense said fingerprint.
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Specification