Fingerprint sensing devices and systems incorporating such
US6411727B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Feb 25, 1999 |
| Grant date | Jun 25, 2002 |
| Priority date | — |
| Expiry date | Feb 25, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06V40/1306
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A fingerprint sensing device comprises an array of capacitive type sense elements (12) each having a sense electrode (14) for forming, together with an overlying fingerprint portion, a capacitance and a transistor (16) connected between the sense electrode and first and second associated address conductors (18, 20). The transistor is arranged with its gate connected to the sense electrode such that, due to the effect of the capacitance and parasitic capacitances in the transistor, a selection signal applied to the first conductor (18) causes the transistor to be turned on or to be held off in the presence of a fingerprint valley or ridge overlying the sense electrode. Fast sampling of the transistor on/off currents produced in the second conductor (20) is possible and improved noise rejection and high signal to noise ratio is obtained. A further transistor (17) may be included in the sense element which is operable to remove any unwanted charge on the gate of the first-mentioned transistor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.