Uneven pattern detector and uneven pattern detecting method
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United States of America Patent
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Dec 27, 2005
Grant Date -
Jan 23, 2003
app pub date -
Jul 8, 2002
filing date -
Jul 12, 2001
priority date (Note) -
In Force
status (Latency Note)
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Abstract
An uneven pattern detector has a structure wherein (a) detecting elements, each being provided with a TFT which is a switching element and a detecting electrode, are arranged in a matrix manner, and (b) a CSA connected to each data line detects charged or discharged electric charges at the respective detecting elements on respective rows sequentially selected by a gate line, whereby a capacitance (a coupled capacitance of Cf and Cx) reflecting fingerprint unevenness on a finger as a detection object can be detected. In the uneven pattern detector, each of the detecting elements is provided with an auxiliary capacitor electrode located so as to face the detecting electrode. This forms an auxiliary capacitor Cs between the auxiliary capacitor electrode and the detecting electrode. Further, a positive-phase input terminal of an operational amplifier of the CSA is connected with the auxiliary capacitor electrode so as to hold the positive-phase input terminal of the operational amplifier of the CSA and the auxiliary capacitor electrode at an identical potential. As a result, the electric charges can be detected by the CSA without being affected by the auxiliary capacitor Cs.
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