Title:
電荷検出回路及びそれを用いた指紋センサ
Document Type and Number:
Japanese Patent JP4447952
Kind Code:
B2
Abstract:
A capacitance detecting circuit detects the variations of capacitances at intersections of a plurality of column lines and a plurality of row lines opposite to the column lines and then converts the variations of capacitances into electrical signals. The capacitance detecting circuit includes a column line driving means that drives the column lines, a comparator that is connected to the row lines to convert charges stored in capacitors formed at the intersections of the driven column lines and the row lines into a measured voltage, and that compares the measured voltage with a predetermined set value to output charging or discharging signals, a constant current source that performs charging or discharging on the charges in response to the charging or discharging signals, and a capacitor that stores charges by means of the charging or discharging current. In the capacitance detecting circuit, a voltage between both ends of the capacitor is output as the electrical signal.
Inventors:
Tatsumi Fuji
Application Number:
JP2004113015A
Publication Date:
April 07, 2010
Filing Date:
April 07, 2004
Export Citation:
Assignee:
ALPS ELECTRIC CO.,LTD.
International Classes:
G01B7/28; A61B5/117; G01R27/26; G06K9/00; G06T1/00
Domestic Patent References:
| JP9046193A | ||||
| JP3048506A | ||||
| JP2003269905A | ||||
| JP2001046359A | ||||
| JP2003035732A | ||||
| JP2003294406A | ||||
| JP1178836A | ||||
| JP11155837A |
Attorney, Agent or Firm:
Sumio Tanai
Masatake Shiga
Tadashi Takahashi
Suzuki Mitsuyoshi
Yasuhiko Murayama
Tadao Takashiba
Masatake Shiga
Tadashi Takahashi
Suzuki Mitsuyoshi
Yasuhiko Murayama
Tadao Takashiba