Electrostatic capacity detection apparatus and fingerprint crosscheck apparatus using the same

• US 20030174871A1
• Filed: 03/05/2003
• Published: 09/18/2003
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yoshioka, Masaki, Yano, Motoyasu, Shinozaki, Keiichi
• Granted Patent: US 6,937,031 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1365 Matching; Classification

Abstract

A capacitance sensor used as a fingerprint sensor is provided which includes, in addition to a sensor array (11) in which sensor cells (100) each with a sense electrode are disposed in the form of an array, a canceling dummy block (14) having, disposed in an area having no relation with any object under detection, one column of dummy cells (141) corresponding to each row in the sensor array (11) and each having a dummy electrode nearly identical in parasitic capacitance to the sense electrode of the sensor cell (100). Also a differentiation output unit (183) is provided to differentiate between a sensed voltage Vsig sensed at the sensor array (11) by a sensing circuit (13) and a sensed voltage Vdmy sensed at the canceling dummy block (14), thereby eliminating the influence of a variation in parasitic capacitance Cp, caused by a production tolerance.

Claims

1. A capacitance sensor comprising:

a sensor array in which sensor cells each having a sense electrode are disposed in the form of an array;

a dummy block having, disposed in a position corresponding to a row in an area outside the sensor array and having no relation with any object under detection, at least one dummy cell having a dummy electrode nearly identical in parasitic capacitance to the sense electrode of the sensor cell; and

a differentiation circuit to differentiate between a sensor cell output from the sensor array and a dummy cell output from the dummy block.

2. The apparatus as set forth in claim 1, wherein the dummy block is formed from one column of dummy cells correspondingly to each row in the sensor array.

3. The apparatus as set forth in claim 2, wherein the dummy block is provided on either side of the sensor array.

4. The apparatus as set forth in claim 1, wherein the charge of the sensor cell is acquired to sense a capacitance developed between the sense electrode and the finger surface for acquisition of fingerprint information.

5. A fingerprint identification system comprising:

a fingerprint sensing means including;

a sensor array in which sensor cells each having a sense electrode are disposed in the form of an array;

a dummy block having, disposed in a position corresponding to a row in an area outside the sensor array and having no relation with any object under detection, at least one dummy cell having a dummy electrode nearly identical in parasitic capacitance to the sense electrode of the sensor cell; and

a differentiation circuit to differentiate between a sensor cell output from the sensor array and a dummy cell output from the dummy block;

a storage means for storing pre-registered fingerprint pattern information; and

a comparison means for comparing fingerprint information acquired by the fingerprint sensing means with registered pattern information stored in the storage means and delivering the result of comparison as a result of dactyloscopy.

6. The apparatus as set forth in claim 5, wherein the dummy block is formed from one column of dummy cells correspondingly to each row in the sensor array.