Electrostatic capacitance sensor and fingerprint collator comprising it

• US 6,882,164 B2
• Filed: 07/04/2002
• Issued: 04/19/2005
• Est. Priority Date: 07/12/2001
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yoshioka, Masaki, Yano, Motoyasu, Shinozaki, Keiichi
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Dole, Timothy J.
• Application Number:
  US10/362,758
• Publication Number:
  US 20040096061A1
• Time in Patent Office: 1,020 Days
• Field of Search: 324/658, 324/663, 324/672, 324/679, 380/59, 382/124, 713/186
• US Class Current: 324/663
• 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 usable as a fingerprint sensor is provided in which a timing controller (16) provides such a switching control as to first cause a switch (SA) in a sensor cell (100-k) to turn on to set the potential at a sense electrode to a reference potential and then a switch SB to turn on after the switch (SA) is turned off, whereby charge is stored from the sensor cell (100-k) into a reference capacitance Cf1 of a sensing circuit (13-k), the sensitivity of sensing the capacitance is raised by increasing the number of times the charge storage is repeated and only signal components are extracted by reducing noise components by averaging.

Claims

1. A capacitance sensor comprising:

sensor cells each including a sense electrode, a first switch connected between the sense electrode and reference potential, and a second switch connected between the sense electrode and a sense line;

a sensing means for storing, into a reference capacitance thereof, a charge outputted from the sensor cell to a sense line via the second switch and converting the charge into a voltage signal; and

a controlling means for controlling the first switch to turn on and then off, and then the second switch to turn on, whereby the storage of the charge from the sensor cell into the reference capacitance of the sensing means is repeatedly done, wherein the controlling means controls the capacitance sensing sensitivity of the sensing means by changing the number of times the storage of the charge from the sensor cell into the reference capacitance of the sensing means is repeated.

2. The apparatus as set forth in claim 1, formed from a semiconductor device.

3. The apparatus as set forth in claim 2, wherein the reference potential is a potential in a semiconductor substrate.

4. The apparatus as set forth in claim 1, wherein:

the sensor cells are laid in the form of an array; and

the sensing means senses a capacitance developed between the sense electrode and a finger surface to obtain fingerprint information by storing the charge of the sensor cell into the reference capacitance thereof.

5. A fingerprint identification system, comprising:

a fingerprint sensing means including;

a sensor array in which there are laid in the form of an array sensor cells each including a sense electrode, a first switch connected between the sense electrode and reference potential, and a second switch connected between the sense electrode and a sense line; and

a sensing means for sensing a capacitance developed between the sense electrode and a finger surface to obtain fingerprint information by storing, into a reference capacitance, a charge outputted from the sensor cell to the sense line via the second switch; and

a controlling means for controlling the first switch to turn on and then off, and then the second switch to turn on, whereby the storage of the charge from the sensor cell into the reference capacitance of the sensing means is repeatedly done;

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

a comparison means for comparing fingerprint information obtained by the fingerprint sensing means with the registered pattern information stored in the storage means and outputting the result of comparison as a result of fingerprint identification, wherein the controlling means controls the sensitivity of the fingerprint sensing means by changing the number of times the storage of the charge from the sensor cell into the reference capacitance of the sensing means is repeated.