Fingerprint sensor

• US 4,577,345 A
• Filed: 04/05/1984
• Issued: 03/18/1986
• Est. Priority Date: 04/05/1984
• Status: Expired due to Term

• Current Assignee: Igor Abramov
• Original Assignee: Igor Abramov
• Inventors: Abramov, Igor
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Todd, Jacqueline
• Application Number:
  US06/597,124
• Time in Patent Office: 712 Days
• Field of Search: 382/4, 324/71.1, 340/825.3, 340/825.31, 340/825.32, 340/825.33, 340/825.34, 357/26, 178/18, 178/19, 178/20
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G07C 9/257 electronically G07C9/26 takes precedence
• CPC Class Codes: G07C 9/26 using a biometric sensor integrated in the pass

Abstract

An electrical method and apparatus for sensing the pattern of ridges and valleys on an individual'"'"'s finger to provide binary electrical signals representative of the sensed pattern. The fingerprint sensor is constructed and defined with an integrated circuit chip having an array of sensing circuits arranged thereon in rows and columns for defining X, Y coordinates. One of the electrodes for each sensing circuit is connected to a contact pad that is electrically exposed on the surface of the integrated circuit chip at a location corresponding to the X, Y coordinate for the individual sensing circuit. A pressure sensitive membrane having a conductive surface facing the array of contact pads is utilized for translating the fingerprint pattern into a conductive pattern of ridges and valleys. The conductive pattern is pressed into electrical engagement with each contact pad opposite a fingerprint ridge. While the conductive pads are in electrical engagement with the membrane, the sensing circuits are sequentially scanned in a preselected timed relationship to produce a binary electrical signal from each sensing circuit having its individual contact pad in circuit relationship with the membrane. The output signals from the rows and columns of sensing signals represent the portion of the fingerprint pattern representative of a ridge. The binary output signals can be processed by known techniques for comparing the sensed fingerprint with known fingerprint patterns.

Claims

1. A method for sensing the ridge and valley fingerprint pattern of a person'"'"'s finger and translating said pattern into electrical signals representative thereof, including the steps of:

stretching a membrane having a conductive surface over an array of electrically conductive contact pads which are electrically insulated from each other and arranged so that each contact pad defines an "X,Y" coordinate of said array, the conductive surface being opposite said pads and spaced therefrom so it is not in electrical contact therewith;

connecting a separate electronic switching circuit to each of said pads;

pressing the person'"'"'s finger against said membrane such that the ridge portions of said person'"'"'s fingerprint pattern forces the membrane into electrical contact with the pads there-opposite, thereby activating the electronic switching circuits connected to said pads; and

scanning the electronic switching circuits to generate an electrical output signal in accordance with the activated and nonactivated switching circuits which represents the fingerprint pattern.

2. A sensor for transforming the ridge and valley fingerprint pattern of a person'"'"'s finger into corresponding electrical output signals comprising:

substrate means having row and column electrodes arranged thereon in an electrically insulated spaced apart relationship to form a grid array which defines a plurality of "X,Y" coordinates;

an array of electrically conductive contact pads, arranged on said substrate in accordance with said array, said pads being electrically insulated from each other, each of said pads corresponding to a separate one of the "X,Y" coordinates of said array;

a plurality of electronic switching circuit means, each having a first electrode connected to one of said row electrodes, a second electrode connected to one of the column electrodes, and a third electrode connected to one of said contact pads;

means for providing a voltage potential between at least two of said switching circuit means electrodes;

a membrane having an electrically conductive surface;

holding means for mounting said membrane in overlying relationship with the array of contact pads with the conductive surface thereof directly opposite said array of contact pads but not in electrical contact therewith, such that when the person'"'"'s finger is pressed against said membrane, the ridge portions of the person'"'"'s fingerprint pattern brings the portions of the membrane there-opposite into electrical contact with the opposing contact pads to activate the switching circuit means connected thereto, the valley portions of the fingerprint pattern not producing such electrical contact or activation of the switching circuit means; and

scanning circuit means for sequentially scanning the row and column electrodes to produce sequential electrical output signals indicative of which of said pads are being brought into contact with the membrane by the finger ridge portions and which of said pads are not being brought into such contact, said electrical signals representing the ridge-valley fingerprint pattern.

3. A finger sensor, as defined in claim 2, wherein said transistor switching circuits each comprise an n-MOS enhancement type transistor with said first electrode comprising the transistor gate electrode, the second electrode comprising the transistor source electrode and the third electrode comprising the transistor drain electrode.

4. A finger sensor, as defined in claim 2 wherein said membrane is secured to said holding means to assume a preselected concave configuration relative to said wafer and to captive the air between the holding means and said membrane.

5. A finger sensor as defined in claim 2 including signal processing means coupled to receive the output signals from said scanning circuit means for identifying the sensed fingerprint pattern.

6. A finger sensor, as defined in claim 2 wherein said substrate means comprises a silicon wafer.