Electric field fingerprint sensor apparatus and related methods

Claim 2

A fingerprint sensor as claimed in Claim 1 wherein said coherent drive means comprises: a drive electrode adjacent said electric field sensing electrodes; a second dielectric layer between said drive electrode and said electric field sensing electrodes; a drive circuit for powering said drive electrode to generate the coherent electric field drive signal having a predetermined frequency, and a finger electrode positioned adjacent said dielectric layer for contact with the finger.

Claim 3

A fingerprint sensor as claimed in Claim 1 or 2 wherein a respective shield electrode associated with each of said electric field sensing electrodes for shielding each electric field sensing electrode from adjacent sensing electrodes, and each shield electrode comprises an electrically conductive layer surrounding a respective electric field sensing electrode with a dielectric layer therebetween, with an active shield driving means for actively driving each of said shield electrodes, preferably said active shield driving means comprising an amplifier operatively connected to each electric field sensing electrode and its associated shield electrode for actively driving the shield electrode with a portion of an output signal from said amplifier.

Claim 4

A fingerprint sensor as claimed in any one of Claims 1 to 3 wherein synchronous demodulator means operatively connected to said electric field sensing electrodes for synchronously demodulating signals therefrom, with dynamic contrast enhancing means operatively connected to said electric field sensing electrodes for dynamically enhancing contrast and uniformity of the fingerprint image output signal, in which said dynamic contrast enhancing means comprises a capacitor matrix operatively connected to said electric field sensing electrodes; and alternating current capacitor matrix drive means for driving said capacitor matrix.

Claim 5

A fingerprint sensor as claimed in any one of Claims 1 to 4 wherein said alternating current capacitor matrix drive means comprises a synchronous demodulator, said dynamic contrast enhancing means comprises a resistor matrix operatively connected to said electric field sensing electrodes, an amplifier operatively connected to each electric field sensing electrode, multiplexing means for selectively reading each of said electric field sensing electrodes, including a substrate; and an active semiconductor layer on said substrate comprising a plurality of semiconductor devices operatively connected to said electric field sensing electrodes.

Claim 6

A fingerprint sensor as claimed in Claim 5 including package means for enclosing said substrate, said active semiconductor layer, said electric field sensing electrodes, said dielectric layer; in which said package means has an opening therethrough in registry with said dielectric layer.

Claim 7

A fingerprint sensor comprising: an array of electric field sensing electrodes; a dielectric layer on said electric field sensing electrodes, said dielectric layer for receiving a finger adjacent thereto; a respective shield electrode associated with each of said electric field sensing electrodes for shielding each electric field sensing electrode from adjacent electric field sensing electrodes; and drive means for applying an electric field drive signal to said electric field sensing electrodes and adjacent portions of the finger so that said electric field sensing electrodes produce a fingerprint image output signal, with each shield electrode comprising an electrically conductive layer surrounding a respective electric field sensing electrode with a dielectric layer therebetween, including active shield driving means for actively driving each of said shield electrodes, in which said active shield driving means comprises an amplifier operatively connected to each electric field sensing electrode and its associated shield electrode for actively driving the shield electrode with a portion of an output signal from the amplifier.

Claim 8

A fingerprint sensor as claimed in Claim 7 wherein said drive means comprises: a drive electrode adjacent said electric field sensing electrodes; a second dielectric layer between said drive electrode and said electric field sensing electrodes; and a drive circuit for powering said drive electrode to generate the electric field drive signal having a predetermined frequency, a finger electrode positioned adjacent said dielectric layer for contact with the finger, a synchronous demodulator means operatively connected to said electric field sensing electrodes for synchronously demodulating signals therefrom, a dynamic contrast enhancing means operatively connected to said electric field sensing electrodes for dynamically enhancing contrast and uniformity of the fingerprint image output signal, with said dynamic contrast enhancing means comprising: a capacitor matrix operatively connected to said electric field sensing electrodes; alternating current capacitor matrix drive means for driving said capacitor matrix, said alternating current capacitor matrix drive means comprises a synchronous demodulator, and said dynamic contrast enhancing means comprises a resistor matrix operatively connected to said electric field sensing electrodes.

Claim 9

A fingerprint sensor comprising: a substrate; an array of electric field sensing electrodes adjacent said substrate; a dielectric layer on said electric field sensing electrodes, said dielectric layer for receiving a finger adjacent thereto; drive means for applying an electric field drive signal to said electric field sensing electrodes and adjacent portions of the finger so that said electric field sensing electrodes produce a fingerprint image output signal; and contrast enhancing means adjacent said substrate and operatively connected to said electric field sensing electrodes for enhancing contrast of the fingerprint image output signal, said contrast enhancing means comprises dynamic contrast enhancing means for dynamically enhancing contrast and uniformity of the fingerprint image output signal, said dynamic contrast enhancing means comprises: a capacitor matrix operatively connected to said electric field sensing electrodes; and alternating current capacitor matrix drive means for driving said capacitor matrix, said alternating current capacitor matrix drive means comprises a synchronous demodulator, said dynamic contrast enhancing means comprises a resistor matrix operatively connected to said electric field sensing electrodes, in which said drive means comprises: a drive electrode adjacent said electric field sensing electrodes; a second dielectric layer between said drive electrode and said electric field sensing electrodes; and a drive circuit for powering said drive electrode to generate the electric field drive signal having a predetermined frequency, and a finger electrode positioned adjacent said dielectric layer for contact with the finger.

Claim 10

A fingerprint sensor as claimed in Claim 9 including a respective shield electrode associated with each of said electric field sensing electrodes for shielding each electric field sensing electrode from adjacent sensing electrodes, active shield driving means for actively driving each of said shield electrodes, synchronous demodulator means operatively connected to said electric field sensing electrodes for synchronously demodulating signals therefrom, and package means for enclosing said substrate, said electric field sensing electrodes, said contrast enhancing means and said dielectric layer; and wherein said package means has an opening therethrough in registry with said dielectric layer.

Claim 11

A computer workstation comprising: a housing; a computer processor positioned within said housing; a display operatively connected to said computer processor; a keyboard operatively connected to said computer processor; and fingerprint sensor means operatively connected to said computer processor and mounted within said housing for protection thereby, said fingerprint sensor means comprising a finger sensing surface exposed through an opening in said housing; said computer processor comprising access control means for permitting operation of the computer workstation only upon determining a match between a fingerprint sensed by said fingerprint sensor means and an authorized reference fingerprint, in which said fingerprint sensor means comprises an electric field fingerprint sensor, including an array of electric field sensing electrodes, a dielectric layer on said electric field sensing electrodes, said dielectric layer for receiving a finger adjacent thereto; and drive means for applying an electric field drive signal to said electric field sensing electrodes and adjacent portions of the finger so that said electric field sensing electrodes produce a fingerprint image output signal.

Claim 12

A computer workstation as claimed in Claim 11 wherein said drive means comprises: a drive electrode adjacent said electric field sensing electrodes; a second dielectric layer between said drive electrode and said electric field sensing electrodes; a coherent drive circuit for powering said drive electrode to generate a coherent electric field drive signal having a predetermined frequency, a respective shield electrode associated with each of said electric field sensing electrodes for shielding each electric field sensing electrode from adjacent sensing electrodes, active shield driving means for actively driving each of said shield electrodes, synchronous demodulator means operatively connected to said electric field sensing electrodes for synchronously demodulating signals therefrom, and dynamic contrast enhancing means operatively connected to said electric field sensing electrodes for dynamically enhancing contrast and uniformity of the fingerprint image output signal.

Claim 14

A method as claimed in Claim 13 including the step of actively driving each of said shield electrodes with a portion of an output signal from an amplifier associated with each electric field sensing electrode, the step of synchronously demodulating signals from said electric field sensing electrodes, and the step of dynamic enhancing contrast and uniformity of the fingerprint image output signal.