Fingerprint detector using ridge resistance sensing array

Claim 2

The detector of Claim 1 wherein the sensing array means comprises: an insulating layer having a first side and a second side; a conducting layer formed on said first side of said insulating layer having an outer surface opposed to said first side, said conducting layer having a plurality of holes therein for exposing said insulating layer; an array of conducting wires extending through said holes and being generally flush with the top surface of said conducting layer; and means for coupling said array of conducting wires to said sampling means.

Claim 3

The detector of Claim 2 wherein said sensing array means forms a voltage divider when a fingerprint ridge completes a circuit by simultaneously contacting said conducting layer and a conducting wire within said array of conducting wires.

Claim 4

The detector of Claim 1 wherein said sensing array means, said sampling means, and said processing means are fabricated within a single integrated circuit package.

Claim 5

The detector of Claim 2 wherein said array of conducting wires is embedded into an insulating layer of a single integrated circuit package.

Claim 6

The detector of Claim 2 wherein said array of conducting wires forms an n x m array, with said processor measuring a velocity function over a known distance when a fingertip and the sensing array means are moved relative to one another.

Claim 7

The detector of Claim 1 which further comprises memory means for storing said reference trajectory signal.

Claim 8

The detector of Claim 2 wherein said conducting wire is small enough in diameter for forming an open circuit when a fingertip valley is passed over said conducting wire.

Claim 9

The detector of Claim 2 wherein said sampling means comprises: a multiplexer for selectively sequencing through a plurality of said conducting wires; and an analog to digital converter for generating a digital bit stream representing said sample trajectory signal.

Claim 10

The detector of Claim 1 wherein said sensing array means is located on a data carrier card at a location to permit a finger to be swiped across said sensing array means to produce said sample trajectory signal.

Claim 11

The detector of Claim 1 wherein said fingerprint detector further comprises means for being activated automatically upon sensing relative contact between a finger and said sensing array means.

Claim 12

The detector of Claim 1 wherein said fingerprint detector further comprises means for interfacing with an external storage device.

Claim 13

A fingerprint detector comprising: (a) a skin resistance sensing array for translating a skin resistance of ridges and valleys of a fingertip into a sample trajectory signal as the fingertip and the skin resistance sensing array are moved relative to one another, said sample trajectory signal representing electrical conductance changes in the skin resistance of the fingertip, said skin resistance sensing array including: (i) an insulating layer having a first side and a second side; (ii) a conducting layer formed on said first side of said insulating layer having a top surface opposed to said first side, said conducting layer having a plurality of holes for exposing said insulating layer; (iii) an array of conducting wires extending from said second side of said insulating layer and through said holes, each conducting wire being centered within each said hole; and said array of conducting wires being flushly aligned with the top surface of said conducting layer; (b) a multiplexer coupled to said skin resistance sensing array for selectively switching between each conducting wire of said skin resistance sensing array; (c) an analog to digital converter coupled to said multiplexer for generating a digital bit stream representing said sample trajectory signal; and (d) a processor coupled to said analog to digital converter for comparing said sample trajectory signal with a reference trajectory signal and producing a verification signal related to a probability that the fingertip generated both the sample trajectory signal and the reference trajectory signal.

Claim 14

The device of Claim 13 wherein said processor is coupled to a storage device, said storage device storing at least one reference trajectory signal.

Claim 15

The device of Claim 14 wherein said storage device is a random access memory (RAM).

Claim 16

The device of Claim 14 wherein said storage device is a read only memory (ROM).

Claim 18

The method of Claim 17 which further comprises the step of: quantizing the sample trajectory signal into a digital bit stream.

Claim 19

The method of Claim 17 which further comprises: mounting an array of conducting wires in a surface of a data carrier card; swiping the fingertip across the array of conducting wires; normalizing the sample trajectory signal; comparing the normalized sample trajectory signal with the stored reference trajectory signal; and producing a verification signal.

Claim 20

The method of Claim 19 wherein said normalizing step is carried out by: standardizing an optimal number of data points to be sampled during one sample trajectory signal period; providing an initial sampling rate; measuring a sample trajectory signal frequency; correcting said sampling rate by a constant multiplier directly related to said sample trajectory signal frequency; and continuously adjusting said sampling rate to acquire said corrected sampling rate, whereby the normalization serves to standardize for fluctuations between fingertip swiping velocity rates.