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US 6,487,306 B1Granted
System and method for deriving a string-based representation of a fingerprint image
AssigneeInternational Business Machines Corporation
InventorsAnil K. Jain, Lin Hong, Rudolf Maarten Bolle, Sharathchandra Umapathirao Pankanti
Life of this patent
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Abstract
The invention is a system and method for deriving a single dimensional representation for a set of points e.g.,minutiae, in image of a two dimensional pattern of lines, e.g. a fingerprint, by creating a one dimensional (string) representation of one or more points (e.g., minutiae) and the respective attributes of each point therein. A landmark point is selected from the two dimensional image, preferably from the set of the points to be represented in single dimension. The relationships of each of the points with reference to the landmark determines a linear order for the points and the attributes associated with each point.
Claims29
A system, for deriving a string representation of an image, comprising:
- a computer having one or more central processing units (CPUs) and a memory;
- one or more images stored in the memory, the image having one or more points;
- a reference landmark selector, executed by the CPU, that selects a landmark;
- and
- a representation unit that determines point attributes associated with individual ones of the image points, that orders and merges the point attributes into a first string, and that composes a plurality of first strings into an ordered second string that represents the image, where the point attributes are ordered with respect to the landmark, where individual ones of the plurality of first strings are ordered within the second string also with respect to the landmark, where said representation unit orders the plurality of first bit strings in a linear order with respect to at least one of the point attributes, where the order is determined by a distance between the landmark and the respective point and by an angle subtended by a vector between the landmark and the respective point and a reference line.
2 more elements
A method for comparing a two-dimensional input fingerprint representation to a template fingerprint representation, comprising the steps of:
- identifying a reference location in both the input fingerprint representation and the template fingerprint representation;
- estimating translation (t=(Δx,Δy)) and rotation (−P) parameters between ridges associated with input minutiae and ridges associated with template minutiae to obtain transformed representations;
- converting the transformed representations into polar coordinate representations with respect to the reference location;
- representing the polar coordinate representations of the input fingerprint representation and the template fingerprint representation as two symbolic strings having an order with respect to the reference location;
- and
- executing a matching algorithm on the two symbolic strings to generate a matching score that indicates a number of matched corresponding minutiae between the input and template fingerprint representations,
- wherein the step of converting the transformed representations into polar coordinate representations comprises a step of computing a tuple comprised of polar coordinate attributes for each minutia, these attributes comprising a radius, an e-angle, and a t-angle, wherein the radius is a Euclidean distance between a given minutia and a respective reference minutia, wherein the e-angle is a counter-clockwise angle subtended by a line segment joining the given minutia and the respective reference minutia with a fixed reference axis passing through the reference minutia;
- and wherein the t-angle for the given minutia is a counter-clockwise angle subtended by the line segment joining the given minutia and the respective reference minutia with a minutia orientation vector, and
- wherein the step of representing comprises a step of ordering the tuples by increasing e-angle.
6 more elements
A method for comparing a two-dimensional input fingerprint representation to a template fingerprint representation, comprising steps of:
- identifying a reference location in both the input fingerprint representation and the template fingerprint representation;
- estimating translation (t=(Δx,Δy)) and rotation (Δθ) parameters between ridges associated with input minutiae and ridges associated with template minutiae to obtain transformed representations;
- converting the transformed representations into polar coordinate representations with respect to the reference location;
- representing the polar coordinate representations of the input fingerprint representation and the template fingerprint representation as two symbolic strings;
- and
- executing a matching algorithm on the two symbolic strings to generate a matching score that indicates a number of matched corresponding minutiae between the input and template fingerprint representations,
- wherein the step of converting the transformed representations into polar coordinate representations comprises a step of computing a tuple comprised of polar coordinate attributes for each minutia, and wherein the step of executing the matching algorithm on the two symbolic strings employs a plurality of consistency thresholds when comparing polar coordinate attributes of a minutia of the input fingerprint representation to polar coordinate attributes of a minutia of the template fingerprint representation, and wherein at least one of the consistency thresholds is adaptively updated as a function of a number of minutiae that are matched.
4 more elements
A system for deriving a string representation of an image, comprising:
- a computer having one or more central processing units (CPUs) and a memory;
- one or more images stored in the memory, the image having one or more points;
- a reference landmark selector, executed by the CPU, that selects a landmark;
- and
- a representation unit that determines point attributes associated with individual ones of the image points, that orders and merges the point attributes into a first string, and that composes a plurality of first strings into an ordered second string that represents the image, where the point attributes are ordered with respect to the landmark, where individual ones of the plurality of first strings are ordered within the second string also with respect to the landmark, and wherein each of the point attributes is represented as a tuple that has an e-angle value, and wherein said representation unit orders said tuples by increasing e-angle values.
2 more elements
A method for processing a two-dimensional input fingerprint representation, comprising steps of:
- processing the input fingerprint representation to identify a plurality of minutiae, individual ones of the identified plurality of minutiae being described by an attribute tuple having values determined by reference to a landmark feature in the input fingerprint image;
- ordering the attribute tuples in accordance with at least one of the values;
- representing individual ones of the ordered tuples as a first bit string to provide a plurality of one dimensional first bit strings;
- composing the plurality of one dimensional first bit strings into a one dimensional second bit string wherein individual ones of the plurality of first bit strings are arranged in order with respect to the landmark feature;
- and
- wherein said at least one of the values is an e-angle, and wherein said ordering step orders the attribute tuples by increasing e-angles.
3 more elements
A method for comparing a two-dimensional input fingerprint representation to a template fingerprint representation, comprising steps of:
- identifying a reference location in both the input fingerprint representation and the template fingerprint representation;
- estimating translation (t=(Δx,Δy)) and rotation (Δθ) parameters between ridges associated with input minutiae and ridges associated with template minutiae to obtain transformed representations;
- converting the transformed representations into polar coordinate representations with respect to the reference location;
- representing the polar coordinate representations of the input fingerprint representation and the template fingerprint representation as two symbolic strings having an order with respect to the reference location;
- executing a matching algorithm on the two symbolic strings to generate a matching score that indicates a number of matched corresponding minutiae between the input and template fingerprint representations, wherein each minutia has at least one attribute represented as a tuple, wherein said at least one attribute is an e-angle, and wherein said representing step orders the attribute tuples by increasing e-angles.
2 more elements
Dependencies are inferred from the claim text.