Apparatus for determining ridge direction patterns
First Claim
Patent Images
1. An apparatus for determining ridge direction patterns comprising:
- an image memory for storing data f(x,y) of an image of a pixel at a coordinates position (x,y) in a picture of a skin surface at a memory address corresponding to said coordinates position (x,y);
means for calculating gradient vectors from data stored in said image memory, X-component and Y-component of said gradient vector at a position (x,y) being α
f(x,y)/α
x and α
f(x,y)/α
y respectively;
gradient vector memory for storing calculated gradient vectors at memory address corresponding to said position (x,y); and
means for analyzing distributions of gradient vectors, wherein a direction perpendicular to a principal axis of said distribution is determined as a ridge direction of a subregion, wherein;
said means for analyzing distributions of gradient vectors calculates said direction of said principal axis of said distribution of said subregion by a multiple regression analysis in which an energy function E(a,b) is defined by E(a,b)=Σ
∥
qi -(api +b)∥
2 where pi and qi respectively represent α
f(x,y)/α
x and α
f(x, y)/α
y at point i in a subregion and Σ
represents summation for all points i in said subregion;
values of variables a,b which minimize said energy function are obtained; and
from the value of `a`, said ridge direction of said subregion is determined.
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Abstract
From an image memory of a fingerprint picture, gradient vectors of the picture are calculated. And from distribution of gradient vectors in a subregion, ridge direction of the subregion are determined, and confidence of the determined direction is also defined.
34 Citations
6 Claims
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1. An apparatus for determining ridge direction patterns comprising:
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an image memory for storing data f(x,y) of an image of a pixel at a coordinates position (x,y) in a picture of a skin surface at a memory address corresponding to said coordinates position (x,y); means for calculating gradient vectors from data stored in said image memory, X-component and Y-component of said gradient vector at a position (x,y) being α
f(x,y)/α
x and α
f(x,y)/α
y respectively;gradient vector memory for storing calculated gradient vectors at memory address corresponding to said position (x,y); and means for analyzing distributions of gradient vectors, wherein a direction perpendicular to a principal axis of said distribution is determined as a ridge direction of a subregion, wherein; said means for analyzing distributions of gradient vectors calculates said direction of said principal axis of said distribution of said subregion by a multiple regression analysis in which an energy function E(a,b) is defined by E(a,b)=Σ
∥
qi -(api +b)∥
2 where pi and qi respectively represent α
f(x,y)/α
x and α
f(x, y)/α
y at point i in a subregion and Σ
represents summation for all points i in said subregion;
values of variables a,b which minimize said energy function are obtained; and
from the value of `a`, said ridge direction of said subregion is determined.
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2. An apparatus for determining ridge direction patterns comprising:
-
an image memory for storing data f(x,y) of an image of a pixel at a coordinates position (x,y) in a picture of a skin surface at a memory address corresponding to said coordinates position (x,y); means for calculating gradient vectors from data stored in said image memory, X-component and Y-component of said gradient vector at a position (x,y) being α
f(x,y)/α
x and α
f(x,y)/α
y respectively;gradient vector memory for storing calculated gradient vectors at memory address corresponding to said position (x,y); and means for analyzing distributions of gradient vectors, wherein a direction perpendicular to a principal axis of said distribution is determined as a ridge direction of a subregion, wherein; said means for analyzing distributions of gradient vectors calculates said direction by a principal component analysis in which variance-covariance matrix of gradient vectors in said subregion is determined;
eigenvalues λ
1, λ
2, (λ
1 >
λ
2) and eigenvectors e1, e2 are determined from said matrix; and
from the eigenvalues and eigenvectors, said ridge direction of said subregion is determined. - View Dependent Claims (3, 4, 5, 6)
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Specification
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Current AssigneeNEC Corporation
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Original AssigneeNEC Corporation
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InventorsKamei, Toshio
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Primary Examiner(s)Boudreau, Leo
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Assistant Examiner(s)SHALWALA, BIPIN H
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Application NumberUS08/455,689Time in Patent Office986 DaysField of Search382/125, 382/124, 382/113, 382/116, 382/193, 382/199, 382/204, 382/266, 382/201US Class Current382/204CPC Class CodesG06V 40/1347 Preprocessing; Feature extr...
