Patent ID: 7916907

Claim:
A method for spatially transforming biometric data for invariant feature extraction comprising the steps of: using a processor to perform the following functions: acquiring and digitizing biometric information from a user and generating the biometric data responsive thereto; pixelating the biometric data to form a biometric image thereof, said image including a plurality of pixels at a corresponding plurality of pixel coordinates of an orthogonal coordinate system, said biometric data oriented in said image at an arbitrary submission angle with respect to a predetermined axis of said image; applying a coordinate transformation to said plurality of pixels of said biometric image to form a transformed biometric image, said transformed biometric image remaining substantially invariant for different submissions of said biometric information at variant submission angles, said transformed biometric image being defined according to one of the following characteristics: var( x i )= k 1 *var( y i ), 1) where “var” is a variance, k 1 is a scalar multiple, and x i , y i represent a plurality of transformed pixel coordinates, such that: x i =( X i +M 1 Y i )/(1 +M 1 2 ) 1/2 and y i =( Y i −M 1 X i )/(1 +M 1 2 ) 1/2 wherein X i , Y i represent said plurality of pixel coordinates of said biometric image; and, wherein for k 1 =1: M 1 =[2 ra +or−Sqrt(4 r 2 a 2 +a 4 −2 a 2 +1)]/( a 2 −1), if a≠ 1 and, M 1 =0, if a=1 where a=sqrt[var(X i )/var(Y i )]; and, r is a correlation coefficient of X i and Y i ; cov( x i ,y i )= k 2 2) where “cov” is a covariance, k 2 is a scalar multiple, and x i , y i represent a plurality of transformed pixel coordinates such that: x i =( X i +M 2 Y i )/(1 +M 2 2 ) 1/2 and y i =( Y i −M 2 X i )/(1 +M 2 2 ) 1/2 wherein X i , Y i represent said plurality of pixel coordinates of said biometric image; and wherein for k 2 =0: M 2 =[(1 −a 2 )+or−Sqrt(4 r 2 a 2 +a 4 −2 a 2 +1)]/2 ra , if r≠ 0 and, M 2 =0, if r=0 where a=sqrt[var(X i )/var(Y i )]; and, r is a correlation coefficient of X i and Yi.