System and methods for transforming biometric image data to a consistent angle of inclination
First Claim
1. 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(xi)=k1*var(yi),
1)where “
var”
is a variance, k1 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates, such that;
xi=(Xi+M1Yi)/(1+M12)1/2 and
yi=(Yi−
M1Xi)/(1+M12)1/2 wherein Xi, Yi represent said plurality of pixel coordinates of said biometric image; and
,wherein for k1=1;
M1=[2ra+or−
Sqrt(4r2a2+a4−
2a2+1)]/(a2−
1), if a≠
1 and,
M1=0, if a=1where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi;
cov(xi,yi)=k2
2)where “
cov”
is a covariance, k2 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates such that;
xi=(Xi+M2Yi)/(1+M22)1/2 and
yi=(Yi−
M2Xi)/(1+M22)1/2 wherein Xi, Yi represent said plurality of pixel coordinates of said biometric image; and
wherein for k2=0;
M2=[(1−
a2)+or−
Sqrt(4r2a2+a4−
2a2+1)]/2ra, if r≠
0and,
M2=0, if r=0where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi.
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Abstract
Biometric data are obtained through a biometric input device (120) and subsequently pixelated via a pixelator (130). The pixelator (130) creates an image of the biometric data. Via a processing unit (110), a relationship between pixels of a transformed version of the image is asserted. Thus, the biometric data is rotated to a consistent inclination based on the relationship between pixels regardless of an orientation in which the biometric data were captured in the original image. Once the image has been transformed, features of the biometric data may be extracted and either stored in a data storage unit (140) or compared with previously stored feature values for validation of the biometric data.
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Citations
16 Claims
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1. A method for spatially transforming biometric data for invariant feature extraction comprising the steps of:
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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(xi)=k1*var(yi),
1)where “
var”
is a variance, k1 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates, such that;
xi=(Xi+M1Yi)/(1+M12)1/2and
yi=(Yi−
M1Xi)/(1+M12)1/2wherein Xi, Yi represent said plurality of pixel coordinates of said biometric image; and
,wherein for k1=1;
M1=[2ra+or−
Sqrt(4r2a2+a4−
2a2+1)]/(a2−
1), if a≠
1 and,
M1=0, if a=1where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi;
cov(xi,yi)=k2
2)where “
cov”
is a covariance, k2 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates such that;
xi=(Xi+M2Yi)/(1+M22)1/2and
yi=(Yi−
M2Xi)/(1+M22)1/2wherein Xi, Yi represent said plurality of pixel coordinates of said biometric image; and wherein for k2=0;
M2=[(1−
a2)+or−
Sqrt(4r2a2+a4−
2a2+1)]/2ra, if r≠
0and,
M2=0, if r=0where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi.- View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for verifying the validity of biometric data by invariant feature extraction, the method comprising the steps of:
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using a processor to perform the following functions; providing an input device for acquiring and digitizing biometric information from a user; providing a storage unit for storing features of said biometric information; acquiring a first sample of said biometric information from said user and generating a first sample of biometric data responsive thereto; pixelating said first sample of biometric data to form a first sample biometric image thereof, said first sample biometric image including a plurality of pixels at a corresponding plurality of pixel coordinates of an orthogonal coordinate system, said first sample of biometric data oriented in said first sample biometric image at an arbitrary first submission angle with respect to a predetermined axis of said first sample biometric image; applying a coordinate transformation to said plurality of pixels of first sample biometric image to form a first transformed biometric image, said first 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(xi)=k1*var(yi),
1)where “
var”
is a variance, k1 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates, such that;
xi=(Xi+M1Yi)/(1+M12)1/2and
yi=(Yi−
M1Xi)/(1+M12)1/2wherein Xi, Yi represent said plurality of pixel coordinates of said biometric image; and
,wherein for k1=1;
M1=[2ra+or−
Sqrt(4r2a2+a4−
2a2+1)]/(a2−
1), if a≠
1 and,
M1=0, if a=1where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi;
cov(xi,yi)=k2
2)where “
cov”
is a covariance, k2 is a scalar multiple, and xi, yi represent a plurality of transformed pixel coordinates such that;
xi=(Xi+M2Yi)/(1+M22)1/2and
yi=(Yi−
M2Xi)/(1+M22)1/2wherein Xi,Yi represent said plurality of pixel coordinates of said biometric image; and wherein for k2=0;
M2=[(1−
a2)+or−
Sqrt(4r2a2+a4−
2a2+1)]/2ra, if r≠
0and,
M2=0, if r=0where a=sqrt[var(Xi)/var(Yi)]; and
, r is a correlation coefficient of Xi and Yi;extracting biometric features from said first transformed biometric image and storing said features in said storage unit; acquiring a second sample of said biometric information from said user and generating a second sample of biometric data responsive thereto; pixelating said second sample of biometric data to form a second sample biometric image thererof, said second sample biometric image including a plurality of pixels at a corresponding plurality of pixel coordinates of said orthogonal coordinate system, said second sample of biometric data oriented in said second sample biometric image at an arbitrary second submission angle with respect to a predetermined axis of said second sample biometric image; applying said transformation to said plurality of pixels of said second sample biometric image to form a second transformed biometric image, said second transformed biometric remaining substantially invariant for different submissions of said biometric information at variant submission angles angle of; extracting said biometric features from said second transformed biometric image; and comparing said biometric features of said second transformed biometric image to corresponding ones of said features stored in said storage unit. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A system for spatially transforming biometric data for invariant feature extraction, the system comprising:
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an input device operable to acquire and digitize biometric information data from a user and generate the biometric data responsive thereto; a pixelator operable to pixelate said biometric data into an image thereof, said image including a plurality of pixels at a corresponding plurality of pixel coordinates in 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; a storage unit operable to store sequences of computer program instructions for a transformation process executable to transform said plurality of pixels of said image into a transformed image, said transformation process involving the solution of a quadratic equation where the equation involves the ratio of variances of the pixel coordinates and a correlation coefficient of the pixel coordinates, said transformed image remaining substantially invariant for different submissions of said biometric information at a plurality of submission angles; and a processing unit coupled to said input device and said storage unit, said processing unit operable to execute said transformation process. - View Dependent Claims (16)
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Specification