Systems and methods with identity verification by comparison and interpretation of skin patterns such as fingerprints

• US 5,909,501 A
• Filed: 09/09/1996
• Issued: 06/01/1999
• Est. Priority Date: 09/09/1996
• Status: Expired due to Term

• Current Assignee: Bioscrypt, Inc. (Advent International Corporation)
• Original Assignee: Arete Associates
• Inventors: Thebaud, Lawrence R.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): MEHTA, BHAVESH M
• Application Number:
  US08/709,302
• Time in Patent Office: 995 Days
• Field of Search: 382/115, 382/116, 382/124, 382/125, 382/190, 382/191, 382/201, 382/206, 382/209, 382/254, 382/260, 382/275, 356/71, 340/825.34
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction
• CPC Class Codes: G06V 40/1365 Matching; Classification
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

Preferably a sensor receives a print image from an authorized person to form a template, and from a candidate to form test data. Noise variance is estimated from the test data as a function of position in the image, and used to weight the importance of comparison with the template at each position. Test data are multilevel, and are bandpassed and normalized--and expressed as local sinusoids--for comparison. A ridge spacing and direction map of the template is stored as vector wavenumber fields, which are later used to refine comparison. Global dilation--and also differential distortions--of the test image are estimated, and taken into account in the comparison. Comparison yields a test statistic that is the ratio, or log of the ratio, of the likelihoods of obtaining the test image assuming that it respectively was, and was not, formed by an authorized user. The test statistic is compared with a threshold value, preselected for a desired level of certainty, to make the verification decision--which controls access to a utilization system such as facilities, equipment, a financial service, or a system for providing or receiving information. Certain forms of the invention also encompass the utilization system. Nonvolatile memory holds instructions for automatic operation as described above.

Claims

1. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for deriving from the test data corresponding multilevel test data that are bandpassed and normalized;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing portions of the bandpassed and normalized multilevel test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

2. The apparatus of claim 1:

further comprising means for extracting from the test data an estimate of noise variance in the test data as a function of position in the test image; and

wherein the estimating means and the comparing means perform said estimating and said comparing, respectively, as a function of position;

wherein the estimating means or the comparing means, or both, comprise means for taking into account the estimated noise variance.

3. The apparatus of claim 1, wherein:

the estimating means comprise means for using a maximum-likelihood method to estimate the distortion field.

4. The apparatus of claim 1, wherein:

the estimating means comprise means for demodulating the test data preliminary to extracting a distortion field therefrom.

5. The apparatus of claim 1, wherein the estimating means comprise:

the estimating means comprise means for avoiding errors due to phase shifts greater than half the local periodicity of the assumed carrier field.

6. The apparatus of claim 1, wherein the estimating means comprise:

means for providing an assumed carrier field for use in demodulating the test data;

means for analyzing the demodulated test data to approximately ascertain distortion associated with the demodulated test data.

7. The apparatus of claim 1, wherein:

the estimating means comprise means for downsampling the test data according to anticipated degree of abruptness of at least one type of distortion, in preparation for estimating the distortion.

8. The apparatus of claim 7:

wherein the estimating means comprise means for downsampling the test data before estimating the distortion;

further comprising means for applying the estimated distortion to approximately equalize the test and reference data with respect to the assumed distortion;

further comprising means for interpolating the estimated distortion, to upsample the estimated distortion for use in the applying means; and

wherein the comparing means compare the thus-approximately-equalized test and reference data.

9. The apparatus of claim 1, wherein:

the estimating means comprise means for using a gradient search to estimate the distortion.

10. Apparatus for verifying the identity of a person by literally and directly comparing a test data set representing a two-dimensional test image of that person'"'"'s skin-pattern print with a reference data set derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed geometrical distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed geometrical distortion of the test image relative to a reference image;

means for literally and directly applying the estimated distortion to approximately equalize the test and reference data sets with respect to the assumed geometrical distortion;

means for literally and directly comparing the test data set with the reference data set, taking into account the estimated geometrical distortion;

wherein the comparing means literally and directly compare at least major fractions of the thus-approximately-equalized test and reference data sets themselves, as distinguished from individual very small subarravs thereof, and also as distinguished from mere measures of correlation between the sets, and also as distinguished from mere measures of distortion of one or both sets;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

11. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision;

means for applying the estimated distortion to approximately equalize the test and reference data with respect to the assumed distortion; and

wherein;

the comparing means compare the thus-approximately-equalized test and reference data; and

the applying and comparing means comprise means for using the estimated distortion to generate a matched filter for use in forming a test statistic; and

further comprising nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

12. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into consideration the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

means for extracting from the test data an estimate of noise variance in the test data as a function of position in the test image; and

wherein;

the estimating means and the comparing means perform said estimating and said comparing, respectively, as a function of position;

the estimating means or the comparing means, or both, comprise means for taking into account the estimated noise variance; and

the taking-into-account means comprise means for weighting the importance of the estimating or comparing, or both, as a function of position in accordance with the noise variance estimate for the corresponding position; and

further comprising nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

13. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

wherein said estimating means comprise;

means for using a maximum-likelihood method to estimate the distortion field, and

means for using the maximum-likelihood-estimated distortion field to generate a matched filter for use in forming a test statistics;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

14. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

wherein;

the estimating means comprise means for using a maximum-likelihood method to estimate the distortion field; and

said using means comprise means for taking account of a priori statistics in estimating the distortion field; and

further comprising nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

15. The apparatus of claim 14, wherein:

said using means comprise means for using a Fourier-space model for taking account of the a priori statistics.

16. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

wherein the estimating means comprise;

means for demodulating the test data preliminary to extracting a distortion field therefrom, and

means for applying information developed from the reference data as a carrier field, in demodulating the test data; and

further comprising nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

17. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

wherein the estimating means comprise;

means for avoiding errors due to phase shifts greater than half the local periodicity of an assumed carrier field, and

means for beginning the estimating with a first approximation that is localized and of small magnitude, and iterating so that progressive approximations propagate in the frequency or spatial domain, or both; and

the avoiding means comprise means for controlling rate of propagation to minimize likelihood of introducing a phase shift greater than half the local periodicity in any single iteration; and

further comprising;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

18. The apparatus of claim 17, wherein the controlling means comprise:

means for monitoring a measure of the rate at which the distortion is changing; and

means, responsive to the monitoring means, for limiting the rate of propagation as a function of position, in accordance with said measure.

19. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

wherein the estimating means comprise means for downsampling the test data according to anticipated degree of abruptness of at least one type of distortion, in preparation for estimating the distortion;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision;

means for extracting from prior statistics an estimate of the power spectral density for distortion fields generally;

means for setting sampling intervals as a function of position, in accordance with the estimate of power spectral density; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

20. A secured system subject to access control based upon surface-relief data from a relieved surface such as a finger;

said system being for use in the presence of an assumed distortion of the relieved surface; and

said system comprising;

utilization means, susceptible to misuse in the absence of a particular such relieved surface that is related to an authorized user, said utilization means being selected from the group consisting of;

a facility,

apparatus,

means for providing a financial service, and

means for providing or receiving information;

sensor means for acquiring surface-relief data from such a relieved surface;

means for processing the data to determine identity of the relieved surface, and for applying the determined identity to control access to the utilization means, said processing and applying means including;

means for expressing the test data in the form of local sinusoids;

means for expressing reference data, related to said particular relieved surface related to the authorized user, in the form of local sinusoids;

means for analyzing the data to estimate the assumed distortion,

means for comparing portions of the sinusoidally expressed test data with the sinusoidally expressed reference data related to said particular relieved surface related to the authorized user, taking into account the estimated distortion, and

means, responsive to the comparing means, for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

21. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means for extracting from the test data an estimate of noise variance in the test data as a function of position in the test image;

wherein the estimating means or the comparing means, or both, comprise means for weighting the importance of the estimating or comparing, or both, as a function of position in accordance with the noise-variance estimate for the corresponding position;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

22. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

wherein said estimating means comprise means for using a maximum-likelihood method to estimate the distortion field and thereby generate a matched filter for use in forming a test statistic;

means for comparing the reference data with the test data, using the test statistic;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

23. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for using a maximum-likelihood method that takes account of a priori statistics, to estimate the assumed distortion of the test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

24. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for applying information developed from the reference data as a carrier field, to demodulate the test data;

means for estimating the assumed distortion of the demodulated test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

further comprising nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

25. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image, said assumed distortion being superimposed on an assumed carrier field; and

said apparatus comprising;

means for estimating the assumed distortion of the test image relative to a reference image;

means for estimating or establishing the assumed carrier field;

means for detecting phase discontinuities or reversals in the skin-pattern print image, to avoid skin-pattern phase shift greater than half the local periodicity of the assumed carrier field;

means for comparing the test data with the reference data, taking into account the estimated distortion substantially free of effects of such skin-pattern phase shift greater than half the local periodicity of the assumed carrier field;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

26. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for establishing a first approximation of the assumed distortion, said first approximation being localized and of small magnitude;

means for establishing further approximations iteratively so that progressive approximations propagate in the frequency or spatial domain, or both, to thereby estimate the overall distortion of the test image relative to a reference image;

means for controlling rate of propagation to minimize likelihood of introducing, in any single iteration, a phase shift greater than half the local periodicity of an assumed carrier field; and

further comprising;

means for comparing the test data with the reference data, taking into account the estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.

27. Apparatus for verifying the identity of a person by comparing test data representing a two-dimensional test image of that person'"'"'s skin-pattern print with reference data derived from a two-dimensional reference skin-pattern print image obtained during a prior enrollment procedure;

said apparatus being for use in the presence of an assumed distortion of the test image relative to the reference image; and

said apparatus comprising;

means for estimating power spectral density of skin-pattern print data;

means for downsampling the test data according to anticipated degree of abruptness of at least one type of distortion;

means for employing the estimated power spectral density in estimating the assumed distortion of the downsampled test image relative to a reference image;

means for comparing the test data with the reference data, taking into account the thereby-estimated distortion;

means responsive to the comparing means for making an identity-verification decision; and

nonvolatile memory means for holding instructions for automatic operation of the foregoing means.