"SYSTEMS & METHODS WITH IDENTITY VERIFICATION BY STREAMLINED COMPARISON & INTERPRETATION OF FINGERPRINTS AND THE LIKE"

• US 20010016055A1
• Filed: 04/11/1997
• Published: 08/23/2001
• Est. Priority Date: 04/11/1997
• Status: Active Grant

• Current Assignee: Bioscrypt, Inc. (Advent International Corporation)
• Original Assignee: Areté Associates, Inc.
• Inventors: THEBAUD, LAWRENCE R., POTTER, RANDALL E., HARKLESS, CURT R., MONRO, JOHN A. Jr.
• Granted Patent: US 6,356,649 B2
• Time in Patent Office: Days
• US Class Current: 382/115
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06V 10/247 by affine transforms, e.g. correction due to perspective effects; Quadrilaterals, e.g. trapezoids
• CPC Class Codes: G06V 40/1359 Extracting features related to ridge properties; Determining the fingerprint type, e.g. whorl or loop
• 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. Power spectral density (PSD) data for the template and candidate are compared, to read out rotation & dilation; these are used to adjust the template or candidate preparatory to a correlation to find translation. After applying the translation, and refinement of the rotation and dilation, normalized spatial correlation values (NSCVs) are used as a measure of quality of the match—and thresholded to make an early rejection or acceptance decision in very clear cases. Where the question is closer, isomorphic adjustment is applied to the entire template or candidate for a fairer comparison in their overlap area. Such comparison proceeds by the same type of PSD analysis—but for multiple subregions in the overlap area. Resulting NSCVs are averaged to obtain a measure of quality of the match, which again is thresholded for a final decision in the closer cases. Noise variance from the test data, vs. position in the image, is used to weight the importance of comparison with the template in each subregion. Nonvolatile memory holds instructions for automatic operation.

Claims

1. Apparatus for acquiring personal skin-pattern print data for use in comparison to verify the identity of a person, said apparatus comprising:

optical means for physically receiving contact by such skin of such person and for, during the contact, forming an optical image of such skin pattern;

optoelectronic means for receiving the optical image from the optical means and generating in response a series of electronic signal arrays derived from such pattern during the contact;

electronic means for monitoring the series of electronic signal arrays during the contact;

means for saving at least one of said electronic signal arrays for use in such comparison;

means, responsive to the electronic monitoring means during the contact, for deferring operation of the saving means until at least one of the electronic signal arrays in the series satisfies a particular condition related to a characteristic of such pattern; and

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

2. The apparatus of

claim 1

, wherein:

said skin contact settles during said contact, and the electronic signal arrays in the series tend to improve as said skin contact settles.

3. The apparatus of

claim 1

, wherein:

said particular condition comprises a test for adequacy of skin-pattern image area, based upon spatial-frequency content of the electronic signal arrays.

4. The apparatus of

claim 3

, wherein:

said particular condition further comprises a test for elapsed time; and

the apparatus further comprises means for prompting such person to shift said skin contact if adequacy of image area is not adequate within a particular elapsed time.

5. The apparatus of

claim 3

, wherein:

said particular condition further comprises a test for quality of signal array within at least part of the image area.

6. The apparatus of

claim 1

, wherein:

said particular condition comprises a test for quality of signal array within at least part of the image area.

7. Apparatus for acquiring personal skin-pattern print data for use in comparison to verify the identity of a person, said apparatus comprising:

means for receiving or generating an electronic signal array corresponding to such skin pattern;

means for defining a plurality of signal wavenumber bands;

means for comparing wavenumber content of the electronic signal array with said plurality of bands;

means, responsive to the comparing means, for selecting a particular one band of said plurality to use in analyzing said electronic signal array to verify the identity of such person; and

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

8. Apparatus for acquiring and providing personal skin-pattern print data for use in comparison to verify the identity of a person, said apparatus comprising:

means for receiving or generating a multilevel electronic signal array corresponding to such skin pattern;

means for preliminarily evaluating or preprocessing, or both, said multilevel electronic signal array;

means for expressing the preliminarily evaluated or preprocessed, or both, signal array in two- or one-bit form;

means for storing or exporting the signal array expressed in said two- or one-bit form; and

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

9. The apparatus of

claim 8

, further comprising:

means for normalizing the signal array in terms of variance before storage or export.

10. The apparatus of

claim 9

, further comprising:

means for spatially downsampling the signal array in terms of variance before storage or export.

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 comprising:

means for extracting such reference data from storage or from an imported data set for use in verification;

preprocessing means for bandpassing, normalizing and smoothing the extracted data for use in verification;

roll means for comparing the data from the preprocessing means with such test data to verify identity; and

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 comprising:

means for deriving from such reference data or such test data, or both, a respective form of a vector gradient field;

means for smoothing such reference data or such test data, or both, under control of the vector-gradient-field form so that said smoothing is substantially along the directions of respective ridges of such skin pattern;

means for applying the smoothed data in making an identity-verification decision; and

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

13. The apparatus of

claim 12

, wherein the deriving means comprise:

means for finding a vector gradient field from a fast Fourier transform of the data;

means for screening the vector gradient field to account for phase jumps; and

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

14. The apparatus of

claim 13

, wherein the vector-gradient-field form is a vector wavenumber field, and the deriving means further comprise:

means for calculating from the gradient field a covariance matrix, and from the covariance matrix a scalar magnitude field for the wavenumber;

means for constructing the vector wavenumber field as said scalar magnitude field with directedness of said vector gradient field; and

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

25. The apparatus of

claim 14

, further comprising:

means for estimating relative dilation of the reference and test images; and

means for applying the estimated relative dilation and rotation to further estimate relative translation of the reference and test images.

15. 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 one or more two-dimensional reference skin-pattern print images obtained during a prior enrollment procedure;

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

said apparatus comprising;

means for computing power spectral density of at least a portion of the test image;

means for applying the power spectral density to estimate such assumed dilation of the test image relative to a reference image;

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

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.

16. The apparatus of

claim 15

, wherein:

the computing means further comprise means for computing power spectral density of at least a portion of the reference image; and

the applying means comprise means for comparing the power spectral densities of the test image and reference image to estimate their relative dilation.

17. The apparatus of

claim 16

, wherein:

the applying means comprise means for interpreting a radial component of power spectral density as a measure of relative dilation.

18. The apparatus of

claim 15

, wherein:

said applying means further comprise means for applying the power spectral density to estimate rotation of the test image; and

the comparing means further comprise means for taking into account the estimated relative rotation.

19. The apparatus of

claim 18

, wherein:

the applying means comprise means for interpreting an angular component of power spectral density as a measure of rotation.

20. The apparatus of

claim 17

, further comprising:

means for applying the estimated relative dilation and rotation to further estimate relative translation of the reference and test images.

21. The apparatus of

claim 15

, further comprising:

means for estimating relative rotation of the reference and test images; and

means for applying the estimated relative dilation and rotation to further estimate relative translation of the reference and test images .

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 one or more two-dimensional reference skin-pattern print images obtained during a prior enrollment procedure;

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

said apparatus comprising;

means for computing power spectral density of at least a portion of the test image;

means for applying the power spectral density to estimate such assumed rotation of the test image relative to a reference image;

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

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. The apparatus of

claim 22

, wherein:

the computing means further comprise means for computing power spectral density of at least a portion of the reference image; and

the applying means comprise means for comparing the power spectral densities of the test image and reference image to estimate their relative rotation.

24. The apparatus of

claim 23

, wherein:

the applying means comprise means for interpreting an angular component of power spectral density as a measure of rotation.

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 one or more two-dimensional reference skin-pattern print images obtained during a prior enrollment procedure;

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

said apparatus comprising;

means for computing power spectral density of at least a portion of such test image and of such reference image, respectively;

means for transforming the respective computed power spectral densities to polar coordinates;

whereby the transformed power-spectral-density information interpreted as rectangular-coordinate data has the form of power-density values plotted on a rectangular grid of ridge spacing and orientation;

means for considering the transformed power spectral densities for such test and reference images together, and reading off from said considered-together power spectral densities an estimate of such assumed relative rotation and dilation; and

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

27. The apparatus of

claim 26

, wherein:

the considering means comprise means for ratioing the respective ridge-spacing and orientation values, or correlating the two transformed power spectral densities, within a hypothesis range of relative rotation and dilation to find an estimate of the most probable relative rotation and dilation.

30. The apparatus of

claim 27

, wherein the comparing means comprise:

means for dividing one of the images into a multiplicity of substantially overlapping subregions that in the aggregate cover substantially the entire said one image; and

means for evaluating the degree of similarity of said test and reference images, with respect to substantially every one of said subregions of which a significant fraction is within said all area common to both images.

31. The apparatus of

claim 30

, wherein the evaluating means comprise:

means for estimating, within each of said subregions in said common area respectively, a further component of relative distortion between test and reference images.

32. The apparatus of

claim 31

, wherein the evaluating means further comprise:

means for forming a composite measure of said further components for all of said subregions in the common area; and

means for thresholding said composite measure to make said decision.

33. The apparatus of

claim 32

:

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 composite-measure forming means comprise means for taking into account the estimated noise variance.

34. The apparatus of

claim 33

, wherein the taking-into-account means comprise:

means for weighting the further component for each of said subregions in the common area, in an inverse relation with the noise-variance estimate for that subregion.

28. 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 relative translation, and at least one component of relative isomorphic distortion, between the test and reference images;

means for adjusting the test or reference image, or both, to allow for said estimated relative translation and component of relative isomorphic distortion;

means for comparing said test and reference images, after said adjustment, within substantially all area that is common to both images, to make an identity-verification decision; and

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

29. The apparatus of

claim 28

, wherein:

the comparing means comprise means for analyzing power spectral densities within said common area to estimate remaining distortions.

35. 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 comprising:

means for comparing a first small region of the reference data with the test data to form a first measure of similarity;

first means for testing said first measure against a first threshold to verify such person'"'"'s identity;

means for, in event the first measure is not high enough for acceptance, then comparing a second small region of the reference data with the test data to form a second measure of similarity;

second means for testing said second measure against a second threshold that is HIGHER than the first threshold, to verify such person'"'"'s identity; and

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

36. The apparatus of

claim 35

, wherein:

the first testing means also test the first measure of similarity against a first, relatively low, rejection threshold to deny verification;

said second comparing means operate only if said first measure of similarity is between said first acceptance and rejection thresholds, whereby the first measure of similarity is neither high enough for acceptance nor low enough for rejection.

37. The apparatus of

claim 36

, wherein:

the second testing means also test the second measure of similarity against a second rejection threshold that is higher than the first rejection threshold, to deny verification.

38. The apparatus of

claim 37

, wherein:

said second small region is smaller than the first small region.

39. The apparatus of

claim 37

, further comprising:

means for, in event said second measure is between said second acceptance and rejection thresholds, whereby the second measure is neither high enough for acceptance nor low enough for rejection, then comparing substantially an entire common area of the test and reference images to make a verification decision.

40. The apparatus of

claim 36

, wherein:

said second small region is smaller than the first small region.

41. The apparatus of

claim 36

, further comprising:

means for, in event said second measure is not high enough for acceptance, then comparing substantially an entire common area of the test and reference images to make a verification decision.

42. The apparatus of

claim 35

, wherein:

said second small region is smaller than the first small region.

43. Apparatus for receiving surface-relief data from a sensor that acquires surface-relief data from a relieved surface such as a finger, and in response controlling access to facilities, equipment, a financial service, or a system for providing or receiving information;

said apparatus being for use in presence of an assumed dilation of the surface, and comprising;

a system for processing the received data to determine identity of the relieved surface, said system including;

means for calculating and comparing power spectral densities of at least a portion of the received data and test data respectively, and analyzing the power spectral density comparison to estimate the assumed dilation,

means for comparing the test data with reference data, taking into account the estimated dilation, and

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

means for applying the determined identity to control access to such facilities, equipment, financial service, or source or reception of information; and

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

44. 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 calculating and comparing power spectral densities of at least a portion of the received data and test data respectively, and analyzing the power spectral density comparison to estimate the assumed distortion,

means for comparing the test data with 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.

45. A method 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 method comprising the steps of;

ratioing or correlating power spectral densities of corresponding regions of the test and reference images to determine relative isomorphic distortion between the images;

using a normalized spatial correlation value as a measure of similarity between corresponding regions of the test and reference images;

making an identity-verification decision based on said normalized spatial correlation value; and

in nonvolatile memory, holding instructions for automatic operation of the above-mentioned steps.

46. The method of

claim 45

, further comprising the steps of:

operating a sensor to acquire the test data; and

responsive to the decision-making step, operating a switch if identity is verified.