Methods for matching ridge orientation characteristic maps and associated finger biometric sensor

• US 20050117785A1
• Filed: 10/01/2004
• Published: 06/02/2005
• Est. Priority Date: 10/01/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: AuthenTec Incorporated (Apple Inc.)
• Inventors: Boshra, Michael
• Granted Patent: US 7,599,530 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1365 Matching; Classification

Abstract

A method for comparing a finger biometric verify ridge orientation characteristic map to a finger biometric enrollment ridge orientation characteristic map may include generating a first probability distribution function substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by less than or equal to a threshold difference. A second probability distribution function may be generated substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by more than the threshold difference. The verify ridge orientation characteristic map may be compared to the enrollment ridge orientation characteristic map to determine a match therewith based upon the first and second probability distribution functions.

Claims

1. A method for processing finger biometric data comprising:

generating an initial ridge orientation characteristic map for the finger based upon the finger biometric data;

estimating an amount of noise in the initial ridge orientation characteristic map; and

adaptively filtering the initial ridge orientation characteristic map based upon the amount of estimated noise therein to generate a final ridge orientation characteristic map.

2. The method of claim 1 wherein estimating the amount of noise comprises:

filtering the initial ridge orientation characteristic map using a fixed filtering level to generate an intermediate ridge orientation characteristic map;

comparing the intermediate ridge orientation characteristic map with the initial ridge orientation characteristic map to determine a variance therebetween; and

estimating the amount of noise based upon the variance.

3. The method of claim 1 wherein generating the initial ridge orientation characteristic map comprises:

tessellating the finger biometric data into an array of cells;

estimating at least one respective gradient for each cell; and

generating the initial ridge orientation characteristic map based upon the estimated gradients.

4. The method of claim 3 wherein estimating the at least one respective gradient for each cell comprises estimating at least one initial gradient for each cell, and summing initial cell gradients from adjacent groups of cells in the array to generate at least one final gradient corresponding to each group;

and wherein generating the initial ridge orientation characteristic map comprises generating the initial ridge orientation characteristic map based upon the final gradients.

5. The method of claim 4 further comprising weighting the initial cell gradients from each group of cells prior to summing.

6. The method of claim 4 wherein the at least one gradient comprises a horizontal gradient, a vertical gradient, and a product of the horizontal and vertical gradients.

7. The method of claim 4 further comprising filtering the estimated gradients prior to generating the initial ridge orientation characteristic map.

8. The method of claim 1 further comprising filtering the finger biometric data prior to generating the initial ridge orientation characteristic map.

9. The method of claim 1 wherein the finger biometric data comprises finger biometric enrollment data, and wherein the final ridge orientation characteristic map comprises an enrollment ridge orientation characteristic map;

and further comprising;

generating a verify ridge orientation characteristic map based upon finger biometric verify data; and

comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map to determine a match therewith.

10. The method of claim 9 further comprising:

generating a first probability distribution function substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by less than or equal to a threshold difference; and

generating a second probability distribution function substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by more than the threshold difference;

and wherein comparing comprises comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map based upon the first and second probability distribution functions.

11. The method of claim 10 wherein comparing comprises comparing based upon a combined probability distribution function comprising a weighted summation of the first and second probability distribution functions.

12. The method of claim 11 wherein one of the first and second probability distribution functions is weighted by a probability k that at least one set of corresponding values of the verify and enrollment ridge orientation characteristic maps will differ from one another by more than the threshold difference, and the other of the first and second probability distribution functions is weighted by 1-k.

13. The method of claim 10 further comprising generating a differential probability distribution function based upon differential properties of adjacent values in at least one of the verify and enrollment ridge orientation characteristic maps;

and wherein comparing further comprises comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map also based upon the differential probability distribution function.

14. The method of claim 13 wherein comparing comprises generating a likelihood ratio based upon the first and second probability distribution functions and the differential probability distribution function.

15. The method of claim 10 further comprising:

generating an initial first probability distribution function and an initial second probability distribution function for a subset of corresponding values of the verify and enrollment ridge orientation characteristic maps; and

determining a relative alignment between the verify and enrollment ridge orientation characteristic maps prior to comparing based upon the initial first and second probability distribution functions.

16. The method of claim 15 further comprising:

dividing at least one of the verify and enrollment ridge orientation characteristic maps into a plurality of sections;

estimating a local deformation associated with each section based upon the determined relative alignment; and

updating the relative alignment between the verify and enrollment ridge orientation characteristic maps based upon the estimated local deformations.

17. The method of claim 15 further comprising generating a match failure if the determined relative alignment is smaller than an alignment threshold.

18. The method of claim 9 further comprising determining an overlap between the verify ridge orientation characteristic map and the enrollment ridge orientation characteristic map;

and wherein comparing comprises comparing the verify ridge orientation characteristic map and the enrollment ridge orientation characteristic map based upon the overlap.

19. The method of claim 9 wherein comparing comprises comparing the verify ridge orientation characteristic map to a plurality of different angular rotations of the enrollment ridge orientation characteristic map.

20. The method of claim 9 wherein comparing comprises comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map based solely upon ridge orientation characteristics.

21-30. -30. (canceled)

31. A method for comparing a finger biometric verify ridge orientation characteristic map to a finger biometric enrollment ridge orientation characteristic map comprising:

generating a first probability distribution function substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by less than or equal to a threshold difference;

generating a second probability distribution function substantially for corresponding values of the verify and enrollment ridge orientation characteristic maps that differ from one another by more than the threshold difference; and

comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map to determine a match therewith based upon the first and second probability distribution functions.

32. The method of claim 31 wherein comparing comprises comparing based upon a combined probability distribution function comprising a weighted summation of the first and second probability distribution functions.

34. The method of claim 31 further comprising generating a differential probability distribution function based upon differential properties of adjacent values in at least one of the verify and enrollment ridge orientation characteristic maps;

and wherein comparing further comprises comparing the verify ridge orientation characteristic map to the enrollment ridge orientation characteristic map also based upon the differential probability distribution function.

36. The method of claim 31 further comprising:

generating an initial first probability distribution function and an initial second probability distribution function for a subset of corresponding values of the verify and enrollment ridge orientation characteristic maps; and

determining a relative alignment between the verify and enrollment ridge orientation characteristic maps prior to comparing based upon the initial first and second probability distribution functions.

39. The method of claim 31 further comprising determining an overlap between the verify ridge orientation characteristic map and the enrollment ridge orientation characteristic map;

and wherein comparing further comprises comparing the verify ridge orientation characteristic map and the enrollment ridge orientation characteristic map based upon the overlap.

33. (canceled)

35. (canceled)

37-38. -38. (canceled)

40-42. -42. (canceled)

43. A finger biometric sensor comprising:

a finger biometric sensing area for sensing finger biometric enrollment data from a finger; and

a processor connected to said finger biometric sensing area for

arranging the finger biometric data into an array of cells,

estimating at least one respective gradient for each cell,

generating an initial ridge orientation characteristic map for the finger based upon the finger biometric data based upon the gradients,

estimating an amount of noise in the initial ridge orientation characteristic map,

adaptively filtering the gradients based upon the amount of estimated noise, and

generating a final ridge orientation characteristic map based upon the filtered gradients.

44. The finger biometric sensor of claim 43 wherein said processor estimates the amount of noise by:

filtering the initial ridge orientation characteristic map using a fixed filtering level to generate an intermediate ridge orientation characteristic map;

comparing the intermediate ridge orientation characteristic map with the initial ridge orientation characteristic map to determine a variance therebetween; and

estimating the amount of noise based upon the variance.

45. The finger biometric sensor of claim 43 wherein said processor arranges the finger biometric data by tessellating the finger biometric data into the array of cells.

46. The finger biometric sensor of claim 43 wherein said processor estimates the at least one respective gradient for each cell by estimating at least one initial gradient for each cell, and summing initial cell gradients from adjacent groups of cells in the array to generate at least one final gradient corresponding to each group;

and wherein said processes generates the initial ridge orientation characteristic map by generating the initial ridge orientation characteristic map based upon the final gradients.

47. The finger biometric sensor of claim 43 wherein the at least one gradient comprises a horizontal gradient, a vertical gradient, and a product of the horizontal and vertical gradients.

48-59. -59. (canceled)