Image distortion compensation technique and apparatus

• US RE41,839 E1
• Filed: 09/13/2007
• Issued: 10/19/2010
• Est. Priority Date: 07/20/2001
• Status: Expired due to Term

• Current Assignee: Activcard Ireland, Limited (Assa Abloy AB)
• Original Assignee: Activcard Ireland, Limited (Assa Abloy AB)
• Inventors: Hamid, Laurence
• Primary Examiner(s): PATEL, KANJIBHAI B
• Application Number:
  US11/854,855
• Time in Patent Office: 1,132 Days
• Field of Search: 382/124, 382/232, 382/254, 382/275, 382/298, 382/284, 359/17, 359/30
• US Class Current: 382/124
• CPC Class Codes: G06K 9/00026 by combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; tracking a sweeping finger movement for specific swipe sensing hardware the groups G06K9/0002, G06K9/00033, G06K9/0004 and G06K9/00046 take precedence

Abstract

A method of compensating for distortion within a composite image is disclosed. A biometric surface is sensed with a swipe imager. The images so provided are assembled into a composite image of the biometric surface. The composite image is then adjusted by insertion or deletion of rows therein to result in an image with a different number of rows.

Claims

1. A method of compensating for distortion within a composite image comprisingthe steps of :

sensing a biometric surface with a swipe imager to provide sensed data;

forming a composite image from sensed data of the a biometric surfacefrom the sensed data ; and

,

adjusting the composite image along a dimension thereof to one of expand or decrease the composite image size along said dimension by one of removing composite image elements along a line perpendicular to said dimension within the composite image and or adding additional image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .

2. A method according to claim 1 wherein the step of adjusting the composite image includes the step of adding rows interspersed at row intervals within the image.

3. A method according to claim 2 wherein the additional rows are added to compensate for compression of the biometric surface during imagingthereof .

4. A method according to claim 3 wherein the surface is a fingertip and wherein the compression results from a downward swipe direction of the fingertip.

5. A method according to claim 4 wherein a row is added to the composite image for every N rows within the composite image.

6. A method according to claim 5 wherein the rows are added at consistent row intervals.

7. A method according to claim 6 wherein the row interval is 4.

8. A method according to claim 6 including the step of determining a row interval based on an amount of compression within the composite image.

9. A method according to claim 2 wherein a row is added to the composite image for every N rows within the composite image.

10. A method according to claim 9 wherein the rows are added at consistent row intervals.

11. A method according to claim 1 further comprisingthe steps of :

determining an amount of compression within the composite image;

adding lines of image elements within the composite image based on the determined amount of compression; and

compensating for image distortion along an axis orthogonal to the dimension.

12. A method according to claim 11 wherein the step of compensating is performed in dependence upon the determined amount of compression.

13. A method according to claim 11 comprising the step of determining a distribution of the compression within the composite image.

14. A method according to claim 13 wherein the step of adding is performed in dependence upon the determined distribution of the compression within the composite image and the step of compensating is performed in dependence upon the determined amount of the compression within the composite image.

15. A method according to claim 1 further comprising the step of determining a distribution of compression within the composite image.

16. A method according to claim 15 wherein the step of adjusting includes a step of inserting additional lines of elements within the composite image in dependence upon the determined distribution of the compression within the composite image, the lines perpendicular to the dimension.

17. A method according to claim 1 wherein the step of adjusting the composite image includes the step of removing rows interspersed at row intervals within the composite image.

18. A method according to claim 17 wherein the rows are removed to compensate for stretching of the biometric surface during imagingthereof .

19. A method according to claim 18 wherein the surface is a fingertip and wherein the stretching results from an upward swipe direction of the fingertip.

20. A method according to claim 19 wherein a row is removed from the composite image for every N rows within the composite image.

21. A method according to claim 20 wherein the rows are removed at consistent row intervals.

22. A method according to claim 21 including the step of determining a row interval based on an amount of stretching within the composite image.

23. A method according to claim 17 wherein a row is removed from the composite image for every N rows within the composite image.

24. A method according to claim 23 wherein the rows are removed at consistent row intervals.

25. A method according to claim 1 further comprisingthe steps of :

determining an amount of stretching;

removing lines of image elements from the composite image based on the determined amount of stretching; and

compensating for image distortion along an axis orthogonal to the dimension.

26. A method according to claim 25 wherein the step of compensating is performed in dependence upon the determined amount of stretching.

27. A method according to claim 25 comprising the step of determining a distribution of the stretching within the composite image.

28. A method according to claim 27 wherein the step of removing is performed in dependence upon the determined distribution of the stretching within the composite image and the step of compensating is performed in dependence upon the determined amount of the stretching within the composite image.

29. A method according to claim 16 comprising the step of determining a distribution of stretching within the composite image.

30. A method according to claim 29 wherein the step of adjusting includes a step of removing lines of composite image elements in dependence upon the determined distribution of the stretching within the composite image, the lines perpendicular to the dimension.

31. A method according to claim 1 wherein the step of adjusting comprisesthe steps of :

determining whether the composite image is stretched or compressed along the dimension;

when the composite image is compressed, adjusting the composite image along the dimension to expand the composite image size along said dimension by adding additional image elements along a line perpendicular to said a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said dimension; and

,

when the composite image is stretched, adjusting the composite image along the dimension to decrease the composite image size along said dimension by removing image elements along a line perpendicular to said a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said at least one dimensiontherein .

32. A method according to claim 1 further comprising a step of determining an amount of one of compression and or stretching along the dimension of the composite image and wherein the step of adjusting of the composite image is performed in order to compensate for a determined amount of the one of compression and or stretching along said dimension.

33. A method according to claim 1 further comprising a step of determining an amount and distribution of one of compression and or stretching along the dimension of the composite image and wherein the step of adjusting of the composite image is performed in order to compensate for a determined amount and distribution of the one of compression and or stretching along said dimension.

34. A swipe contact imager comprising:

a platen across which a biometric surface is to be passed for imaging thereof;

an imaging circuit for sensing a biometric surface passing across the platen and for providing image data relating to portions thereof; and

a processor for forming that forms a composite image from the image data and for adjusting adjusts the composite image along a dimension thereof to one of expand or decrease the composite image size along said dimension by one of removing composite image elements along a line perpendicular to said dimension within the composite image and or adding additional image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .

57. The swipe contact imager of claim 34, further comprising a force measurer configured to measure an amount of force applied to the platen when the biometric surface passes the platen.

58. The swipe contact imager of claim 57 wherein the processor is configured to adjust the composite image based on the measured amount of force.

59. The swipe contact imager of claim 57 wherein the force measurer is configured to measure an amount of force applied to the platen in at least two regions, and wherein the processor is configured to adjust the composite image according to the amount of force applied in the at least two regions.

35. A storage medium having stored therein data, the data indicative of instructions for performing the steps of whose contents cause a computing system to perform a method, comprising:

sensing a biometric surface with a swipe imager to provide sensed data;

forming a composite image of the from sensed data of a biometric surfacefrom the sensed data ; and

,

adjusting the composite image along a dimension thereof to one of expand or decrease the composite image size along said the dimension by one of removing composite image elements along a line perpendicular to said the dimension within the composite image and or adding additional image elements along a line perpendicular to said the dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .

36. A The storage medium according to of claim 35 wherein the data relating to the step of adjusting the composite image includes data relating to a step of adding rows interspersed at row intervals within the image.

37. A The storage medium according to of claim 36wherein the instructions relate to , the method further comprising adding a row to the composite image for every N rows within the composite image.

38. A The storage medium according to of claim 37wherein the instructions relate to , the method further comprising adding the rows at consistent row intervals.

39. A The storage medium according to of claim 38 wherein the row interval is 4.

40. A The storage medium according to of claim 38wherein the data relates to instructions for performing the step of , the method further comprising determining a row interval based on an amount of compression within the composite image.

41. A The storage medium according to of claim 35wherein the data relates to instructions for performing the comprising the step of , the method further comprising:

determining an amount of compression within the composite image;

adding lines of image elements within the composite image based on the determined compression; and

compensating for image distortion along an axis orthogonal to the dimension in dependence upon the determined amount of compression.

42. A The storage medium according to of claim 41wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of the compression within the composite image.

43. A The storage medium according to of claim 42 wherein the data relating to instructions for performing the step of adding includes data relating to instructions for performing the step of adding in dependence upon the determined distribution of the compression within the composite image.

44. A The storage medium according to of claim 35wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of compression within the composite image.

45. A The storage medium according to claim 44 wherein the data relating to instructions for performing the step of adjusting the composite image includes data relating to instructions for performing the step of inserting additional lines of elements within the composite image in dependence upon the determined distribution of the compression within the composite image, the lines being perpendicular to the dimension.

46. A The storage medium according to of claim 35 wherein the data relating to instructions for performing the step of adjusting the composite image includes data relating to instructions for performing the step of removing rows interspersed at row intervals within the composite image.

47. A The storage medium according to of claim 46wherein the data relates to instructions for performing the step of , the method further comprising determining a row interval based on an amount of stretching within the composite image.

48. A The storage medium according to of claim 35wherein the data relates to instructions for performing the steps of , the method further comprising:

determining an amount of stretching;

removing lines of image elements from the composite image based on the determined amount of stretching; and

compensating for image distortion along an axis orthogonal to the dimension in dependence upon the determined amount of stretching.

49. A The storage medium according to of claim 48 wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of the stretching within the composite image.

50. A The storage medium according to of claim 49 wherein the data relates to instructions for performing the step of removing in dependence upon the determined distribution of the stretching within the composite image and the step of compensating is performed in dependence upon the determined amount of the stretching within the composite image.

51. A The storage medium according to of claim 45 wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of stretching within the composite image.

52. A The storage medium according to of claim 51 wherein the data relating to instructions for performing the step of adjusting includes data relating to performing a step of removing lines of composite image elements in dependence upon the determined distribution of the stretching within the composite image, the lines being perpendicular to the dimension.

53. A The storage medium according to of claim 35 wherein the data relating to instructions for performing the step of adjusting include instructions relating to performing the steps of further comprises:

determining whether the composite image is stretched or compressed along the dimension;

when the composite image is compressed, adjusting the composite image along the dimension to expand the composite image size along said the dimension by adding additional image elements along a line perpendicular to said the a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said the dimension; and

,

when the composite image is stretched, adjusting the composite image along the dimension to decrease the composite image size along said the dimension by removing image elements along a line perpendicular to said the a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said the at least one dimension therein.

54. A The storage medium according to of claim 35 wherein the data relates to instructions for performing the step of determining an amount of one of compression and or stretching along the dimension of the composite image and wherein the instructions relate to adjusting the composite image is performed in order to compensate compensates for a determined amount of the one of compression and or stretching along said or dimension.

55. A The storage medium according to of claim 35 wherein the data relates to instructions for performing the step of determining an amount and distribution of one of compression and or stretching along the dimension of the composite image and wherein the instructions relate to adjusting the composite image in order to compensate compensates for a determined amount and distribution of the one of the compression and or stretching along said or dimension.

56. A swipe contact imager comprising:

means for sensing a biometric surface and for providing image data relating to portions thereof; and

means for forming a composite image from the image data and adjusting the composite image along a dimension thereof to expand or decrease the composite image size along said dimension by removing composite image elements along a line perpendicular to said dimension within the composite image or adding image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimension.