System and method for counting ridges in a captured print image

• US 20060133656A1
• Filed: 01/30/2006
• Published: 06/22/2006
• Est. Priority Date: 08/02/2002
• Status: Abandoned Application

• Current Assignee: Sonavation, Inc.
• Original Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Inventors: Smith, David C., Cannon, Gregory L.
• Application Number:
  US11/341,377
• Publication Number:
  US 20060133656A1
• Time in Patent Office: Days
• US Class Current: 382/125
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

A system and method for counting ridges in a captured print image frame is described. A pixel path through the captured print image frame is traversed. A hysteresis band for the pixel path is determined. A number of crossings of the determined hysteresis band is counted while traversing the pixel path. A number of print ridges based on the counted number of hysteresis band crossings is determined.

Claims

1-34. -34. (canceled)

35. A method for counting print ridges in a captured print image frame, comprising the steps of:

(1) traversing a pixel path through the captured print image frame;

(2) counting a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path; and

(3) determining a number of print ridges in the captured print image frame based on the counted number of crossing of the first pixel intensity threshold and the second pixel intensity threshold.

36. The method of claim 35, wherein step (3) comprises determining the number of print ridges by dividing the counted number of first pixel intensity threshold and second pixel intensity threshold crossings by two.

37. The method of claim 35, further comprising the step of:

(4) determining the first pixel intensity threshold and the second pixel intensity threshold.

38. The method of claim 37, wherein step (4) comprises determining a third pixel intensity threshold based on a first maximum pixel intensity value and a first minimum pixel intensity value in the captured print image frame.

39. The method of claim 38, wherein step (4) further comprises determining a delta value based on the first maximum pixel intensity value and the first minimum pixel intensity value in the captured print image frame.

40. The method of claim 39, wherein step (4) further comprises determining the first pixel intensity threshold as a sum of the third pixel intensity threshold and the delta value.

41. The method of claim 39, wherein step (4) further comprises determining the second pixel intensity threshold as a difference of the third pixel intensity threshold and the delta value.

42. The method of claim 35, further comprising the steps of:

(4) traversing a second pixel path across the captured print image frame; and

(5) repeating steps (2) and (3) using the second pixel path.

43. The method of claim 35, further comprising the steps of:

(4) storing the number of print ridges; and

(5) evaluating the stored number of print ridges to determine a quality of the captured fingerprint image.

44. A print scanner system, comprising:

an optical system enabled to direct light to an imaging surface of a platen of the optical system;

a camera enabled to capture a print image frame from light reflected by the print surface and directed to the camera by the optical system;

a memory coupled to the camera and enabled to store the captured print image frame; and

a ridge counter coupled to the memory and enabled to traverse a pixel path through the captured print image frame, count a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path, and determine a number of print ridges in the captured print image frame based on the counted number of crossings.

45. The print scanner system of claim 44, wherein the ridge counter is enabled to determine the number of print ridges by dividing the number of crossings by two.

46. The print scanner system of claim 44, wherein the ridge counter is enabled to determine a region of interest in the captured print image frame.

47. The print scanner system of claim 44, wherein the ridge counter is enabled to determine a first pixel intensity threshold and a second pixel intensity threshold.

48. The print scanner system of claim 47, wherein the ridge counter is enabled to determine a third pixel intensity threshold based on a first maximum pixel intensity value and a first minimum pixel intensity value in the captured print image frame.

49. The print scanner system of claim 48, wherein the ridge counter is enabled to determine a delta value based on the first maximum pixel intensity value and first minimum pixel intensity value in the captured print image frame.

50. The print scanner system of claim 49, wherein the ridge counter is enabled to determine the first pixel intensity threshold as a sum of the third pixel intensity threshold and the delta value.

51. The print scanner system of claim 49, wherein the ridge counter is enabled to determine the second pixel intensity threshold as a difference of the third pixel intensity threshold and the delta value.

52. A ridge counter embodied in software and including control logic for counting print ridges in a captured print image frame, comprising:

first control logic means for enabling a processor to traverse a pixel path through the captured print image frame;

second control logic means for enabling a processor to count a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path; and

third control logic means for enabling a processor to determine a number of print ridges in the captured print image frame based on the counted number of first pixel intensity threshold crossings and second pixel intensity threshold crossings.

53. The ridge counter of claim 52, further comprising fourth control logic means for enabling a processor to determine the number of print ridges by dividing the counted number of crossings of the first pixel intensity threshold and the second pixel intensity threshold by two.

54. The ridge counter of claim 52, further comprising fourth control logic means for enabling a processor to determine the first pixel intensity threshold and the second pixel intensity threshold.