Claims
- 1. A method for counting print ridges in a captured print image frame, comprising the steps of:
(A) traversing a pixel path through the captured print image frame; (B) determining a hysteresis band for the pixel path; (C) counting a number of crossings of the determined hysteresis band while traversing the pixel path; and (D) determining a number of print ridges based on the counted number of hysteresis band crossings.
- 2. The method of claim 1, wherein the hysteresis band is defined by a hysteresis band first edge value and a hysteresis band second edge value, wherein step (B) comprises the steps of:
(1) measuring a first ridge pixel value peak for the pixel path; (2) measuring a first valley pixel value peak for the pixel path; (3) selecting a hysteresis band center pixel value between the first ridge pixel value peak and the first valley pixel value peak; (4) calculating the hysteresis band first edge value by adding a delta value to the selected hysteresis band center pixel value; and (5) calculating the hysteresis band second edge value by subtracting the delta value from the selected hysteresis band center pixel value.
- 3. The method of claim 2, wherein step (3) comprises the step of:
calculating an average pixel value of the first ridge pixel value peak and the first valley pixel value peak; and setting the hysteresis band center pixel value to the calculated average pixel value.
- 4. The method of claim 2, further comprising the step of:
calculating the delta value according to the following equation delta value=|(first valley pixel value peak−first ridge pixel value peak)|/6.
- 5. The method of claim 2, wherein step (A) comprises the step of:
detecting pixel values sequentially along the pixel path.
- 6. The method of claim 5, wherein step (C) comprises the steps of:
detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band first edge value to the hysteresis band second edge value; and detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band second edge value to the hysteresis band first edge value.
- 7. The method of claim 1, wherein step (D) comprises the step of:
dividing the counted number of hysteresis band crossings by two to determine the number of print ridges.
- 8. The method of claim 1, further comprising the steps of:
(E) traversing a second pixel path across the captured print image frame; and (F) repeating steps (C) and (D) using the second pixel path.
- 9. The method of claim 1, further comprising the steps of:
(E) determining a second hysteresis band; (F) traversing a second pixel path across the captured print image frame; and (G) repeating steps (C) and (D) using the second determined hysteresis band and the second pixel path.
- 10. The method of claim 1, further comprising the steps of:
(E) determining a second hysteresis band; (F) traversing the pixel path across the captured print image frame a second time; and (G) repeating steps (C) and (D) using the second determined hysteresis band and the second traversal of the pixel path.
- 11. A method for counting fingerprint ridges, comprising the steps of:
(A) identifying a region of interest in a stored fingerprint image frame; (B) determining a pixel path through the region of interest; (C) traversing the determined pixel path; (D) determining a hysteresis band for the determined pixel path; (E) counting a number of crossings of the determined hysteresis band while traversing the determined pixel path; (F) determining a number of fingerprint ridges based on the counted number of hysteresis band crossings; and (G) storing the number of fingerprint ridges determined in step (F).
- 12. The method of claim 11, further comprising the step of:
(H) capturing a fingerprint image; and (I) storing the captured fingerprint image to be accessed as the stored fingerprint image frame.
- 13. The method of claim 12, further comprising the step of:
(J) evaluating the stored number of fingerprint ridges to determine a quality of the captured fingerprint image.
- 14. The method of claim 11, further comprising the step of:
(H) repeating steps (B)-(G) at least one additional time.
- 15. The method of claim 11, further comprising the step of:
(H) evaluating the stored number of fingerprint ridges to determine a quality of the stored fingerprint image frame.
- 16. The method of claim 11, wherein the hysteresis band is defined by a hysteresis band first edge value and a hysteresis band second edge value, wherein step (D) comprises the steps of:
(1) measuring a first ridge pixel value peak for the determined pixel path; (2) measuring a first valley pixel value peak for the determined pixel path; (3) selecting a hysteresis band center pixel value between the first ridge pixel value peak and the first valley pixel value peak; (4) calculating the hysteresis band first edge value by adding a delta value to the selected hysteresis band center pixel value; and (5) calculating the hysteresis band second edge value by subtracting the delta value from the selected hysteresis band center pixel value.
- 17. The method of claim 16, wherein step (3) comprises the step of:
calculating an average pixel value of the first ridge pixel value peak and the first valley pixel value peak; and setting the hysteresis band center pixel value to the calculated average pixel value.
- 18. The method of claim 16, further comprising the step of:
calculating the delta value according to the following equation delta value=|(first valley pixel value peak−first ridge pixel value peak)|/6.
- 19. The method of claim 16, wherein step (C) comprises the step of:
detecting pixel values sequentially along the determined pixel path.
- 20. The method of claim 19, wherein step (E) comprises the steps of:
detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band first edge value to the hysteresis band second edge value; and detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band second edge value to the hysteresis band first edge value.
- 21. The method of claim 11, wherein step (F) comprises the step of:
dividing the counted number of hysteresis band crossings by two to determine the number of fingerprint ridges.
- 22. A system for counting fingerprint ridges in a captured fingerprint image frame, comprising:
a ridge counter module that includes
means for traversing a pixel path through the captured fingerprint image frame, means for determining a hysteresis band for the pixel path, means for counting a number of crossings of the determined hysteresis band while traversing the pixel path, and means for determining a number of fingerprint ridges based on the counted number of hysteresis band crossings.
- 23. The system of claim 22, wherein the hysteresis band is defined by a hysteresis band first edge value and a hysteresis band second edge value, said hysteresis determining means comprises:
means for measuring a first ridge pixel value peak for the pixel path; means for measuring a first valley pixel value peak for the pixel path; means for selecting a hysteresis band center pixel value between the first ridge pixel value peak and the first valley pixel value peak; means for calculating the hysteresis band first edge value by adding a delta value to the selected hysteresis band center pixel value; and means for calculating the hysteresis band second edge value by subtracting the delta value from the selected hysteresis band center pixel value.
- 24. The system of claim 23, wherein said means for selecting a hysteresis band center pixel value comprises:
means for calculating an average pixel value of the first ridge pixel value peak and the first valley pixel value peak; and means for setting the hysteresis band center pixel value to the calculated average pixel value.
- 25. The system of claim 23, further comprising:
means for calculating the delta value according to the following equation delta value=|(first valley pixel value peak−first ridge pixel value peak)|/6.
- 26. The system of claim 23, wherein said means for traversing a pixel path comprises:
means for detecting pixel values sequentially along the pixel path.
- 27. The system of claim 26, wherein said means for counting a number of crossings comprises:
means for detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band first edge value to the hysteresis band second edge value; and means for detecting a hysteresis band crossing when sequentially detected pixel values range from the hysteresis band second edge value to the hysteresis band first edge value.
- 28. The system of claim 22, wherein said means for determining a number of fingerprint ridges comprises:
means for dividing the counted number of hysteresis band crossings by two to determine the number of fingerprint ridges.
- 29. The system of claim 22, further comprising:
a camera that captures a fingerprint image and outputs said captured fingerprint image frame.
- 30. The system of claim 29, further comprising:
a memory that stores said captured fingerprint image frame, and is accessible by said ridge counter module.
- 31. The system of claim 29, further comprising:
a platen that has a finger application area.
- 32. The system of claim 31, further comprising:
an illumination source that provides light to illuminate said finger application area to produce said fingerprint image.
- 33. The system of claim 32, further comprising:
an optical system that directs said light to said camera.
- 34. The system of claim 31, further comprising:
a controller that includes said ridge counter module and controls said illumination source and said camera.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No. 60/400,103, filed Aug. 2, 2002 (Atty. Dkt. No.1823.0680000), which is herein incorporated by reference in its entirety.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60400103 |
Aug 2002 |
US |