Method and apparatus for rolled fingerprint capture

• US 6,483,932 B1
• Filed: 08/19/1999
• Issued: 11/19/2002
• Est. Priority Date: 08/19/1999
• Status: Expired due to Term

• Current Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Original Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Inventors: Martinez, Chris J., Scott, Walter Guy
• Primary Examiner(s): AHMED, SAMIR ANWAR
• Application Number:
  US09/377,597
• Time in Patent Office: 1,188 Days
• Field of Search: 382/115, 382/124, 382/125, 382/127, 235/380, 235/492, 902/3, 902/4, 902/25, 340/5.82, 340/5.83, 283/68, 356/71, 705/1, 705/26, 705/42
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement

Abstract

A method and apparatus for rolled fingerprint capture is described. The start of a fingerprint roll is detected. A plurality of fingerprint image frames are captured. A centroid window corresponding to each of the plurality of captured fingerprint image frames is determined. Pixels of each determined centroid window are knitted into a composite fingerprint image. The end of the fingerprint roll is detected.

Claims

1. A method for rolled fingerprint capture, comprising the steps of:

(1) detecting the start of a fingerprint roll, including the steps of;

(a) generating a pixel intensity difference count value between a current fingerprint image frame and a previous fingerprint image frame, including the steps of comparing the intensity of a plurality of pixels in the current fingerprint image frame to the intensity of a corresponding plurality of pixels in the previous fingerprint image frame, and summing pixels determined to have different intensities during said comparing step to generate the pixel intensity difference count value, and

(b) determining whether the generated pixel intensity difference count value is greater than a start roll sensitivity threshold value;

(2) capturing a plurality of fingerprint image frames;

(3) determining a centroid window corresponding to each of the plurality of captured fingerprint image frames;

(4) knitting pixels of each determined centroid window into a composite fingerprint image; and

(5) detecting the end of said fingerprint roll.

5. The method of claim 1, wherein step (iv) comprises the steps of:

(a) comparing the intensity of each pixel of the determined centroid window to the intensity of a corresponding pixel of a composite fingerprint image; and

(b) replacing the pixel of the composite fingerprint image with the corresponding pixel of the determined centroid window if the pixel of the determined centroid window is darker than the corresponding pixel of the composite fingerprint image.

2. A method for rolled fingerprint capture, comprising the steps of

(1) detecting the start of a fingerprint roll, including the steps of:

(a) generating a pixel intensity difference percentage value between a current fingerprint image frame and a previous fingerprint image frame, including the steps of comparing the intensity of a plurality of pixels in the current fingerprint image frame to the intensity of a corresponding plurality of pixels in the previous fingerprint image frame to obtain a pixel intensity difference count value, and calculating the pixel intensity difference percentage value to be a ratio of the pixel intensity difference count value to the number of the plurality of pixels present in a fingerprint image frame; and

(b) determining whether the generated pixel intensity difference percentage value is greater than a start roll sensitivity threshold percentage value;

(2) capturing a plurality of fingerprint image frames;

(3) determining a centroid window corresponding to each of the plurality of captured fingerprint image frames;

(4) knitting pixels of each determined centroid window into a composite fingerprint image; and

(5) detecting the end of said fingerprint roll.

3. The method of claim 2, wherein step (a) comprises the steps of:

(i) capturing a current fingerprint image frame; and

(ii) comparing the intensity of each pixel of the current fingerprint image frame to the intensity of a corresponding pixel of a previously captured fingerprint image frame.

4. The method of claim 2, wherein step (a) further comprises the step of:

finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

6. method for detecting the start of a fingerprint roll in a rolled fingerprint capture system comprising the steps of:

(a) capturing a first fingerprint image frame;

(b) capturing a second fingerprint image frame;

(c) generating a pixel intensity difference count value between the second fingerprint image frame and the first fingerprint image frame, including the steps of

(1) comparing the intensity of a plurality of pixels in the second fingerprint image frame to the intensity of a corresponding plurality of pixels in the first fingerprint image frame, and

(2) summing pixels determined to have different intensities during step (1) to generate the pixel intensity difference count value; and

(d) determining whether the generated pixel intensity difference count value is greater than a start roll sensitivity threshold value.

7. The method of claim 6, wherein step (1) comprises the step of:

(i) comparing the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame.

8. The method of claim 6, wherein step (1) comprises the step of:

finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

9. A method for detecting the start of a fingerprint roll in a rolled fingerprint capture system, comprising the steps of:

(a) capturing a first fingerprint image frame;

(b) capturing a second fingerprint image frame;

(c) generating a pixel intensity difference percentage value between the second fingerprint image frame and a first fingerprint image frame, including the steps of

(1) comparing the intensity of a plurality of pixels in the second fingerprint image frame to the intensity of a corresponding plurality of pixels in the first fingerprint image frame to obtain a pixel intensity difference count value, and

(2) calculating the pixel intensity difference percentage value to be a ratio of the pixel intensity difference count value to the number of the plurality of pixels; and

(d) determining whether the generated pixel intensity difference percentage value is greater than a start roll sensitivity threshold percentage value.

10. The method of claim 9, wherein step (1) comprises the step of:

(i) comparing the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame.

11. The method of claim 9, wherein step (1) comprises the step of:

finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

12. The method of claim 11, wherein step (1) further comprises the step of:

counting the compared pixels found to be different to produce the pixel intensity difference count value.

13. A system for rolled fingerprint capture, comprising:

a fingerprint roll start detector module that detects the start of a fingerprint roll in a fingerprint image capturing area, wherein the fingerprint roll start detector module generates a pixel intensity difference count value between a first fingerprint image frame and a second fingerprint image frame, wherein the fingerprint roll start detector module compares the intensity of a plurality of pixels in the second fingerprint image frame to the intensity of a corresponding plurality of pixels in the first fingerprint image frame and sums the pixels determined to have different intensities to generate the pixel intensity difference count value, and wherein the fingerprint roll start detector module determines whether the generated pixel intensity difference count value is greater than a start roll sensitivity threshold value.

14. The system of claim 13, wherein said fingerprint roll start detector module compares the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame to obtain the pixel intensity difference count value.

15. The system of claim 13, wherein said fingerprint roll start detector module finds compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

16. A system for rolled fingerprint capture, comprising:

a fingerprint roll start detector module that detects the start of a fingerprint roll in a fingerprint image capturing area, wherein the fingerprint roll start detector module generates a pixel intensity difference percentage value between a first fingerprint image frame and a second fingerprint image frame, wherein the fingerprint roll start detector module compares the intensity of a plurality of pixels in the second fingerprint image frame to the intensity of a corresponding plurality of pixels in the first fingerprint image frame to obtain a pixel intensity difference count value, and calculates the pixel intensity difference percentage value to be a ratio of the pixel intensity difference count value to the number of the plurality of pixels present in a fingerprint image frame, and wherein the fingerprint roll start detector module determines whether the generated pixel intensity difference percentage value is greater than a start roll sensitivity threshold percentage value.

17. The system of claim 16, wherein said fingerprint roll start detector module compares the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame to obtain a pixel intensity difference count value, and uses the pixel intensity difference count value to produce the pixel intensity difference percentage value, which is a percentage ratio of the pixel intensity difference count value to a total number of pixels present in a fingerprint image frame.

18. The system of claim 16, wherein said fingerprint roll start detector module finds compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

19. A system for detecting the start of a fingerprint roll in a rolled fingerprint capture system, comprising:

means for capturing a first fingerprint image frame;

means for capturing a second fingerprint image frame;

means for generating a pixel intensity difference count value between the second fingerprint image frame and the first fingerprint image frame, said means for generating including means for comparing the intensity of a plurality of pixels in the current fingerprint image frame to the intensity of a corresponding plurality of pixels in the previous fingerprint image frame, and means for summing pixels determined to have different intensities by said means for comparing to generate said pixel intensity difference count value; and

means for determining whether the generated pixel intensity difference count value is greater than a start roll sensitivity threshold value.

20. The system of claim 19, wherein said means for comparing comprises:

means for comparing the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame to obtain the pixel intensity difference count value.

21. The system of claim 19, wherein said means for comparing comprises;

means for finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

22. A system for detecting the start of a fingerprint roll in a rolled fingerprint capture system, comprising:

means for capturing a first fingerprint image frame;

means for capturing a second fingerprint image frame;

means for generating a pixel intensity difference percentage value between the second fingerprint image frame and a first fingerprint image frame, said means for generating including means for comparing the intensity of a plurality of pixels in the current fingerprint image frame to the intensity of a corresponding plurality of pixels in the previous fingerprint image frame to obtain a pixel intensity difference count value, and means for calculating the pixel intensity difference percentage value to be a ratio of the pixel intensity difference count value to the number of the plurality of pixels present in a fingerprint image frame; and

means for determining whether the generated pixel intensity difference percentage value is greater than a start roll sensitivity threshold percentage value.

23. The system of claim 22, wherein said means for comparing comprises:

means for comparing the intensity of each pixel of the second fingerprint image frame to the intensity of a corresponding pixel of the first fingerprint image frame to obtain a pixel intensity difference count value.

24. The system of claim 22, wherein said means for comparing comprises:

means for finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

25. The system of claim 22, wherein said means for comparing comprises:

means for counting the compared pixels found to be different to produce the pixel intensity difference count value.