System and Method for Improved Scanning of Fingerprint Edges

• US 20100119124A1
• Filed: 11/10/2008
• Published: 05/13/2010
• Est. Priority Date: 11/10/2008
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Satyan, Pallavi
• Granted Patent: US 8,391,568 B2
• Time in Patent Office: Days
• 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 fingerprint analysis method for partial fingerprint scanners that has an improved ability to resolve fingerprints from the tips of fingers, as well as an improved ability to cope with suboptimal finger swipes. The method uses various extrapolation methods to more accurately determine the position of a scanned fingertip is as the tip of the finger passes a partial fingerprint scanner. The method also monitors the image characteristics of the partial fingerprint image returned by the partial fingerprint scanner, and uses these image characteristics to determine exactly where the image of the fingertip itself is lost, and imaging of non-fingerprint data begins. By combining the most probable fingertip position as a function of time data obtained from extrapolated finger motion data, with image analyzed fingerprint images more precisely determined to be near the fingertip edges, superior fingerprint images extending closer to the edge of the fingerprint may be obtained.

Claims

1. A method of assembling an image of a fingerprint from a series of partial fingerprint images and finger position data obtained by a partial fingerprint imager comprising:

obtaining finger tip position data as the finger swipes the partial fingerprint imager;

determining the motion parameters versus time of the finger tip, and compensating for inadequate finger position data by extrapolating the motion parameters to determine probable fingertip position versus time as the tip of the fingertip swipes over the partial fingerprint imager.

2. The method of claim 1, in which the partial fingerprint images are obtained using a partial fingerprint imager composed of a linear array of individual sensing elements. wherein the loss of precise fingertip motion parameters during at least a portion of the finger swipe is compensated for by extrapolating the motion parameters

3. The method of claim 1, in which the partial fingerprint images are obtained using a deep finger penetrating radio frequency (RF) based partial fingerprint imager.

4. The method of claim 1, in which the partial fingerprint imager has additional sensing elements capable of sensing the relative finger location or movement of the bulk of the finger.

5. The method of claim 1, in which the motion parameters are selected from the group consisting of finger acceleration, velocity, or distance.

6. The method of claim 1, in which a coordinate or location of a partial fingerprint image in a complete fingerprint image is computed by extrapolating the motion parameters.

7. A method of assembling an image of a fingerprint from a series of partial fingerprint images composed of multiple pixels, each pixel having a pixel value, the method comprising:

assembling an image of a fingerprint from a series of partial fingerprint images, wherein the partial fingerprint images are analyzed for the presence of non-fingerprint image data, and are rejected or deemphasized if the non-fingerprint data is detected.

8. The method of claim 7, in which the partial fingerprint images are obtained using a deep finger penetrating radio frequency (RF) based partial fingerprint imager.

9. The method of claim 7, in which the presence of non-fingerprint image data is determined by a method selected from the group consisting of standard deviation, standard deviation squared, analysis of variance (ANOVA), analysis of covariance (ANCOVA), squared deviations, T-tests, and Fourier analysis of the pixel values within the individual partial fingerprint images.

10. The method of claim 7, in which the presence of non-fingerprint image data is determined by a method selected from the group consisting of standard deviation, standard deviation squared, analysis of variance (ANOVA), analysis of covariance (ANCOVA), squared deviations, T-tests, and Fourier analysis of the pixel values between the individual partial fingerprint images.

11. The method of claim 7, in which assembling the image of a fingerprint further comprises setting a weight parameter associated with each pixel, the weight parameter indicating the relative importance for that particular pixel for subsequent image analysis;

in which pixels consistent with the image being a fingerprint image (reliable pixels) are given a weight parameter indicating that the reliable pixels are important for subsequent image analysis;

in which pixels consistent with the image being a non-fingerprint image (non-reliable pixels) are deemphasized by being given a weight parameter indicating that non-reliable pixels are less important than the reliable pixels for subsequent image analysis.

12. The method of claim 7, in which assembling the image of a fingerprint further comprises adjusting the pixel value associated with each pixel, the pixel value indicating the relative contrast between the height and dept of the fingerprint ridges;

in which pixels consistent with the image being a fingerprint image (reliable pixels) treated so as to preserve the contrast between the relative height and depth of the fingerprint ridges;

in which pixels consistent with the image being a non-fingerprint image (non-reliable pixels) are treated so as to diminish the contrast between the relative height and depth of the fingerprint ridges.

13. A method of assembling an image of a fingerprint from a series of partial fingerprint images composed of multiple pixels, each pixel having a pixel value and finger position data obtained by the partial fingerprint imager the method comprising:

obtaining a series of finger tip position data as the finger swipes the partial fingerprint imager, determining the motion parameters versus time of the finger tip compensating for inadequate finger position data by extrapolating the motion parameters to determine probable fingertip position versus time as the tip of the fingertip swipes over the partial fingerprint imager;

assembling an image of a fingerprint from a series of partial fingerprint images, and analyzing the partial fingerprint images for the presence of non-fingerprint image data; and

processing the partial fingerprint images by rejecting or deemphasizing the partial fingerprint images; and

combining the probable fingertip position versus time data with the processed partial fingerprint images.

14. The method of claim 13, in which the partial fingerprint images are obtained using a partial fingerprint imager composed of a linear array of individual sensing elements.

15. The method of claim 13, in which the partial fingerprint images are obtained using a deep finger penetrating radio frequency (RF) based partial fingerprint imager.

16. The method of claim 13, in which the partial fingerprint imager has additional sensing elements capable of sensing the relative finger location or movement of the bulk of the finger.

17. The method of claim 13, in which the image of a fingerprint is subsequently analyzed versus a database of authorized fingerprint images for security verification purposes.

18. The method of claim 13, in which the motion parameters are selected from the group consisting of finger acceleration, velocity, or distance.

19. The method of claim 13, in which extrapolating the motion parameters is used to compensate for the loss of precise fingertip motion parameters the final portions of the finger swipe.

20. The method of claim 13, in which the at least a portion of the finger swipe is the final portion of the finger swipe where the tip of the finger passes over the partial fingerprint imager.

21. The method of claim 13, in which the presence of non-fingerprint image data is determined by a method selected from the group consisting of standard deviation, standard deviation squared, analysis of variance (ANOVA), analysis of covariance (ANCOVA), squared deviations, T-tests, and Fourier analysis of the pixel values within the individual partial fingerprint images.

22. The method of claim 13, in which the presence of non-fingerprint image data is determined by a method selected from the group consisting of standard deviation, standard deviation squared, analysis of variance (ANOVA), analysis of covariance (ANCOVA), squared deviations, T-tests, and Fourier analysis of the pixel values between the individual partial fingerprint images.

23. The method of claim 13, in which a coordinate or location of the partial fingerprint image in a complete fingerprint image is computed by extrapolating the motion parameters.

24. The method of claim 23, in which combining the probable fingertip position versus time data with the processed partial fingerprint images comprises selecting pixels where both the probable fingertip position versus time data and the processed partial fingerprint images are in agreement that the pixel represents fingerprint data, and rejecting pixels where both the probable fingertip position versus time data and the processed partial fingerprint images are in agreement that the pixel does not represent fingertip data.

25. The method of claim 23, in which combining the probable fingertip position versus time data with the processed partial fingerprint images further comprises setting a weight parameter associated with each pixel, the weight parameter indicating the relative importance for that particular pixel for subsequent image analysis;

in which pixels where the probable fingertip position versus time data and the processed partial fingerprint images are in agreement that the pixel does represent fingertip data (non-disputed pixels) are given a weight parameter indicating that the non-disputed pixels are important for subsequent image analysis;

in which pixels where the probable fingertip position versus time data and processed partial fingerprint images are in disagreement that the pixel represents fingertip data (disputed pixels) are given a weight parameter indicating that the disputed pixels are less important than the non-disputed pixels for subsequent image analysis.

26. The method of claim 23, in which combining the probable fingertip position versus time data with the processed partial fingerprint images further comprises adjusting the pixel value associated with each pixel, the pixel value indicating the relative contrast between the height and dept of the fingerprint ridges;

in which pixels where the probable fingertip position versus time data and processed partial fingerprint images are in agreement that the pixel does represent fingertip data (non-disputed pixels) are treated so as to preserve the contrast between the relative height and depth of the fingerprint ridges;

in which pixels where the probable fingertip position versus time data and the processed partial fingerprint images are in disagreement that the pixel represents fingertip data (disputed pixels) are treated so as to diminish the contrast between the relative height and depth of the fingerprint ridges.