System and method for improved scanning of fingerprint edges

• US 8,391,568 B2
• Filed: 11/10/2008
• Issued: 03/05/2013
• Est. Priority Date: 11/10/2008
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Satyan, Pallavi
• Primary Examiner(s): Akhavannik, Hadi
• Application Number:
  US12/268,260
• Publication Number:
  US 20100119124A1
• Time in Patent Office: 1,576 Days
• Field of Search: 382/125, 382/124
• 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 a two dimensional image of a fingerprint from a series of one-dimensional linear fingerprint images, formed by a linear one-dimensional array of gap sensor elements aligned generally orthogonally to a direction of motion of a finger, comprising:

obtaining position data versus time for the position of the finger as the finger swipes the linear one dimensional array, in the direction of finger motion;

determining motion versus time for the finger, based at least in part on the position data versus time as the finger swipes the linear one-dimensional array;

removing poor fingerprint image data contained in at least one of the series of one-dimensional linear fingerprint images, by determining from the motion a probable finger position in relation to the linear one dimensional array versus the time of the at least one of the series of one-dimensional linear fingerprint images; and

including the at least one of the series of one-dimensional linear fingerprint images in the two dimensional image of the fingerprint based upon the probable finger position and an analysis of the content of the at least one of the series of linear one-dimensional fingerprint images.

2. The method of claim 1,

wherein the including step compensates for loss of precise finger position data during at least a portion of the swipe of the finger.

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

4. The method of claim 1, in which the one-dimensional linear 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 includes the group consisting of finger acceleration, velocity, or distance.

6. The method of claim 1, in which a coordinate or location of a one-dimensional linear fingerprint image in a complete fingerprint image is computed utilizing finger motion.

7. A method of assembling a two-dimensional image of a fingerprint from a series of one-dimensional linear fingerprint images, formed by a linear one-dimensional array of gap sensor elements aligned generally orthogonally to a direction of motion of a finger composed of multiple pixels, each pixel defined by gap sensor element, each pixel having a pixel value, the method comprising:

obtaining position data versus time for the position of the finger as the finger swipes the linear one dimensional array, in the direction of finger motion;

determining motion versus time for the finger, based at least in part on the position data versus time as the finger swipes the linear one-dimensional array; and

removing poor fingerprint image data contained in at least one of the series of one-dimensional linear fingerprint images, by determining from the motion probable finger position in relation to the linear one dimensional array versus the time of the at least one of the series of one-dimensional linear fingerprint images; and

including the at least one of the series of linear one-dimensional fingerprint images in the two dimensional image of the fingerprint based upon the probable finger position and an analysis of the content of the at least one of the series of linear one-dimensional fingerprint images.

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

9. The method of claim 7, in which the analysis of the content of the at least one of the series of linear one-dimensional fingerprint images is performed 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 8, in which the analysis of the content of the at least one of the series of linear one-dimensional fingerprint images is performed 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 analysis of the content of the at least one of the series of linear one-dimensional fingerprint images 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 reliable pixels, consistent with the image being a fingerprint image, are given a weight parameter indicating that the reliable pixels are important for subsequent image analysis; and

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

12. The method of claim 7, in which analysis of the content of the at least one of the series of linear one-dimensional fingerprint images comprises adjusting the pixel value associated with each pixel, the pixel value indicating the relative contrast between the height and depth of the fingerprint ridges;

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

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

13. A method of assembling a two dimensional image of a fingerprint from a series of one-dimensional linear fingerprint images, formed by a linear one-dimensional array of gap sensor elements aligned generally orthogonally to a direction of motion of a finger, composed of multiple pixels, each pixel having a pixel value, the method comprising:

obtaining position data versus time for the position of the finger as the finger swipes the linear one dimensional array, in the direction of finger motion;

determining motion versus time of the finger, based at least in part on the position data versus time as the finger swipes the linear one-dimensional array;

removing poor fingerprint image data contained in at least one of the series of one-dimensional linear fingerprint images, by determining from the motion probable finger position in relation to the linear one dimensional array versus time as the finger swipes over the linear one dimensional array; and

assembling an image of a fingerprint from a series of linear one-dimensional fingerprint images, and including the at least one of the series of linear one-dimensional fingerprint images in the two dimensional image of the fingerprint based upon the probable finger position and an analysis of the content of the at least one of the series of linear one-dimensional fingerprint images for the presence of non-fingerprint image data.

14. The method of claim 13, in which the linear one-dimensional fingerprint images are obtained using a deep finger penetrating radio frequency (RF) based linear one-dimensional fingerprint imager.

15. The method of claim 13, in which the linear one-dimensional fingerprint imager has additional sensing elements capable of sensing the relative finger location or movement of the bulk of the finger.

16. 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.

17. The method of claim 13, in which the motion includes the group consisting of finger acceleration, velocity, or distance.

18. The method of claim 13, including compensating for the loss of precise fingertip motion data in final portions of the finger swipe.

19. The method of claim 13, in which the analysis of the content of the at least one of the series of linear one-dimensional fingerprint images for 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.

20. The method of claim 13, in which the analysis of the content of the at least one of the series of linear one-dimensional fingerprint images for 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.

21. The method of claim 13, in which a coordinate or location of the at least one of the series of linear one-dimensional fingerprint images in the two dimensional image is computed using finger motion.

22. The method of claim 21, in which the analysis of the probable finger position versus time and the content of the at least one of the series of linear one-dimensional fingerprint images comprises selecting pixels where both the probable finger position versus time and the content of the at least one of the series of linear one-dimensional fingerprint images are in agreement that the pixel represents fingerprint data, and rejecting pixels where both the probable finger position versus time and the content of the at least one of the series of linear one-dimensional fingerprint images are in agreement that the pixel does not represent fingerprint data.

23. The method of claim 21, in which the analysis of the probable finger position versus time and the content of the at least one of the series of linear one-dimensional 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 non-disputed pixels, representing fingerprint data, are given a weight parameter indicating that the non-disputed pixels are important for subsequent image analysis;

in which disputed pixels representing non-fingerprint data are given a weight parameter indicating that the disputed pixels are less important than the non-disputed pixels for subsequent image analysis.

24. The method of claim 21, in which the analysis of the probable finger position versus time and the content of the at least one of the series of linear one-dimensional fingerprint images further comprises adjusting the pixel value associated with each pixel, the pixel value indicating the relative contrast between the height and depth of the fingerprint ridges;

in which non-disputed pixels, representing fingerprint data, are treated so as to preserve the contrast between the relative height and depth of the fingerprint ridges;

in which disputed pixels, where there is disagreement that the pixel represents fingerprint data are treated so as to diminish the contrast between the relative height and depth of the fingerprint ridges.

25. A tangible machine readable medium storing instructions that, when executed by a computing device, cause the computing device to perform 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:

assembling a two dimensional image of a fingerprint from a series of one-dimensional linear fingerprint images, formed by a linear one-dimensional array of gap sensor elements aligned generally orthogonally to a direction of motion of a finger;

obtaining position data versus time for the position of the finger as the finger swipes the linear one dimensional array, in the direction of finger motion;

determining motion versus time for the finger, based at least in part on the position data versus time as the finger swipes the linear one-dimensional array;

removing poor fingerprint image data contained in at least one of the series of one-dimensional linear fingerprint images, by determining from the motion a probable finger position in relation to the linear one dimensional array versus the time of the at least one of the series of one-dimensional linear fingerprint images; and

including the at least one of the series of linear one-dimensional fingerprint images in the two dimensional image of the fingerprint based upon the probable finger position and an analysis of the content of the at least one of the series of linear one-dimensional fingerprint images.