Method and Apparatus for Fingerprint Image Reconstruction

• US 20080205714A1
• Filed: 12/14/2007
• Published: 08/28/2008
• Est. Priority Date: 04/16/2004
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Satyan, Pallavi, Geoffroy, David Joseph, Benkley, Fred George
• Granted Patent: US 8,131,026 B2
• Time in Patent Office: Days
• US Class Current: 382/126
• CPC Class Codes: G06F 2203/0338 Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• 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

Enhanced accuracy finger position and motion sensors devices, algorithms, and methods are disclosed that can be used in a variety of different applications. The sensors can be used in conjunction with partial fingerprint imagers to produce improved fingerprint scanners. Such improved scanners can use image analysis techniques, such as interpolation between partial fingerprint images to correct for missing data, or discarding redundant partial fingerprint image data, to produce adequate fingerprint images even when the finger has not been applied to the sensor using an optimum technique.

Claims

1. A method of reconstructing a fingerprint image from a series of partial fingerprint images of a finger surface, said method comprising:

Moving the finger surface over a partial fingerprint imager and capturing a series of partial fingerprint images of said fingerprint;

calculating the speed at which said partial fingerprint imager traverses the finger surface;

determining if said speed is above a preset fast swipe value;

if said speed is above said preset fast swipe value, filling in the gaps by generating additional synthetic partial fingerprint images by interpolating between partial fingerprint images on either side of said gaps;

if said speed is below said preset fast swipe value, then determining if said speed is below a preset slow swipe value; and

if said speed is below said preset slow swipe value, discarding redundant partial fingerprint images;

and reconstructing the fingerprint image of said finger surface using the resulting partial fingerprint images.

2. The method of claim 1, in which the series of partial fingerprint images are captured at a defined rate of partial fingerprint images per second.

3. The method of claim 1, in which the fast swipe value is set at a level where there are likely to be gaps between the regions of the finger surface that are imaged by the partial fingerprint imager.

4. The method of claim 1, in which the slow swipe value is set at a level where there are likely to be substantial overlap between the regions of the finger surface that are imaged by the partial fingerprint imager.

5. The method of claim 1, in which the speed at which said partial fingerprint imager traverses said finger surface is determined by data collected by at least one finger position sensor array.

6. The method of claim 5, in which the finger position sensing array is a deep finger penetrating radio frequency (RF) based sensing array.

7. The method of claim 5, in which the finger position sensing array is an optical sensing array.

8. The method of claim 1, in which the partial fingerprint imager is a deep finger penetrating radio frequency (RF) based sensing array.

9. The method of claim 1, in which interpolating between partial fingerprint images on either side of said gaps is done using a non-adaptive algorithm selected from the group consisting of bicubic, bilinear, lanczos, nearest neighbor, sinc, spline algorithms.

10. The method of claim 1, in which interpolating between partial fingerprint images on either side of said gaps is done using an adaptive algorithm.

11. The method of claim 1, in which interpolating between different fingerprint images on either side of said gaps uses anti-aliasing algorithms.

12. The method of claim 1, in which redundant partial fingerprint images are detected and discarded by selecting partial fingerprint images suspected of being redundant, computing a sum of the differences between the pixels of the partial fingerprint images suspected of being redundant, and determining if this sum is less than a preset threshold.

13. A method of reconstructing a fingerprint image from a series of partial fingerprint images of a finger surface, said method comprising:

Moving the finger surface over a partial fingerprint imager and capturing a series of partial fingerprint images of said fingerprint surface at a known rate of partial image acquisition per second;

calculating the speed at which said partial fingerprint imager traverses the finger surface;

determining if said speed is above a preset fast swipe value, said fast swipe value being set at a level where there are likely to be gaps between the regions of the finger surface that are imaged by the partial fingerprint imager;

if said speed is above said preset fast swipe value, filling in the gaps by generating additional synthetic partial fingerprint images by interpolating between partial fingerprint images on either side of said gaps;

if said speed is below said preset fast swipe value, then determining if said speed is below a preset slow swipe value, said slow swipe value being set at a level where there are likely to be substantial overlap between the regions of the finger surface that are imaged by the partial fingerprint imager; and

if said speed is below said preset slow swipe value, discarding redundant partial fingerprint images;

and reconstructing the fingerprint image of said finger surface using the resulting partial fingerprint images.

14. The method of claim 13, in which the speed at which said partial fingerprint imager traverses said finger surface is determined by data collected by at least one finger position sensor array.

15. The method of claim 14, in which the finger position sensing array is a deep finger penetrating radio frequency (RF) based sensing array.

16. The method of claim 14, in which the finger position sensing array is an optical sensing array.

17. The method of claim 13, in which the partial fingerprint imager is a deep finger penetrating radio frequency (RF) based sensing array.

18. The method of claim 13, in which interpolating between partial fingerprint images on either side of said gaps is done using a non-adaptive algorithm selected from the group consisting of bicubic, bilinear, lanczos, nearest neighbor, sinc, spline algorithms.

19. The method of claim 13, in which interpolating between partial fingerprint images on either side of said gaps is done using an adaptive algorithm.

20. The method of claim 13, in which interpolating between different fingerprint images on either side of said gaps uses anti-aliasing algorithms.

21. The method of claim 13, in which redundant partial fingerprint images are detected and discarded by selecting partial fingerprint images suspected of being redundant, computing a sum of the differences between the pixels of the partial fingerprint images suspected of being redundant, and determining if this sum is less than a preset threshold.

22. A method of reconstructing a fingerprint image from a series of partial fingerprint images of a finger surface, said method comprising:

Moving the finger surface over a deep finger penetrating radio frequency (RF) based partial fingerprint imager and capturing a series of partial fingerprint images of said fingerprint surface at a known rate of partial image acquisition per second;

calculating the speed at which said partial fingerprint imager traverses the finger surface using a deep finger penetrating radio frequency (RF) based finger position sensor array;

determining if said speed is above a preset fast swipe value, said fast swipe value being set at a level where there are likely to be gaps between the regions of the finger surface that are imaged by the partial fingerprint imager;

if said speed is above said preset fast swipe value, filling in the gaps by generating additional synthetic partial fingerprint images by interpolating between partial fingerprint images on either side of said gaps;

if said speed is below said preset fast swipe value, then determining if said speed is below a preset slow swipe value, said slow swipe value being set at a level where there are likely to be substantial overlap between the regions of the finger surface that are imaged by the partial fingerprint imager; and

if said speed is below said preset slow swipe value, discarding redundant partial fingerprint images;

and reconstructing the fingerprint image of said finger surface using the resulting partial fingerprint images.

23. The method of claim 22, in which interpolating between partial fingerprint images on either side of said gaps is done using a non-adaptive algorithm selected from the group consisting of bicubic, bilinear, lanczos, nearest neighbor, sinc, spline algorithms.

24. The method of claim 22, in which interpolating between partial fingerprint images on either side of said gaps is done using an adaptive algorithm.

25. The method of claim 22, in which interpolating between different fingerprint images on either side of said gaps uses anti-aliasing algorithms.

26. The method of claim 22, in which redundant partial fingerprint images are detected and discarded by selecting partial fingerprint images suspected of being redundant, computing a sum of the differences between the pixels of the partial fingerprint images suspected of being redundant, and determining if this sum is less than a preset threshold.