Method and apparatus for fingerprint image reconstruction

• US 8,131,026 B2
• Filed: 12/14/2007
• Issued: 03/06/2012
• Est. Priority Date: 04/16/2004
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Benkley, Fred George, Geoffroy, David Joseph, Satyan, Pallavi
• Primary Examiner(s): Koziol, Stephen R
• Assistant Examiner(s): DRENNAN, BARRY T
• Application Number:
  US11/957,311
• Publication Number:
  US 20080205714A1
• Time in Patent Office: 1,544 Days
• Field of Search: None
• US Class Current: 382/124
• 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 image sections of the fingerprint;

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

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

if the speed is above the preset fast swipe value, filling in any gap intermediate partial fingerprint image segments by generating an additional synthetic partial fingerprint image segment by interpolating between partial fingerprint image segments on either side of the gap;

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

if the speed is below the preset slow swipe value, detecting any redundant portion of a partial fingerprint image segment; and

reconstructing the fingerprint image of the finger surface using the partial fingerprint image segments and inserting any additional synthetic image segment and removing any redundant portion of any partial fingerprint image segment.

2. The method of claim 1, in which the series of partial fingerprint image segments are captured at a defined rate of partial fingerprint image segments 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 partial fingerprint image segments 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 overlaps between the partial fingerprint image segments that are imaged by the partial fingerprint imager.

5. The method of claim 1, in which the speed at which the partial fingerprint imager traverses the 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 image segments on either side of the gap done using a non-adaptive algorithm selected from the group consisting of bicubic, bilinear, lanczos, nearest neighbor, sinc and spline algorithms.

10. The method of claim 1, in which interpolating between partial fingerprint image segments on either side of the gap is done using an adaptive algorithm.

11. The method of claim 1, in which interpolating between different fingerprint image segments on either side of the gap uses an anti-aliasing algorithm.

12. The method of claim 1, in which redundant partial fingerprint image segments are detected and discarded by selecting a portion of each partial fingerprint image segment suspected of being redundant, computing a sum of the differences between the pixels of the respective portions 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 image segments of a finger surface, the method comprising:

moving the finger surface over a partial fingerprint imager and capturing a series of partial fingerprint image segments of the fingerprint surface at a known rate of partial fingerprint image segment acquisition per second;

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

determining if the speed is above a preset fast swipe value, the fast swipe value being set at a level where there are likely to be gaps between adjacent ones of the partial fingerprint image segments;

if the speed is above the preset fast swipe value, filling in any gap intermediate partial fingerprint image segments by generating an additional synthetic partial fingerprint image segment by interpolating between partial fingerprint image segments on either side of the gap;

if the speed is below the preset fast swipe value, then determining if the speed is below a preset slow swipe value, the slow swipe value being set at a level where there are likely to be overlaps between adjacent ones of the partial fingerprint image segments;

the speed is below the preset slow swipe value, detecting any redundant portion of a partial fingerprint image segment;

and reconstructing the fingerprint image of the finger surface using the resulting partial fingerprint image segments and inserting any additional synthetic image segment and removing any redundant portion of any partial fingerprint image segment.

14. The method of claim 13, in which the speed at which the partial fingerprint imager traverses the 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 image segments on either side of the gap is done using a non-adaptive algorithm selected from the group consisting of bicubic, bilinear, lanczos, nearest neighbor, sinc and spline algorithms.

19. The method of claim 13, in which interpolating between partial fingerprint image segments on either side of the gap is done using an adaptive algorithm.

20. The method of claim 13, in which interpolating between different fingerprint image segments on either side of the gap uses an anti-aliasing algorithm.

21. The method of claim 13, in which a redundant portion of a partial fingerprint image segment is detected and discarded by selecting a portion of each partial fingerprint image segment suspected of being redundant, computing a sum of the differences between pixels of the respective portions of the partial fingerprint image segments 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, the 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 image segments of the fingerprint surface at a known rate of partial image segment acquisition per second;

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

determining if the speed is above a preset fast swipe value, the fast swipe value being set at a level where there are likely to be gaps between adjacent ones of the partial fingerprint image setments;

if the speed is above the preset fast swipe value, filling in any gap intermediate partial fingerprint image segments by generating an additional synthetic partial fingerprint image segment by interpolating between partial fingerprint image segments on either side of the gap;

if the speed is below the preset fast swipe value, then determining if the speed is below a preset slow swipe value, the slow swipe value being set at a level where there are likely to be overlap between adjacent ones of the partial fingerprint image segments;

if the speed is below the preset slow swipe value, discarding any redundant portions of partial fingerprint image segments; and

reconstructing the fingerprint image of the finger surface using the partial fingerprint image segments and adding in any additional synthetic partial fingerprint image segments and deleting any redundant portions of any partial fingerprint image segment.

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

24. The method of claim 22, in which interpolating between partial fingerprint image segments on either side of the gap is done using an adaptive algorithm.

25. The method of claim 22, in which interpolating between different fingerprint image segments on either side of the gap uses anti-aliasing algorithms.

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