SYSTEM AND METHOD TO REMOVE ARTIFACTS FROM FINGERPRINT SENSOR SCANS

• US 20090154779A1
• Filed: 12/14/2007
• Published: 06/18/2009
• Est. Priority Date: 12/14/2007
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Chan, Philip Yiu Kwong, Satyan, Pallavi
• Granted Patent: US 8,204,281 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 10/993 Evaluation of the quality of the acquired pattern
• 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 device for removing common artifacts, such as stiction, from fingerprint scans created by partial fingerprint scanners. The partial fingerprint scanner data is assessed to determine if successive partial fingerprint images are overly similar to each other, which can occur during stiction. If this similarity exceeds a preset threshold, then at least some of the overly similar partial images will be removed (redacted) from the overall image dataset. The complete overall image is generated from the redacted data set. This method is particularly useful for creating “intelligent” low-cost, low power partial fingerprint scanners and scanner driver chips that can pre-process the partial fingerprint data that is generated during the course of a finger swipe, and remove stiction artifacts on a real-time or near-real time basis using relatively simple and low power on-chip processing circuits, and then send the corrected data to more sophisticated processors for subsequent fingerprint analysis.

Claims

1. A method to correct artifacts in biometric images assembled from a plurality of partial images, said method comprising;

repeatedly performing multiple iterations of a numeric comparison between an earlier partial biometric image and a later partial biometric image using a comparison function;

for each iteration, incrementing said earlier partial biometric image and said later partial biometric image;

determining if the results of said comparison function are less than a preset limit;

if the results are less than said preset limit, redacting said later partial biometric image, fetching the next later partial biometric image, and then repeating said numeric comparison until the results of said comparison function exceed said preset limit;

if the results are greater than said preset limit, retaining said later partial biometric image.

2. The method of claim 1, in which the biometric images are fingerprint images, and the partial biometric images comprise partial fingerprint images.

3. The method of claim 1, in which the artifacts are artifacts selected from the group consisting of stiction artifacts, retinal movement artifacts, and iris movement artifacts.

4. The method of claim 1, in which a complete biometric image is constructed from the non-redacted results retained by claim 1.

5. The method of claim 4, in which the complete biometric images is subsequently analyzed versus a database of authorized biometric images for security verification purposes.

6. The method of claim 1, in which the redaction is performed by discarding the partial images that are less than or equal to the preset limit.

7. The method of claim 1, in which the redaction is performed by an averaging function performed over the range of redacted images, and a single average image is substituted for the range of redacted images.

8. A method to reduce the distorting effect of stiction on fingerprint images assembled from a plurality of partial fingerprint images, said method comprising:

repeatedly performing multiple iterations of a numeric comparison between an earlier partial fingerprint image and a later partial fingerprint image using a comparison function;

for each iteration, incrementing said earlier partial fingerprint image and said later partial fingerprint image;

determining if the results of said comparison function are less than a preset limit;

if the results are less than said preset limit, redacting said later partial fingerprint image, fetching the next later partial fingerprint image and then repeating said numeric comparison until the results of said comparison function exceed said preset limit;

if the results are greater than said preset limit, retaining said later partial fingerprint image.

9. The method of claim 8, in which the partial fingerprint images are obtained using a sensor composed of a linear array of individual sensing elements.

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

11. The method of claim 8, in which each partial fingerprint image has a time stamp associated with said partial image that shows the time order in which said partial image was acquired.

12. The method of claim 8, in which the partial fingerprint images are obtained using a sensor with sensing elements capable of sensing relative finger location or movement.

13. The method of claim 12, in which each said partial fingerprint image has a location coordinate associated with said partial image that shows the finger pad location in which said partial image was acquired.

14. The method of claim 8, wherein time data or finger location data associated with said later partial fingerprint image is adjusted to correct for the difference between said time data or finger location data associated with said earlier partial fingerprint image and said time data or finger location data associated with said later partial fingerprint image and said difference is used to correct the time data or finger location data associated with the next sequential earlier partial fingerprint.

15. The method of claim 8, in which the comparison function computes a function of the arithmetic differences between a given linear array sensor location on said earlier partial fingerprint image relative to said a given linear array sensor location on said later partial fingerprint image over the length of the sensor linear array.

16. The method of claim 8, in which the comparison function computes the absolute value of the arithmetic differences between a given linear array sensor location on said earlier partial fingerprint image relative to said a given linear array sensor location on said later partial fingerprint image over the length of the sensor linear array.

17. The method of claim 8, in which the comparison function computes the sum of the squares or higher polynomial values of the arithmetic differences between a given linear array sensor location on said earlier partial fingerprint image relative to:

said a given linear array sensor location on said later partial fingerprint image over the length of the sensor linear array.

18. An integrated circuit chip for driving a partial fingerprint sensor, said chip comprising:

circuitry to acquire partial fingerprint images from said sensor;

memory to store at least a reference partial fingerprint image and a new partial fingerprint image;

circuitry to perform image correcting algorithms on said partial fingerprint images to correct said partial fingerprint images for distortion.

19. The integrated circuit chip of claim 18, in which the circuitry performs a numerical comparison of said reference partial fingerprint image and said new partial fingerprint image, and redacts said new partial fingerprint image if the result of said numerical comparison is less than a preset limit;

And in which the distortion is a distortion caused by stiction.

20. The integrated circuit chip of claim 18, in which the integrated circuit chip can additionally drive one or more finger location sensors.

21. The integrated circuit chip of claim 18, in which the chip can receive input from outside circuitry and change its numerical comparison or redaction criteria depending upon the results of this input.

22. An integrated circuit chip for driving a partial fingerprint sensor, said chip comprising:

circuitry to acquire partial fingerprint images from said sensor;

memory to store at least a reference partial fingerprint image and a new partial fingerprint image;

circuitry to perform a numerical comparison of said reference partial fingerprint image and said new partial fingerprint image, and redact said new partial fingerprint image if the result of said numerical comparison is less than a preset limit.

23. The integrated circuit chip of claim 22, in which the circuitry to acquire partial fingerprint images comprises deep finger penetrating radio frequency (RF) circuitry.

24. The integrated circuit chip of claim 22, in which the integrated circuit chip can additionally drive one or more finger location sensors.

25. The integrated circuit chip of claim 22, in which the processor used to perform said numerical comparisons is a microprocessor core selected from the group consisting of ARM or MIPS or 8051 or x86 or MSP430 processor cores.

26. The integrated circuit chip of claim 22 in which the chip can receive input from outside circuitry and change its numerical comparison or redaction criteria depending upon the results of this input.