System for determining the motion of a fingerprint surface with respect to a sensor surface

• US 8,693,736 B2
• Filed: 09/14/2012
• Issued: 04/08/2014
• Est. Priority Date: 09/11/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Benkley, Fred George, Geoffroy, David Joseph
• Primary Examiner(s): Patel, Jayesh A
• Application Number:
  US13/618,321
• Publication Number:
  US 20130094715A1
• Time in Patent Office: 571 Days
• Field of Search: 382/115, 382/124, 382/127, 382/312, 382/107
• US Class Current: 382/107
• CPC Class Codes: G06T 7/248 involving reference images or patches
• 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 motion tracking method and system is provided for sensing features of a fingerprint along an axis of finger motion, where a linear sensor array has a plurality of substantially contiguous sensing elements configured to capture substantially contiguous overlapping segments of image data. A processing element is configured to receive segments of image data captured by the linear sensor array and to generate fingerprint motion data. Multiple sensor arrays may be included for generating directional data. The motion tracking data may be used in conjunction with a fingerprint image sensor to reconstruct a fingerprint image using the motion data either alone or together with the directional data.

Claims

1. A system for determining the motion of a fingerprint surface with respect to a sensor surface, comprising:

at least one linear array of fingerprint imaging sensor elements disposed on a sensing sensor surface generally perpendicularly to a swiping axis of motion of a finger being imaged by the at least one linear array of fingerprint imaging sensor elements and configured to sense portions of a fingerprint image to be reconstructed into a full fingerprint;

a first linear one-dimensional fingerprint motion image features sensor array configured to sense at least a first set and a second set of fingerprint image features located along a longitudinal axis of the first linear one-dimensional fingerprint motion image features sensor array on the sensor surface, the longitudinal axis of the first linear one-dimensional fingerprint image motion features sensor array forming a first angle with the at least one linear array of fingerprint imaging sensor elements, the first set and the second set overlapping along the longitudinal axis of the first one dimensional fingerprint motion image features sensor array, and the first set temporally separated from the second set;

a digital data generator configured to generate digital data representing a plurality of pixels corresponding to the first set and a plurality of pixels corresponding to the temporally separated second set representing each of the at least a first set and a second set of fingerprint image features;

a processor configured to generate a list of similarity match scores for each plurality of pixels corresponding to the first set and the second set by successively pixel shifting the plurality of pixels corresponding to the first set with respect to the plurality of pixels corresponding to the second set along the linear axis;

the processor configured to generate fingerprint motion data by computing a similarity matching score for each pixel shift until a match is found for a given pixel shift, indicated by a maximum similarity matching score;

the processor configured to generate fingerprint motion and direction data based on the pixel shift and the axis of the first fingerprint image features sensor array.

2. The system of claim 1 for determining the motion of a fingerprint surface with respect to a sensor surface, comprising:

a second linear one dimensional fingerprint motion image features sensor array configured to sense at least a third set and a fourth set of fingerprint image features located along a longitudinal axis of the second linear fingerprint motion image features sensor array on a sensor surface, the longitudinal axis of the second linear one-dimensional fingerprint motion image features sensor array forming a second angle with the at least one linear array of fingerprint imaging sensor elements, the third set and the fourth set overlapping along the longitudinal axis of the first one dimensional fingerprint motion image features sensor array, and the third set temporally separated from the fourth set;

the digital data generator configured to generate digital data representing a plurality of pixels corresponding to the third set and a plurality of pixels corresponding to the temporally separated fourth set representing each of the at least two sets of fingerprint image features;

the processor configured to generate a list of similarity match scores for each of the plurality of pixels corresponding to the third set and each of the plurality of pixels corresponding to the fourth set by successively pixel shifting the plurality of pixels corresponding to the third set with respect to the plurality of pixels corresponding to the fourth set;

the processor configured to generate fingerprint motion data by computing a similarity matching score for each pixel shift until a match is found for a given pixel shift, indicated by a maximum similarity matching score;

the processor configured to generate fingerprint velocity data and direction data based at least in part on the pixel shift and the axis of the second fingerprint image features sensor array.

3. The system of claim 1, further comprising a fingerprint image reconstruction processor configured to reconstruct the full fingerprint image using at least in part the fingerprint motion data.

4. A non-transitory machine readable medium, storing instructions that, when executed by a computing device, cause the computing device to perform a method for determining motion of a fingerprint surface with respect to a sensor surface, comprising:

sensing at least two temporally separated sets, each of a plurality of pixels in a fingerprint image along a sensor axis of the sensor surface, the sensing performed by a linear array of fingerprint image feature detection sensors spaced along the sensor axis;

storing digital data corresponding to each of the plurality of pixels in each of the at least two sets of a plurality of pixels;

processing the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing the digital data corresponding to each of the plurality of pixels in a first of the at least two sets of a plurality of pixels in the fingerprint image to the digital data corresponding to each of the plurality of pixels in a second of the at least two sets of a plurality of pixels in the fingerprint image, through sequentially shifting the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets, until a match is found for the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets;

estimating the distance D traveled by the fingerprint surface with respect to the sensor surface by multiplying a pixel shift required to achieve the match times a pitch of the image feature detection sensors; and

computing the velocity measurement D/T of the fingerprint surface with respect to the sensor surface by dividing the estimated distance D by the temporal difference T between sensing the first set of the at least two sets and the second set of the at least two sets.

5. A non-transitory machine readable medium, storing instructions that, when executed by a computing device, cause the computing device to perform a method for determining motion of a fingerprint surface with respect to a sensor surface, comprising:

collecting at least a first image sample and a second image sample from a linear sensor array, wherein each of the at least a first image sample and a second image sample has a series of pixel values corresponding to substantially contiguous fingerprint image features along an axis of the linear sensor array, taken at different times;

generating a list of similarity match scores by comparing the respective series of pixels corresponding to each of the at least a first image sample and a second image sample;

determining a pixel shift between the at least the first image sample and the second image sample resulting in a highest similarity match score;

estimating the distance traveled by multiplying the pixel shift times a pitch of sensors in the linear sensor array; and

computing a velocity estimate by dividing the estimated distance by the time expended between collecting the first image sample and the second image sample with the highest match score.

6. A non-transitory machine readable medium, storing instructions that, when executed by a computing device, cause the computing device to perform a method for determining motion of a fingerprint surface with respect to a sensor surface, comprising:

collecting at least a first image and a second image, each image comprising values for each of a plurality of pixels in a first linear image sensor array along a first axis of the array taken respectively at a first time and a second time;

generating a list of similarity match scores for each of a plurality of pixel shifted versions of the at least the first image and the second image;

determining a pixel shift between the at least the first image and the second image that results in a highest similarity match score;

estimating the distance traveled along the first axis by multiplying the number of pixels in the pixel shift by a pitch of sensors in the linear image sensor array; and

computing the velocity of the fingerprint surface with respect to the sensor surface and producing a velocity value equal to multiplying the distance traveled by the difference between the first time and the second time.

7. The machine readable medium of claim 6, the method further comprising:

collecting from at least a second linear image sensor array having a second axis at least a third image and a fourth image;

generating a list of similarity match scores for each of a plurality of pixel shifted versions of the at least a third image and a fourth image that has a next highest similarity match score to compute a velocity of the fingerprint in the second axis by determining a pixel shift in the second axis with a highest similarity match score; and

computing by the processor, a velocity and direction as a vector sum of the velocity in the first axis and the velocity in the second axis.

8. A system comprising:

a fingerprint image sensor, including a first linear array of image feature detection sensors spaced along a first axis of motion with respect to the image sensor, configured to sense at least two temporally separated sets, each of a plurality of pixels in a fingerprint image along the first axis of motion;

a memory configured to store digital data corresponding to each of the plurality of pixels in each of the at least two sets;

a processor configured to process the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing the digital data corresponding to each of the plurality of pixels in a first of the at least two sets of a plurality of pixels in the fingerprint image to the digital data corresponding to each of a plurality of pixels in a second of the at least two sets of a plurality of pixels in the fingerprint image, through sequentially shifting the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets, and to compute a respective list of similarity match scores for the first set of a plurality of pixels and the second set of a plurality of pixels for each of a plurality of pixel shift positions, until a match is found for the pixels in the first set with respect to the pixels in the second set, as indicated by the occurrence of a highest of the computed similarity match scores, the processor also configured to estimate a distance D traveled by the fingerprint surface with respect to the sensor surface by multiplying a pixel shift required to achieve the match times the physical distance between image feature detection sensors in the first linear array as measured from centerline to centerline of the respective image feature detection sensors, and the processor also configured to compute a first velocity measurement D/T of the fingerprint surface with respect to the sensor surface by dividing the estimated distance D by the temporal difference between sensing of the first of the at least two sets and the second of the at least two sets in the first axis.

9. The system of claim 8, further comprising the processor further configured to sense portions of a fingerprint image to be reconstructed into a full fingerprint image using the fingerprint motion data.

10. A system comprising:

a first fingerprint image sensor, including a first linear array of image feature detection sensors spaced along a first axis of motion with respect to the fingerprint image sensor, configured to sense at least two temporally separated sets, each of a plurality of pixels in a fingerprint image along the first axis of motion;

a memory configured to store digital data corresponding to each of the plurality of pixels in each of the at least two sets;

a processor configured to process the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing the digital data corresponding to each of the plurality of pixels in a first of the at least two sets of a plurality of pixels in the fingerprint image to the digital data corresponding to each of a plurality of pixels in a second of the at least two sets of a plurality of pixels in the fingerprint image, through sequentially shifting the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets, and to compute a respective list of similarity match scores for the first set of a plurality of pixels and the second set of a plurality of pixels for each of a plurality of pixel shift positions, until a match is found for the pixels in the first set with respect to the pixels in the second set, as indicated by the occurrence of a highest of the computed similarity match scores, the processor also configured to estimate a distance D traveled by the fingerprint surface with respect to the sensor surface by multiplying a pixel shift required to achieve the match times the physical distance between image feature detection sensors in the first linear array as measured from centerline to centerline of the respective image feature detection sensors, and the processor also configured to compute a first velocity measurement D/T of the fingerprint surface with respect to the sensor surface by dividing the estimated distance D by the temporal difference between sensing of the first of the at least two sets and the second of the at least two sets in the first axis;

a second fingerprint image sensor, including a second linear array of image feature detection sensors spaced along a second axis with respect to the fingerprint image sensor, configured to sense at least two temporally separated sets, each of a plurality of pixels in a third fingerprint image and a fourth fingerprint image along the second axis of motion;

the memory also configured to store digital data corresponding to each of the plurality of pixels in each of the third fingerprint feature image and the fourth fingerprint feature image along the second axis;

the processor further configured to process the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing the digital data corresponding to each of the plurality of pixels in the third fingerprint feature image in the second axis to the digital data corresponding to each of the plurality of pixels in a fourth fingerprint feature image in the second axis, through sequentially shifting the pixels in the third image with respect to the pixels in the fourth image, and to compute a respective list of similarity match scores for the first set of a plurality of pixels and the second set of a plurality of pixels for each of a plurality of pixel shift positions, until a match is found for the pixels in the third image with respect to the pixels in the fourth image, as indicated by the occurrence of a highest of the computed similarity match scores;

the processor also configured to estimate a distance D traveled by the fingerprint surface with respect to the sensor surface in the second axis by multiplying a pixel shift required to achieve the match times the physical distance between the fingerprint feature image sensors in the second linear array as measured from centerline to centerline of the respective image feature detection sensors; and

the processor also configured to compute a first velocity measurement D/T of the fingerprint surface with respect to the sensor surface in the second axis by dividing the estimated distance D by the temporal difference between sensing of the third image and the fourth image;

the processor also configured to determine which of the first sensor array and the second sensor array produced a highest similarity match score and to select the one of the first sensor array and the second sensor array that produced the highest similarity match score to represent a principal axis of motion; and

the processor also configured to generate fingerprint motion and direction data using the velocity in the principle axis of motion and the velocity in the other axis of motion.

11. A non-transitory machine readable medium, storing instructions that, when executed by a computing device, cause the computing device to perform a method for determining motion of a fingerprint surface with respect to a sensor surface, comprising:

sensing at least two temporally separated sets, each of a plurality of pixels in a fingerprint image along an axis of motion of a fingerprint surface with respect to a sensor surface the sensing performed by a linear array of image feature detection sensors spaced along the axis of motion;

storing digital data corresponding to each of the plurality of pixels in each of the at least two sets;

processing the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing the digital data corresponding to each of the plurality of pixels in a first of the at least two sets of a plurality of pixels in the fingerprint image to the digital data corresponding to each of the plurality of pixels in a second of the at least two sets of a plurality of pixels in the fingerprint image through sequentially shifting the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets, until a match is found for the pixels in the first and second sets;

estimating the distance D traveled by the fingerprint surface with respect to the sensor surface by multiplying the pixel shift required to achieve the match times the physical distance between the pixels in the image feature detection sensor as measured from centerline to centerline of the respective image feature detection sensors;

computing the velocity measurement D/T of the fingerprint surface with respect to the sensor surface by dividing the estimated distance D by the temporal difference between sensing the first of the at least two sets and the second of the at least two sets; and

reconstructing a fingerprint image using the velocity.

12. A non-transitory machine readable medium, storing instructions that, when executed by a computing device, cause the computing device to perform a method for determining motion of a fingerprint surface with respect to a sensor surface, comprising:

sensing at least two temporally separated sets, each of a plurality of pixels in a fingerprint image along an axis of motion of a fingerprint surface with respect to a sensor surface the sensing performed by a linear array of image feature detection sensors spaced along the axis of motion;

storing digital data corresponding to each of the plurality of pixels in each of the at least two sets;

processing, via a computing device, the digital data to generate fingerprint motion data, wherein generating fingerprint motion data comprises comparing, via the computing device, the digital data corresponding to each of the plurality of pixels in a first of the at least two sets of a plurality of pixels in the fingerprint image to the digital data corresponding to each of the plurality of pixels in a second of the at least two sets of a plurality of pixels in the fingerprint image through sequentially shifting the pixels in the first of the at least two sets with respect to the pixels in the second of the at least two sets, until a match is found for the pixels in the first and second sets;

estimating, via the computing device, the distance D traveled by the fingerprint surface with respect to the sensor surface by multiplying the pixel shift required to achieve the match times the physical distance between the pixels in the image feature detection sensor as measured from centerline to centerline of the respective image feature detection sensors; and

computing, via the computing device, the velocity measurement D/T of the fingerprint surface with respect to the sensor surface by dividing the estimated distance D by the temporal difference between sensing the first of the at least two sets and the second of the at least two sets.