Method and apparatus for fingerprint motion tracking using an in-line array

• US 8,447,077 B2
• Filed: 09/11/2006
• Issued: 05/21/2013
• Est. Priority Date: 09/11/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Benkley, Fred George, Geoffroy, David Joseph
• Primary Examiner(s): ZARKA, DAVID PETER
• Application Number:
  US11/519,383
• Publication Number:
  US 20100284565A1
• Time in Patent Office: 2,444 Days
• Field of Search: 382/124
• US Class Current: 382/124
• 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 method of 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.

2. A method of 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, by a processor in communication with the linear sensor array, 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, by the processor, 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.

3. A method of 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, by a processor in communication with the first linear image sensor array, 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, by the processor, 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.

4. The method of claim 3, 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, by a processor in communication with the second linear image sensor array, 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.

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

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

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

processor means for 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 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 for computing 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 means also being for estimating 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 means also being for computing 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 sensing means, including a second linear array of image feature detection sensors spaced along a second axis with respect to the sensing means, for sensing 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 means being for storing 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 means being for 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 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 computing 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 means also being for estimating 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 means also being for computing 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 means for determining which of the first sensor array and the second sensor array produced a highest similarity match score and for selecting 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 means being for generating fingerprint motion and direction data using the velocity in the principle axis of motion and the velocity in the other axis of motion.

6. The system of claim 5, further comprising:

the processor means being for producing navigation data using the fingerprint motion data.

7. The system of claim 5, further comprising the processor means being for sensing portions of a fingerprint image to be reconstructed into a full fingerprint image using the fingerprint motion data.

8. The system of claim 5, further comprising the processor means being for sensing portions of a fingerprint image to be reconstructed into a full fingerprint image using fingerprint motion and direction data.

9. A method of determining motion of a fingerprint surface with respect to a sensor surface, comprising:

sensing, via a computing device, 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;

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; and

reconstructing a fingerprint image using the velocity.

10. A method of determining motion of a fingerprint surface with respect to a sensor surface, comprising:

sensing, via a computing device, 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.