US5659626A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fingerprint identification system
Assignee: General Dynamics Mission Systems Inc
•
Filing: 1994-10-20
•
Granted: 1997-08-19
•
Expires: 2014-10-20
Abstract
Abstract A method for locating minutia in a gray scale image of a fingerprint using a pair of filters, called "Gabor" and "Minutia" filters, includes determining direction and spacing of ridges at regularly spaced pixels, aligning filters by ridge direction, determining outputs of filters where Gabor Filter has high level output when in parallel ridge flow and, due to phase discontinuity at a minutia, low level output when in neighborhood of a minutia. The Minutia filter exhibits opposite phenomenon, having low level output in parallel ridge flow and high output in neighborhood of a minutia. A method for creating a state map of a fingerprint includes determining image quality, identifying minutia locations, determining areas of good quality where minutia are present, areas of good quality where no minutia are present and areas where quality is below a predetermined value to reliably determine presence or absence of minutia. A method for determining location of, associating, and determining number of ridges between cores and deltas in digitized gray scale of a fingerprint image by Direct Estimation of Orientated Patterns includes determining ridge angle and frequency at regularly spaced pixels, computing gradients of ridge angles, ordering gradient according to size, creating vector field of image, measuring curling of vector field, locating cores and deltas, tracing path of constant value ridge angle between deltas and cores, calculating line integral of vector frequency along straight line from delta to core.
Inventors
- 👤 James R. Ort
- 👤 Douglas L. Lange
- 👤 Frederick W. Kiefer
- 👤 Raymond J. Dennison
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 20:13
CPC Classifications
G; G06; G06V; G06V40/00; G06V40/10; G06V40/12; G06V40/1347; G06V40/1359; G07; G07C; G07C9/00; G07C9/30; G07C9/32; G07C9/37
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
188 words
A method of detecting minutia in a fingerprint image comprising the steps of scanning a gray scale image of a fingerprint, determining the direction of fingerprint ridges at multiple, spaced apart locations within the fingerprint, determining the spacing of fingerprint ridges at said multiple, spaced apart locations, orienting a pair of filters over each of said multiple locations by reference to said ridge direction at each of said locations, adjusting the area of said filters by reference to the spacing of said ridges at each of said locations whereby said filter observes a predetermined number of ridges, one of said filters having a high level output when observing parallel fingerprint ridge flow and a low output when the ridge flow in not parallel, the other of said filters having a low level output when observing parallel fingerprint ridge flow and a high output when the ridge flow is not parallel, monitoring the outputs of said filters at each of said locations, locating a minutia by reference to simultaneous changes in the outputs of both filters, and recording those locations indicating non-parallel ridges as an indication of a minutia.
Claim 2
Independent Claim
188 words
A method of detecting minutia in a fingerprint image comprising the steps of scanning a gray scale image of a fingerprint, determining the direction of fingerprint ridges at multiple, spaced apart locations within the fingerprint, determining the spacing of fingerprint ridges at said multiple, spaced apart locations, orienting a pair of filters over each of said multiple locations by reference to said ridge direction at each of said locations, adjusting the area of said filters by reference to the spacing of said ridges at each of said locations whereby said filter observes a predetermined number of ridges, one of said filters having a high level output when observing parallel fingerprint ridge flow and a low output when the ridge flow in not parallel, the other of said filters having a low level output when observing parallel fingerprint ridge flow and a high output when the ridge flow is not parallel, monitoring the outputs of said filters at each of said locations, locating a minutia by reference to simultaneous changes in the outputs of both filters, and recording those locations indicating non-parallel ridges as an indication of a minutia.
Claim 3
Dependent Claim
35 words
The method of claim 1 further comprising the step of determining the ratio of magnitude of the output of one filter relative to the other filter as an indication of the presence of a minutia.
Claim 4
Dependent Claim
24 words
The method of claim 1 wherein one of said filters is a Gabor Filter and the other of said filters is a Minutia filter.
Claim 5
Dependent Claim
50 words
The method of claim 1 further including the steps of determining the quality of the image at each location, identifying areas of good quality containing minutiae, separately identifying areas of good quality without minutiae, and identifying areas that are either poor quality or indeterminant as to the presence of minutia.
Claim 6
Independent Claim
132 words
A method of detecting and recording the location of minutia in a fingerprint image comprising the steps of scanning a gray scale image of a fingerprint, determining the direction of fingerprint ridges at multiple, spaced apart locations within the fingerprint, determining the spacing of fingerprint ridges at said multiple, spaced apart locations, orienting a filter over each of said multiple locations by reference to said ridge direction at each of said locations, adjusting the area of said filter by reference to the spacing of said ridges at each of said locations whereby said filter observes a predetermined number of ridges, said filter having an output level which is a function of relative angle of ridges adjacent the location being observed, and recording those locations indicating non-parallel ridges as an indication of minutia.
Claim 7
Independent Claim
132 words
A method of detecting and recording the location of minutia in a fingerprint image comprising the steps of scanning a gray scale image of a fingerprint, determining the direction of fingerprint ridges at multiple, spaced apart locations within the fingerprint, determining the spacing of fingerprint ridges at said multiple, spaced apart locations, orienting a filter over each of said multiple locations by reference to said ridge direction at each of said locations, adjusting the area of said filter by reference to the spacing of said ridges at each of said locations whereby said filter observes a predetermined number of ridges, said filter having an output level which is a function of relative angle of ridges adjacent the location being observed, and recording those locations indicating non-parallel ridges as an indication of minutia.
Claim 8
Dependent Claim
229 words
Apparatus for locating minutiae contained in a fingerprint image comprising means for determining the direction of fingerprint ridges at multiple locations, means for determining the spacing of said fingerprint ridges at each of said multiple locations, means responsive to said direction determining means and said spacing determining means for detecting a phase discontinuity in the ridge flow of the fingerprint image at each of said multiple locations, wherein said means for determining the phase discontinuity in the ridge flow of fingerprint image, which indicates a ridge ending or bifurcation, comprises a Gabor filter having a high level output when observing parallel fingerprint ridge flow and a low output when the ridge flow is not parallel, a Minutiae Filter having a low level output when observing parallel fingerprint ridge flow and a high output when the ridge flow is not parallel, means responsive to said direction determining means for aligning said Gabor Filter and said Minutiae Filter with the fingerprint at each of said multiple locations, means responsive to said spacing determining means for adjusting the size of said Gabor Filter and said Minutiae Filter calculation kernel to view a predetermined number of fingerprint ridges, and means for determining the ratio of the outputs of said filters as they are aligned at each of said multiple locations to identify minutiae, and means for recording the location of said phase discontinuities.
Claim 9
Dependent Claim
229 words
Apparatus for locating minutiae contained in a fingerprint image comprising means for determining the direction of fingerprint ridges at multiple locations, means for determining the spacing of said fingerprint ridges at each of said multiple locations, means responsive to said direction determining means and said spacing determining means for detecting a phase discontinuity in the ridge flow of the fingerprint image at each of said multiple locations, wherein said means for determining the phase discontinuity in the ridge flow of fingerprint image, which indicates a ridge ending or bifurcation, comprises a Gabor filter having a high level output when observing parallel fingerprint ridge flow and a low output when the ridge flow is not parallel, a Minutiae Filter having a low level output when observing parallel fingerprint ridge flow and a high output when the ridge flow is not parallel, means responsive to said direction determining means for aligning said Gabor Filter and said Minutiae Filter with the fingerprint at each of said multiple locations, means responsive to said spacing determining means for adjusting the size of said Gabor Filter and said Minutiae Filter calculation kernel to view a predetermined number of fingerprint ridges, and means for determining the ratio of the outputs of said filters as they are aligned at each of said multiple locations to identify minutiae, and means for recording the location of said phase discontinuities.
Claim 10
Independent Claim
138 words
A method for creating and recording for future use an image state map containing image quality and areas of minutiae locations of a fingerprint image comprising the steps of converting a fingerprint image into a digitized gray scale image comprising a plurality of individual pixels, determining the quality of the fingerprint image at regularly spaced individual pixels, determining the quality of minutiae located on said fingerprint image, determining the location of minutiae within said fingerprint image, recording on said state map those areas where no minutiae are detected, identifying on said state map those areas where minutiae are present, and recording on said state map those areas where the quality of the image is too poor to reliably determine the presence or absence of minutiae or where minutiae were detected having a quality value below a predetermined value.
Claim 11
Independent Claim
138 words
A method for creating and recording for future use an image state map containing image quality and areas of minutiae locations of a fingerprint image comprising the steps of converting a fingerprint image into a digitized gray scale image comprising a plurality of individual pixels, determining the quality of the fingerprint image at regularly spaced individual pixels, determining the quality of minutiae located on said fingerprint image, determining the location of minutiae within said fingerprint image, recording on said state map those areas where no minutiae are detected, identifying on said state map those areas where minutiae are present, and recording on said state map those areas where the quality of the image is too poor to reliably determine the presence or absence of minutiae or where minutiae were detected having a quality value below a predetermined value.
Claim 12
Independent Claim
83 words
A method of determining the location of core and delta features in an image of a fingerprint comprising the steps of scanning a gray scale image of a fingerprint, measuring and mapping ridge angle and ridge frequency and associated image quality, computing a gradient map, finding and rank ordering gradient features and measuring and recording associated image quality, and applying vector field mathematics of Direct Estimation of Orientated Patterns to said gradient map to determine core and delta type to each gradient feature.
Claim 13
Independent Claim
83 words
A method of determining the location of core and delta features in an image of a fingerprint comprising the steps of scanning a gray scale image of a fingerprint, measuring and mapping ridge angle and ridge frequency and associated image quality, computing a gradient map, finding and rank ordering gradient features and measuring and recording associated image quality, and applying vector field mathematics of Direct Estimation of Orientated Patterns to said gradient map to determine core and delta type to each gradient feature.
Claim 14
Dependent Claim
40 words
The method of claim 8 further including the step of detecting an associated pair of deltas and cores, or cores and cores, by tracing a path of constant value ridge angle between said deltas and cores, or cores and cores.
Claim 15
Dependent Claim
19 words
The method of claim 9 further including the step of determining the ridge count between associated cores and deltas.
Claim 16
Dependent Claim
34 words
The method of claim 10 wherein the step of determining ridge count includes the step of calculating the line integral of the vector ridge frequency along a straight line from one feature to another.
Claim 17
Dependent Claim
131 words
Apparatus for recording in machine readable form the existence and location of cores and deltas in an image of a fingerprint, said apparatus including means for converting a fingerprint image into a digitized gray scale image comprising a plurality of individual pixels, means for determining the ridge angle and quality of the fingerprint image at regularly spaced individual pixels to create a Ridge Angle Map and an image quality map, means for computing the gradients of said Ridge Angle Map to derive the location of possible cores and deltas, means for sorting the gradients according to size, means for creating a vector field representation of said fingerprint image, means for detecting and measuring the curling of said vector field, and means responsive to said detecting means for identifying cores and deltas.
Claim 18
Dependent Claim
131 words
Apparatus for recording in machine readable form the existence and location of cores and deltas in an image of a fingerprint, said apparatus including means for converting a fingerprint image into a digitized gray scale image comprising a plurality of individual pixels, means for determining the ridge angle and quality of the fingerprint image at regularly spaced individual pixels to create a Ridge Angle Map and an image quality map, means for computing the gradients of said Ridge Angle Map to derive the location of possible cores and deltas, means for sorting the gradients according to size, means for creating a vector field representation of said fingerprint image, means for detecting and measuring the curling of said vector field, and means responsive to said detecting means for identifying cores and deltas.
Claim 19
Dependent Claim
39 words
The apparatus of claim 12 further comprising means for detecting an associated pair of deltas and cores, or cores and cores, by tracing a path of constant value ridge angle between said deltas and cores, or cores and cores.
Claim 20
Dependent Claim
20 words
The apparatus of claim 13 further including means for calculating the number of fingerprint ridges between associated deltas and cores.
Claim 21
Dependent Claim
37 words
The apparatus of claim 14 wherein said means for calculating the number of fingerprint ridges includes means for calculating the line integral of the vector frequency along a straight line from a delta to an associated core.
References Cited (Backward Citations)
US3419287A
Cited
US3564266A
Cited
US4015240A
Cited
US3893080A
Cited
US3928842A
Cited
US4185270A
Cited
US4151512A
Cited
US4135147A
Cited
US4083035A
Cited
US4047154A
Cited
US4208651A
Cited
US4229023A
Cited
US4310827A
Cited
US4325570A
Cited
CA1181176A
Cited
US4752966A
Cited
US4646352A
Cited
US4944021A
Cited
US4607384A
Cited
US4905293A
Cited
US4872203A
Cited
US4685145A
Cited
US4747147A
Cited
USD303251S
Cited
US5187747A
Cited
US4876726A
Cited
US4817183A
Cited
US4785171A
Cited
US4790564A
Cited
US5040223A
Cited
US5040224A
Cited
US4947442A
Cited
US5109428A
Cited
US5177792A
Cited
US5050220A
Cited
US5140642A
Cited
US5420937A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-08-18 | 2001-02-17 | 2001-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-08-18 | 2005-02-17 | 2005-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-08-18 | 2009-02-17 | 2009-08-19 | $7700.00 | Window Closed / Lapsed |