Patent EP0635526A1 successfully refreshed from Google Patents.
EP0466039A2
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EP
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Image comparison method
Assignee: Yozan Inc
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Filing: 1991-07-04
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Granted: —
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Expires: 2011-07-04
Abstract
Abstract A method for comparing two images including ridges with each other, comprising steps from i) to iv). i) Calculating density value of each pixel of an image to be examined and reference image; ii) detecting a direction with minimal change between each pixel and adjacent one, concerning to each pixel; iii) dividing the image to be examined and reference image, calculating an index according to the direction with minimal change as to each block; iv) using the index, it is judged if the image to be examined and reference image substantially coincide to each other.
Inventors
- 👤 Ryohei Kumagai
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 15:08
CPC Classifications
G; G07; G07C; G07C9/00; G07C9/20; G07C9/22; G07C9/25; G07C9/257; G06; G06V; G06V40/00; G06V40/10; G06V40/12; G06V40/1347
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
97 words
A method for comparing two images including ridges with each other, comprising steps from i) to iv) below. i) Calculating density value of each pixel of an image to be examined and reference image; ii) Detecting a direction with minimal density change between each pixel and adjacent one, concerning to each pixel; iii) Dividing said image to be examined and reference image, calculating an index according to said direction with minimal change as to each block; iv) Using said index, it is judged if said image to be examined and reference image substantially coincide to each other.
Claim 2
Independent Claim
92 words
A method for comparing two images including ridges with each other, comprising steps from i) to iv) below. i) Calculating density value of each pixel of an image to be examined and reference image; ii) Detecting a direction with minimal change between each pixel and adjacent one, concerning to each pixel; iii) Calculating a ratio of said direction with minimal change as to said image to be examined and reference image; iv) Using said ratio, it is judged if said image to be examined and reference image substantially coincide to each other.
Claim 3
Dependent Claim
24 words
A method for comparing two images claimed in Claim 1, wherein said direction with minimal density change is obtained according to a partial differential.
Claim 4
Dependent Claim
36 words
A method for comparing two images claimed in Claim 3, wherein said partial differential is stored in a memory and substituted by smaller partial differential so that the minimal value of said partial differential is obtained.
Claim 5
Dependent Claim
25 words
A method for comparing two images claimed in Claim 4, wherein direction codes of 1 to 8 are stored in said memory representing said direction.
Claim 6
Dependent Claim
47 words
A method for comparing two images claimed in Claim 1, wherein: i) An image is divided into a plurality of blocks each of which is divided into a plurality of subblocks; ii) The mean value of index of subblocks is defined as a direction of a block.
Claim 7
Dependent Claim
23 words
A method for comparing two images claimed in Claim 1, wherein a complement of a total variance is defined as said total variance.
Claim 8
Dependent Claim
21 words
A method for comparing two images claimed in Claim 7, wherein said complement defined as said total variance is calculated by
Claim 9
Dependent Claim
17 words
A method for comparing two images claimed in Claim 1, wherein an index is defined as correlation.
Claim 10
Dependent Claim
19 words
A method for comparing two images claimed in Claim 9, wherein said index defined as correlation is calculated by
Claim 11
Dependent Claim
20 words
A method for comparing two images claimed in Claim 1, wherein an index is defined as a distance between classes.
Claim 12
Dependent Claim
22 words
A method for comparing two images claimed in Claim 11, wherein said index defined as a distance between classes is calculated by
Claim 13
Dependent Claim
31 words
A method for comparing two images claimed in Claim 6, wherein a subblock including pixels of a number less than a predetermined value is ignored in said calculation of said index.
Claim 14
Dependent Claim
34 words
A method for comparing two images claimed in Claim 6, wherein fingerprint input is required again when number of subblocks including pixels of a number less than a predetermined value reaches a predetermined value.
References Cited (Backward Citations)
No citation records indexed.
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