Image comparison method
First Claim
Patent Images
1. A method for identifying a ridge sample object as similar to a ridge master object comprising steps of:
- illuminating the master object;
capturing a master image depicting ridges of the master object, the master image being represented by master ridge pixels;
detecting a master pixel direction having a minimum change in density from every one of a group of master ridge pixels, said master ridge pixels group including a majority of the master ridge pixels, to all pixels adjacent to and near every one of the master ridge pixels in said master ridge pixels group, thereby detecting a distribution of the master pixel directions having a minimum change in density for the entire master image based on the majority of master ridge pixels in said master ridge pixels group;
storing master pixel directions in a memory;
illuminating a sample object;
capturing a sample image depicting ridges of the sample object, the sample image being represented by sample ridge pixels;
detecting a sample pixel direction having a minimum change in density from every one of a group of sample ridge pixels, said sample ridge pixels group including a majority of the sample ridge pixels, to all pixels adjacent to and near every one of the sample ridge pixels in said sample ridge pixels group, thereby detecting a distribution of sample pixel directions having a minimum change in density for the entire sample image based on the majority of sample ridge pixels in said sample ridge pixels group;
detecting a measure of correspondence relating master pixel directions for a majority of master ridge pixels with sample pixel directions for a majority of sample ridge pixels; and
determining whether the measure of correspondence satisfies a predetermined condition, thereby identifying the sample object as similar to the master object.
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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.
36 Citations
11 Claims
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1. A method for identifying a ridge sample object as similar to a ridge master object comprising steps of:
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illuminating the master object; capturing a master image depicting ridges of the master object, the master image being represented by master ridge pixels; detecting a master pixel direction having a minimum change in density from every one of a group of master ridge pixels, said master ridge pixels group including a majority of the master ridge pixels, to all pixels adjacent to and near every one of the master ridge pixels in said master ridge pixels group, thereby detecting a distribution of the master pixel directions having a minimum change in density for the entire master image based on the majority of master ridge pixels in said master ridge pixels group; storing master pixel directions in a memory; illuminating a sample object; capturing a sample image depicting ridges of the sample object, the sample image being represented by sample ridge pixels; detecting a sample pixel direction having a minimum change in density from every one of a group of sample ridge pixels, said sample ridge pixels group including a majority of the sample ridge pixels, to all pixels adjacent to and near every one of the sample ridge pixels in said sample ridge pixels group, thereby detecting a distribution of sample pixel directions having a minimum change in density for the entire sample image based on the majority of sample ridge pixels in said sample ridge pixels group; detecting a measure of correspondence relating master pixel directions for a majority of master ridge pixels with sample pixel directions for a majority of sample ridge pixels; and determining whether the measure of correspondence satisfies a predetermined condition, thereby identifying the sample object as similar to the master object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for regulating access to a restricted region comprising:
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a light source; an optical path directing light from the light source to a measuring location at which an object having ridges can be positioned; means for transforming an optical image to an electrical signal; an optical path directing light from the measuring location to said transforming means; image processing apparatus, responsive to said transforming means; blocking means for preventing access to the restricted region; and releasing means for disabling the blocking means when receiving a signal from the image processing apparatus; wherein the image processing apparatus comprises; i) means for capturing a master image depicting ridges of a master object, the master image being represented by master ridge pixels, and for capturing a sample image depicting ridges of a sample object, the sample image being represented by sample ridge pixels; ii) means for detecting a plurality of master pixel directions, one for each of a majority of the master ridge pixels, each master pixel direction indicating a direction having a minimum change in density from the master ridge pixel to all pixels adjacent to and near the master ridge pixel; iii) means for storing the master pixel directions; iv) means for detecting a plurality of sample pixel directions, one for each of a majority of the sample ridge pixels, each sample pixel direction indicating a direction having a minimum change in density from the sample ridge pixel to all pixels adjacent to and near the sample ridge pixel; v) means for detecting a measure of correspondence relating master pixel directions for a majority of master ridge pixels with sample pixel directions for a majority of sample ridge pixels; and vi) means for signaling the releasing means when the measure of correspondence satisfies a predetermined condition.
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Specification