Authentication device and authentication method
First Claim
Patent Images
1. An authentication apparatus comprising:
- a light source that emits an infrared light beam onto a finger;
image pick-up means that picks up an image of the finger by using a transmitted light beam, and thus outputs an image signal;
low-frequency brightness component extracting means that extracts a low-frequency brightness component signal from the image signal by using a low-pass filter;
middle-frequency brightness component extracting means that extracts a middle-frequency brightness component signal from the image signal by using a middle-pass filter;
correction means that corrects the middle-frequency brightness component signal by using the low-frequency brightness component signal;
quaternary-value converting means that converts the corrected middle-frequency brightness component signal into quaternary values such that the quaternary values are distributed at a predetermined ratio;
storage means that stores a quaternary-valued image obtained from the quaternary-value conversion by the quaternary-value converting means;
correlation coefficient calculating means that calculates a correlation coefficient between a quaternary-valued evaluation image as an object of evaluation and a quaternary-valued registered image by using a pattern matching method based on a normalized correlation method, the quaternary-valued evaluation image obtained from the quaternary-value conversion by the quaternary-value converting means, the quaternary-valued registered image being beforehand stored in the storage means; and
judgment means that judges whether or not the quaternary-valued evaluation image and the quaternary-valued registered image are images picked up from the same finger on a basis of the correlation coefficient which is calculated by the correlation coefficient calculating means.
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Abstract
In view of the fact that the reproducibility of a finger vein pattern is deteriorated in an image of the finger vein due to external scattered light, displacement, change in the amount of blood flow and the like, a multiple-valued pattern matching method is adopted so that such changes can be dealt with by converting a data map itself into a multiple-valued map.
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Citations
8 Claims
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1. An authentication apparatus comprising:
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a light source that emits an infrared light beam onto a finger; image pick-up means that picks up an image of the finger by using a transmitted light beam, and thus outputs an image signal; low-frequency brightness component extracting means that extracts a low-frequency brightness component signal from the image signal by using a low-pass filter; middle-frequency brightness component extracting means that extracts a middle-frequency brightness component signal from the image signal by using a middle-pass filter; correction means that corrects the middle-frequency brightness component signal by using the low-frequency brightness component signal; quaternary-value converting means that converts the corrected middle-frequency brightness component signal into quaternary values such that the quaternary values are distributed at a predetermined ratio; storage means that stores a quaternary-valued image obtained from the quaternary-value conversion by the quaternary-value converting means; correlation coefficient calculating means that calculates a correlation coefficient between a quaternary-valued evaluation image as an object of evaluation and a quaternary-valued registered image by using a pattern matching method based on a normalized correlation method, the quaternary-valued evaluation image obtained from the quaternary-value conversion by the quaternary-value converting means, the quaternary-valued registered image being beforehand stored in the storage means; and judgment means that judges whether or not the quaternary-valued evaluation image and the quaternary-valued registered image are images picked up from the same finger on a basis of the correlation coefficient which is calculated by the correlation coefficient calculating means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An authentication method comprising the steps of:
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emitting an infrared light beam onto a finger; picking up an image of the finger by using a transmitted light beam, and thus outputting an image signal; extracting a low-frequency brightness component signal from the image signal by using a low-pass filter; extracting a middle-frequency brightness component signal from the image signal by using a middle-pass filter; correcting the middle-frequency brightness component signal by using the low-frequency brightness component signal; converting the corrected middle-frequency brightness component signal into quaternary values such that the quaternary values are distributed at a predetermined ratio; storing a quaternary-valued image obtained by from the quaternary value conversion; calculating a correlation coefficient between a quaternary-valued evaluation image as an object of evaluation, and a quaternary-valued registered image by using a pattern matching method based on a normalized correlation method, the quaternary-valued evaluation image obtained by from the quaternary value conversion, the quaternary-valued registered image being beforehand stored; and judging whether or not the quaternary-valued evaluation image and the quaternary-valued registered image are images picked up from the same finger on a basis of the correlation coefficient.
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Specification