The present application claims priority from Japanese Patent Application No. 2010-055293 filed on Mar. 12, 2010, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to a finger vein authentication unit.
2. Description of the Related Art
In the biometric authentication technique, since vein authentication uses a vein pattern in a living body, it is more difficult to perform falsification and manipulation as compared with finger print authentication. A safer biometric authentication unit can be realized with the vein authentication. A finger vein authentication unit using a finger vein pattern can be miniaturized more than other vein authentication units such as a palm vein authentication unit and is easily assembled in equipment, so that it is expected to be applied to various fields.
The finger vein authentication unit captures an image of the vein by capturing an image of a finger by an infrared camera having near-infrared light sensitivity by emitting near infrared light to the finger by using the fact that the vein of a finger absorbs near infrared light and the portion other than the vein transmits near infrared light, and uses the vein pattern for authentication.
Japanese Unexamined Patent Application Publication No. 2002-83298 discloses a person authentication unit using finger vein authentication, which detects finger contour from a captured image and corrects a turn of a finger image captured.
Japanese Unexamined Patent Application Publication No. 2003-30632 and Japanese Unexamined Patent Application Publication No. 2006-155575 disclose a configuration of determining a finger placement position by guiding means which guides a finger to a placement position and a button switch provided at a fingertip. Japanese Unexamined Patent Application Publication No. 2007-325793 discloses a configuration of recognizing an outside shape range of a finger by a position sensor having a touch panel and turning on a corresponding near-infrared-light source. The position sensor can detect a turn or tilt of the finger. However, concrete description is not given.
To accurately perform authentication using a vein pattern, it is important to make imaging parameters at the time of registration and those at the time of authentication the same and match a registered vein pattern and a vein pattern to be authenticated as vein patterns of the same part of a finger. In the case where the imaging parameters at the time of registration and those at the time of authentication are different, for example, in the case where a finger placement position in an authentication unit at the time of registration and that at the time of authentication are different from each other, an image of the vein captured by an infrared camera at the time of registration and that at the time of authentication become different from each other, so that vein patterns extracted look different.
Due to this, false rejection may occur such that although the user himself/herself enters an authentication input, the unit determines that another person enters the input because of the vein patterns which look different. There is also the possibility of occurrence of false acceptance such that although another person enters an authentication input, due to a positional deviation of a finger, a match in the vein patterns is determined by chance.
When the positional deviation between the finger at the time of registration and that at the time of authentication lies in a range of a certain degree, like in the Japanese Unexamined Patent Application Publication No. 2002-83298, there is provided a method of extracting the contour of the finger from a captured image, performing a positional correction on a turn or floating of the finger, or the like on the basis of the contour, and performing authentication. In the case where the finger placement position is largely different from the normal position, it is difficult to make a correction using the contour data.
Further, in a small-sized open-type finger vein authentication unit preventing the influence of outside light by forming the image pickup window narrower than a finger and completely closing the image pickup window with a finger, the contour of a finger is not included in a captured image. Consequently, a positional deviation and a turn of the finger placement position cannot be corrected using the finger contour data.
To avoid the problem, like in the Japanese Unexamined Patent Application Publication No. 2003-30632 and Japanese Unexamined Patent Application Publication No. 2006-155575, there is proposed a finger vein authentication unit which makes the user put his/her finger on the same finger placement position by providing the finger placement part with a switch and a sensor. However, although a turn of a finger in the same plane using the optical axis of the infrared camera as an axis can be prevented, a turn of a finger around the axis of the finger as a center cannot be prevented.
There is also proposed a finger vein authentication unit having a dent in a finger guide part shown in
In the finger vein authentication unit 100, when the depth of the fingertip guiding part 3 is increased to prevent a deviation of a finger, a finger having normal thickness can be placed normally as shown in
The present invention provides a finger vein authentication unit for performing biometric authentication by capturing a finger vein pattern from an image pickup window by an infrared camera using near-infrared light, wherein a touch sensor having a plurality of detection regions which are continuous in XY directions is mounted in a fingertip placement part provided on the outside of the image pickup window, a finger displacement amount from a correct finger placement position in the finger vein authentication unit is detected from fingertip shape data detected by the touch sensor and finger contour data detected by the infrared camera, a finger vein pattern obtained is corrected, and the same finger vein pattern as that at the time of registration to the finger vein authentication unit is automatically obtained.
Further, the finger displacement amount corresponds to a deviation caused by turn of a finger in the same plane around an optical axis of the infrared camera as a center, or a positional deviation in a direction of turn around the axis of the finger as a center or the positional deviation in the axis directions of the finger.
Preferably, the finger placement part has an almost flat shape.
Preferably, when the finger displacement amount exceeds a predetermined threshold value, guidance information is output and notified to the user so that the user puts his/her finger in a correct placement position.
The present invention also provides a finger vein authentication unit for performing biometric authentication by capturing a finger vein pattern from an image pickup window which is closed with a finger by an infrared camera using near-infrared light, wherein a first touch sensor having a plurality of detection regions which are continuous in XY directions is mounted in a fingertip placement part provided on the outside of the image pickup window, a second touch sensor having a plurality of detection regions which are continuous in XY directions is mounted in a finger base placement part provided on the outside of the image pickup window, a finger displacement amount from a correct finger placement position is detected from fingertip shape data and finger base shape data detected by the first and second touch sensors, correction is made, and the same finger vein pattern as that at the time of registration to the finger vein authentication unit is automatically obtained.
Further, the touch sensor is provided with a pressure sensor for detecting a pressing force to the touch sensor.
The touch sensor may be a resistive touch sensor.
In the present invention, a touch sensor having a plurality of detection regions which are continuous in XY directions is mounted in a fingertip placement part provided on the outside of an image pickup window, a finger displacement amount from a correct finger placement position is detected from fingertip shape data detected by the touch sensor and finger contour data detected by an infrared camera, a finger vein pattern is corrected, and the same finger vein pattern as that at the time of registration to the finger vein authentication unit is automatically obtained. Consequently, the user-friendly finger vein authentication unit in which the fingertip placement part is formed in an almost flat shape to make a finger easily put and, simultaneously, authentication precision is high can be realized.
Embodiments of the present invention will be described below with reference to the drawings.
The touch sensor 5 provided for the fingertip placement part can accurately detect a finger contact part and a finger non-contact part and, when a finger is put, obtains data of the position and shape of the fingertip.
The infrared camera 6 obtains a vein pattern P of the finger 4 and a contour 9 of the finger as image data. The data of the two kinds is joined and detection portion end points of the finger 4 detected by the touch sensor 5 are set as A and A′. Lines A-B and A′-B′ are drawn in parallel to the contour 9 of the finger obtained in the image from the points A and A′, and image data on the inside of the lines and data detected by the touch sensor 5 is synthesized to obtain contact contour data 10. As shown in
The process will be described concretely. A specific area in the image of the entire finger 4 captured is set as a template generation area 11. At the time of generating a template by cutting the image in the template generation area 11, in the case where the finger 4 is put obliquely, how oblique the finger 4 is put is detected from the contact contour data 10, and a finger vein image is rotated on the image processing apparatus 200 so that the finger becomes almost perpendicular on the basis of the data. Next, by cutting the image in the temperate generation area 11, even when the finger 4 is put obliquely with respect to the finger placement position in the finger vein authentication unit 101, vein data in the same position as that when the finger 4 is put in the normal position can be obtained.
In the case where the finger placement position is deviated from the predetermined position in the axis direction of the finger, the fingertip portion is included in the finger contact contour data 10. Consequently, how much the finger placement position is deviated from the contact contour data 10 in the axis direction is detected, and the finger vein image is moved on the image processing apparatus 200 on the basis of the data. Subsequently, the image in the template generation area 11 is cut out, thereby enabling the vein data in the same position as that at the time of registration to be obtained even when the finger placement position is deviated in the finger axis direction. By correcting turn of the finger and the position in the finger axis direction in the finger contact contour data 10 as described above, even when the finger placement position is deviated slightly, the template for matching can be accurately generated.
A check is made on the data obtained by the touch sensor 5 in the beginning of registration and authentication. In the case where the fingertip is out of the touch sensor detection area 7 as shown in
Next, detection of turn of the finger will be described. The contour points of the finger by the touch sensor 5 are set as A and A′ as shown in
When the difference between the A-B distance and the A′-B′ distance exceeds a threshold value, it is determined that the finger turns, a guidance is output to put the finger correctly so that the user can put the finger in the correct position, and data is obtained again. By comparing the position data of the touch sensor 5 with contour data extracted from an image captured by the infrared camera 6, turn around the finger axis direction as a center can be detected.
As described above, by mounting the touch sensor on the fingertip side, the finger placement position, turn in the same plane using the optical axis of the camera as an axis, and turn around the finger axis direction as a center are detected. The vein data is corrected, and the guidance to put the finger properly is given to the user. Therefore, the high-precision and user-friendly finger vein authentication unit can be realized.
In a small-sized open-type finger vein authentication unit, an image pickup window W is set narrower than the finger. By completely close the image pickup window W with the finger, the influence of outside light is eliminated. In this case, the image pickup window W is small and only the part of an image acquisition area can be imaged, so that the finger contour line cannot be obtained in the image of the infrared camera 6. In this case, by mounting a touch sensor also on the finger base side, a turn of the finger can be detected without contour data.
As shown in
A portion in the finger to which the vein pattern in the image acquisition area 14 corresponds is determined from the data obtained as described above and, on the basis of the portion, matching with the collation template is performed. In such a manner, the high-precision finger vein authentication unit can be realized.
In the conventional technique, the portion in the finger to which the vein pattern obtained from the image pickup window cannot be known. Consequently, in the case where the finger is deviated or turns, authentication cannot be performed after matching the position of a vein pattern to be authenticated and the position of a vein pattern registered. There is the possibility that false acceptance such that a pattern of another person matches or false rejection such that the user is recognized as another person occurs, and the recognition rate deteriorates. However, when the portion in the finger to which the vein pattern corresponds can be determined as in the embodiment, authentication can be performed after matching the position of a vein pattern to be recognized with the position of a registered vein pattern. Therefore, deterioration in the authentication rate caused by deviation or turn of the finger can be suppressed.
When the force of pressing the finger is strong, the fingertip becomes flatter, the contact face with the touch sensor 5 increases, and data detected by the touch sensor 5 becomes different from that at the time of registration. On the contrary, when the force of pressing the finger is weak, the contact face with the touch sensor 5 becomes smaller, and data detected by the touch sensor 5 may differ from data at the time of registration. When data detected by the touch sensor 5 at the time of registration and that at the time of authentication differs, it may deteriorate the authentication rate.
To avoid such a case, as shown in
Also when a contact-type touch sensor 50 in which registration films and electrodes are disposed in an X-Y matrix is used in place of the touch sensor 5 of the static-electric type used for detecting the position and shape of the fingertip in the finger vein authentication units of the first to third embodiments, the position and shape of the fingertip can be detected in a manner similar to the touch sensor of the static-electric type.
As shown in
Number | Date | Country | Kind |
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2010-055293 | Mar 2010 | JP | national |