JP2004070943A - Finger authentication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformize photographing conditions for each authentication, the identification of which can not be guaranteed in the conventional technology to a low cost in an operation system with no burden to a user. <P>SOLUTION: An authentication device is provided with a guiding means such as a design or molding which makes the user to recall a part at which a finger should be placed or approached, wherein a contact means such as a button switch is provided at a part where a fingertip should be placed and an optical opening part is provided at a part where an part to be imaged for authentication, a light source for emitting near-infrared light at the part to be imaged, and an imaging means for photographing an image made by the near-infrared light that transmits the part to be imaged. In addition, for the contact means, a starting means for starting authentication when a contact is connected and a shielding means for interrupting outdoor daylight intruding into the imaging means are provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an authentication device for identifying an individual using biological information, and more particularly to a finger authentication device based on a blood vessel pattern of a finger.
[0002]
[Prior art]
Expectations for personal authentication technology are increasing for the purpose of safe management of property and information. In particular, biometric authentication technology that uses a part of the human body as a key has attracted attention because there is less risk of unauthorized use due to loss or theft as compared with conventional management using a password or key. As biometric authentication techniques, various methods using fingerprints, blood vessels patterns of the face and iris, hands and fingers, and the like have been studied. Among them, the authentication method using the finger blood vessel pattern does not remind the crime like a fingerprint or irradiates the eye directly with light like an iris, so there is little psychological resistance, There is an advantage that forgery is difficult because the internal features are read instead of the surface.
Specifically, the authentication based on the finger blood vessel pattern is realized as follows. First, a light source that emits near-infrared light is prepared, and a camera is installed facing the camera so as to capture the light. The camera is equipped with an optical filter that passes only wavelengths in the near infrared region. At the time of authentication, a finger is inserted between the camera and the light source, and an image of the finger at that time is taken. The components in the blood absorb the near-infrared light well, so that the blood vessel portion appears dark without transmitting the light. The image of the blood vessel pattern captured in this manner is compared with the registered image of the blood vessel pattern, and personal authentication is performed.
[0003]
[Problems to be solved by the invention]
In order to correctly detect a match of a blood vessel pattern, images must be acquired under the same imaging conditions at the time of registration and at the time of authentication. For example, if the finger is rotated, the obtained blood vessel pattern is also greatly different. Movement and rotation that does not change the surface of the finger being photographed can be corrected by simple image processing, but rotation that reverses the back of the finger can be corrected by image processing because there is an unknown part. Can not. In this regard, for example, as an authentication device using a blood vessel pattern of the back of the hand, it is essential to hold the guide bar with four fingers, so that the position of the back of the hand to be imaged is corrected so as to be constant for each individual. Attempts have been made. However, in the case of a finger blood vessel, when tension is applied such as grasping, the blood vessel may be compressed and the blood vessel pattern may be lost as described above. In addition, a method of providing a guide rail and placing a finger at a specific position is also conceivable, but it is necessary to learn a correct placement method, and it cannot be said that anyone can use it easily.
The obtained blood vessel pattern also changes depending on the posture of the finger when inserted into the authentication device. For example, in a finger that is excessively stretched by applying force, blood vessels may be partially compressed due to pressure on blood vessels due to tension of the epidermis. Further, even if the external light that illuminates the entire authentication device changes, the brightness and contrast of the obtained image change, which affects the authentication accuracy. This is because normal sunlight and illumination light also include light in the near-infrared region, and the light wraps around and affects the blood vessel pattern.
An object of the present invention is to make shooting conditions for each authentication uniform at low cost in an operation system that does not burden the user, which could not be guaranteed with the conventional technology.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, in the finger authentication device of the present invention, a guide portion for determining the position of the finger, a switch portion which is turned on / off by a tip portion of the finger, and a place where the finger is arranged are sandwiched. The present invention provides a finger authentication device including: a light source configured to irradiate transmitted light transmitted through a finger; an imaging unit; and an authentication unit that performs an authentication operation of an image captured by the imaging unit when the switch unit is turned on. .
Further, a guide portion for positioning the finger in a bent posture, a light source provided so as to sandwich the place where the finger is arranged, and a light source for irradiating transmitted light passing through the finger, an imaging unit, and an image captured by the imaging unit A finger authentication device having an authentication unit for performing the authentication operation of (1).
As a result, the position of the finger can be naturally guided to a specific position, and furthermore, since the blood vessels are not compressed, stable collation can be performed on the captured image, and as a result, authentication can be performed. Accuracy can be significantly improved.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, one embodiment of the present invention will be described in detail.
FIG. 1 is a schematic diagram of an authentication device 100 for implementing the present invention. The main body is roughly divided into two parts, a light source unit 102 and an imaging unit 104. A space is provided between the light source unit and the imaging unit, and a finger is inserted into the space at the time of authentication. The light source unit covers the upper part of the space where the finger is inserted like a roof, and plays a role of blocking light so that illumination from the ceiling or the like does not directly enter the imaging unit. Here, an example in which the side wall of the space does not exist is shown. However, the side wall may be provided to prevent external light from entering from the side. In this case, in order to improve the authentication accuracy, it is preferable to apply a paint such as an antireflection agent for preventing irregular reflection of near-infrared light to the side wall, or to configure the side wall with an antireflection material. In the light source unit, a light source 106 that emits near-infrared light with a wavelength of about 810 nanometers is installed so as to emit light toward the camera 114 side of the imaging unit. By inserting a finger between the light source and the camera, near-infrared light is transmitted through the finger, and an image of the finger is obtained by photographing the near-infrared light with the camera. The guide groove 112 presents the correct insertion position and orientation of the finger in a form that is easy to intuitively understand. When the finger is placed in accordance with the guide groove, the button switch 108 is located at the portion corresponding to the fingertip, and the opening 110 is located at the portion before and after the first and second joints of the finger. The opening 110 is covered with a transparent glass or acrylic plate to prevent light from passing through and prevent foreign matter from entering the authentication device. Since the camera 114 needs an optical filter that transmits only light in the near-infrared wavelength region, the two functions are combined into one plate by using an optical filter plate instead of the glass or acrylic plate. You can also.
[0006]
Authentication starts when the user presses the button switch 108. The operation itself of pressing the button is an act that many people frequently perform in their daily lives, and can be naturally blended even in a series of operation systems related to authentication. The position of the fingertip when the finger is naturally placed to press the button can be almost constant or at least easily reproduced by a person. When the position of the fingertip is determined, the finger is guided by the guide groove 112 and the orientation of the finger as a whole is inevitably determined. Is determined similarly. In addition, when the button is pressed, the direction in which the joint bends is determined, so that the finger pad naturally naturally faces the vertical direction with respect to the button concave direction. Therefore, the face of the finger to be photographed does not change due to the rotation of the finger's waist, such as when the back of the finger or the abdomen is photographed.
Further, when the button is pressed, the finger naturally bends and does not unnecessarily apply tension to the epidermis other than at the fingertip, so that the pattern is less likely to be lost due to pressure on the blood vessel. In addition, in a naturally bent state, a finger does not touch the glass surface of the opening 110, and blood vessels are not pressed or stained by contact with the glass surface.
[0007]
Furthermore, if the position of the finger can be made substantially constant by these, the area of the opening can be made small enough to cover the finger and avoid the incidence of external light, thereby preventing the change in brightness and contrast due to external light. it can. Conventionally, since the finger position cannot be fixed, it has been necessary to search for a part having the same pattern as that at the time of registration from the image of the finger captured over a wide area with a large opening. For this reason, high-cost arithmetic hardware is required for searching for the pattern, and the large aperture makes it easy for external light to enter and is vulnerable to noise. However, the provision of the button solves this problem.
[0008]
In addition, in the conventional authentication technique based on the finger blood vessel pattern, since a user-initiated authentication start request unit using a switch or the like is not provided, when the authentication process is started is determined by the authentication device, which gives confusion to the user. There was also danger. As described above, the installation of the button switch is very effective as a means for improving operability by itself. Note that the guide groove 112 is not limited to the illustrated shape. Also, the finger does not necessarily need to contact the guide groove. For example, a wire-shaped guide or a simple finger-shaped guide may be used. In short, it is only necessary that the finger can be uniquely guided.
[0009]
FIG. 11 is a three-view drawing showing another embodiment of the invention shown in FIG. 1 is different from that of FIG. As shown in FIG. 11, the lower part of the space provided with the opening has a different distance in the height direction of the upper part of the space between the near side and the far side where the finger is inserted. The light source 106 corresponding to the upper part of the space and the surface of the opening 110 corresponding to the lower part of the space are formed so as to draw an arc. Here, between the upper arc and the lower arc, the former has a larger curvature. With this configuration, when a finger is inserted, for example, even when the belly of the finger is directed sideways or obliquely, the arc is formed narrower and deeper into the space. As it goes, it is naturally corrected so that the belly of the finger faces downward. Further, the near-infrared light from the light source 106 is evenly radiated, and the distance from the camera 114 to the opening 110 becomes uniform, so that more accurate authentication can be performed.
[0010]
FIG. 2 is an example of a schematic block diagram of a system configuration for realizing the present invention. Reference numeral 200 denotes a hand, which is inserted between the light source 106 and the camera 114 to acquire an image signal of a blood vessel pattern when the switch 108 is pressed. The image signal of the camera 114 is converted into digital data by the image input device 202 and stored in the memory 210 via the input / output interface 206 of the computer 204. The switch 108 is also connected via an input / output interface, and an on / off state is stored in the memory 210 or an interrupt signal is generated for the CPU 208 as soon as the switch is turned on. When the CPU 208 confirms that the state of the switch 108 has been turned on, or detects an interrupt signal that has been turned on, the CPU 208 starts and executes a software program for performing authentication. Based on the processing result of the program, various kinds of control such as displaying the result on the display 212 and sending an appropriate signal to the control target 216 to open and close the door are performed. The keyboard 214 is used to input, for example, auxiliary information related to authentication such as a personal identification number.
[0011]
FIG. 12 is an assembled perspective view of the finger authentication device shown in FIG. 11 and FIG.
FIG. 3 shows an example of the software flow executed by the hardware, in particular, the CPU 208. In the process 300, an initial value is assigned to a temporary variable required for initializing the entire hardware or executing a program. When the transition to the initial state is completed, the program enters an idling state and waits for the switch 108 to be turned on (302). When the switch is turned on, the image of the finger taken by the camera 114 is taken into the memory 210 (304). Image processing is performed on the captured image data to extract the characteristics of the blood vessel pattern (306), and a collation search is performed for any pattern that matches the already registered pattern (308). If there is a matching pattern (310), a signal indicating that a proper access right has been authenticated to a control target such as a device or a software program that requires authentication, or a signal for identifying an authenticated individual. The data is transmitted (312). Then, it waits again until the next switch is turned on. The power on / off of the hardware can be used also as the button switch 108. The power is turned on by the button switch 108, and the software flow is sequentially executed up to a process 310 excluding the process 302, and up to 312 if the authentication is successful, and then the power is turned off again. As a result, power consumption during standby can be reduced. Similarly, a mode in which only ON / OFF of the light source is controlled is also conceivable. The light source is turned on when the button switch 108 is turned on, and turned off when the authentication process is completed. Depending on the configuration, turning on and off the power of the entire system may take a long time to start. Therefore, when importance is placed on convenience, only power saving of the light source portion is performed. The turning on and off of the light source may be physically linked with the switch 108, or a switch circuit such as a relay or a transistor may be connected to the input / output interface 206 of the computer 204 to electronically control the switch of the light source. . In the method using such an electronic control circuit, the circuit can be diverted to a power control method by switching on / off of a switch at high speed, that is, so-called PWM (Pulse Width Modulation) control, and the brightness of the light source is controlled stepwise. It becomes possible to do. Since the thickness of the finger varies from person to person, some people may not be able to see the blood vessel pattern well with a uniform amount of light.However, it is necessary to continuously image while controlling the light amount until the blood vessel pattern appears best. Thus, the accuracy of the authentication can be improved. Further, if a sensor for measuring the thickness of the finger is added, the relationship between the thickness of the finger and the optimal light amount is calculated and stored in advance, so that an optimal blood vessel pattern can be obtained with a smaller number of images.
[0012]
FIG. 9 shows a flowchart of a process for controlling the light amount according to the thickness of the finger. In the process 900, an initial value is assigned to a temporary variable required for initializing the entire hardware or executing a program. When the transition to the initial state is completed, the program enters an idling state and waits for the switch 108 to be turned on (step 902). When the switch is turned on, first, the thickness of the finger is measured by a sensor or the like, and the initial light intensity of the light source 106 is set using a reference table in which a set of the thickness and the initial light intensity value is registered in advance. Subsequently, an image of the finger is photographed by the camera 114 and taken into the memory 210 (step 906). The captured image data is subjected to a blood vessel pattern feature extraction process 908 to check whether a blood vessel pattern is present (step 912). If not, the light amount is changed (step 910), and the image is captured again from the camera. In the direction of changing the light amount, when the image area of the finger portion is entirely bright, the light amount is strongly predicted to tend to be saturated, so that the light amount is decreased. Since the S / N ratio of the transmitted light is expected to decrease due to weakness, the operation is performed in a direction to increase the light amount. The overall brightness of the finger area can be easily measured from the average value of the constituent pixels. Then, a collation search is performed for a pattern that matches the pattern that has already been registered (step 914). If there is a pattern that matches (step 916), the control target such as a device or a software program requiring authentication is determined. In response to this, a signal indicating that the valid access right has been authenticated or identification data of the authenticated individual is transmitted (step 918). Then, it waits again until the next switch is turned on.
[0013]
FIG. 10 shows an example of a method for measuring the thickness of a finger without using a sensor. FIG. 10A shows a surface of the light source projected by a camera facing the light source. A central light source 106 is surrounded by a surface 1000 coated with a paint that suppresses or absorbs near infrared rays. On the surface, a bar-shaped marking 1002 made of a material that easily reflects near-infrared light is provided. When the light source shines, there is a sharp contrast between 1000 and 1002. When photographing with a camera, the luminance difference between the two becomes very large. As shown in FIG. 10-B, when the finger 200 is held over a light source, the area where the marking is hidden changes according to the thickness of the finger. In the image area of the finger portion, the brightness difference between the blood vessel and the other portion does not become extremely large. Therefore, when the finger covers the marking portion, the brightness difference existing in the marking portion disappears. That is, the position coordinates of where the large difference in the luminance is interrupted give the outer position of the finger, which can be obtained by a very simple difference process. To get the thickness of the finger, it is only necessary to have at least two markings, but since the thickness of the finger is not uniform due to nodes etc., using four markings as shown in the figure, More accurate thickness can be determined. Further, if four points are used, even when the finger is inserted with a slight inclination, the inclination angle can be obtained.
[0014]
FIG. 4 is an enlarged view of a part where a finger is inserted in a side view of the embodiment of the authentication apparatus. There is a near-infrared light source 106 at the top, an optical aperture 110 at the bottom, and a camera 114 below it. Reference numeral 400 denotes a touch portion of the button switch, and when the finger is directly touched and pressed, the contact switch 108 is turned on. Reference numeral 108 denotes a push switch with a spring, which is in a conductive state only while it is being pressed, and when released, automatically returns to an initial position by a spring and is in an insulated state. As shown in the figure, between the opening 110 and the button 400, if the finger is designed to draw an arc so as to bend naturally, the finger will bend without fail. It is even less likely to occur. In addition, by installing the glass plate forming the opening 110 below or by providing the finger rest 402, the base of the finger floats up with respect to the opening 110, so that the opening 110 and the finger Vascular compression due to contact can be more reliably prevented.
[0015]
FIG. 13 shows another embodiment of an enlarged view of a portion where a finger is inserted when viewed from the side. The position of the button switch 1301 is different from that of FIG. In the button switch 1301 of FIG. 13, unlike the button switch 400 of FIG. 4, the operation of the contact switch 108 is performed by an operation of pushing a finger into the back. In this case, pressing the button switch 1301 results in a more unnatural operation than the button switch 400 in FIG. 4. For example, by using the button switch 1301 as a switch unit that does not involve a click operation such as a touch sensor, it is more comfortable. An operational feeling can be obtained. FIG. 5 is a diagram showing the button 400 in a further enlarged manner. The surface to be touched by the finger is shaped such as a dent so that the finger just fits, and the position of the fingertip is more surely brought to the same position every time. You can not. Also, as shown in FIG. 4, the height of the button is limited to just fit the abdomen of the fingertip, and a space is provided at the top to extend the nail for a long time or to use a false nail. Even those who do can press the button without difficulty. FIG. 6 is an enlarged view of the finger rest 402 provided at the base of the finger. Although it may be a simple plate-like projection, as shown in the figure, by processing the semi-circle slightly larger than the thickness of the finger, lateral displacement when the finger is placed can be naturally prevented. In this case, the finger rest 402 is a variation of the above-described guide groove 112 rather than an independent means, and also serves as a guide as to where to place a finger.
[0016]
FIG. 7 is an example of another variation of the authentication device 100. In the example of FIG. 1, the light source unit 102 is provided in a roof-like shape for light shielding from ceiling lighting or the like, but for the user, on the contrary, a feeling of psychological anxiety of inserting a finger into the shielded space is provided. May be fueled. Therefore, as shown in FIG. 7, by disposing the light source obliquely above the finger, it is possible to eliminate a cover that completely hides the finger from the user's view. In the example shown in the figure, diagonal roof-type light sources are provided on both sides of the opening, and the light sources 106 are arranged. The light sources are provided at two places on both sides because if the light source is located at one place, there is a possibility that the transmitted light of the finger will be deviated and become a spot, and a correct blood vessel pattern may not be obtained.
[0017]
FIG. 8 is an example of another optical system arrangement of the authentication device 100. Light source 800 provides a reflective light source to transmissive light source 106. These two light sources can be turned on / off in any combination under the control of the computer 204. For example, visible light may be generated by the reflection light source 800, and the surface of the finger may be imaged by the camera 114. In the above embodiment, the optical filter transmits only the near-infrared region. However, here, a variable or switchable optical filter 802 can be provided so that the optical filter can be switched to pass visible light as necessary. And This makes it possible to image a biometric feature such as a fingerprint pattern on the finger surface, and simultaneously perform authentication using the biometric feature on the finger surface and the blood vessel pattern, thereby improving the authentication accuracy.
[0018]
In the above, the advantage brought about by the use of the button switch in the authentication device has been described. However, the operation of pressing the button means the contact with the device, and is not without the possibility of causing a sense of hygiene resistance. This can be mitigated by using an antibacterial material generally used recently for the device housing and the button. In particular, even if the characters "antibacterial" can be printed on the housing, the psychological effect is large. In the device configuration of the present invention, the sensor unit for acquiring the blood vessel pattern does not need to appear on the housing surface, and antibacterial processing on the device surface is very easy. Biometric authentication methods that require the sensor to directly touch the living body, such as fingerprints, often have difficulty in making the sensor antibacterial, but there is no problem with the present invention.
[0019]
In the above embodiment, a mechanical push switch is used as an example of a button switch. However, a switch that conducts electricity by touching, for example, an electrostatic switch may be used instead of the switches 400 and 108. Alternatively, using a combination of a light source and an optical sensor, a configuration may be adopted in which a fingertip comes to a predetermined position and a switch is turned on when light is blocked. In this case, similarly, various sensors such as a human sensor can be used.
[0020]
FIG. 14 shows a finger authentication device including a numeric keypad. By using the numeric keypad 1401, even in the event that the authentication by the finger fails, the authentication can be performed by using a password registered in advance. Further, by combining the authentication with the finger and the authentication with the personal identification number, more reliable authentication can be performed. Furthermore, depending on whether authentication is performed with a finger or authentication using a personal identification number, applications such as changing the operation after authentication can be performed.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the position of a finger | toe is guided naturally to a specific position, a stable collation can be performed to a picked-up image, without having to perform alignment or rotation correction, Since there is no missing blood vessel pattern, the accuracy of authentication can be improved.
[Brief description of the drawings]
FIG. 1 shows an example of an apparatus configuration for realizing the present invention.
FIG. 2 is an example of an apparatus system configuration for realizing the present invention.
FIG. 3 shows an example of a software flow for realizing the present invention.
FIG. 4 is an example of a cross-sectional view of a finger insertion portion of the device.
FIG. 5 shows an example of the shape of a button switch.
FIG. 6 shows an example of the shape of a finger rest.
FIG. 7 is another example of a device configuration for realizing the present invention.
FIG. 8 shows an example of an optical system configuration for realizing the present invention.
FIG. 9 is an example of a software flow for performing light quantity control according to the present invention.
FIG. 10 is an example of a configuration for measuring the thickness of a finger according to the present invention.
FIG. 11 is a three-sided view of a finger authentication device that realizes the present invention.
FIG. 12 is an assembled perspective view of a finger authentication device that realizes the present invention.
FIG. 13 is a second embodiment of a cross-sectional view of a finger insertion portion of the device.
FIG. 14 is an example of a finger authentication device including a numeric keypad.
[Explanation of symbols]
Reference Signs List 100 authentication device housing, 102 authentication device light source unit, 104 authentication device imaging unit, 106 near infrared light source, 108 button switch, 110 optical opening unit, 112 guide groove, 114 camera, 200 Hand, 202: image input device, 204: computer, 206: input / output interface, 208: central processing unit, 210: memory, 212: display device, 214: keyboard, 216: control target.

Claims (13)

A guide part for determining the position of the finger,
A switch unit that is turned on and off by the tip of the finger,
A light source that is provided so as to sandwich the place where the finger is arranged, and irradiates transmitted light that passes through the finger, and an imaging unit,
An authentication unit configured to perform an authentication operation of an image captured by the imaging unit when the switch unit is turned on. A guide portion for positioning the finger in a bent position,
A light source that is provided so as to sandwich the place where the finger is arranged, and irradiates transmitted light that passes through the finger, and an imaging unit,
An authentication unit that performs an authentication operation of an image captured by the imaging unit. 3. The finger authentication apparatus according to claim 2, wherein the guide has a rounded shape that draws an arc. The said guide part is provided with the said light source in the upper part, and the optical opening in the lower part, The curvature of the arc of this light source is formed larger than the curvature of the arc of this opening. Finger authentication device. The distance between the upper part and the lower part of the guide part in the height direction is formed so that the distance of the part corresponding to the base of the finger is larger than the distance of the part corresponding to the tip of the finger. 3. The finger authentication device according to 1 or 2. The finger authentication device according to claim 1, wherein a shape of a portion of the switch unit touched by the finger is formed by forming a recess indicating a position of a fingertip. The finger authentication device according to claim 1, wherein the guide has a projection-shaped structure provided at a lower portion thereof to prevent the opening from coming into contact with a finger. The said guide part is provided with the optical opening part in the lower part, The said opening part has the shape and the area which can be concealed with the finger | toe from external light, such as sunlight, The Claim 1 or 2 characterized by the above-mentioned. Finger authentication device. The finger authentication device according to claim 1, wherein the finger authentication device includes a measurement unit that measures a thickness of the finger, and controls a light amount of the light source based on a measurement result by the measurement unit. apparatus. 9. The finger authentication device according to claim 8, wherein the measurement unit analyzes an output image from the imaging unit and measures the thickness of the finger. The said guide part is provided with the optical opening part in the lower part, The coating material of an anti-reflective material is apply | coated to the surface partial area | region of the said guide part other than this opening part. Finger authentication device. A guide part for determining the position of the finger,
A switch unit that is turned on and off by the tip of the finger,
A light source that irradiates transmitted light passing through the finger and a reflection light source that irradiates reflected light that reflects the finger, and an imaging unit, which are provided so as to sandwich the place where the finger is arranged,
An authentication unit configured to perform an authentication operation of an image captured by the imaging unit when the switch unit is turned on. 13. The finger authentication device according to claim 12, wherein the imaging unit includes an optical filter, and when switching between the transmission light source and the reflection light source, also switches a transmission wavelength range of the optical filter.

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