JP4200687B2 - Biometric authentication device and program for realizing the device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a personal authentication technique for identifying a person using individual differences in a vein image of a finger as biometric information, and more particularly to a technique for improving forgery resistance in the authentication process.
[0002]
[Prior art]
The personal authentication technology is used in situations where it is necessary to confirm the identity of the person, such as access control to restricted areas, automatic teller machines such as banks, and permission to connect to computer equipment systems. In particular, as a personal authentication technique based on biometric information, a method using a fingerprint, an iris, a vein on the back of the hand, a palm shape, a voiceprint, or the like is widely known. Japanese Patent Laid-Open No. 2001-184507 discloses a technique for capturing a blood vessel pattern image of near-infrared light that is transmitted to the living body after being irradiated and scattered in the living body, and performing personal authentication based on the image. Has been.
[0003]
Conventionally, in personal authentication, in many cases, the biometric information of a person to be authenticated is measured by a predetermined method, and the person is authenticated by confirming the coincidence with static information registered in advance. In the coincidence comparison with the static information, it is necessary to prevent impersonation caused by applying a duplicate artifact of a part of the person's elaborate living body to a measuring means for authentication. It is more desirable as a method for improving anti-counterfeiting to confirm whether the measurement process reflects the life activity of a person or the life activity of the person who should be authenticated as a method of monitoring impersonation.
[0004]
[Problems to be solved by the invention]
As a method for solving the above problem, Japanese Patent Application Laid-Open No. 11-45338 discloses a technique that enables authentication only with a living finger, not a counterfeit finger, by measuring myoelectric potential. In the case of using a detection means that comes into contact with a finger for detection of a human life activity, not limited to a sensor for measuring an electric potential, it is necessary to sufficiently consider sensory stimulation given to a measurement subject. Assuming outdoor installations that are cold or extremely hot, the local temperature of the finger rises and falls due to contact heat transfer, or the blood flow changes due to temperature-sensitive stimuli or unexpected stimuli for the subject. May affect measurement. In addition, the detection means that comes into contact with the finger has applications that should take into account psychological resistance to hygiene, such as entering and leaving a room used by a large number of people at a restaurant service store.
[0005]
In addition, even when adding a function to detect the life activity of the person to be authenticated to the authentication method for the purpose of ensuring higher reliability, it is normal to permit authentication under the compatibility conditions of both, so trust in the failure of the authentication device. From the standpoint of ensuring reliability, increasing the number of measurement devices may lead to a decrease in reliability and an increase in cost.
[0006]
[Means for Solving the Problems]
In view of the above problems, the present invention measures near-infrared light irradiating means on a living body and means for capturing a plurality of images of living body transmitted infrared light, and measures temporal changes in luminance values of the plurality of images by processing the captured image information. Determining whether the person to be authenticated is alive by means for performing detection, means for detecting venous vascular network information and pulse from the captured image, and means for detecting the pulse of the person to be authenticated based on the detected blood vessel information. Provides a means to do.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment of the present invention will be described below.
[0008]
FIG. 1 shows a configuration example of a personal authentication apparatus using a finger vein pattern. Irradiated infrared light 104 having a wavelength of 700 to 1000 nm is irradiated from the light source 101 driven by the illumination circuit 102 to the finger 107 through the infrared light transmitting filter 103 and the irradiation lens 105. The transmitted light 109 that has passed through the finger 107 and the vein 106 in the finger can be acquired by an image sensor 111 such as a charge coupled device (CCD) system by the light transmitted through the infrared light transmission filter 110.
[0009]
The image sensor 111 is subjected to exposure integration time, gamma correction control, and the like by the image sensor drive circuit 112. The readout output of the image sensor 111 is converted into a numerical gradation luminance value by the analog / digital conversion circuit 113 and input to the image arithmetic circuit 114. The image calculation circuit 114 performs finger contour extraction, vein network portion enhancement processing, and the like from the obtained image, and creates vein feature data 115 (a). A control circuit 116 composed of a microprocessor or the like takes in the output of the image arithmetic circuit 114. At the same time, the control circuit 116 reads the registration data 117 recorded in the recording unit 122 as necessary, and performs correlation calculation with the vein feature data 115 (a) to authenticate the person. The registration data 117 is feature data of the venous vascular network extracted from the finger image, similarly to the vein feature data 115 (a). In order to perform personal authentication, it is only necessary to have at least one registered image and at least one captured image.
[0010]
In addition to the authentication (verification) of the person, the pulse, which is a life activity, is detected from the acquired image from the image sensor 111. A plurality of temporally continuous images are acquired, and the sum or average value of pixel values (luminance values) in a specific area of the finger image extracted from the background is defined as luminance information data 115 (b). The luminance information data 115 (b) is input to the control circuit 116. The control circuit 116 performs autoregressive analysis on the time change of the input luminance information data 115 (b) and detects a pulse as a biological feature. It is determined whether or not blood is flowing through the imaging target by detecting the pulse, that is, whether or not the imaging target is a living body. The main absorption of near-infrared light in the living body is caused by hemoglobin hemoglobin. Since the luminance value change in the image acquired by the image sensor 111 reflects the quantitative change of blood in the imaged range, the luminance value change corresponds to the pulse.
[0011]
In addition to the identity authentication (verification) of the person, after confirming the life activity, an unlocking permission command is output to the key unlocking circuit 121, and the key opening / closing circuit 121 performs the unlocking operation. The audio circuit 118 drives the speaker 119, receives the audio data signal SND from the control circuit 116, and transmits a speech from the speaker 119. If necessary, the control circuit 116 can send a message to the subject and analyze the pulse fluctuation caused by the psychological sway given by the message.
[0012]
Next, the result of detecting the pulse using a plurality of images is shown. Using an infrared light with a wavelength of 810 nm as a light source, a contour portion of a finger was detected by image processing from an image acquired at 30 frames / second using a CCD imaging device, and a time course of luminance values inside the finger was plotted. The result is shown by 201 in FIG. The horizontal axis represents time, and the vertical axis represents normalized luminance values.
[0013]
The image acquired by measurement is a gray scale of 256 gradations, the luminance value is normalized by a value from 0 to 1, and the average value of the normalized luminance value in the region from the first finger joint to the tip is shown. The change in the normalized luminance value corresponded to a pulse with a period of about 1 second. Since the change in the normalized luminance value returns from the artery inside the finger to the vein via the capillary network, in many cases, the change in the luminance value tends to appear at the fingertip. Therefore, it is possible to detect the pulse with high accuracy and efficiency by obtaining the temporal change of the calculation result such as the above average value so as to include at least the change of the luminance value of the tip portion from the first joint of the finger.
[0014]
In the pulse detection described above, the security strength can be changed by changing the measurement time. In applications where high security is required even if the quick response required for authentication is limited, the measurement object takes a few seconds and the waveform shown in FIG. Can be estimated with high accuracy. As an example, a plurality of extreme values 201 of normalized luminance value changes can be captured, and the average of those adjacent time intervals Th can be used as the pulse period.
[0015]
On the other hand, when it is necessary to focus on quick response, the pulse measurement time is shortened to about several hundred milliseconds, and even if one period is not observed in the waveform of FIG. It is possible to determine that the person to be authenticated is alive by detecting that there is (inclination in the plot of FIG. 2).
[0016]
FIG. 3 shows a flowchart of the authentication procedure using the method described above. First, when the illumination circuit 102 is activated, the light source 101 is turned on, and the image sensor 111, the image sensor drive circuit 112, the analog / digital conversion circuit 113, and the image calculation circuit 114 are interlocked and a finger is inserted into the space under illumination. , And the finger position detection 301 is performed by extracting the center and tip position of the finger from the image. If it is not in the permissible visual field according to the determination branch 302 regarding whether it is in the permissible visual field suitable for measurement, the finger position detection 301 is repeated. If necessary, a sound explaining how to hold the finger correctly can be sent to the person to be measured via the speaker 119 of the audio circuit 118 to prompt appropriate finger positioning. The above flow is performed by reading and executing a program recorded in the system by the control circuit 116.
[0017]
When the finger is placed within the predetermined allowable visual field, the personal authentication calculation 303 is performed using the acquired image. The calculation is performed by the image calculation circuit 114 using a vein network image, for example, in a method disclosed in Japanese Patent Laid-Open No. 2001-184507. If it is not determined to match in the determination branch 304 of the personal authentication, the finger position detection 301 is repeated again.
[0018]
Next, a plurality of images are typically acquired at 30 frames / second, and the living body detection measurement 305 is performed by pulse measurement that measures the temporal change in the average value of the normalized luminance value of the fingertip portion described above. When it is confirmed that the subject is a human living body by pulse measurement, the security lock unlocking 307 is performed by the branch 306 of the living body detection determination.
[0019]
Next, FIG. 4 shows an example in which a living body detection determination including a question and answer voice is performed. After determining the identity in the identity authentication decision branch 304 in the same operation as in FIG. As for audio output, the audio of question and answer is output to the speaker 119 via the audio circuit 118 by the output of the control circuit 116. The message can, for example, generate irregular and multiple contents that are supposed to cause psychological upset for those who intend to impersonate. When the person to be authenticated is a living body, the fluctuation that the pulse cycle is gradually shortened is obtained from the psychological fluctuation induced by this. From the interval measurement of the pulse cycle Th in FIG. 2, the measurement branch 306 can accumulate the measurement value of the pulse cycle Th in time series, and the decision branch 306 can be performed in the aspect of the temporal variation.
[0020]
In addition to the method of presenting audio, the output of the lighting circuit 102 may be rapidly increased in a pulse manner to control to emit a flash from the light source 101, or to display images that have a psychological effect on the display means. A similar psychological effect can be induced.
In the flow disclosed in FIG. 3 and FIG. 4 described above, living body detection may be performed before authentication.
[0021]
Furthermore, it is possible to determine the body condition of the person to be authenticated based on the pulse information such as the pulse period Th. It is also possible to detect tachycardia, arrhythmia, etc. by detecting the pulse period. When tachycardia or arrhythmia is observed, the control circuit 121 can be set not to release the security lock, or can send emergency support information to the outside via the communication means 120. In addition, a message such as “Are you feeling bad?” Can be generated from the speaker 119. At the time of authentication at the entrance of a condominium or the like, it is possible to issue an alarm so as to call the manager that the person to be authenticated may be psychologically upset.
[0022]
Next, FIG. 5 shows an embodiment in which a plurality of authentication systems are linked. For example, the authentication device 503 of the present invention is used as the first device for opening and closing the main entrance 501 of the daily attendance route. Next, after passing through a path 505 having a long distance as long as a sufficient amount of physical exercise load is expected as a walking section or a step 506 having a sufficient height difference, another authentication of the present invention is performed for the door 502 to the entrance management area 508. The device 504 is used as the second device. The authentication device 503 and the authentication device 504 are connected to each other via a communication path 507. The person to be authenticated who is permitted by the authentication device 503 is given the authority to pass the door 502 after authenticating the door 502 only by a communication using the communication means 120 of the authentication device 503. Automatic unlocking by the authentication device 504 is not permitted unless the route 505 or the rising staircase 506 is moved within a predetermined time to reach the authentication device 504. By restricting the travel time from the authentication device 503 to the authentication device 504, an exercise load is imposed on the person to be authenticated, so the pulse rate rises and the pulse cycle becomes shorter. If the subject's psychosomatic state is normal, the change in the pulse cycle is considered to fall within a predetermined range for each individual difference, and whether the acquired pulse information falls within the range stored in advance. When the determination is made and the deviation is made, it can be estimated that an unusual event has occurred, and the access permission procedure for the access management area 508 can be changed. Further, if the pulse period measurement data is accumulated and displayed in the recording means 122 together with the daily individual authentication results, a measurement system that can be correlated with health can be constructed.
While confirming that the person to be authenticated is a living body and performing personal authentication to enhance security, a log function of health and psychological state can be easily added to the system.
[0023]
【The invention's effect】
As described above, the present invention can detect a pulse which is “biological” information without contact, and can acquire a personal authentication and “biological” information, thereby adding a function with high reliability. It becomes. Furthermore, by performing authentication based on “biological” information, it is possible to realize high security for enhancing anti-counterfeiting and at the same time add a health management function to the system.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an apparatus configuration according to an embodiment of the present invention.
FIG. 2 is a diagram showing a detection result of a pulse period based on a finger image.
FIG. 3 is a flowchart of an authentication procedure.
FIG. 4 is a flowchart of an authentication procedure for presenting a stimulus to a person to be authenticated.
FIG. 5 is a configuration diagram of a system that authenticates by giving an exercise load.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Light source, 102 ... Illumination circuit, 103, 110 ... Infrared light transmission filter, 104 ... Irradiation infrared light, 105 ... Irradiation lens, 107 ... Finger, 106 ... Vein, 109 ... Transmission light, 111 ... Imaging element, 112 DESCRIPTION OF SYMBOLS ... Image sensor drive circuit, 113 ... Analog / digital conversion circuit, 114 ... Image operation circuit, 115 (a) ... Vein feature data, 115 (b) ... Luminance value information data, 116 ... Control circuit, 117 ... Registration data, 118 DESCRIPTION OF SYMBOLS ... Audio circuit, 119 ... Speaker, 120 ... Communication means, 121 ... Key opening / closing circuit, 122 ... Recording means, SND ... Audio data signal, 201 ... Extreme value 201 of normalized luminance value change, Th ... Pulse cycle, 301 ... Finger Position detection, 302 ... branch in permissible visual field, 303 ... identity authentication calculation, 304 ... identity authentication decision branch, 305 ... biometric detection measurement, 306 ... biopsy Determination of branching, 307 ... unlocking, 501 ... main gate entrance, 502 ... door 503 ... authentication unit, 505 ... path, 506 ... rising staircase, 508 ... entrance controlled area.

Claims (6)

Light source means for generating irradiation light, which is infrared light, on a predetermined part of a finger of an authenticator who is a non-contact authentication target with the apparatus ;
The imaging means of the irradiation light that has passed through a predetermined part of the finger of the authenticator who is the authentication target , and a control means,
The control means includes
Acquiring a plurality of images to be authenticated continuously in time using the imaging means;
Detecting temporal changes in blood vessel images of the plurality of captured images;
Extracting a pulse period from the detected temporal change, and determining the state of the authenticator based on the temporal change of the pulse period;
A biometric authentication device that controls to execute a step of performing authentication using the photographed image and pre-registered authentication data before the step of determining the state of the authenticator.   The biometric authentication device according to claim 1, wherein the determining step makes an abnormality when the time change of the pulse period exceeds a predetermined value. Recording means for recording and storing the extracted pulse cycle data;
The biometric authentication device according to claim 1, further comprising display means for displaying the accumulated pulse cycle data.   In the determining step, it is determined whether or not the time-varying pulse period falls within the range of the authenticator's pulse period in advance. The biometric authentication device according to any one of claims 1 to 3. Connected to a stimulus presentation device for presenting a stimulus to the authenticator,
The determining step includes determining whether or not the state of the authenticator is abnormal by using a time change of the pulse cycle when a stimulus is presented to the authenticator from the stimulus presentation device. The biometric authentication apparatus according to claim 1, wherein the biometric authentication apparatus is characterized in that Connected to the locking means,
The biometric authentication device according to any one of claims 1 to 5, wherein release of the key of the locking means is controlled based on the determination result of the state of the authenticator.

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