JP4567479B2 - Biological information measuring device and biological information measuring method - Google Patents

Description

  The present invention relates to a biometric information detection technique including fingerprint recognition for ensuring security and preventing information leakage.

  Personal authentication systems that apply fingertip fingerprint pattern recognition are relatively inexpensive and easy for the user to operate. Therefore, door unlocking systems, computer system terminals and mobile phones for the purpose of security and leakage prevention It is widely used for user authentication of personal digital assistants (PDAs).

  However, since it is the principle of recognizing a two-dimensional fingerprint pattern using an optical image sensor or a semiconductor sensor, it is possible to deceive personal authentication by using a counterfeit product obtained by copying the fingerprint pattern by some method such as resin. It has been pointed out that it is possible and cannot completely eliminate fraudulent acts.

  In order to solve the above problem, a countermeasure for recognizing a plurality of fingerprint patterns as shown in Patent Document 1 and a countermeasure for detecting blood using an optical sensor as shown in Patent Document 2 have been devised. The former can be fraudulent by using a plurality of pattern imitations, and the latter is a computer system that performs sufficiently high-speed digital signal processing, a digital-analog converter (DAC), an LED, etc. It is also possible to synthesize deceptive signals by combining light sources, and it is difficult to completely eliminate fraud.

In addition, a personal authentication system that recognizes a venous blood vessel pattern of a palm of a living body using an infrared sensor has been put into practical use. However, in principle, it is difficult to reduce the size of the system, and a portable small terminal (PDA) or It is almost impossible to mount on mobile phones and wristwatch-type electronic devices.
JP 2003-281508 A JP 07-308308 A

  As described above, the conventional personal authentication system applying fingerprint pattern recognition can deceive personal authentication, and cannot completely eliminate fraudulent acts and is difficult to miniaturize. Have. Therefore, the present invention can eliminate the imitation product that is not a living body that duplicates the fingerprint and the deception means by synthesizing the optical signal while using the fingerprint detection sensor, and can improve the accuracy of the authenticity determination and ensure high security. It aims at providing a biological information measuring device.

  In order to solve the above problems, the biological information measuring device and the biological information measuring method of the present invention detect a signal waveform corresponding to the flow velocity of blood flowing in a blood vessel using an ultrasonic sensor, and detect the signal waveform detected. When it is determined whether or not to authenticate the measurement target as a living body based on the processing results such as blood flow velocity, pulse rate, and signal waveform feature extraction obtained by the processing, and when it is determined that it is a living body (human body) The personal authentication process is performed.

  Although it is a low-priced and small device using a fingerprint sensor, it is possible to eliminate imitations by duplicating fingerprints and illegal acts by deceptive means for synthesizing optical signals, thereby ensuring high security. Since the device is small and can be realized at low cost, it can be easily mounted on a so-called wearable terminal device such as a portable small terminal (PDA), a mobile phone, and a wristwatch type electronic device. In addition, it is technically difficult to synthesize reflected ultrasound with an appropriate spectrum that mimics Doppler shift associated with blood flow, corresponding to incident ultrasound with a frequency of 10 MHz or higher, and is effective in eliminating fraud. .

(Embodiment 1)
First, the structure of an Example is demonstrated based on drawing. FIG. 1 is a block diagram showing the configuration of the biological information measuring apparatus of the present invention. 2 and 3 show a blood flow velocity sensor used in the present invention. 2 shows an example using an optical fingerprint reading sensor 9 as a fingerprint sensor, and FIG. 3 shows an example using a semiconductor fingerprint reading sensor 11. FIG. 4 is a schematic diagram showing an outline of the principle of ultrasonic Doppler signal measurement.

The blood flow velocity sensor 10 is a combination of two pairs of ultrasonic sensors, that is, an ultrasonic sensor 1a including a transmitting element 2a and a receiving element 3a, and an ultrasonic sensor 1b including a transmitting element 2b and a receiving element 3b. is there. The transmitting elements 2a and 2b and the receiving elements 3a and 3b of the ultrasonic sensors 1a and 1b are all piezoelectric vibrating elements in which an electrode thin film is formed on a piezoelectric ceramic plate. In the present embodiment, the ultrasonic frequency is 15 MHz. The oscillation control circuit 22 is means for controlling the switching circuit inside the oscillation circuit 21 to switch the oscillation circuit 21 on / off and the oscillation frequency. The switching timing is controlled by a clock inside the speed calculation unit 51, and no error occurs in the speed calculation by switching. By repeating frequency switching and on / off at non-constant intervals, it is possible to make it more difficult to synthesize deceptive signals. In the present invention, two pairs of ultrasonic sensors 1a and 1b are used and arranged on the sensor support substrate 10 so that the directions of directivity of ultrasonic emission and reception are not parallel to each other. As shown in FIG. 4, the blood flow velocity sensor 10 is contacted with a living body 71 (such as a subject's fingertip) as a measurement target, and the blood flow velocity is measured simultaneously with fingerprint recognition or immediately before or after fingerprint recognition. To do.
The ultrasonic wave (transmission wave 13a) emitted from the transmitting element 2a of the ultrasonic sensor 1a propagates through the living tissue and is reflected by the blood flowing through the blood vessel. The reflected wave 14a changes to a signal subjected to Doppler shift according to the blood flow speed. This reflected wave is received by the receiving element 3a. Similarly for the ultrasonic sensor 1b, the ultrasonic wave (transmitted wave 13b) emitted from the transmitting element 2b is reflected by the Doppler shift due to blood flow and detected by the receiving element 3b, but the ultrasonic sensors 1a and 1b Then, the directivity directions in which ultrasonic waves are emitted are different. The blood flow velocity can be calculated from the angle difference α between the ultrasonic sensors 1a and 1b and the Doppler shift frequencies ΔFa and ΔFb obtained from the signals of the ultrasonic sensors 1a and 1b.

  The ultrasonic measurement unit 50 includes a blood flow velocity sensor 10 including two pairs of ultrasonic sensors 1, two sets of detection circuits 23, a filter circuit 24, an amplification circuit 25, and an A / D converter 26. The signals of the receiving elements 3a and 3b that have received the reflected waves 14a and 14b are detected by the detection circuits 23a and 23b, and only the Doppler shift signal component from which the ultrasonic carrier component (base component) is removed is extracted. The frequency components unnecessary for the A / D conversion process are removed by the filter circuits 24a and 24b, and amplified by the amplifier circuits 25a and 25b, respectively. The Doppler shift signal is an analog signal, but is converted into digital data by the A / D converters 26 a and 26 b and temporarily stored in the buffer memory 41.

The speed calculation unit 51 includes a buffer memory 41 and an arithmetic processing device 43. The buffer memory 41 temporarily stores measurement data from the ultrasonic sensor 1. The data in each buffer memory is sent to the arithmetic processing unit 43 every fixed amount. The arithmetic processing unit 43 receives data from each sensor digitized by each A / D converter via the digital input / output unit 44, and performs arithmetic processing by the functions of the signal arithmetic processing unit 45 and the general-purpose arithmetic processing unit 46. The blood flow velocity from which the noise component is removed is calculated. In addition, as will be described later, the arithmetic processing unit 43 determines whether or not to authenticate the measurement target as a living body depending on whether or not the calculated blood flow velocity or pulse rate is within a predetermined range. A signal calculation processing unit 45 or a general-purpose calculation processing unit 46 having a function of determining or extracting a specific pattern from the detected flow velocity waveform and determining whether or not to authenticate the measurement object as a living body from the information of this pattern have.
If the arithmetic processing unit 43 operates at a sufficiently high speed with respect to the sampling rate of the measurement data, the buffer memories 41 and 42 can be omitted. The signal arithmetic processing unit 45 is a device that performs signal processing at a high speed with a special hardware configuration. If the processing speed of the general-purpose arithmetic processing unit 46 is high, the signal arithmetic processing unit 45 can be omitted.

  As shown in FIG. 3, the blood flow velocity is measured by bringing the blood flow sensor 10 into contact with a living body 71 (in this embodiment, the fingertip of the subject) as a measurement target. The ultrasonic wave (transmission wave 78a) emitted from the transmitting element 2a of the ultrasonic sensor 1a propagates through the living tissue and is reflected by the blood flowing through the blood vessel. The reflected wave 14a changes to a signal subjected to Doppler shift according to the blood flow velocity. This reflection is received by the receiving element 3a. Similarly, for the ultrasonic sensor 1b, the ultrasonic wave (transmitted wave 78b) emitted from the transmitting element 2b is reflected by the Doppler shift due to blood flow and detected by the receiving element 3b, but the ultrasonic wave is emitted. Directional direction is different. The signals of the reflected waves 79a and 79b received by the receiving elements 3a and 3b are detected by the detection circuits 23a and 23b, respectively, and only the Doppler signal component from which the ultrasonic carrier component (base component) is removed is extracted. Further, high frequency components unnecessary for A / D conversion processing are removed by the filter circuits 24a and 24b, and then amplified by the amplification circuits 25a and 26b, respectively. Although this Doppler signal is an analog signal, it is converted into digital data by the A / D converters 26a and 26b, temporarily stored in the buffer memory 41, and then stored in the main memory via the digital input / output unit 44 of the arithmetic processing unit 43. The data is transferred to the unit 42 and stored.

  The digital data of the respective Doppler signals of the ultrasonic sensor 1a and the ultrasonic sensor 1b obtained by the above measurement is subjected to Fourier transform (FFT) processing in the signal arithmetic processing unit 45 and the general-purpose arithmetic processing unit 46 of the arithmetic processing unit 43, so that the frequency The data is converted into distribution (spectrum) data, and the frequency distribution data is stored in the main storage unit 42. Assuming that the sampling frequency of A / D conversion is fs = 20 kHz and the number of FFT processes is Nf = 256, the frequency distribution data every 0.0128 seconds is Nf = 512, and the frequency distribution is every 0.0256 seconds. (However, the number of FFT processing data and the time interval of the FFT processing do not necessarily match. For example, 256 pieces of data can be processed at intervals of 0.01 seconds.) is there).

    If the frequency shift obtained from the data of the ultrasonic sensor 1a by the above method is Fa and the frequency shift obtained from the data of the ultrasonic sensor 1b is Fb, the blood flow velocity Vh can be derived by the following equation.

  Here, α is an angle formed by directivity of emission and reception of the ultrasonic waves of the two ultrasonic sensors, c is a sound velocity in the living body, and Fs is a transmission frequency (drive frequency) of the ultrasonic sensors.

  As described above, the blood flow velocity is measured, and if the velocity is not 10 cm / sec or more, for example, it is determined that the arithmetic processing device 43 is not a living body. Further, since the pulse cycle (peak-to-peak time difference) or pulse rate is obtained from the blood flow velocity waveform, it is determined that the pulse rate is also incorrect, that is, not a living body. In addition, for example, if the pulse rate is abnormally large, there may be a possibility that the criminal is threatened and performing authentication work. In this case, it can also be determined that an illegal act has occurred. It is.

  The fingerprint reader 53 detects a fingerprint pattern by the imaging unit 33 including the optical fingerprint reading sensor 9 having the imaging element 6 or the semiconductor fingerprint reading sensor 11, and temporarily stores the detected fingerprint pattern image data in the buffer memory 31. The image data is subjected to pattern extraction processing such as binarization processing in the image data processing device 32 and is output to the data search processing device 47 in the personal authentication device 54. The blood flow velocity measurement in the arithmetic processing device 43 is performed. If it is determined that the living body is being measured, a determination signal to that effect is output from the arithmetic processing unit 43, and the data search processing unit 47 outputs the fingerprint pattern image data output from the fingerprint reading unit 53 and Registered in advance in a database in a storage area on the storage (external storage device) 48 or network 49. Comparing the fingerprint pattern was performing personal authentication.

  On the other hand, when it is determined that the living body is not measured by the blood flow velocity measurement, a determination signal to that effect is output from the arithmetic processing unit 43 and personal authentication is not performed.

In FIG. 1, a plurality of processing units (processors) are prepared. However, when a processing unit having a sufficiently large processing capability (high speed) can be prepared, each processing step is assigned to each processing unit. A plurality of arithmetic functions may be combined with the same arithmetic processing unit without causing them to occur.
(Embodiment 2)
FIG. 5 is a measurement example of the blood flow velocity waveform obtained by the blood flow velocity sensor of the apparatus of the present invention. As shown in FIG. 5, the change in blood flow velocity accompanying the pulse of the living body is complicated, and it is difficult to create a flow having a speed change imitating that of a living body with a simple reciprocating or rotating mechanical pump. Therefore, features can be extracted from the blood flow velocity waveform, and can be distinguished from the flow artificially created by the mechanical pump, and fraud can be eliminated. For example, the ratio of the time difference 83 between the minimum value and the maximum value to the pulse period 86, the ratio of the time difference 84 between the first peak and the second peak to the pulse period 86, the intensity ratio between the first peak and the second peak, and the amplitude (peak value) The above-described function (for example, a determination program) for determining whether or not to authenticate the measurement object as a living body from the waveform pattern of the blood flow velocity waveform such as the fluctuation size and period of the pulse and the fluctuation magnitude and period of the pulse cycle is signaled Since the arithmetic processing unit 45 or the general-purpose data processing unit 46 is provided, it can be distinguished from an artificial flow. It is possible to digitize the characteristics of the blood flow velocity waveform for each individual in advance and register it in the database in the storage area of the storage 48 or network 49 and compare it with the measured waveform. Security can be ensured.

  A biometric information measuring device for personal authentication by recognizing biometric fingerprint patterns for the purpose of ensuring security, preventing leakage of corporate information and personal information, etc. Is available. It can be easily mounted on a so-called wearable terminal device such as a portable small terminal (PDA), a mobile phone, and a wristwatch type electronic device.

It is a block diagram which shows the structure of the measuring apparatus which concerns on this invention. It is the top view (a) and sectional drawing (b) which show the structure of the sensor which concerns on this invention. It is the top view (a) and sectional drawing (b) which show the structure of the sensor which concerns on this invention. It is a figure which shows the structure of the sensor which concerns on this invention. It is an illustration figure which shows the example of the blood-flow velocity waveform obtained in the biological information measuring device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Ultrasonic sensor 2a, 2b Transmitting element 3a, 3b Receiving element 4 Sensor support member 5 Lens 6 Imaging element 7 Protective glass 8 Optical filter 9 Optical fingerprint reading sensor 10 Blood flow velocity sensor 11 Semiconductor fingerprint reading sensor 21a, 21b Oscillation circuit 22 Oscillation control circuit 23a, 23b Detection circuit 24a, 24b Filter circuit 25a, 25b Amplification circuit 26a, 26b A / D converter 31 Buffer memory 32 Image data processing device 41a, 41b Buffer memory 42 Main storage unit 43 Arithmetic processing device 44 Digital Input / Output Unit 45 Signal Operation Processing Unit 46 General-purpose Operation Processing Unit 47 Data Search Processing Unit 48 Storage 49 Network 50 Ultrasonic Measurement Unit 51 Speed Calculation Unit 53 Fingerprint Reader 54 Personal Authentication Device 64 Drive Voltage (a)
65 Drive voltage (b)
66 A / D conversion timing 71 Living body (fingertip)
72 Arterial blood vessel 78 Transmitted wave 79 Reflected wave 80 Blood flow velocity waveform 81 First peak intensity 82 Second peak intensity 83 Time difference between minimum and maximum values 84 Time difference between first peak and second peak 85 Amplitude 86 Pulse cycle

Claims (8)

An image pickup unit that detects and outputs a fingerprint pattern, processes the output fingerprint pattern and outputs image data, and detects a signal waveform corresponding to the flow velocity of blood flowing through a blood vessel in the living body. a measuring unit for outputting Te, the measurement object based on the processing results obtained by the signal processing of the signal waveform output from the measuring unit determines whether to authenticate as the living body, and outputs the result of judgment judged A calculation unit having a function, and a personal authentication device that performs a personal authentication process based on the determination result in the calculation unit and the image data output from the fingerprint reader ,
The measuring unit converts a pair of ultrasonic sensors, each of which includes a transmitting unit that inputs an ultrasonic wave into the living body and a receiving unit that receives a reflected wave of the incident ultrasonic wave reflected by the blood, at different angles. With two pairs on the substrate,
The imaging unit is disposed on the substrate between each of the ultrasonic sensors, and includes a flat surface facing the living body,
Each of the ultrasonic sensors comprises an inclined surface that is inclined with respect to the flat surface,
The biological information measuring apparatus according to claim 1, wherein a surface constituted by the flat surface and the inclined surface has a concave shape for arranging the living body. The processing result of the arithmetic unit is the flow rate or pulse rate in said living body, said determining a feature to be made by whether or not within a predetermined range the flow rate or the pulse rate is predetermined The biological information measuring device according to claim 1.   The biological information according to claim 1, wherein the processing result in the arithmetic unit is a waveform pattern of the signal waveform corresponding to the flow velocity, and the determination is made by extracting features of the waveform pattern. measuring device. Features of the waveform pattern may be the time difference of the minimum and maximum values of the first waveform in the signal waveform is any or any combination of the time difference between the first peak and the second peak of the first waveform The biological information measuring device according to claim 3. An imaging unit that detects and outputs a fingerprint pattern, and a measurement unit that detects and outputs a signal waveform corresponding to a flow velocity of blood flowing through a blood vessel in a living body, and image data obtained by performing image processing on the fingerprint pattern and the signal waveform A biometric information measuring method used in a biometric information measuring apparatus for performing personal authentication processing using
The measuring unit converts a pair of ultrasonic sensors, each of which includes a transmitting unit that inputs an ultrasonic wave into the living body and a receiving unit that receives a reflected wave of the incident ultrasonic wave reflected by the blood, at different angles. With two pairs on the substrate,
The imaging unit is disposed on the substrate between each of the ultrasonic sensors, and includes a flat surface facing the living body,
Each of the ultrasonic sensors comprises an inclined surface that is inclined with respect to the flat surface,
The surface constituted by the flat surface and the inclined surface has a concave shape for arranging the living body,
And outputting the image data, detects the signal waveform to determine the measurement object based on the processing results obtained by the signal processing of the detected the signal waveform to determine whether to authenticate as the biometric and outputting the result, and performing the personal authentication process based on the image data and the determination result
A biological information measuring method comprising : The processing result is the flow rate or pulse rate of the in vivo claim wherein judgment is characterized to be made by whether or not within a predetermined range the flow rate or the pulse rate is predetermined 5 The biological information measuring method according to 1 . The biological information measuring method according to claim 5 , wherein the processing result is a waveform pattern of the signal waveform corresponding to the flow velocity, and the determination is made by extracting features of the waveform pattern. Features of the waveform pattern may be the time difference of the minimum and maximum values of the first waveform in the signal waveform is any or any combination of the time difference between the first peak and the second peak of the first waveform The biological information measuring method according to claim 7 .

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