Identification device

Abstract

We provide an identification device based on a new principle. [Solution] The identification device 10 includes a blood vessel position detection means 110 that acquires information on the location of blood vessels in an individual animal, and an individual difference determination means 120 that determines the similarity or similarity of individual animals based on the detected blood vessel positions. The blood vessel position detection means 110 includes a light irradiation means 111 and a photoacoustic detection means 112, and is capable of identifying the course of blood vessels in three dimensions using the photoacoustic effect. It can acquire location information of deep blood vessels, including arteries, and realizes stable biometric authentication that is less affected by environmental changes or physical condition.

Description

Technical Field

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[0001] The present invention relates to an identification device.

Background Art

[0002] Conventionally, fingerprint authentication and vein authentication are known as methods for identifying an individual using biometric information. Fingerprint authentication is a method of optically reading a fingerprint pattern formed on the surface of a fingertip and verifying the identity by comparing it with a previously registered fingerprint pattern. Vein authentication is a method of irradiating the palm or finger with near-infrared light, imaging a vein pattern using light absorption by hemoglobin in the blood, and verifying the identity by comparing it with a previously registered vein pattern. <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The objective of this invention is to provide a novel technology.

[0007] For example, one challenge is to provide stable biometric authentication technology that is less susceptible to environmental changes or physical conditions. For example, one challenge is to achieve highly accurate individual identification using deep vascular information, including arteries. For example, one challenge is to improve the accuracy of identification based on the complex positional relationship between veins and arteries. For example, one challenge is to build an authentication system that is difficult to forge using three-dimensional vascular anatomy information. For example, the challenge is to provide a simple and practical device configuration specifically for authentication, which differs from medical imaging diagnostic equipment. [Means for solving the problem]

[0008] The problem of the present invention is solved by an identification device having a blood vessel position detection means for acquiring information on the position of blood vessels in an individual animal, and an individual difference determination means for determining the differences between individual animals based on the detected blood vessel positions. [Effects of the Invention]

[0009] The present invention can solve one or more of the problems of the invention. For example, it enables stable biometric authentication that is less susceptible to environmental changes or physical conditions. For example, by utilizing information on deep blood vessels, including arteries, highly accurate individual identification can be achieved. For example, by utilizing the complex positional relationship between veins and arteries, the accuracy of identification can be improved. For example, by utilizing three-dimensional vascular anatomy information, it is possible to construct an authentication system that is difficult to forge.

[0010] For example, a practical identification device can be provided by using a simple device configuration specifically designed for authentication. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of the configuration of an identification system in which an identification device and an external server according to one embodiment of the present invention are connected via a network. [Figure 2] This figure shows an example of the hardware configuration of the identification device in the identification system shown in Figure 1. [Figure 3] Figure 2 is a block diagram of the identification device and external server shown. [Figure 4] This figure shows an example of the light irradiation means and photoacoustic detection means of this embodiment. [Figure 5] This figure shows the light irradiation means and photoacoustic detection means shown in Figure 4 from a different angle than in Figure 4. [Figure 6] This is an example of an image obtained by imaging veins and arteries using the identification device of this embodiment. [Modes for carrying out the invention]

[0012] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0013] <First Embodiment> The first embodiment describes the basic configuration of an identification device that uses photoacoustic effects to acquire information about the location of an animal's blood vessels and determines the similarities and differences between individual animals based on the acquired blood vessel location information. The identification device of this embodiment is characterized by its ability to acquire three-dimensional location information of blood vessels located deep within the body, which cannot be obtained by fingerprints or conventional vein authentication.

[0014] [Overall structure] Figure 1 shows an example of the configuration of an identification system in which an identification device and an external server according to one embodiment of the present invention are connected via a network. As shown in FIG. 1, the identification device 10 of the present embodiment is connected to an external server 30 via a network NW. The identification device 10 acquires information regarding the position of the blood vessels of an individual animal and transmits this information to the external server 30. The external server 30 collates the blood vessel position information received from the identification device 10 with the individual-specific blood vessel position information stored in advance, and returns the collation result to the identification device 10. The identification device 10 outputs an individual identification determination result based on the collation result received from the external server 30.

[0015] The network NW may be, for example, the Internet, a dedicated line, a wireless communication network, or a combination thereof. It is desirable that the communication between the identification device 10 and the external server 30 is encrypted. Thereby, highly confidential biometric information such as blood vessel position information can be securely transmitted.

[0016] FIG. 2 is a block diagram showing an example of the hardware configuration of the identification device in the identification system shown in FIG. 1.

[0017] The identification device 10 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a bus 14, an input / output interface 15, an input unit 16, an output unit 17, a storage unit 18, a communication unit 19, and a drive 20.

[0018] The CPU 11 executes various processes according to a program recorded in the ROM 12 or a program loaded from the storage unit 18 into the RAM 13. In the RAM 13, data and the like necessary for the CPU 11 to execute various processes are also appropriately stored.

[0019] The CPU 11, ROM 12, and RAM 13 are interconnected via the bus 14. The input / output interface 15 is also connected to this bus 14. The input unit 16, output unit 17, storage unit 18, communication unit 19, and drive 20 are connected to the input / output interface 15.

[0020] The input unit 16 is configured, for example, with a keyboard, and is used to input various types of information. The output unit 17 consists of a display such as an LCD and a speaker, and outputs various information as images and sounds. The memory unit 18 is composed of DRAM (Dynamic Random Access Memory) and stores various types of data. The communication unit 19 communicates with other devices (for example, the external server 30 in Figure 1) via a network NW, including the Internet.

[0021] The drive 20 is appropriately equipped with removable media 21, such as a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory. Programs read from the removable media 21 by the drive 20 are installed in the storage unit 18 as needed. Furthermore, the removable media 21 can store various types of data stored in the storage unit 18, just as the storage unit 18 does.

[0022] The identification device 10 may also include a photoacoustic detection means (for example, a photoacoustic detection means 112 having a plurality of photoacoustic probes 112p as shown in Figure 4) as an input unit 16. Furthermore, the identification device 10 may acquire data obtained by the plurality of photoacoustic probes of the photoacoustic detection means (described later) via a general-purpose input unit 16 or a communication unit 19. Furthermore, the identification device 10 may also include a light irradiation means (for example, the light irradiation means 111 shown in Figure 4) as an output unit 17. Additionally, the identification device 10 may control the light irradiation means, described later, via a general-purpose output unit 17 or a communication unit 19.

[0023] Although not shown in the diagram, the external server 30 in Figure 1 can also have a configuration that is basically the same as the hardware configuration shown in Figure 2. Therefore, the explanation of the hardware configuration of the external server 30 in Figure 1 will be omitted.

[0024] Through the cooperation of various hardware and software constituting the identification system shown in Figure 1, including the identification device 10 shown in Figure 2, it becomes possible to execute various processes for identification and authentication by the identification device.

[0025] Figure 3 is a block diagram of the identification device and external server shown in Figure 2. As shown in Figure 3, the identification device 10 has a blood vessel position detection means 110 and an individual difference / sameness determination means 120. The blood vessel position detection means 110 has a light irradiation means 111 and a photoacoustic detection means 112. The individual difference / sameness determination means 120 has a blood vessel position signal processing means 121 and an individual difference / sameness determination result output means 122. The external server 30 has an individual blood vessel position information storage means 310 and a blood vessel position information matching means 320. Processing in each means is realized by the CPU of each device. Furthermore, the individual blood vessel position information storage means 310 is realized by storing it in a region of the storage unit and controlling and managing it by the CPU or the like.

[0026] In this embodiment, the configuration in which the individual blood vessel location information storage means 310 and the blood vessel location information matching means 320 are provided on an external server 30 is described, but some or all of these means may be included in the identification device 10. For example, in a small-scale authentication system, it is possible to integrate all functions into the identification device 10. On the other hand, in a large-scale authentication system with many identification devices 10 installed, it is desirable to consolidate the functions on the external server 30 from the viewpoint of centralized management of individual blood vessel location information and load balancing of the matching process.

[0027] [Means for detecting blood vessel position] The blood vessel position detection means 110 is a means for acquiring information regarding the position of blood vessels in an individual animal. The blood vessel position detection means 110 of this embodiment is characterized by acquiring blood vessel position information using the photoacoustic effect. The photoacoustic effect is a phenomenon in which, when a substance absorbs pulsed light, the absorbed energy is converted into heat, and this heat causes the substance to expand instantaneously, generating ultrasound. This phenomenon is a physical phenomenon explained by the Grüneisen equation and is a technology that has already been put into practical use in the medical field.

[0028] Figure 4 shows an example of the light irradiation means and photoacoustic detection means of this embodiment. Figure 5 shows the light irradiation means and photoacoustic detection means shown in Figure 4 from a different direction than in Figure 4. As shown in Figures 4 and 5, the blood vessel position detection means 110 includes a light irradiation means 111 and a photoacoustic detection means 112.

[0029] In this embodiment, this photoacoustic effect can be applied to individual identification. Specifically, it utilizes the property of hemoglobin contained in red blood cells present in the body of an animal to absorb light. When pulsed light is shone on an animal, the hemoglobin in the red blood cells flowing through the blood vessels absorbs the light energy, resulting in the generation of ultrasound. By detecting this ultrasound, the location of the blood vessel, which is the source of the ultrasound, can be identified in three dimensions.

[0030] [Light irradiation means] The light irradiation means 111 is a means for irradiating an animal with light. In this embodiment, it is desirable that the light irradiated is pulsed light. By using pulsed light, the absorption of light energy occurs instantaneously, and a clear photoacoustic signal can be obtained.

[0031] The wavelength of the irradiated light should preferably include infrared light. In particular, it is preferable to use light in the wavelength range known as the "light window" in relation to living organisms, i.e., the range of 700 nm to 2 μm. Light in this wavelength range is absorbed and scattered relatively little by living tissues and can penetrate deep into the body. From the viewpoint of efficiently acquiring information on the location of blood vessels, the range of 700 nm to 920 nm is more preferable, and the range of 750 nm to 850 nm is particularly preferable.

[0032] A specific example of the light irradiation means 111 is a laser light source. For example, an Nd:YAG laser, a titanium-sapphire laser, or a semiconductor laser can be used. These laser light sources can generate pulsed light of a desired wavelength. The full width at half maximum (FWHM) of the pulsed light may be between 10 nsec and 200 μsec. If the FWHM is too short, it becomes difficult to realize the light source, and if it is too long, the intensity of the photoacoustic signal decreases, so this range is practical.

[0033] The light intensity is arbitrary as long as it allows information about the location of blood vessels to be obtained, but it does not need to be strong enough to harm the animal. The light intensity may be 5 mJ / cm² or more, or 10 mJ / cm² or more, on the animal surface, for example. However, it is desirable that the light intensity be set so as not to exceed the maximum permissible exposure dose specified in the laser safety standards.

[0034] The irradiation range of the light is arbitrary as long as information about the location of the blood vessels can be obtained. An appropriate irradiation range can be set depending on the body part to be identified. For example, when targeting blood vessels in the fingers, the minimum width of the irradiation range may be 10 mm to 20 mm. When targeting the palm of the hand, the minimum width of the irradiation range may be 2 cm to 10 cm. By imaging a wider area at once, the course pattern of the blood vessels can be obtained over a wider area, and the identification accuracy can be improved. Here, the minimum width refers to the distance between the parallel lines that have the shortest distance between them among the parallel lines that can enclose the irradiation area. For example, the minimum width of both a square with sides of 10 mm and a perfect circle with a diameter of 10 mm is 10 mm.

[0035] The identification device 10 of this embodiment can pinpoint the location of blood vessels at greater depths than conventional vein authentication devices. It can reach depths of up to 30 mm. This is because it utilizes the photoacoustic effect to detect ultrasound generated from within the body, rather than reflected light from the body surface. Since ultrasound attenuates less in biological tissue than light, it can detect signals from deep within the body.

[0036] [Photoacoustic detection means] The photoacoustic detection means 112 is a means for detecting photoacoustic waves, or ultrasound, emitted from animals. As shown in Figure 4, the photoacoustic detection means 112 is configured to have a plurality of photoacoustic probes 112p.

[0037] Pulsed light irradiated onto an animal is absorbed by red blood cells flowing through the blood vessels. When hemoglobin in the red blood cells absorbs the light energy, this energy is converted into heat. This thermal energy causes the hemoglobin and its surrounding environment to expand instantaneously, and this expansion generates ultrasound. The generated ultrasound propagates through the living tissue and is detected by a photoacoustic probe 112p placed on the body surface.

[0038] The photoacoustic probe 112p is an element that converts ultrasound into electrical signals. For example, a piezoelectric element can be used. A piezoelectric element can convert mechanical vibrations caused by ultrasound into electrical signals. As for the material of the photoacoustic probe 112p, for example, lead zirconate titanate (PZT) or polyvinylidene fluoride (PVDF) can be used.

[0039] In the photoacoustic detection means 112 of this embodiment, the number and arrangement of photoacoustic probes 112p are arbitrary as long as information regarding the position of the animal's blood vessels can be obtained. However, in order to obtain three-dimensional positional information of the blood vessels, it is desirable to arrange multiple photoacoustic probes 112p at different positions. In the example shown in Figure 4, multiple photoacoustic probes 112p are arranged in a hemispherical shape. With such an arrangement, ultrasound generated from the blood vessels can be detected from multiple directions, and the three-dimensional position of the blood vessels, which are the source of the ultrasound, can be calculated.

[0040] Figure 5 shows the light irradiation means 111 and photoacoustic detection means 112 shown in Figure 4, viewed from a different direction (above). As shown in Figure 5, the light irradiation means 111 is positioned at the center of the photoacoustic detection means 112, and multiple photoacoustic probes 112p are arranged in a circular pattern around it. The multiple photoacoustic probes 112p are dispersed on a hemispherical surface, which allows for the detection of ultrasound generated from blood vessels from various angles. This three-dimensional arrangement makes it possible to acquire positional information of the blood vessels in the depth direction (Z-axis direction) with high accuracy.

[0041] Medical photoacoustic imaging devices typically use hundreds of densely arranged photoacoustic probes to generate high-resolution three-dimensional images. However, the identification device 10 of this embodiment is intended for individual identification and does not require detailed visualization of blood vessel morphology as in medical diagnosis. Therefore, the number of photoacoustic probes 112p may be fewer than that of medical devices. For example, in a miniaturized blood vessel position detection means, the number of photoacoustic probes 112p may be only a few dozen. Such a configuration makes it possible to mount the identification device 10 on portable communication devices such as smartphones.

[0042] The arrangement of the photoacoustic probe 112p is not limited to a hemispherical shape. For example, it may be arranged in a planar shape. A planar arrangement is advantageous for making the device thinner. Alternatively, an arrangement shape such as an arc or cylinder may be adopted depending on the shape of the body part being measured.

[0043] [Method for determining individual differences and similarities] The individual difference determination means 120 is a means for determining the differences between individual animals based on the position of blood vessels detected by the blood vessel position detection means 110. The individual difference determination means 120 includes a blood vessel position signal processing means 121 and an individual difference determination result output means 122.

[0044] [Means for processing blood vessel position signals] The blood vessel position signal processing means 121 is a means for processing the photoacoustic wave signal detected by the photoacoustic detection means 112. The signal output from the photoacoustic detection means 112 is an analog signal. The blood vessel position signal processing means 121 includes at least a photoacoustic wave digitization means for converting this analog signal into a digital signal.

[0045] The photoacoustic wave digitization means is implemented, for example, by an analog-to-digital converter. The analog-to-digital converter samples the electrical signal output from the photoacoustic probe 112p at a predetermined sampling frequency and converts it into digital data. The sampling frequency is set according to the frequency components of the ultrasound to be detected. For example, by setting the sampling frequency to 10 MHz or higher, ultrasonic signals up to several MHz can be faithfully digitized.

[0046] The vascular position signal processing means 121 may include, in addition to the photoacoustic wave digitization means, noise reduction means, cutoff means, reconstruction means, etc. The noise reduction means removes electrical noise and biological noise from the digitized signal. For example, a bandpass filter can be used to remove components outside the frequency band of the ultrasound signal.

[0047] The cutoff means is a method for removing the portion of the signal whose amplitude is below a predetermined threshold. This makes it possible to remove weak noise components and extract only the clear signal from the blood vessels.

[0048] The reconstruction means calculates the position of a blood vessel based on the positions of multiple photoacoustic probes 112p and the signals detected by each photoacoustic probe 112p. Specifically, it calculates the three-dimensional coordinates of the blood vessel, which is the source of the ultrasound, from the arrival time and amplitude of the ultrasound detected by each photoacoustic probe 112p. Such calculation methods are already established techniques in the field of ultrasound imaging, and methods such as the delay and sum method can be used.

[0049] The vascular position information obtained from the vascular position signal processing means 121 may be expressed as a set of coordinates where the blood vessels are located. In this case, it is desirable that the coordinates be three-dimensional coordinates. Alternatively, the vascular position information may represent the blood vessels with an approximation curve. For example, the course of the blood vessels can be represented as a polynomial approximation curve in three-dimensional space.

[0050] Furthermore, since the identification device 10 of this embodiment is intended for individual identification, the blood vessel position signal processing means 121 does not necessarily have to include means for visualizing the position of blood vessels in three dimensions. Medical photoacoustic imaging devices require a function to generate and display three-dimensional images so that physicians can visually confirm the morphology of blood vessels. However, for individual identification, it is sufficient to obtain the position information of blood vessels as numerical data, and visual display is not essential. This configuration can reduce the cost of the device and improve processing speed.

[0051] [Individual Difference / Sameness Determination Result Output Method] The individual difference / similarity determination result output means 122 is a means for outputting a determination result regarding individual differences / similarity based on the output result from the blood vessel position information matching means 320. The output of the individual difference / similarity determination result may be done by display, by voice, or by outputting it as an electrical signal to another device or system.

[0052] For example, when the identification device 10 of this embodiment is used as part of an access control system, the individual identity determination result output means 122 can output a signal indicating successful authentication to an electric lock control device, thereby unlocking the door. Also, when used for identity verification in financial transactions, the individual identity determination result output means 122 can output a signal indicating successful authentication to a transaction processing system, thereby authorizing the execution of the transaction.

[0053] The individual difference / identity determination result output means 122 may include a display device for displaying the determination result. For example, a liquid crystal display, an organic EL display, or an LED indicator can be used as the display device. It is desirable to provide a visually easy-to-understand display, such as displaying green for successful authentication and red for unsuccessful authentication.

[0054] Furthermore, the individual difference / identity determination result output means 122 may include a speaker that outputs the determination result as sound. For example, it can output a voice message "Authentication successful" when authentication is successful, and a voice message "Authentication failed" when authentication fails.

[0055] [External Server] The external server 30 has individual blood vessel location information storage means 310 and blood vessel location information matching means 320.

[0056] [Means for storing individual blood vessel location information] The individual blood vessel location information storage means 310 is a means for storing blood vessel location information on an individual basis. The information stored in the individual blood vessel location information storage means 310 includes at least information for identifying the individual and the blood vessel location information of that individual.

[0057] The information used to identify an individual may be personal information such as name, employee number, or membership number if the animal is a human. Alternatively, any information that uniquely identifies the individual, such as an identification ID, is acceptable. The identification ID may be a string of characters consisting of numbers, letters, or a combination thereof.

[0058] The blood vessel position information may be data obtained from the blood vessel position signal processing means 121. For example, it may be a set of three-dimensional coordinates indicating the position of a blood vessel, or parameters of an approximation curve representing a blood vessel. The blood vessel position information must be stored in a format that can be used by the blood vessel position information matching means 320, which will be described later.

[0059] The individual blood vessel location information storage means 310 is implemented, for example, as a database. The database may be in any format, such as a relational database or a NoSQL database. It is desirable that the blood vessel location information stored in the database be encrypted. This prevents the leakage of blood vessel location information even if the database is accessed illegally.

[0060] [Means for verifying blood vessel location information] The blood vessel location information matching means 320 is a means for matching the blood vessel location information of the animal to be identified with the blood vessel location information stored in the individual blood vessel location information storage means 310.

[0061] The matching method varies depending on the intended use of the identification device 10. When used for identity verification (authentication), the blood vessel location information matching means 320 evaluates the degree of agreement between the blood vessel location information of the animal to be identified and the blood vessel location information corresponding to the identification ID declared by the animal to be identified. If the degree of agreement is above a predetermined threshold, authentication is considered successful; if it is below the threshold, authentication is considered unsuccessful.

[0062] When used for individual identification, the blood vessel location information matching means 320 sequentially compares the blood vessel location information of the animal to be identified with all the blood vessel location information stored in the individual blood vessel location information storage means 310, and identifies the individual with the highest degree of match.

[0063] Various methods can be used to evaluate the degree of agreement. For example, one method involves calculating the distance between the coordinate point clouds that constitute the two blood vessel location information sets, and evaluating the degree of agreement as higher the distance. Machine learning methods can also be applied. For example, deep learning models such as convolutional neural networks (CNNs) can be used to extract features of the blood vessel location information, and the degree of agreement can be evaluated based on the distance in the feature space.

[0064] Prior to evaluating the degree of agreement, the vascular position information of the animals to be identified may be aligned. When an animal places its palm on the measuring device, it is difficult for it to place it in exactly the same position and posture each time. Therefore, it is necessary to correct for positional and rotational errors during measurement. Such corrections can be achieved by translation and rotational transformation in three-dimensional space. In addition, scale transformation may be performed to correct for individual differences in palm size and differences in the degree to which the palm is opened during measurement.

[0065] [Identification process] The identification process using the identification device 10 of this embodiment will now be explained. First, the animal to be identified places a part of its body, such as its palm, on the measuring unit of the identification device 10. The light irradiation means 111 irradiates the palm with pulsed infrared light. The irradiated light penetrates the skin of the palm and reaches the red blood cells flowing in the blood vessels beneath the skin. The hemoglobin contained in the red blood cells absorbs the light, and ultrasound is generated by the photoacoustic effect.

[0066] Multiple photoacoustic probes 112p of the photoacoustic detection means 112 detect ultrasound waves generated from blood vessels. The detected ultrasound signals are digitized by the blood vessel position signal processing means 121 and subjected to processing such as noise reduction. Subsequently, the reconstructing means calculates the three-dimensional position information of the blood vessels.

[0067] The calculated blood vessel location information is transmitted to the external server 30 via the network NW. The blood vessel location information matching means 320 of the external server 30 compares the received blood vessel location information with the blood vessel location information stored in the individual blood vessel location information storage means 310 and calculates the degree of agreement. If the calculated degree of agreement is above a predetermined threshold, authentication is determined to be successful; if it is below the threshold, authentication is determined to be unsuccessful. The determination result is returned to the identification device 10.

[0068] The individual difference / identity determination result output means 122 of the identification device 10 outputs the determination result received from the external server 30. If authentication is successful, for example, a message such as "Authentication successful" is displayed and a green lamp is lit. If authentication fails, for example, a message such as "Authentication failed" is displayed and a red lamp is lit.

[0069] With the configuration described above, the identification device 10 of this embodiment can achieve highly accurate and stable individual identification by utilizing three-dimensional positional information of blood vessels located deep within the body, which cannot be obtained by conventional fingerprint authentication or vein authentication.

[0070] <Second Embodiment> The second embodiment describes a configuration that distinguishes between arteries and veins and improves the accuracy of individual identification by utilizing the combined positional relationship between the two. The identification device of this embodiment is characterized by having a function to irradiate with light of multiple wavelengths, in addition to the basic configuration of the first embodiment.

[0071] [Principle of distinguishing between arteries and veins] Blood vessels consist of arteries, which carry oxygen-rich blood, and veins, which carry oxygen-poor blood. The hemoglobin in the blood flowing through arteries is oxygenated hemoglobin, which is bound to oxygen. On the other hand, the hemoglobin in the blood flowing through veins is deoxygenated hemoglobin, which has released oxygen. Oxygenated hemoglobin and deoxygenated hemoglobin have different light absorption properties. Specifically, the degree of absorption differs depending on the wavelength of light.

[0072] This property can be used to distinguish between arteries and veins. In this embodiment, the light irradiation means 111 irradiates with two different wavelengths of light. For example, it irradiates with 756 nm infrared light and 797 nm infrared light. Oxygenated hemoglobin contained in arteries absorbs 797 nm light better than 756 nm light. Therefore, the photoacoustic signal from the arteries for a 797 nm light pulse is stronger than the photoacoustic signal for a 756 nm light pulse.

[0073] On the other hand, deoxygenated hemoglobin in veins absorbs 756 nm light better than 797 nm light. Therefore, the photoacoustic signal from veins is stronger for a 756 nm light pulse than for a 797 nm light pulse. In this way, by comparing the intensity ratio of the photoacoustic signals for two different wavelengths of light, it is possible to distinguish whether a blood vessel is an artery or a vein.

[0074] Figure 6 shows images of veins and arteries captured by the identification device of this embodiment. As shown in Figure 6, by using light of multiple wavelengths, arteries and veins can be distinguished and visualized. However, the identification device of this embodiment does not necessarily need to generate such images; it is sufficient if the positional information of arteries and veins can be obtained as numerical data.

[0075] Figure 6 shows images composed of photoacoustic signals for a 756 nm light pulse (left), images composed of photoacoustic signals for a 797 nm light pulse (right), and an image in the center showing the combined signals of both wavelengths color-coded according to oxygen saturation. In the center image, blood vessels displayed in warm colors (red to yellow) are arteries with high oxygen saturation, and blood vessels displayed in cool colors (blue to green) are veins with low oxygen saturation. In this way, by analyzing the intensity ratio of the photoacoustic signals for two different wavelengths, it is possible to distinguish whether each blood vessel is an artery or a vein.

[0076] [Multiple wavelength light irradiation means] The light irradiation means 111 of this embodiment can irradiate with light of at least two different wavelengths. It is desirable to select wavelengths that clearly show the difference in light absorption characteristics between oxygenated hemoglobin and deoxygenated hemoglobin. For example, a combination of 756 nm and 797 nm can be used. Alternatively, a combination of wavelengths close to this, such as 750 nm and 800 nm, may also be used.

[0077] One method for irradiating with light of multiple wavelengths is to use multiple laser light sources. For example, a laser light source emitting 756 nm light and a laser light source emitting 797 nm light can be set up separately and irradiated alternately or simultaneously. When irradiated alternately, the photoacoustic signals for each wavelength of light can be detected in a temporally separated manner, making signal processing easier.

[0078] Alternatively, a tunable laser may be used. A tunable laser can emit light of multiple wavelengths from a single laser light source. Using a tunable laser simplifies the configuration of the device.

[0079] In this embodiment, the wavelengths of light irradiated are not limited to two types. Three or more wavelengths of light may be irradiated. For example, to simultaneously visualize lymphatic vessels, light with a wavelength around 835 nm may be added. Since lymphatic vessels do not contain hemoglobin, they exhibit different light absorption characteristics than blood vessels. In particular, when a contrast agent such as indocyanine green (ICG) is injected into lymphatic vessels, they strongly absorb light with a wavelength around 835 nm, allowing for clear detection of lymphatic vessels.

[0080] [Utilizing the positional relationship between arteries and veins] The identification device of this embodiment can acquire arterial and vein position information separately. Furthermore, the relative positional relationship between arteries and veins can be used as identification information. The relative positional relationship between arteries and veins, particularly the morphology of the parts where they approach or intersect, varies greatly from individual to individual. By utilizing this characteristic, the identification accuracy can be significantly improved.

[0081] The vascular location information stored in the vascular location information storage means 310 may include information that distinguishes between arteries and veins. For example, for each blood vessel, flag information indicating whether it is an artery or a vein may be added. In addition to the location coordinates of the blood vessel, information on the oxygen saturation level in that blood vessel may also be included. Oxygen saturation is defined as the ratio of the oxygenated hemoglobin concentration to the total hemoglobin concentration, and is high in arteries and low in veins.

[0082] The blood vessel position information matching means 320 may evaluate the degree of agreement by considering the relative positional relationship between arteries and veins. For example, in addition to matching the positions of arteries and veins respectively, it is possible to extract feature quantities such as the closest approach distance between arteries and veins, the intersection angle, and the length of parallel sections, and evaluate the degree of agreement of these feature quantities.

[0083] [Advantages of arterial detection] In this embodiment, the target of blood vessel location detection does not necessarily have to be both veins and arteries; it may be just one or the other. However, there are advantages to detecting only arteries. Arteries are often located deeper in the body than veins. Blood vessels located deep in the body are less affected by the external environment than blood vessels closer to the body surface. For example, in a low-temperature environment, veins close to the body surface tend to constrict, but arteries located deep inside the body are relatively less affected. Therefore, by utilizing the location information of arteries, robust identification against environmental changes can be achieved.

[0084] It should be noted that the position of arteries may change in response to the heartbeat. However, for arteries in the palms and fingers, the positional change due to pulsation is relatively small, and the impact on identification accuracy is limited. Furthermore, it is possible to actively utilize the positional change due to pulsation. For example, by acquiring vascular position information at multiple points in time and using the temporal change pattern as identification information, it is possible to achieve both biometric detection and individual identification simultaneously. This can prevent fraudulent authentication using forged biometric information.

[0085] <Third Embodiment> The third embodiment describes the configuration of an identification device that utilizes three-dimensional vascular anatomy information, and a simplified device configuration specifically for authentication purposes. The identification device of this embodiment is characterized by its ability to acquire three-dimensional positional information of blood vessels while omitting complex image display functions such as those found in medical imaging diagnostic devices, thereby achieving miniaturization and cost reduction.

[0086] [Detection of three-dimensional blood vessel pathways] The identification device of this embodiment can determine the location of blood vessels in three dimensions. This is achieved by arranging multiple photoacoustic probes 112p of the photoacoustic detection means 112 in two or three dimensions. In the example shown in Figure 4, multiple photoacoustic probes 112p are arranged in a hemispherical shape. This arrangement allows for the detection of ultrasound generated from blood vessels from various directions.

[0087] The positions of each photoacoustic probe 112p are known. By analyzing the arrival time of the ultrasonic signal detected by each photoacoustic probe 112p, the three-dimensional coordinates of the blood vessel, which is the source of the ultrasonic waves, can be calculated. Specifically, the distance to the source of the ultrasonic waves is calculated from the time when the ultrasonic waves were detected by each photoacoustic probe 112p and the propagation speed of the ultrasonic waves in the biological tissue. By combining the distance information from multiple photoacoustic probes 112p, the three-dimensional coordinates of the source can be identified based on the principle of triangulation.

[0088] Blood vessels are not points, but rather linear structures with a certain length. Therefore, blood vessel position information is represented as a set of multiple three-dimensional coordinate points. By connecting these coordinate points, the course of the blood vessels can be understood in three dimensions. The course of the blood vessels may be represented, for example, as a polyline, spline curve, or polynomial approximation curve in three-dimensional space.

[0089] [Utilization of vascular bifurcations] In the course of blood vessels, particularly important features are the locations where vessels branch. The branching patterns of blood vessels vary greatly from individual to individual and remain largely unchanged throughout life. Therefore, the three-dimensional coordinates of blood vessel branching points are extremely useful information for individual identification.

[0090] The blood vessel location information may include information about the locations where blood vessels branch. For example, it may include information such as the three-dimensional coordinates of the branching point, the branching angle, the diameter of the blood vessel before branching, and the diameter of each blood vessel after branching. The blood vessel location information matching means 320 can achieve efficient and highly accurate individual identification by focusing on matching this information about blood vessel branching points.

[0091] Furthermore, as described in the second embodiment, when distinguishing and detecting arteries and veins, information about the entanglement of arteries and veins is also important. The three-dimensional morphology of areas where arteries and veins are close together, run parallel, or intersect varies particularly greatly from person to person. By including information about such areas in the vascular position information, the identification accuracy can be further improved.

[0092] [Simplification of equipment] The identification device of this embodiment does not necessarily have to include means for visualizing the location of blood vessels. Medical photoacoustic imaging devices require a function to generate and display three-dimensional images of blood vessels on a display so that physicians can visually confirm the morphology of the blood vessels and use this to aid in diagnosis. However, the identification device of this embodiment is intended to determine the similarities and differences between individuals, and it is not necessary for humans to visually confirm the morphology of the blood vessels.

[0093] Therefore, the identification device of this embodiment can omit image generation means and image display means for visualizing blood vessel position information as an image. This simplifies the device configuration and reduces costs. Furthermore, since computational processing for image generation is unnecessary, processing speed can be improved.

[0094] Specifically, the blood vessel position signal processing means 121 only needs to have the function of calculating the position coordinates of blood vessels from photoacoustic signals; it does not need to have the function of imaging these coordinates. The position coordinates of blood vessels are transmitted as numerical data to the external server 30 and used for matching processing by the blood vessel position information matching means 320.

[0095] The individual difference / identity determination result output means 122 only needs to output the determination result based on the matching result, for example, "authentication successful" or "authentication failed." This output can be done as a simple text display, a lamp light, an audio message, or an electrical signal. There is no need to display an image of blood vessels.

[0096] [Optimization of the number and placement of photoacoustic probes] In medical photoacoustic imaging devices, it is common to densely arrange hundreds of photoacoustic probes to generate high-resolution three-dimensional images. However, in the identification device of this embodiment, it is sufficient to acquire vascular position information with the accuracy necessary for individual identification, and it is not necessary to generate high-resolution images required for medical diagnosis.

[0097] Therefore, the number of photoacoustic probes 112p in the identification device of this embodiment may be less than that of a medical device. For example, by arranging several tens of photoacoustic probes 112p, blood vessel position information can be acquired with sufficient accuracy for individual identification. By reducing the number of photoacoustic probes, the cost of the device can be reduced and miniaturization can be achieved.

[0098] The arrangement of the photoacoustic probes 112p can also be optimized according to the application. While Figure 4 shows a hemispherical arrangement, it is not limited to this. For example, if minimizing the device's thickness is a priority, the photoacoustic probes 112p may be arranged in a planar or gently curved shape. Even with such arrangements, if multiple photoacoustic probes 112p are positioned at different locations, three-dimensional positional information of blood vessels can be acquired.

[0099] With future miniaturization of the device in mind, the identification device of this embodiment is also envisioned to be mounted on portable communication devices such as smartphones. In this case, the number and arrangement of the photoacoustic probes 112p will be designed to fit within the casing of the smartphone. For example, several dozen photoacoustic probes 112p can be arranged in a planar manner on the back of the smartphone, and the user can acquire blood vessel location information by placing their palm on the smartphone.

[0100] Furthermore, it is conceivable that the identification device could be mounted on a wall. For example, a wall-mounted identification device could be installed at the entrance of an office building, allowing employees to enter and exit by simply waving their palm. In such applications, minimizing the thickness and weight of the device is important, and it is desirable to minimize the number of photoacoustic probes.

[0101] [Improve the efficiency of data processing] The identification device of this embodiment achieves improved data processing efficiency by omitting image generation processing. Medical photoacoustic imaging devices require processing large amounts of data obtained from hundreds of photoacoustic probes to generate high-resolution three-dimensional images. This image generation processing requires a high-performance computer and long processing time.

[0102] On the other hand, in the identification device of this embodiment, it is sufficient to calculate the position coordinates of blood vessels from the photoacoustic signal, and image processing is unnecessary. Calculating position coordinates requires less computation than image generation and can be performed at high speed. This reduces the time from when the user places their palm over the device until the authentication result is displayed, providing a comfortable user experience.

[0103] Furthermore, by omitting the image generation process, the performance requirements for the computer installed in the identification device 10 can be relaxed. Instead of a high-performance computer, a small embedded computer or microcontroller can be used. This makes it possible to reduce the cost, miniaturize the device, and lower its power consumption.

[0104] [Improved security] A key feature of this embodiment is that the blood vessel position information acquired by the identification device is three-dimensional. Information acquired by conventional fingerprint or vein authentication is essentially two-dimensional. Two-dimensional information is relatively easy to reproduce as photographs or printed materials, thus posing a risk of forgery.

[0105] On the other hand, three-dimensional vascular position information cannot be replicated as simple photographs or printed materials. To forge the three-dimensional course pattern of blood vessels, it is necessary to create a three-dimensional structure with optical and acoustic properties similar to those of the human body, which is extremely difficult. Therefore, the identification device of this embodiment has high resistance to forgery.

[0106] Furthermore, as described in the second embodiment, biometric detection can also be performed by detecting positional changes caused by arterial pulsation. In other words, individual identification can be performed while confirming that the target of identification is a living human being. This makes it possible to reliably prevent fraudulent authentication using forged biometric information.

[0107] [Application Areas] The identification device of this embodiment can be applied to various fields due to its high identification accuracy and stability. For example, it can be applied to access control in facilities with high security levels. It can ensure reliable identity verification in facilities requiring high levels of security, such as government agencies, research facilities, and data centers.

[0108] Furthermore, it can be applied to identity verification in financial transactions. It can be used as an authentication method in place of PINs or cards at bank ATMs, securities company trading terminals, etc. Blood vessel location information cannot be forgotten like a PIN, nor can it be lost like a card. Also, it cannot be known to others like a fingerprint, thus achieving a high level of security.

[0109] Furthermore, it can be applied to identifying individuals in criminal investigations. Conventional fingerprint matching cannot identify individuals if fingerprints cannot be collected or if they are not registered in a fingerprint database. By using the identification device of this embodiment, it may be possible to identify individuals from the location information of blood vessels in the palm of the hand.

[0110] The identification device of this embodiment is not limited to identifying humans. It can also be applied to the identification of individual animals such as livestock. However, in animals with dense fur, the photoacoustic signal from blood vessels may be attenuated due to the scattering and absorption of light by the fur. Therefore, it is desirable to measure areas with little to no fur. In humans, the palms of the hands are hairless and are suitable for measurement.

[0111] As described above, the identification device of the third embodiment utilizes three-dimensional vascular pathway information while omitting complex image display functions such as those found in medical imaging diagnostic devices, thereby realizing a simple and practical device configuration specifically for authentication purposes.

[0112] <Variation> In addition to the embodiments described above, the following modifications can be adopted. These modifications may be implemented individually or in combination.

[0113] [Modified example 1: Combination of lymphatic vessel information] This modification further improves identification accuracy by combining lymphatic vessel location information with blood vessel location information. Lymphatic vessels are tubular structures distributed throughout the body parallel to blood vessels, and lymph fluid flows through them. The course patterns of lymphatic vessels, like those of blood vessels, vary greatly from person to person, and can therefore be useful information for individual identification.

[0114] Unlike blood vessels, lymphatic vessels do not contain hemoglobin, and therefore cannot generate photoacoustic signals in the same way as blood vessels. In this modified example, a contrast agent is administered to the lymphatic vessels. For example, indocyanine green (ICG) can be used as the contrast agent. ICG has the property of absorbing near-infrared light and is a safe contrast agent that is already widely used in the medical field.

[0115] When ICG is injected subcutaneously, it is taken up by the lymphatic vessels and flows through them along with the lymphatic fluid. When light is shone on it in this state, the ICG in the lymphatic vessels absorbs the light, and ultrasound is generated by the photoacoustic effect. By detecting this ultrasound, the positional information of the lymphatic vessels can be obtained.

[0116] The light absorption characteristics of ICG differ from those of hemoglobin. Specifically, ICG strongly absorbs light with a wavelength around 835 nm. Therefore, by irradiating with light with a wavelength around 835 nm in addition to the two wavelengths of light described in the second embodiment (e.g., 756 nm and 797 nm), blood vessels and lymphatic vessels can be distinguished and detected. Specifically, structures that generate a strong photoacoustic signal in response to 756 nm and 797 nm light are blood vessels, and structures that generate a strong photoacoustic signal in response to 835 nm light are lymphatic vessels.

[0117] The information stored in the blood vessel position information storage means 310 may include not only the position information of blood vessels but also the position information of lymphatic vessels. It may also include information regarding the relative positional relationship between blood vessels and lymphatic vessels. For example, it may include information such as the length of the section in which blood vessels and lymphatic vessels run parallel, the distance between them, and the location of intersections.

[0118] The vascular location information matching means 320 can evaluate the degree of agreement using both vascular location information and lymphatic vessel location information. By utilizing a combined pattern of vascular and lymphatic vessels, the identification accuracy can be further improved. In particular, when identification is difficult with vascular information alone, for example in the identification of twins, it may be possible to improve the identification accuracy by using lymphatic vessel information in combination.

[0119] Furthermore, methods for detecting lymphatic vessels without using contrast agents are also being considered. Lymphatic fluid within lymphatic vessels has a different composition and optical properties than blood. With technological advancements, it may become possible in the future to detect lymphatic vessels without contrast agents by utilizing these differences.

[0120] [Modification 2: Focused use of vascular branching patterns] This modification achieves efficient and highly accurate individual identification by focusing on the branching points of blood vessels rather than the entire course of the vessels. Blood vessel branching patterns vary greatly from individual to individual and remain largely unchanged throughout life. Therefore, blood vessel branching points are extremely useful feature points for individual identification.

[0121] The blood vessel position signal processing means 121 may have a function to automatically extract blood vessel branching points from the detected blood vessel position information. Extraction of blood vessel branching points can be achieved, for example, by applying skeletalization processing and branching point detection algorithms known in the field of image processing. Specifically, the location where one blood vessel branches into two or more blood vessels is identified from a set of three-dimensional coordinates representing the course of the blood vessel.

[0122] The following information can be obtained from the extracted blood vessel branching points: Firstly, the three-dimensional coordinates of the blood vessel branching point. These coordinates may be expressed as the relative position from a reference point on the body of the animal being identified. Secondly, the branching angle. The branching angle is defined as the angle between the direction vector of the blood vessel before branching and the direction vector of each blood vessel after branching. Thirdly, the diameter of the blood vessel. The diameter of the blood vessel before branching and the diameter of each blood vessel after branching can be measured. Fourthly, the branching morphology. It can be determined whether the blood vessel is bifurcated or has three or more branches.

[0123] The information stored in the blood vessel location information storage means 310 may include detailed information about blood vessel branching points. For example, for each individual, information such as the three-dimensional coordinates of multiple blood vessel branching points, branching angles, and blood vessel diameters may be stored. Compared to information about the entire blood vessel course, the amount of data for blood vessel branching points is small, and it can be stored and processed efficiently.

[0124] The blood vessel location information matching means 320 can focus on matching information about blood vessel branching points. Specifically, it determines the correspondence between blood vessel branching points detected from the target animal and stored blood vessel branching points, and evaluates the degree of agreement of the three-dimensional coordinates, branching angles, and blood vessel diameters of the corresponding blood vessel branching points. By evaluating the degree of agreement for all blood vessel branching points and calculating an overall degree of agreement, it is possible to determine the similarities and differences between individuals.

[0125] By focusing on vascular bifurcations, the following advantages can be obtained: Firstly, improved processing speed. Compared to matching the entire course of the blood vessels, only a limited number of vascular bifurcations need to be matched, reducing the amount of computation and enabling faster processing. Secondly, improved identification accuracy. Since vascular bifurcations are features that show particularly large individual differences, focusing on them can achieve high identification accuracy. Thirdly, improved robustness. While the entire course of the blood vessels may deform to some extent depending on the posture and pressure during measurement, the relative positional relationship of vascular bifurcations is relatively stable. Therefore, robust identification can be achieved against fluctuations in measurement conditions.

[0126] [Modification 3: Utilization of oxygen saturation information] This modified version utilizes information on blood oxygen saturation in the blood vessels, in addition to location information, for individual identification. Oxygen saturation is an indicator of the percentage of hemoglobin in the blood that is bound to oxygen. Oxygen saturation is usually high, above 95%, in arteries, and lower, around 70%, in veins.

[0127] As described in the second embodiment, oxygen saturation can be measured by irradiating with light of multiple wavelengths and analyzing the intensity ratio of the photoacoustic signal for each wavelength. Specifically, the difference in the light absorption characteristics of oxygenated hemoglobin and deoxygenated hemoglobin is utilized. By using light of two or more wavelengths, the oxygen saturation in each blood vessel can be measured quantitatively.

[0128] Oxygen saturation is useful not only for distinguishing between arteries and veins, but also as information that reflects an individual's metabolic characteristics. For example, the distribution of oxygen saturation in peripheral blood vessels may differ between people who exercise regularly and those who do not. Furthermore, the distribution of oxygen saturation may also differ between smokers and non-smokers, and between healthy individuals and those with certain diseases.

[0129] However, oxygen saturation levels fluctuate depending on an individual's health condition, whether they are exercising or at rest, and the oxygen concentration of the environment. Therefore, directly using the absolute value of oxygen saturation for individual identification may not be appropriate. In this modified method, the spatial distribution pattern of oxygen saturation is utilized. Specifically, the relative levels of oxygen saturation in multiple blood vessels within the measurement range, the gradient of oxygen saturation, etc., are extracted as features and used for individual identification.

[0130] For example, oxygen saturation can be measured in multiple areas of the palm, and the difference in oxygen saturation between these areas can be used as a feature. This feature is expected to remain relatively stable even if the absolute oxygen saturation at the time of measurement fluctuates. The blood vessel position information storage means 310 stores information about the distribution pattern of oxygen saturation along with the position information of blood vessels for each individual. The blood vessel position information matching means 320 can achieve more accurate individual identification by evaluating the degree of agreement using both the position information of blood vessels and the distribution pattern of oxygen saturation.

[0131] [Variation 4: Use of time-series changes] This modification utilizes the time-series changes in the positional information of blood vessels for individual identification and biometric detection. In particular, the position of arteries changes in accordance with the heartbeat. This fluctuation pattern reflects an individual's heart rate pattern and can be used as additional information for individual identification. Furthermore, by detecting this fluctuation, it is possible to confirm that the person being identified is a living human being, thereby preventing fraudulent authentication using forged biometric information.

[0132] In this modified example, the light irradiation means 111 irradiates light continuously or repeatedly at short time intervals. For example, it irradiates pulsed light approximately 20 to 100 times per second. The photoacoustic detection means 112 detects a photoacoustic signal corresponding to each pulse of light irradiation. The blood vessel position signal processing means 121 analyzes a plurality of photoacoustic signals obtained in a time series and calculates the temporal change in the position of the blood vessel.

[0133] The heartbeat causes periodic fluctuations in blood pressure within the arteries. When blood pressure rises, the arteries expand and their position changes slightly. When blood pressure falls, the arteries constrict and return to their original position. Although this positional change is relatively small in the arteries of the palm and fingers, it can be detected by the high spatial resolution of the identification device in this embodiment.

[0134] The following features can be extracted from the detected changes in arterial position: Firstly, the period of fluctuation, which corresponds to the heart rate. Secondly, the amplitude of fluctuation, which reflects the strength of the arterial pulsation. Thirdly, the waveform of fluctuation. The waveform of the pressure wave propagating from the heart through the arteries reflects the elastic properties of an individual's blood vessels, and therefore individual differences exist. Fourthly, the phase difference between multiple arteries. If multiple arteries exist within the measurement range, the phase relationship of the pulsations in each artery reflects the connectivity of the blood vessels and can be useful information for individual identification.

[0135] The blood vessel position information storage means 310 may store, for each individual, the position information of the blood vessels, along with feature quantities related to changes in the position of the blood vessels. The blood vessel position information matching means 320 can evaluate the degree of agreement using both the position information of the blood vessels and the feature quantities of changes in position.

[0136] Furthermore, this modification is also effective for biometric detection. When attempting fraudulent authentication using forged biometric information, such as artificial materials mimicking blood vessel patterns, it is extremely difficult to reproduce the positional changes caused by heartbeats. Therefore, by detecting changes in the position of blood vessels and confirming that these changes exhibit patterns specific to a living heartbeat, it is possible to verify that the object being identified is a living human being. This significantly improves the security of the identification device.

[0137] [Variation 5: Selection of measurement site] This modification allows the identification device to select from multiple body parts, rather than limiting the measurement site to the palm of the hand. Blood vessels suitable for individual identification exist in various parts of the body. By allowing selection of the measurement site, flexible operation tailored to different applications and situations becomes possible.

[0138] Potential measurement sites include the palms, fingers, backs of the hands, wrists, forearms, tops of the feet, and ankles. These areas all have blood vessels relatively close to the body surface, making them suitable for detection using photoacoustic methods. Each site has its own advantages and disadvantages.

[0139] The palm of the hand is a suitable area for measurement because it is hairless and has a rich distribution of blood vessels. Furthermore, the act of placing the palm on the device is natural and easily accepted. On the other hand, because the palm has a relatively large surface area, the measuring device also needs to be of a certain size.

[0140] Fingers are smaller than palms, making it easier to create compact measuring devices. For example, a cylindrical measuring device into which a finger is inserted can be constructed. On the other hand, because fingers have fewer blood vessels than palms, the amount of information available for identification may be less.

[0141] The wrist and forearm contain relatively large arteries, making it easy to obtain clear photoacoustic signals. It is also possible to construct a measuring device in the shape of a wristwatch. However, these areas may have body hair, and the effects of light scattering and absorption by this hair must be considered.

[0142] The tops of the feet and ankles, like the hands, have a distribution of blood vessels and can be used for individual identification. For example, measurements can be taken by placing the foot on a measuring device installed on the floor. This configuration has the advantage of enabling hands-free authentication.

[0143] The identification device of this modified example may have a configuration that can accommodate multiple measurement sites. For example, the shape and arrangement of the light irradiation means 111 and the photoacoustic detection means 112 may be adjustable according to the measurement site. Alternatively, multiple measurement units corresponding to multiple measurement sites may be provided and selected for use according to the application.

[0144] The blood vessel position information storage means 310 may store blood vessel position information for multiple measurement sites for each individual. This allows authentication to be performed using another measurement site if authentication at a certain measurement site is difficult for any reason. For example, if a person has an injury to their hand, their foot can be used, enabling flexible operation.

[0145] Furthermore, depending on the security level, authentication can be combined using multiple measurement sites. For example, in situations requiring particularly high security, authentication can be performed using both the palm and the foot, and final authentication can only be considered successful if both are successful. Such multi-factor authentication can further enhance security.

[0146] [Extreme modification 6: Automatic adaptation to aging] This modified system maintains high-precision identification over long periods by automatically adapting to age-related changes in an individual's vascular pattern. While the basic structure of a human's vascular pattern remains unchanged throughout life, factors such as aging, changes in health status, and weight fluctuations can cause gradual changes in blood vessel diameter, location, and blood flow. To address these age-related changes, this modified system incorporates an automated adaptation mechanism using machine learning.

[0147] The individual blood vessel location information storage means 310 may have the function of storing blood vessel location information for each individual at multiple points in the past. For example, for a given individual, it may store chronological blood vessel location information such as the blood vessel location information at the time of initial registration, the blood vessel location information one month later, and the blood vessel location information three months later. Each blood vessel location information is accompanied by information on the date and time of measurement.

[0148] The blood vessel location information matching means 320 may include a machine learning model. The machine learning model learns time-series data of an individual's past blood vessel location information and predicts trends in changes in blood vessel patterns over time. For example, a regression model, a time-series prediction model, or a neural network can be used.

[0149] The specific processing flow is as follows: First, each time an individual uses the identification device, the blood vessel location information at that moment is acquired. If authentication is successful, the acquired blood vessel location information is added to the individual's time-series data. From the accumulated time-series data, a machine learning model learns the trends in changes in blood vessel patterns. For example, it can detect trends such as a particular blood vessel gradually becoming wider, or the position of a certain blood vessel branching point gradually shifting.

[0150] During the next authentication, the machine learning model will compare the current vascular pattern predicted by the model with the actually measured vascular pattern. Since the predicted vascular pattern is closer to the current actual vascular pattern compared to using past registration data, authentication accuracy will improve.

[0151] Such an automated adaptation mechanism offers the following advantages. First, it maintains authentication accuracy over a long period. If only the blood vessel pattern at the time of initial registration is used as the basis, authentication accuracy may gradually decrease due to changes over time. In this modified version, the system continuously learns changes in the blood vessel pattern and updates the basis, thus maintaining high authentication accuracy over a long period. Second, it reduces the need for re-registration. In conventional biometric authentication systems, if authentication accuracy decreases due to changes over time, users had to be asked to re-register. In this modified version, because it adapts automatically, authentication accuracy can be maintained without requiring users to re-register.

[0152] Furthermore, it is desirable that predictions made by machine learning models be used only as supplementary information. In other words, authentication should not be determined solely by the degree of agreement with the predicted vascular pattern, but rather by evaluating the degree of agreement with vascular patterns at multiple past points in time as well, and making a comprehensive judgment. This will minimize the impact on authentication accuracy even if the machine learning model makes an incorrect prediction.

[0153] Furthermore, if a sudden change in the vascular pattern is detected, i.e., if there is a large discrepancy between the predicted vascular pattern and the actual vascular pattern, the system may issue a warning. This suggests the possibility of some kind of health problem. For example, it could indicate vascular blockage or abnormal blood flow. Such warnings can encourage users to seek medical attention, and the identification device can potentially assist in health management.

[0154] [Variation 7: Multimodal Integrated Authentication] This modified version constructs a more robust authentication system by combining vascular position information obtained by photoacoustic methods with other biological information obtained from the same light irradiation. When light is shone on a living organism, not only is ultrasound generated by the photoacoustic effect, but light is also reflected from the surface of the organism. By analyzing this reflected light, superficial biological information such as the distribution of skin pigment, texture, and the distribution of capillaries can be obtained.

[0155] The identification device in this modified example may have a reflected light detection means in addition to the photoacoustic detection means 112. The reflected light detection means may be implemented as, for example, an optical camera, an image sensor, or a photodiode array. The reflected light detection means detects the reflected light of the light irradiated by the light irradiation means 111.

[0156] The following information can be obtained from reflected light: Firstly, skin color. Skin color is determined by the amount and distribution of melanin pigment, and there are significant individual differences. Secondly, skin texture. The palms of the hands have unique patterns called palm prints. Palm prints, like fingerprints, are features that can be used for personal identification. Thirdly, the distribution of capillaries near the surface. The distribution pattern of capillaries also varies from person to person.

[0157] By combining this superficial biometric information with deep blood vessel location information obtained by photoacoustic methods, multi-layered authentication can be achieved. Specifically, the blood vessel location signal processing means 121 has the function of processing not only the signal from the photoacoustic detection means 112 but also the signal from the reflected light detection means. The signal from the reflected light detection means is analyzed to extract feature quantities such as skin color, texture, and capillary distribution.

[0158] The individual blood vessel location information storage means 310 stores surface biological information in addition to deep blood vessel location information for each individual. Surface biological information is represented, for example, as a histogram of skin color, characteristic points of palm prints, and capillary distribution patterns.

[0159] The blood vessel location information matching means 320 evaluates the degree of agreement using both deep blood vessel location information and surface biological information. For example, the degree of agreement of the deep blood vessel location information and the degree of agreement of the surface biological information can be calculated separately, and these can be weighted and added together to calculate an overall degree of agreement. Alternatively, a machine learning model may be used to calculate the overall degree of agreement from multiple features.

[0160] This type of multimodal integrated authentication offers the following advantages: Firstly, improved authentication accuracy. By combining multiple different types of biometric information, identification accuracy can be improved compared to using a single biometric. In particular, when identifying individuals with similar vascular patterns, combining surface biometric information makes identification easier. Secondly, enhanced security. Forging multiple biometric pieces of information is more difficult than forging a single biometric piece of information. Therefore, resistance to impersonation is improved. Thirdly, it complements information when one type of information is difficult to obtain. For example, if there is a skin injury, it may be difficult to obtain surface biometric information, but deep vascular information may still be obtainable. Conversely, even if it is difficult to obtain deep vascular information for some reason, authentication can still be performed using surface biometric information.

[0161] Furthermore, the increase in device cost due to the addition of the reflected light detection means is limited. Optical cameras and image sensors are already widely available components and can be obtained at relatively low cost. In addition, since the light emitted by the light irradiation means 111 is shared, no additional light source is required. Therefore, this modified configuration is a practical one that can significantly improve authentication accuracy and security with minimal cost increase.

[0162] [Variation 8: Correction of environmental conditions] This modification improves robustness to variations in measurement conditions by sensing the temperature of the measurement site and the contact pressure during measurement, and correcting for the influence of these environmental conditions on the appearance of blood vessels. Blood vessels, especially veins, are susceptible to the effects of temperature and pressure. Blood vessels constrict in low-temperature environments and dilate in high-temperature environments. Furthermore, if the measurement site is pressed too hard against the measuring device, blood vessels near the surface may be compressed, reducing blood flow and potentially weakening the photoacoustic signal.

[0163] The identification device of this modified example may include a temperature sensor and a pressure sensor. The temperature sensor measures the skin surface temperature of the measurement site. Examples of temperature sensors include infrared thermometers, thermistors, and thermocouples. The pressure sensor measures the pressure when the measurement site comes into contact with the measuring device. Examples of pressure sensors include pressure-sensitive films, load cells, and piezoelectric sensors.

[0164] The blood vessel position signal processing means 121 acquires signals from the temperature sensor and the pressure sensor and records the temperature and pressure at the time of measurement. Furthermore, the blood vessel position signal processing means 121 may have a function to correct the influence of temperature and pressure on the blood vessel position information.

[0165] A specific example of temperature correction is explained below. The blood vessel position signal processing means 121 calculates the difference between the measured skin surface temperature and the reference temperature. The reference temperature is set to a value in the range of, for example, 30°C to 35°C. Based on the temperature difference, the correction amount for the diameter and position of the blood vessels is calculated. For example, if the measured temperature is lower than the reference temperature, it is presumed that the blood vessels are constricted, so the diameter of the blood vessels is corrected by expanding it by a certain coefficient. In addition, since the position of the blood vessels may also change slightly due to the constriction of blood vessels, position correction is also performed. The parameters for correction, i.e., the relationship between the temperature difference and the correction amount, can be determined by prior experiments.

[0166] A specific example of pressure correction is explained below. If the pressure when the measurement site contacts the measuring device is too high, blood vessels near the surface are compressed, reducing blood flow within the vessels. This can lead to a decrease in the intensity of the photoacoustic signal, potentially making it difficult to detect blood vessels. If the measured pressure exceeds a predetermined threshold, the blood vessel position signal processing means 121 outputs an instruction to the user to reduce the pressure. This instruction can be given, for example, by displaying text on a display device, an audio message, or vibration.

[0167] Furthermore, even when the pressure is within an appropriate range, differences in pressure can alter the appearance of blood vessels. The blood vessel position signal processing means 121 may correct the blood vessel position information based on the measured pressure. For example, considering that at high pressures, photoacoustic signals from blood vessels near the surface tend to be weaker, the signal intensity of blood vessels near the surface may be corrected.

[0168] The blood vessel location information stored in the individual blood vessel location information storage means 310 may include information on the temperature and pressure at the time the information was acquired. When the blood vessel location information matching means 320 matches the blood vessel location information acquired from the animal to be identified with the stored blood vessel location information, it may evaluate the degree of agreement by considering the difference in temperature and pressure at the time the two were acquired.

[0169] For example, if the stored vascular location information was obtained under conditions of 32°C temperature and 50 g / cm² pressure, and the vascular location information from the target animal was obtained under conditions of 28°C temperature and 70 g / cm² pressure, the difference in conditions between the two should be taken into consideration. Specifically, the stored vascular location information should be corrected to the current measurement conditions (28°C temperature, 70 g / cm² pressure) before comparison. Alternatively, the vascular location information from the target animal may be corrected to the measurement conditions of the stored information (32°C temperature, 50 g / cm² pressure) before comparison.

[0170] By correcting for these environmental conditions, the following advantages are obtained. Firstly, robustness to variations in measurement conditions is improved. Even with variations in conditions due to seasonal temperature changes or differences in hand placement during measurement, stable authentication accuracy can be maintained. Secondly, usability is improved. In conventional systems, it was necessary to strictly control the conditions during measurement in order to ensure authentication accuracy. For example, instructions such as warming the hands to a certain temperature before measurement or placing the hands with a certain pressure were required. In this modified version, variations in conditions are automatically corrected, so the user does not need to be conscious of strict condition management and can receive authentication with natural actions.

[0171] It should be noted that there are limits to the range of temperature and pressure correction. In extremely low or high temperatures, or extremely strong or weak pressures, proper correction may be difficult. Therefore, it is desirable for the identification device to confirm that the temperature and pressure are within the appropriate range and to warn the user if they are outside the range. For example, if the skin surface temperature is below 20°C or above 40°C, a message such as "Your hand temperature is not appropriate. Please wait a while and try again" may be displayed.

[0172] Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc. that can achieve the objectives of the present invention are considered to be included in the present invention.

[0173] Furthermore, the system configuration shown in Figure 1 and the hardware configuration of the identification device 10 shown in Figure 2 are merely illustrative examples for achieving the objectives of the present invention and are not particularly limited.

[0174] Furthermore, the functional block diagram shown in Figure 3 is merely illustrative and not particularly limiting. In other words, it is sufficient that the information processing system in Figure 1 has the functionality to execute the various processes described above as a whole, and the functional blocks and databases used to realize this functionality are not particularly limited to the example in Figure 3.

[0175] Furthermore, the location of the functional blocks and database is not limited to Figure 3, but can be any location. For example, at least a portion of the functional blocks and database located on the identification device 10 side may be transferred to another information processing device (not shown).

[0176] Furthermore, the series of processes described above can be executed by hardware or by software. Furthermore, a single functional block may consist of hardware alone, software alone, or a combination of both.

[0177] When a series of processes are executed by software, the programs that make up that software are installed on a computer or other device from a network or storage medium. The computer may be a computer that is built into dedicated hardware. Furthermore, a computer can be any computer capable of performing various functions by installing various programs, such as a server, a general-purpose smartphone, or a personal computer.

[0178] Such recording media containing programs may consist not only of removable media (not shown) distributed separately from the main unit of the device to provide the program to the user, but also of recording media provided to the user in a state where they are pre-installed in the main unit of the device.

[0179] In this specification, the step of describing a program to be recorded on a recording medium includes not only processes that are performed chronologically in that order, but also processes that are not necessarily performed chronologically, but are executed in parallel or individually.

[0180] [Note 1] A means for detecting the location of blood vessels in an individual animal, Individual difference determination means for determining individual differences in animals based on the location of the detected blood vessels, An identification device having

[0181] According to Appendix 1, it may be possible to achieve the effect of providing a different identification method from conventional fingerprint authentication and vein authentication by enabling individual identification based on a new principle utilizing photoacoustic effects.

[0182] [Note 2] The aforementioned blood vessel position detection means is A means for irradiating the animal with light, and Photoacoustic detection means for detecting photoacoustic waves emitted from the aforementioned animal, An identification device as described in Appendix 1, having the following features.

[0183] According to Appendix 2, by utilizing a physical phenomenon called the photoacoustic effect, it may be possible to obtain non-invasive location information of blood vessels located deep within the body.

[0184] [Note 3] The light emitted by the aforementioned light irradiation means is pulsed light. The identification device described in Appendix 2.

[0185] According to Appendix 3, by using pulsed light, a clear photoacoustic signal can be obtained due to the instantaneous absorption of light energy, which may result in improved accuracy in detecting the location of blood vessels.

[0186] [Note 4] The location of the blood vessels includes the location of the arteries in animals. An identification device as described in any one of the items 1 to 3 of the appendix.

[0187] According to Appendix 4, by utilizing information from arteries located deep within the body, it may be possible to achieve robust identification in response to low-temperature environments and changes in physical condition.

[0188] [Note 5] The light irradiation means can irradiate with light of two or more different wavelengths. The identification device described in Appendix 2 or 3.

[0189] According to Appendix 5, by using light of multiple wavelengths, it may be possible to obtain the effect of distinguishing and detecting arteries and veins by utilizing the difference in light absorption characteristics between oxygenated hemoglobin and deoxygenated hemoglobin.

[0190] [Note 6] The information regarding the location of the blood vessels is information regarding the relative positions of veins and arteries. The identification device described in Appendix 4 or 5.

[0191] According to Appendix 6, by utilizing the complex positional relationship between arteries and veins, particularly the characteristics of the areas where they approach or intersect, it may be possible to significantly improve the accuracy of identification.

[0192] [Note 7] The aforementioned identification device is capable of identifying the course of blood vessels in three dimensions. An identification device as described in any one of the items 1 to 6 of the appendix.

[0193] According to Appendix 7, by utilizing three-dimensional vascular anatomy information, which differs from conventional two-dimensional biometric information, it may be possible to achieve highly secure authentication that is difficult to forge.

[0194] [Note 8] The photoacoustic detection means has a plurality of photoacoustic probes, The plurality of photoacoustic probes are arranged in two or three dimensions. An identification device as described in any one of the appendices 2, 3, 5 through 7.

[0195] According to Appendix 8, by arranging multiple photoacoustic probes in two or three dimensions, it may be possible to detect ultrasound generated from blood vessels from various directions and obtain the effect of calculating the three-dimensional position of blood vessels with high accuracy.

[0196] [Note 9] The information relating to the location of the blood vessel includes information relating to the location where the blood vessel branches. An identification device as described in any one of the items 1 to 8 of the appendix.

[0197] According to Appendix 9, by utilizing information on blood vessel branching points, where individual differences are particularly large, it may be possible to achieve efficient and highly accurate individual identification.

[0198] [Note 10] This does not include means for visualizing the location of the blood vessels. An identification device as described in any one of the items 1 through 9 of the appendix.

[0199] According to Appendix 10, by omitting complex image display functions such as those found in medical imaging diagnostic equipment, it may be possible to achieve a simple and practical device configuration specialized for authentication, thereby reducing costs and miniaturizing the device.

[0200] [Note 11] Connected to an external server via the network, The external server has individual vascular location information storage means for storing individual vascular location information, and vascular location information matching means for matching the vascular location information. An identification device as described in any one of the items 1 to 10 of the appendix.

[0201] According to Appendix 11, by coordinating with an external server, it may be possible to achieve the effect of centralized management of individual blood vessel location information and load balancing of matching processing in a large-scale authentication system that installs numerous identification devices.

[0202] [Note 12] The aforementioned individual difference / identity determination means is A blood vessel position signal processing means including a photoacoustic wave digitization means that converts the photoacoustic wave signal detected by the photoacoustic detection means into a digital signal, and Individual difference / sameness determination result output means for outputting individual difference / sameness determination results, An identification device having the features described in any one of the appendices 2, 3, 5, 8 to 11.

[0203] According to Appendix 12, by digitizing and processing analog signals, advanced signal processing such as noise reduction can be applied, which may result in improved accuracy in acquiring vascular position information.

[0204] [Note 13] The information regarding the location of the blood vessel includes information on the oxygen saturation of the blood in the blood vessel. The identification device described in Appendix 5 or 6.

[0205] According to Appendix 13, by utilizing information that reflects an individual's metabolic characteristics, such as oxygen saturation, as an additional identification element, it may be possible to further improve the accuracy of identification.

[0206] [Note 14] The blood vessel position detection means acquires information regarding the position of the blood vessel at multiple points in time, The information regarding the location of the blood vessel includes information regarding its changes over time. An identification device as described in any one of the items 1 to 13 of the appendix.

[0207] According to Appendix 14, by detecting patterns of arterial position changes caused by heartbeats, it may be possible to simultaneously achieve biometric detection and individual identification, thereby preventing fraudulent authentication using forged biometric information.

[0208] [Note 15] The system further includes a reflected light detection means for detecting light reflected from the aforementioned animal, The individual difference determination means determines the differences between individual animals based on information regarding the location of the blood vessels and information obtained from the reflected light. An identification device as described in any one of the appendices 2, 3, 5, 8, or 12 through 14.

[0209] According to Appendix 15, multimodal authentication combining deep vascular information and surface biometric information may improve authentication accuracy and security, and may also have the effect of being able to compensate for the difficulty in obtaining one type of information with the other.

[0210] The identification device of the present invention can be applied to various industrial fields where biometric authentication technology is required. For example, in the security industry, it can be used in access control systems for critical facilities, identity verification systems in financial institutions, and authentication systems for various services requiring personal authentication. In the medical industry, it can be used in patient identification systems and access control systems for medical information. Furthermore, it can be applied to personal identification systems in law enforcement agencies and immigration control systems in border control. Compared to conventional biometric authentication technologies, the identification device of the present invention has high identification accuracy and stability, making it particularly useful in situations where a high level of security is required. [Explanation of Symbols]

[0211] 10 Identification device 30 External Servers N Network 110 Blood vessel position detection means 111 Light irradiation means 112 Photoacoustic detection means 112p photoacoustic probe 120 Individual Difference / Similarity Determination Method 121 Blood vessel position signal processing means 122 Individual Difference / Similarity Determination Result Output Means 310 Individual blood vessel location information storage means 320 Blood vessel position information matching means

Claims

1. A means for detecting the location of blood vessels in an individual animal, Individual difference determination means for determining individual differences in animals based on the location of the detected blood vessels, An identification device having

2. The location of the blood vessels includes the location of the arteries in animals. The identification device according to claim 1.

3. The information regarding the location of the blood vessels is information regarding the relative positions of veins and arteries. The identification device according to claim 2.

4. The aforementioned identification device is capable of identifying the course of blood vessels in three dimensions. An identification device according to any one of claims 1 to 3.

5. This does not include means for visualizing the location of the blood vessels. An identification device according to any one of claims 1 to 4.

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