CN101231690A - Biometric pattern detection method, biometric pattern detection device, biometrics authentication method, and biometrics authentication device - Google Patents

Abstract

The invention discloses a living tissue mode detection method, a living tissue mode detection device, a biostatistics authentication method and a biostatistics authentication device. The invention allows reliable biometric authentication without risk of forgery or the like. The invention allows biometric authentication and biometric authentication. Detects the concave-convex distribution pattern of deep skin tissue covered by epidermal tissue to extract a unique pattern of living tissue. Biometric authentication is performed based on the detected pattern. The concavo-convex distribution pattern is optically detected by utilizing the difference in optical properties between the epidermis tissue and the deep skin tissue. In this case, long-wavelength light such as near-infrared light is used as illumination light projected onto skin tissue. A branched portion of a subcutaneous blood vessel was used as a portion to be detected. The portion to be examined is determined based on the structure of the bifurcation, in which case subcutaneous blood vessels can be used for biopsy identification.

Description

Biometric pattern detection method, biometric pattern detection device, biometrics authentication method, and biometrics authentication device

This application is an invention patent application with an application date of May 7, 2003, an application number of 03813962.6, and an invention title of "Live tissue pattern detection method, biometric pattern detection equipment, biometric authentication method, and biometric authentication equipment" divisional application.

technical field

The present invention relates to a new biometric pattern detection method and a biometric pattern detection device for obtaining a pattern of a deep skin layer such as the dermis, and more particularly to a biometric authentication method and a biometric authentication device.

Background technique

Fingerprints, palm prints, etc. are widely used for personnel authentication. These patterns are skin ridge patterns in which part of the epidermal tissue is embedded in the concave-convex structure of the dermis, so they can be directly observed from the outside. That is, the above-mentioned pattern basically corresponds to the deep structure of the skin such as the dermis or the like. Parts of the skin such as palms, soles, etc. have a specific structure different from other parts of the skin, where the epidermal structure corresponds to the structure of the dermis beneath the epidermal tissue, leading to several physiological advantages, such as the tactile nerves whose terminals are located deep in the skin to the outside High sensitivity to stimuli, greater toughness to friction, etc. Generally, fingerprints have been used for personal authentication because the high stability of the underlying deep structure makes the fingerprint basically exhibit sufficient stability.

However, the above-mentioned biometric authentication using fingerprints does not have sufficient security against so-called "spoofing" and the like. That is, fingerprints are easily left on various objects, and the fingerprints left on the objects can be easily observed, thereby causing the risk of other people forging fingerprints.

On the other hand, it is expected that biometric authentication using epidermal tissue of other parts can avoid the above-mentioned risks such as forgery. However, the epidermal tissue undergoes changes due to its metabolism during the 28-day cycle. In addition, the epidermal tissue is prone to various states due to rough skin, dry skin, and the like. Therefore, the epidermal tissue of other parts does not have sufficient stability. In addition, it has been known from measurements that the pattern of the epidermal tissue of the base of the fingers, palm area, etc. does not correspond at all to the underlying pattern, but in some cases its epidermal tissue pattern is formed in relation to the underlying pattern Orthogonal, except in special cases such as fingerprints, which makes it difficult to use such parts in biometric authentication.

That is to say, the pattern of the epidermal tissue of a large part of the human body (including the palm such as the palm area, etc., the base of the fingers, the skin of the back of the hand, etc.) is different from the pattern of the underlying deep structure, except for fingerprints such as fingerprints, where Except for the special case where the epidermal tissue corresponds directly to the deep structure, thus allowing its external observation. In addition, due to the scattering and absorption of visible light from the 6-layer epithelial structure by melanin in the basal cells and the like, it is difficult to externally observe the underlying deep structures. This makes it difficult to develop a ring-type authentication device in which person authentication is performed using a pattern of skin in contact with the inner surface of the ring when the user wears the ring.

On the other hand, like well-known examples of fingerprints and the like, the deep structure under the epidermal tissue is basically unique to an individual and exhibits sufficient stability over time. Note that tattoos caused by pigment being injected into the deep structures, and stretch marks caused by pregnancy also have the same stability due to the nature of the underlying deep structures of the epithelial tissue. Therefore, it is expected that the pattern underlying the epithelial cell organization, that is, the deep structure of the epithelial cell organization is properly used for biometric authentication. However, the above-mentioned patterns cannot be directly observed and cannot be left on objects through contact with them, so authentication devices using deep structured patterns have not been developed, although deep structured patterns have the same biometric authentication performance as fingerprints.

In order to solve the above-mentioned problems, the present invention has been proposed, and it is therefore an object of the present invention to provide a biometric pattern detection method and a biometric pattern detection device for obtaining concavities and convexities of deep structures under epithelial cell tissues that cannot be directly observed Distribution of roughness structure (pattern under epithelial tissue), or pattern of blood vessels under epithelial tissue. Furthermore, it is an object of the present invention to provide a biometric authentication method and a biometric authentication device that allow stable biometric authentication while preventing "spoofing" risks such as forgery or the like.

Contents of the invention

The inventors of the present invention have conducted various studies to achieve the above objects. As a result, it was found that it was possible to discriminate the epidermal tissue and the deep skin tissue using the difference in properties (optical properties, electrical properties, and temperature difference) between the epidermal tissue and the deep skin tissue, and to clearly detect those that were difficult to visually observe due to the shielding of the epidermis Bump distribution pattern in deep skin tissue. Therefore, it was found that any desired part of the skin and subcutaneous tissue of the user's entire body can be detected, and a pattern in which the epidermis pattern corresponds to a special part such as a fingerprint, etc., and the thus detected pattern can be applied to biometrics authentication (Personnel Authentication).

The present invention has been made based on the information thus obtained. That is, for the living tissue pattern detection method according to the present invention, the unevenness distribution pattern of the deep skin tissue covered by the epidermal tissue is detected using the difference in properties (optical properties, electrical properties, and temperature difference) between the deep skin tissue and the epidermal tissue , thereby extracting a unique pattern of living tissue. Furthermore, the living tissue pattern detecting device according to the present invention includes means for detecting the concavo-convex distribution pattern of the deep skin tissue covered with the epidermal tissue. Furthermore, with the biometric authentication method according to the present invention, the concavo-convex distribution pattern of the skin deep tissue covered with the epidermal tissue is detected to compare it with a previously registered pattern, thereby performing biometric authentication. In addition, the biometric authentication device according to the present invention includes means for detecting a concavo-convex distribution pattern of the deep skin tissue covered with the epidermal tissue, and compares the pattern thus detected with a pattern registered in advance, thereby performing biometric authentication .

The present invention is proposed based on the basic idea of performing authentication not using epidermis patterns, but patterns of deep skin tissue such as dermis patterns. The concavo-convex distribution patterns (patterns) of deep tissues are unique to individual living tissues like fingerprints, palm prints, foot prints, etc., and change little over time, that is, exhibit high stability. Furthermore, the deep tissue of a larger part of the skin has a pattern different from that of the epidermis, except for a special part such as a fingertip with a fingerprint that can be observed from the outside, and the like. Furthermore, patterns in deep tissues are covered by epidermal tissue, making visual observation difficult from the outside. Furthermore, even if the tissue comes into contact with any object, it will not leave an imprint on that object. Therefore, it is almost impossible for others to forge such a pattern.

Furthermore, with the present invention, the system does not detect dead tissue without nuclei, such as structures such as skin keratinization, in particular fingerprints, etc., but deep tissue of the skin as living tissue, as described above. Skin deep tissue does not retain its pattern if deep tissue is excised from a living human body. For example, deep skin tissue has capillaries therein, and the pattern of blood flow composition within the capillaries is unique to living tissue. Furthermore, if the tissue is excised from a living human body, the aforementioned pattern is immediately lost due to vasoconstriction, blood retention, blood loss, etc. This affects the pattern of the deep tissue throughout the skin. Thus, with the present invention, biometric authentication and biometric authentication are integrated, thereby reducing the risk of "spoofing" using user tissue to unexpected levels, and achieving true "biometric authentication".

Utilizing the fact that the structural difference between the epidermal tissue composed of simple cells or their dead cells and the dermal tissue as a densely connected tissue results in a difference in its scattering properties and refractive properties, it is possible to optically detect the above-mentioned deep skin tissue such as the dermis Bump distribution pattern, and this results in a difference in polarization or frequency of the incoming and returning light.

Specifically, firstly, polarized light is projected onto the tissue, and reflected light is detected through a polarizing filter whose polarization plane is orthogonal to that of the above-mentioned polarized light, thereby detecting the above-mentioned concavo-convex distribution pattern. In this case, polarized light is projected on the tissue surface and the reflected light is filtered with a polarizing filter whose plane of polarization is orthogonal to the aforementioned polarization, thus only detecting depolarizations due to scattering in living tissue Light, such as backscattered light, light split due to birefringence, etc., to extract patterns of tissues whose properties cause the light to scatter, such as the underlying dermis, such as the epidermis. In particular, such an arrangement is made that, for example, near-infrared light or the like, which has a property of easily passing through the epidermal tissue and is easily scattered in the dermal tissue, is used as the above-mentioned polarized light, thereby reducing the difference caused by the polarized light in the living tissue. The detrimental effect caused by absorption, and effectively detect the pattern of the subcutaneous tissue under the epidermis due to the desired optical properties (scattering properties, birefringent properties, etc.) of the subcutaneous tissue under the epidermis.

Next, an arrangement is made such that the illuminating light is projected onto the tissue and causes interference between a part of the illuminating light and the reflected light, so that a change in the wavelength component of the reflected light is detected in the form of an interferogram, thereby extracting the unique model. In this case, the system causes interference between the reflected or scattered light of the skin and the incident light serving as reference light divided by a half-mirror or the like, whereby a beat pattern (interference pattern) ) to detect changes in wavelength components caused by birefringence or scattering in the internal structure of the skin. Such a beat profile has properties unique to individual living tissue, allowing authentication using the beat profile.

Furthermore, with the biometric authentication method and the biometric authentication device according to the present invention, an arrangement is made such that the subcutaneous tissue structure covered by the epidermal tissue is electrically detected using the difference in electrical properties between the epidermal tissue and the deep skin tissue , and the subcutaneous tissue structures thus detected are compared with previously registered patterns, allowing biometric authentication. Furthermore, an arrangement is made such that the subcutaneous tissue structure covered by the epidermal tissue is detected using the temperature difference between the epidermal tissue and the deep skin tissue, and the subcutaneous tissue structure thus detected is compared with a pattern registered in advance, thereby allowing Perform biometric authentication.

Description of drawings

Fig. 1 is a schematic diagram showing skin tissue.

FIG. 2 is a schematic diagram showing an example of a detection device (authentication device) for obtaining a dermal tissue image using polarization caused by backscattering of light.

Fig. 3 is a schematic diagram showing an example of a detection device (authentication device) for obtaining a scattered light image from a desired depth of the skin.

Figure 4 is a schematic diagram depicting a birefringence measurement setup using optical heterodyne interferometry (opticl heterodyne interferometry).

FIG. 5 is a schematic diagram showing an example of a detection device (authentication device) that detects a tissue pattern under the epidermis using a scattering property pattern obtained due to interference of light returned from the skin.

FIG. 6 is a schematic diagram showing an example of a detection device (authentication device) having a structure in which a plurality of beat detection devices are arranged.

Fig. 7 is a schematic diagram showing an example of a detection device (authentication device) having a structure in which a movable mirror is provided for the lighting unit to project light onto the skin.

FIG. 8 is a schematic diagram showing an example of a detection device (authentication device) having a function of determining a portion to be authenticated based on a venous blood vessel pattern.

FIG. 9 is a characteristic diagram showing absorption spectra of oxidized hemoglobin and reduced hemoglobin.

FIG. 10 is a characteristic diagram showing the difference in transmittance of hemoglobin and water in living tissue.

FIG. 11 is a schematic diagram showing an example of a detection device (authentication device) that performs pattern detection by differential interferometry using near-infrared light.

Fig. 12 is a schematic diagram showing an example of a skin surface potential detection device.

Fig. 13 is another schematic diagram showing an example of a skin surface potential detection device.

FIG. 14 is a schematic diagram showing a subcutaneous tissue pattern detection device having a structure in which a plurality of skin surface potential detection devices are two-dimensionally arrayed.

Fig. 15 is a waveform diagram showing potential waveforms observed while walking.

Detailed ways

The biometric pattern detection method, biometric pattern detection device, biometric authentication method and biometric authentication device of the present invention will be described in detail below with reference to the accompanying drawings.

For example, biometric authentication using fingerprints has a risk of being falsified by other persons since imprints (fingerprints) are easily left on another object and can be easily observed. As a countermeasure, it is necessary to perform biometric authentication for determining whether the detected fingerprint was obtained without via unauthorized means. The reason for this is that biometric authentication using fingerprints is basically a measurement of the histological structure of dead tissue without nuclei, such as the cornified layer of the skin, by optical or electrical detection.

The security performance of biometric authentication using the above-mentioned fingerprint, iris, etc. depends not only on the detection accuracy but also on the above-mentioned living tissue identification. For example, other persons can subvert biometric authentication when using fingerprints for biometric authentication and have obtained tissue for biometric authentication. This allows others to easily "cheat" resulting in zero degradation of system security. In addition, the above-mentioned "cheating" with organizations leads to new additional risks of serious danger to the user's body and life, as well as financial risks in the event of a breach of the security of conventional credit cards. The aforementioned serious danger to the body and life of the user is hereafter referred to as "surgical danger".

Biometric authentication needs to provide not only sufficient limited security performance already proposed in conventional authentication techniques, but also sufficient security performance against surgical hazards (almost never proposed in traditional methods) to guarantee user safety.

That is, the security features of the biometric authentication include two security features. One security feature depends on the precision of the "authentication" used to identify whether the organization to be authenticated matches that of the user. Another security feature depends on the accuracy of the "live tissue identification" used to determine whether the tissue being authenticated is live tissue, ie, to confirm that the tissue is not dead tissue removed from the user's body. Conventional biometric authentication techniques only provide the accuracy and reliability of the former security feature. In this case, "biometric authentication" as used herein basically means authentication without "living tissue identification", and thus does not refer to true biometric authentication. Therefore, from a practical point of view, conventional safety systems with such problems lead to additional hazards, ie surgical hazards.

For the simplest method of spoofing without using any specific technique and equipment, the spoofing is performed using tissue excised from the user's body such as fingers, arms, eyeballs, etc. This simplest method of breaching the security of biometric authentication leads to new additional and serious dangers to the life and body of the user, which cannot be replaced by money, even in the case of minor financial losses . Therefore, conventional biometric authentication methods utilizing fingerprints, iris inside the eye, etc. are reserved as adjuncts for other primary authentication means, or as adjuncts in limited form for non-essential transactions and the like. This makes it difficult to widely use conventional biometric authentication.

On the other hand, it is relatively easy to forge fingerprints and the like. As a countermeasure against fingerprint forgery, the electrostatic capacity or electrostatic induction between the finger and the electrode is measured to detect the distance between the skin surface and the electrode, thereby detecting the pattern of the fingerprint, which utilizes the fact that due to sweat secreted from living tissue, etc. etc. Moisture (water) containing salt, the surface of the skin acts as a conductive material. This is an example of biometric authentication with "live tissue authentication". The reason is that it is impossible to perform the above measurement without moisture as electrolyte solution containing salt from sweat secreted by living tissue or the like.

However, although the above detection method requires moisture acting as an electrolyte on the surface of the object to be authenticated, the object does not have to be alive. That is, with the above detection method, "living tissue authentication" is not performed to confirm, for example, that the object to be authenticated has not been excised from the user's body. Therefore, with the above detection method, it is difficult to reject unauthorized means such as forging a fingerprint composed of a gel material having water retention, or a finger that has been excised from the user's body and subjected to spraying or soaking of physiological saline solution.

In addition, for biometric authentication using DNA or the like, although it is difficult to falsify DNA, it is basically impossible to distinguish whether the DNA sample to be authenticated belongs to the user's living body or is obtained from the user's dead body or hair by duplication with PCR (polymerization chain reaction). The resulting DNA consists of DNA blocks. Therefore, biometric authentication using DNA does not include "living tissue identification". Therefore, biometric authentication using DNA requires some kind of countermeasure, such as a new type of discrete sensor for detecting the blood flow in the finger by an appropriate method, such as using infrared rays, etc., and "biometric authentication" to identify whether the sample is Belongs to the user's living body.

In this case, "biometric authentication" is performed by 2 means. One is "authentication" and the other is "living tissue identification". That is, conventional "biometric authentication" not only depends on "authentication" that actually acts as a "front door", but also depends on "biological tissue identification" that actually acts as a "back door", where different physical principles are used in separate detection devices In the implementation of "live tissue identification". Therefore, the problem with the conventional "biometric authentication" is that if other people break the security of the "biometric authentication" which acts as a back door, the security of the biometric authentication security is broken, thereby causing a risk of "spoofing", and Risk of surgical hazard. For "living tissue authentication", the system authenticates whether the tissue to be authenticated is alive or dead. However, living tissue is of great diversity, so "live tissue discrimination" must be performed on individual tissue samples with a sufficiently wide range of thresholds, which can be determined by the standing theory of what life is (the central dogma). Learned. This leads to the fundamental problem of poor security of conventional "biometric authentication" against "spoofing". That is, with conventional "biometrics authentication" having separate means consisting of "authentication" means and "living tissue identification" means, others can easily find and analyze the identification mechanism for identifying tissue dead or alive. Therefore, there is a need for a "true" biometric authentication that integrates "authentication" means and "living tissue identification" means, that is, biometric authentication without the above-mentioned "back door".

With the present invention, biometric authentication is performed based on the concavo-convex distribution pattern of epithelial deep structural tissue, such as the dermis, rather than the pattern of epidermal tissue such as the above-mentioned fingerprint.

FIG. 1 is a schematic diagram showing skin tissues roughly classified as epidermis 1 and dermis 2 . The epidermis 1 is a stratified squamous epithelium composed of cornified layer 11 , clear layer 12 , granular layer 13 , acanthocyte layer 14 , base layer 15 and basement membrane 16 . Note that the layer consisting of the granular layer 13, spiny cell layer 14, and basal layer 15 is called "Malpighian layer".

The cornified layer 11 has a lamellar liquid crystal structure composed of a bilayer film composed of intercellular oils of the stratum corneum. The transparent layer 12 has a cholesteric liquid crystal structure and the granular layer 13 consists of cells whose cytoplasm contains basic structures called "hyaline keratinous granules" whose optical properties lead to the reflection and scattering of light (like beads). ). On the other hand, the base layer 15 has melanin particles. As described above, skin tissue has a multilayer structure with various optical scattering/absorption properties resulting from each layer, resulting in an advantage of preventing exposure of living tissue to ultraviolet rays and the like. In particular, the skin 1 has a dichroic property for ultraviolet rays due to a multilayer structure composed of thin films each having a different refractive index. However, the epidermis 1 is a translucent tissue with relatively high scattering properties in the visible light range, except for light absorption due to melanin. Note that the skin 1 has high transparency in a longer wavelength range than red visible light or near-infrared light. Accordingly, the light reflected by the blood flow of the capillaries in the dermis 2 underlying the epidermis 1 is scattered. Scattered light is observed as skin color or skin color. Note that skin color basically depends on the distribution of melanin and blood flow of capillaries in the dermis. There is no flow of electrolyte fluids such as blood or lymph in the epidermis 1 , so the epidermis 1 essentially acts as a dielectric medium as exemplified by the stratum corneum 11 .

Dermis 2, on the other hand, has a substantially different structure compared to epidermis 1 . Unlike the epidermis 1 which consists of simple cells without capillaries, the dermis 2 basically consists of dense fibronectin tissue composed of collagen or elastin, and a pattern of capillaries.

Dermis 2 is classified into papillary and reticular layers. The papillary dermis is in contact with the epidermal tissue through a basement membrane serving as the lowermost layer of the epidermal tissue, consists of connective tissue and capillary patterns, and has the terminals of sensory nerves. The reticular layer is composed of collagen with an array structure, elastin for connecting the collagen structures to each other, and fillers to fill the spaces in between. The dermis 2 contains a large amount of electrolyte fluid due to the flow of a large number of capillaries and lymph, etc., resulting in a very high electrical conductivity compared to the epidermis 1 .

[Methods using optical properties]

While collagen and elastic fiber tissue forming the connective tissue of the dermis 2 exhibit high optical birefringence properties, epidermal tissue does not exhibit birefringence properties. On the other hand, the skin 1 has optical properties that cause light to scatter, and polarizing properties that cause light to be polarized due to the scattering. In terms of fundamental mechanism, tissue exhibits a unique vertical/horizontal polarization ratio that depends on the size and shape of the scattering particles within it.

Rayleigh scattering occurs where the wavelength of the electromagnetic wave is much larger than the particle size.

Mie scattering occurs where the wavelength of the electromagnetic wave typically matches the particle size. (This scattering makes cloud particles, aerosols and cumulonimbus appear white in color)

In the case where the wavelength of the electromagnetic wave is much smaller than the particle size, the electromagnetic wave passes through the object geometrically. (eg, a rainbow made of rain particles, ice crystals)

The dermis 2 whose thickness is greater than a certain thickness appears white, like milk agar. In addition, the dermis 2 has an optical property that the longer the wavelength of light, the easier it is to pass through the dermis 2 . On the other hand, the shorter the wavelength of light, the easier it is to scatter. We consider Dermis 2 to contain a large amount of absorbing pigment. In this case, the short-wavelength light scattered by the shallow portion returns to the observer's eyes with a higher probability. However, due to the absorption of light by the pigments, the long wavelength light returns to the observer with a lower probability. Therefore, the capillaries in the superficial part of the skin appear bright red when viewed from the outside, while the venous vessels and hemangiomas located in the relatively deep part appear relatively blue. Note that while moles (birthmarks) caused by melanocytes at the border of the dermis and epidermis appear relatively brown when viewed from the outside, blue nevi located in the dermis appear relatively blue when viewed from the outside, where the name and color unanimous. In addition, nevus of Ota and fetal spots caused by dermal melanocytes appear relatively blue from clinical observation.

With the present invention, the system detects the concavo-convex distribution pattern and the like of the deep structure of the skin (eg, dermal tissue) using the difference in optical or electrical properties between dermal tissue and epidermal tissue, thereby performing biometric authentication. For example, filtering reflected light from tissue samples to exploit differences in scattering/polarization properties of reflected light to incident white light between dermal and epidermal tissues to identify connective tissue, collagen fibrous tissue, etc. in deeper sections dermis and epidermis. This allows the user to clearly distinguish dermal tissue (where dermal tissue is difficult to see due to occlusion by the epidermal tissue) from epidermal tissue. In particular, an advantage of the present invention is that it allows person authentication by detecting patterns of dermal tissue by utilizing any part of the user's body, as well as the skin or subcutaneous tissue of specific parts such as fingerprints etc. where the dermal tissue pattern matches the epidermal tissue pattern .

FIG. 2 shows an example of the construction of a detection device for obtaining an optical image of the dermis 2 below the epidermis having a very rich scattering mechanism as described above. The detection device has a structure in which light returned due to scattering and birefringence is allowed to pass through a receiver of the detection device while passing through a polarizing device including a polarizing plate at a light emitting unit and a light receiving unit having polarization planes orthogonal to each other , to prevent light reflected from the epidermis from being received.

The following describes specific structures. First, the illumination optical system includes a light source 21 , an optical lens 22 and a polarizer 23 for the illumination unit. Any suitable light source such as an LED or the like can be used as the light source 21 . Note that a light source for emitting long-wavelength light such as near-infrared light or the like is preferably used as the light source 21 because such long-wavelength light has properties of easily passing through epidermal tissue and being reflected by dermal tissue. This structure allows the acquisition of patterns of tissue using optical properties such as scattering properties, birefringence properties and the like.

On the other hand, the imaging optical system includes an imaging device (solid-state image sensor such as a CCD) 24 serving as a light receiving device, an imaging lens group 25 and a receiving unit polarizing plate 26 . Furthermore, a half mirror 27 is arranged on the optical path between the above-mentioned illumination optical system and imaging optical system. Note that the above-described illumination optical system and imaging optical system are arranged to have polarization planes orthogonal to each other.

For the detection device described above, the illuminating light is projected from the light source 21 to the skin with a single polarization plane determined by the polarizing plate 23 of the illuminating unit. On the other hand, the imaging optical system includes a receiving unit polarizing plate 26 whose polarization plane is orthogonal to that of the illuminating unit polarizing plate 23 . Therefore, reflected light from the epidermis tissue by simple reflection passes with a polarization plane orthogonal to that of the receiving-unit polarizing plate 26 , and thus such reflected light is intercepted by the receiving-unit polarizing plate 26 .

Illumination light projected from the illumination optical system to the skin reaches deep skin tissue (for example, dermal tissue), causing scattering or birefringence of the light due to various tissues, thereby generating its polarization. Reflected light such as backscattered light passes through the half mirror 27, and is introduced into the above-mentioned imaging optical system. In this case, the reflected light is polarized so as to allow the reflected light to pass through the receiving unit polarizer 26 , so that the backscattered light reaches the imaging device 24 .

Birefringence due to reflection or scattering in dermal tissue including connective tissue, collagen, etc., having properties that cause light birefringence, the above scattered or reflected light exhibits a phase shift with respect to incident light. Note that the epidermal tissue does not contain the aforementioned materials having properties that cause birefringence of light. For this embodiment, by detecting the phase difference of light between epidermal tissue and dermal tissue, the system discriminates scattered/reflected light from epidermal tissue and from dermal tissue (resulting in birefringence of light).

Furthermore, an arrangement may be made in which the system allows only reflected light having a phase shift due to birefringence in dermal tissue within a predetermined wavelength range to pass through a band-pass filter such as a dichroic filter or the like, and only detects The light is so selected that only tissue causing birefringence of the light is selectively detected and allows external observation of dermal tissue in a non-invasive manner.

On the other hand, as an example of skin measurement using polarized light, there is known a method in the cosmetic industry in which skin is observed through polarized light using the optical properties of a polarizing filter in the visible range. For example, there is known a measurement method for estimating the skin surface in which cosmetic factors such as skin luster, skin brightness, etc. are measured (see Japanese Examined Patent Application Laid-Open Specification No. 3,194,152, or Japanese Examined Utility Model Registration Application No. 7-22655).

However, this conventional measurement method is not configured for observing the underlying tissues of the epidermis, such as dermal tissue, etc., but for estimating the skin surface using visible light from a cosmetic and appearance point of view. That is, the disclosed solution is merely a method of obtaining an image of the skin from scattered light of the skin using visible light, while using the well-known property of depolarization of light due to scattering to prevent keratosis of the epidermis, etc. The image quality is degraded by the excessively bright reflected light directly reflected by the layer, so that a stable skin image is obtained.

Although this conventional method using visible light has the function of detecting scattered light of the epidermis, the use of visible light makes it difficult to accurately detect the state of the dermis due to the absorption or interception of visible light by acanthocytes or basal cells containing melanin. In addition, this makes it difficult to form an image by extracting light that is birefringent due to dermal tissue. A method has not yet been proposed in which the structure of the dermal tissue is observed using the following properties: the dermis layer comprising connective tissue, collagen tissue, etc. exhibits strongly anisotropic optical properties resulting in birefringence of light compared to the epidermis, and The epidermal tissue exhibits a high transmittance of near-infrared light different from visible light, that is, the structure of the dermal tissue is observed using the scattering properties and birefringence properties of the densely connected tissue forming the dermal tissue; this is newly proposed in this application.

As described above, the detection apparatus described above has a function of detecting the structure of the dermis (eg, unevenness distribution pattern) using the scattering properties or the birefringence properties of the densely connected tissue forming the dermis. Note that the shortcoming of the detection device with the structure shown in Figure 2 is the increased noise due to the scattered light of the epidermis and the scattered light of the dermal tissue below the surface of the dermis to be detected, the subcutaneous tissue, etc., making The SN ratio drops. Fig. 3 shows an example of an effective structure of a detection device for solving the above-mentioned problems, in which illumination light is projected to the skin at a shallow angle, and the aperture of the imaging optical system is limited.

The detection device shown in FIG. 3 also includes a movable mirror 28, and has a structure in which illumination light is projected from an illumination optical system to the skin in an oblique direction. Furthermore, the detection device comprises imaging optics arranged just above the tissue to be measured, allowing direct detection of backscattered and side scattered light without the half mirror 27 . Furthermore, the detection device contains a light shield 29 for limiting the aperture so that only light returning from the portion just below the aperture is allowed to reach the imaging device 24 .

With the detection device having such a structure, the illumination light projected from the illumination optical system passes through the tissue from the epidermis to the deep structure of the skin (dermis) in an oblique direction. In this case, in the region on the right shown in the drawing, there is light scattering due to the very shallow portion, i.e., epidermal tissue, thereby preventing the scattered light from the very shallow portion from being restricted by the shading plate 29. The aperture reaches the imaging optics. In the same way, there is scattering of light due to the very deep portion in the region on the left shown in the drawing, thereby preventing the scattered light from the very deep portion from reaching the imaging optical system through the aperture restricted by the shading plate 29 . On the other hand, for the detection device in which the angle of the above-mentioned movable mirror 28 is adjusted so that the position of the dermal tissue on which the incident light is projected is just below the above-mentioned imaging optical system, only scattered light from this area (dermal tissue) reaches the imaging optical system. system.

A detection method using birefringence of dermal tissue is described below. First, an arrangement may be made in which a well-known method for detecting birefringence is used, for example, using an optical method that converts the phase difference between illumination light and reflected light or transmitted light into a phase difference of a beat signal. Heterodyne interferometry instead of the method using a bandpass filter as described above.

The legend to Figure 4 shows the mechanism of this solution. The detection apparatus has a structure in which oscillating light is projected from a light source such as a stabilized transverse Zeeman laser (STZL) 31 to a sample 33 through a half mirror 32, and transmitted light (signal light) passing through a polarizing plate 34 is detected by a photodetector 35. ). Meanwhile, the half mirror 32 reflects a part of the oscillation light emitted from the stabilized transverse Zeeman laser 31 , after which the reflected light (reference light) passes through the polarizing plate 35 , thereby detecting the reference light by the photodetector 37 . Next, the phase difference of the light detected by the above-mentioned photodetectors 35 and 37 is measured by an electronic phase meter 38 .

Here, linear polarizers (polarizers 34 and 36) are used to cause interference between the 2 light waves. Note that this mechanism allows the measurement of the birefringence of light with a precision determined by the electronic phase meter 38 . Typically, the electronic phase meter 38 exhibits a measurement accuracy of 0.1 degrees (or greater), allowing the birefringence of light to be measured with a high precision of approximately 1/4000 of the wavelength of light.

The mechanism of optical heterodyne interferometry is described below. First, the electric field component Er of the reference light and the electric field component Es of the signal light are expressed as follows.

E _r ＝a _r cos(2πf _r t+φ _r ) (1)

E _s ＝a _s cos(2πf _s t+φ _s ) (2)

Here, a _r and a _s represent the amplitude of the reference light and the amplitude of the signal light, respectively. In the same way, fr and _fs denote the frequency of the reference light and the _frequency of the signal light, respectively, and _Φr and _Φs denote the phase of the reference light and the phase of the signal light, respectively.

In general, the light intensity I is expressed as the square of the electric field component, so the light intensity I obtained by superimposing 2 light waves is expressed as follows.

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&lang;</span>{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rang;</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">s</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">s</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; )</span>$

Note that, in the above expressions, the symbol "<>" represents an average value over time. On the other hand, f _b (=f _{s -fr} ) represents an optical-beat frequency, and the symbol "Δ" (=Φ _s -Φ _r ) represents a phase difference between two light components.

The photoelectric current detected by the photodetector is divided into DC components represented by the first and second terms of expression (3), and represented by the third term of expression (3) according to the sinusoidal wave having frequency f _b The AC component of the shape change. The AC signal is called an "optical beat signal". For optical heterodyne interferometry, the amplitude (2a _s a _r ), frequency (f _b ) or phase (Δ) of the optical beat signal is measured electrically, and according to the amplitude (a _s ) of the optical signal, the frequency (f _s ) or phase (Φ _s ) to obtain information.

Specifically, for the measurement of dermal tissue, let the refractive indices of skin tissue causing birefringence of light be n _x and _ny , and the thickness of the tissue through which light passes is d, then the following expressions (4) and (5 ) denote phase delays Φ _x and Φ _y .

${\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;n</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;n</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

With the present embodiment, light having frequency components slightly different from each other, such as STZL (Stabilized Transverse Zeeman Laser) oscillation light or the like is projected to the sample. In this case, the light intensity signal I detected by the photodetector is expressed as follows.

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&lang;</span>{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rang;</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="x"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">x</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">y</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="x"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">x</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">y</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="x"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">x</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">y</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="x"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">x</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="S2007101697520E00011.png,S2007101697520E00021.png"\; state="\{\{state\}\}">y</figure-callout></span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&delta;nd</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

Note that the symbol "Δ" represents a phase difference between 2 components of light, and the symbol "δn" represents a difference in refractive index (=magnitude of birefringence). As shown in Expression (6), the phase difference between the two light components is represented by the phase difference of the beat signal. This allows the magnitude of birefringence to be measured by measuring the phase of the optical beat signal with an electronic phase meter 38 or the like.

Note that for the above measurements, the orientation of the main axis needs to be detected in advance, and the polarization plane of the STZL oscillating light is adjusted to precisely match the orientation of the main axis. Therefore, there is a need for a measurement in which a phase difference is detected while rotating the polarization plane of STZL oscillation light around the optical axis, thereby detecting the magnitude of birefringence and the direction of the main axis. However, this measurement method leads to the problems of a very complex structure of the authentication device, complex user operations and a very long detection time. Also, in this case, it is necessary to strictly fix the position and orientation of the authentication device when the user fits. Furthermore, the authentication device needs to fit tightly to the user's body without loosening so as not to deviate from the fitted position even under user activity.

For the present embodiment, skin including a bifurcated structure of subcutaneous blood vessels is used as the skin to be authenticated. The direction of the above-mentioned main axis can be easily obtained by using the bifurcated structure. For example, an arrangement may be made in which the orientation of the main axis and the positional relationship between the bifurcation structures are determined and stored in advance at the time of user registration, thereby allowing the main axis to be adjusted in a simple manner according to the position and direction of the vessel bifurcation structures at the time of user authentication .

On the other hand, an arrangement may be made in which the deep structure of the skin is detected using the interference of light, thereby solving the above-mentioned problems. That is, the object of the present invention is not to provide a measurement of the magnitude of birefringence, but to provide a detection method for detecting a user's unique property by measuring the internal structure of the skin using birefringence or scattering of light. For this scheme, the system causes interference between the incident and scattered light from the skin without any polarizer, and the frequency change between the incident and scattered light is obtained in the form of a beat signal by detecting the interference of the light , in which a characteristic is utilized that when light is projected onto the skin, the frequency of the light changes due to backscattering or birefringence of the light occurring in the internal structure of the skin such as the dermis or the like.

Fig. 5 shows a structural example of such a detection device. The detection equipment has the same structure as that of the detection equipment shown in FIG. The half mirrors 45 are arranged orthogonally to each other. Note that for the current scheme, neither the illumination optical system nor the imaging optical system contains polarizers. In the absence of a polarizer, the current detection device includes a reference mirror 46 for guiding a part of the illumination light projected from the light source 41 of the illumination optical system into the imaging device 43 of the imaging optical system.

A part of light emitted from a light source 41 such as a white LED or the like is projected on the skin surface through a half mirror 45 . When the above part of the illumination light is projected onto the skin, various scattering and birefringence of the light occur in the internal structure of the skin, and the scattered light returns to the half mirror 45 . While illuminating, the system causes a beat phenomenon (interference) between the return light and the light reflected from the half mirror 45 to the reference mirror 46 and reflected by the reference mirror 46, thereby creating form an interference pattern.

In addition, an arrangement may be made in which the above-mentioned beat frequency is detected for each area in the detection range of the skin so that a continuous pattern of the internal structure under the epidermis is obtained from the beat frequency waveform chart thus obtained. Examples of specific schemes for obtaining the above-mentioned continuous pattern include: a scheme in which a plurality of beat frequency detection devices are arranged as shown in FIG. 6; and, as shown in FIG. Scheme of movable mirrors. The former scheme has a structure in which a plurality of beat frequency detection devices 50 are arranged in a so-called "array" shape, and each beat frequency detection device 50 includes an illumination optical system composed of the above-mentioned illumination light source 41 and optical lens 42, and An imaging optical system composed of an imaging device 43 such as a CCD or the like and an optical lens 44 (the illumination optical system and the imaging optical system are arranged orthogonally to each other through a half mirror 45 ), thereby according to the signal detected by each beat detection device 50 Obtain a continuous pattern of the internal structure beneath the epidermis.

On the other hand, for the latter solution, the above-mentioned movable mirror 51 is used to perform light illumination and return light detection of each beat frequency detection device 50 . The latter scheme has a structure in which the mirror control unit 52 controls the angle of the movable mirror 51 based on the control information from the angle/interference pattern adjustment unit 53 . The above-mentioned angle/interferogram adjustment unit 53 receives the interferogram information from the above-mentioned beat detection device 50 . Next, the received interference pattern is compared with the previously stored and registered interference pattern in the skin interference pattern storage unit 54 in the skin interference pattern storage/comparison unit 55, thereby allowing biometric authentication.

The above method does not require a polarizer which is indispensable for detection of a phase difference or the like, thereby having the advantage of allowing authentication without precise adjustment of the optical axis. This allows stable authentication even if the orientation of the watch-type authentication device or the like worn by the user changes due to, for example, a malfunction in wearing by the user, looseness in wearing by the user, or the like.

In actual use, the authentication device needs to be adjusted so as to face the organization to be authenticated when the authentication device worn by the user is loose or the like.

On the other hand, an arrangement can be made in which the interferogram is registered for a wide skin area containing the target area. However, this scheme requires pattern matching processing for searching for a matching pattern in the above-mentioned wide area, resulting in a large processing load. Such a large load is undesirable for a mobile authentication device in terms of power consumption and the like.

For example, consider the special case of biometric authentication using skin patterns such as fingerprints and the like. In this case, the center of a swirl pattern, a horseshoe pattern, etc. can be easily detected, and in addition, the area of the surface of the finger having such a structure is narrow, thereby facilitating the search for a position to be authenticated. However, except for a limited special part, other common parts have a relatively large area compared to a fingertip, and have a swirl pattern different from a fingerprint, a fine skin pattern that does not have a geometry that is conducive to searching for a location to be authenticated, This makes it very difficult to search for an area to authenticate.

In order to solve the above-mentioned problem, an arrangement may be made in which skin patterns are registered for a wide area in advance as described above, and the system determines whether a pattern detected at the time of authentication is included in the above-registered patterns. However, this solution leads to registration for a very large area (very cumbersome), and causes problems such as excessive processing load during authentication and excessively long processing time of the authentication device. For an ideal scenario, it would be best to register a skin pattern for the entire body. However, as mentioned above, this solution is not really desirable. Also, in this case, it is difficult to determine a "wide area". In an actual situation, the authentication device will deviate from the authentication area due to the flexibility of the human body or the difference in the position where the authentication device is worn for each authentication.

An efficient method for searching for a skin to be authenticated in a target area is described below. For this method, near-infrared light instead of white light is used as incident light, which has a wavelength range that allows light to pass through tissue with a high transmission coefficient, and causes abnormal absorption of light by reduced hemoglobin contained in venous blood or the like. The authentication device detects a venous blood vessel pattern using backscattered light detected from subcutaneous tissue, and searches for a target region to be authenticated based on the thus obtained venous blood vessel pattern. For the current approach, the target region to be authenticated is the region containing patterns or bifurcations of vein vessels that are distinct from the others. This allows searching for the same skin area to be authenticated in a deterministic manner, even if the user wears the wristwatch-type personal authentication device with some displacement, or loosening of the contact surface between the authentication device and the user's skin.

FIG. 8 shows an example of a detection device having a function of searching a target area to be authenticated according to a vein vessel pattern. The detection device shown in Fig. 8 has the same structure as Fig. 7, except that a near-infrared light source is used as the light source 41 of the beat frequency detection device 50, and also includes a subcutaneous vein position detection unit 61, a subcutaneous vein position comparison unit 62 and a subcutaneous vein position comparison unit 62. It is outside the structure of the vein data storage unit 63 that stores the vein blood vessel data. This configuration allows obtaining images of the capillaries of the subcutaneous veins 60 , which are venous vessels located in the shallowest part of the skin, extending along the dermis.

Tissues exhibit significantly low absorbance for infrared rays in the wavelength range of 700 to 1200 nm, ie, tissues have the property of allowing the light to pass through easily, so this wavelength range is called "spectral analysis window". Note that although epidermal tissue has properties that cause reflection and scattering of visible light and ultraviolet rays, almost 80% of light in the above wavelength range passes through the tissue. On the other hand, hemoglobin contained in blood selectively absorbs near-infrared light of a specific wavelength in such a wavelength range of near-infrared light having such properties. Specifically, as shown in FIG. 9 , oxidized hemoglobin (HbO ₂ ) exhibits the same absorbance as reduced hemoglobin (Hb) at a wavelength of 805 nm. On the other hand, reduced hemoglobin (Hb) exhibits higher absorbance than oxidized hemoglobin (HbO ₂ ) at a wavelength of 660 nm, and oxidized hemoglobin (HbO ₂ ) exhibits higher absorbance than reduced hemoglobin (Hb) at a wavelength of 940 nm. of absorbance. In addition, hemoglobin has different spectral properties from water in tissues.

Therefore, a blood vessel image can be obtained by detecting a difference between hemoglobin and water in tissue using the above properties. Furthermore, the difference between arterial blood vessels and venous blood vessels can be detected using the difference in absorbance of arterial blood vessels and venous blood vessels at appropriately selected wavelengths. In order to detect venous blood vessel patterns, an arrangement may be made in which the light source includes an illumination device for irradiating near-infrared light having a wavelength of 805 nm, and the near-infrared light is projected onto tissue through, for example, a polarizing plate. Incident light causes 3 phenomena: reflection of light, scattering and birefringence, and return light caused by the above-mentioned types of phenomena is detected. In this case, reflected light from the skin surface degrades the image quality of internal structures beneath the skin surface. Therefore, with the present proposal, an image of the internal structure is obtained with a CCD camera or the like through the polarizing plate 26 arranged in such a manner that its polarization plane is orthogonal to that of the polarizing plate 23 . This allows images to be obtained using only depolarized light such as scattered light and rays split by birefringence, while filtering reflections through the stratum corneum, lucid layer, granular layer, etc. forming the epidermal tissue with the same polarization plane as the incident light of reflected light.

Although the description has been made for the detection device shown in FIGS. 2 and 3 (detecting the dermis by excluding return light except for scattered light from the tissue to be detected), for the current scheme, the capillaries in the dermis in selectively absorbing incident light with a properly selected wavelength because, unlike the case with a white light source, materials other than hemoglobin in blood vessels within skin tissue exhibit low absorbance at this wavelength, i.e. have a high transmission coefficient , thereby obtaining a clear image of the capillary pattern within the dermis by backscattering of light at the deeper portion as the background.

The pattern consisting of blood flow in capillaries is unique to individual tissues. Furthermore, in the event that tissue is excised from the user's body, the above-mentioned patterns are immediately lost due to vasoconstriction, blood retention, blood loss, and the like. In addition, arrangements may be made where the system detects changes in absorbance corresponding to heartbeats using the absorbance of oxidized hemoglobin at a wavelength of 940 nm, thereby allowing biopsy identification and obtaining images of patterns of subcutaneous capillaries. Additionally, the current protocol may incorporate additional methods in which it is determined whether the tissue is normal living tissue or resected from the user by detecting a decrease or loss of absorbance of oxidized hemoglobin at a wavelength of 940 nm caused by an extreme decrease in oxygen concentration in the tissue caused by pulmonary circulation failure Dead tissue, the assay takes advantage of the fact that different types of hemoglobin exhibit different absorbance, for example deoxygenated hemoglobin exhibits a higher absorbance at 660nm than oxyhemoglobin, and oxyhemoglobin exhibits a higher absorbance at 940nm than deoxygenated hemoglobin Higher absorbance, etc.

The above method integrates biometrics authentication and living tissue identification. That is, even though the tissue is made alive by soaking in a physiological saline solution, the system is able to identify and reject tissue excised from the user's body by detecting the absence of blood flow. In this case, the tissue to be certified needs to exhibit normal pulmonary circulation, normal heartbeat, normal blood flow, and a normal ratio of hemoglobin in the blood. Therefore, if someone else surgically amputates the user's arm to "cheat", the arm's blood vessels would need to be connected to a heart-lung machine and the heartbeat waves accurately reproduced. Therefore, it is difficult to "spoof" in the current situation where mobile heart-lung machines are not available. Even if mobile heart-lung machines become available in the future, this "cheat" will still require advanced surgical techniques and surgical equipment to perform: amputation of the arm from the body; connection of arm vessels to the heart-lung machine; delicate vascular and nerve management; The changes in the tissue produced by the vital response to the tissue; the stability of the tissue after blood flow is restored; etc., are highly impractical. On the other hand, it would be more difficult to fake the exact same 3D structure of fine capillaries (resulting in the same scattering of light) than tissue excised from the user's body.

A detection method for detecting patterns under the epidermis using differential interferometry is described below. Differential interferometry is one of the observation methods using a microscope in which the phase difference between illuminating light and returning light depending on the thickness of the sample and the difference in refractive index is converted into contrast or color contrast, allowing observation that provides reliable impressions. Typically, the dermis is difficult to detect with bright field optics or visual observation. This protocol takes advantage of the fact that differential interference optics allow the user to visualize cell nuclei, which is difficult to visualize with ordinary microscopes without smears. Note that although the above-described differential interference optical system allows detection of the dermis in the case where the dermis appears as the top layer, it is difficult to detect the dermis in normal conditions. That is, in the normal case where the dermis is covered with the epidermis, although the surface of the epidermis can be observed by this method, it is difficult to detect the epidermis without some specific method due to the reflection, scattering and shielding of light. .

Although a white light source is used for an ordinary differential interference optical system, for the present invention, a near-infrared light source and a near-infrared CCD are also used as a differential interference optical system. This allows the detection of bump patterns in the dermal layer beneath the epidermis in a non-invasive manner.

Fig. 11 shows a specific scheme example. The detection device includes an illumination optical system and an imaging optical system, wherein the illumination optical system includes a near-infrared light source 71 and a polarizing prism 72 , and the imaging optical system includes an imaging device 73 such as a CCD and a polarizing prism 74 . The illumination optical system and the imaging optical system are arranged with optical paths orthogonal to each other through the half mirror 75 . Illumination light is projected from the illumination optical system to the skin by the reflection of the half mirror 75, and the return light (reflected light) passes through the half mirror 75 so that the light reaches the imaging optical system. Note that the Wollaston prism 76 and the objective lens 77 are arranged on the optical path between the above-mentioned half mirror 75 and the skin.

The illumination light projected from the near-infrared light source 71 is converted into light having the same polarization plane by the polarizing prism 72 , and is reflected to the Wollaston prism 76 by the half mirror 75 . The illumination light projected onto the Wollaston prism 76 is split into two beams (beam A and beam B) having polarization planes orthogonal to each other, and then the two beams are projected onto the object (tissue). Note that the distance between beam A and beam B is equal to or less than the resolution of the objective lens. The 2 beams reflected by the object are then recombined into a single beam by a Wollaston prism 76 . The individual light beams thus recombined pass through the half mirror 75, and are converted by the polarizing prism 74 into light having the same polarization plane. With this structure, the reflection of the two light beams A and B at the stepped portion causes an optical path difference therebetween, resulting in interference of the light beams when the light beams pass through the polarizing prism 74. Note that where the optical path difference matches half the wavelength of beams A and B, the light appears brightest due to interference. Interferograms can be observed by an ordinary differential interference optical system using a white light source, allowing users to visually observe transparent objects with reliable impressions. However, visual observation is difficult with the present scheme using near-infrared light. Therefore, this solution includes, for example, a CCD, an imaging device 73 for obtaining a near-infrared image.

[Methods using electrical properties]

Another method of the present invention is described below in which biometric authentication is performed by using the difference in electrical properties to obtain the concavo-convex pattern or the like of the deep structure below the epidermis (eg, dermal tissue).

Fig. 12 shows a scheme example of a detection device, in which the potential of the skin is detected by electrostatic induction, and the depth of the dermal tissue is detected according to the detected potential, so as to obtain the internal mode under the epidermis. With the present detection device, the electrostatic capacitance between the detection electrode and the dermis is detected using the fact that the epidermis relatively exhibits a property close to a dielectric, while the dermis exhibits high conductivity.

In order to detect electrostatic capacitance, the detection device shown in FIG. 12 includes a plurality of fine electrodes 121 , and these fine electrodes 121 are two-dimensionally arranged by micromachining technology to form a detection electrode plane in contact with the skin surface. At the time of measurement, an electrostatic capacitance is formed between each fine electrode 121 on the detection electrode plane and the dermis. Next, the distance distribution about the subcutaneous conductive layer under each fine electrode 121 is calculated based on the electrostatic capacitance, which depends on the distance between the electrode and the conductive layer, to obtain the subcutaneous tissue structure. That is, with the present detection device, an electrostatic capacitance is formed between each fine electrode 121 forming a detection electrode plane positioned parallel to the skin and the skin, and the terminal voltage of each capacitance is measured, thereby obtaining the structure of the dermis.

The cylindrical metal case 122 stores the above-mentioned fine electrodes 121 fixed by the insulating support member 123 . The fine electrode 121 is electrically connected to the case 122 through a resistor 124 having high resistance. There is a gap between the fine electrode 121 and the case 122 . When the case 122 is in contact with the skin, the fine electrode 121 described above faces the skin with a predetermined gap between the fine electrode 121 and the skin at the opening 122a of the case 122 .

Note that this detection device has a problem that the output signal is very unstable, because the skin surface, which has a property close to a dielectric, is easily affected by electrostatic induction caused by external AC power supply or noise from fluorescent lamps, etc., and the surface structure of the skin is due to the stratum corneum It is easy to show various states due to the separation of etc. In order to solve the above-mentioned problems, there is known a method for detecting fingerprints and the like in which an output signal is detected while applying a high-frequency electric signal to a human body. This method can be applied to the detection of tissue structures in which the epidermis pattern corresponds to the dermis pattern such as a fingerprint or the like. However, the above method cannot be applied to the detection of dermal patterns of other skin tissues in which the epidermal pattern does not correspond to the dermal pattern. The reason is that, in this case, the detection device detects the skin pattern. Unlike fingerprints, epidermal patterns that do not correspond to dermal patterns do not exhibit sufficient stability, and therefore, the methods described above cannot be used for biometric authentication using the detection of this tissue.

Therefore, in order to solve the above-mentioned problems, the detection device according to the present solution includes, for example, a dielectric thin film 125 arranged at the opening of the metal shell 122, as shown in FIG. 13 . During measurement, the dielectric film 125 is positioned between the metal shell 122 and the skin to which the detection device is pressed down. Meanwhile, the dielectric film 125 is in contact with the metal case 122 storing the fine electrode 121 and connected to the ground, thereby also forming an electrostatic capacitance between the case 122 and the skin. In addition, this structure has the advantage of suppressing adverse effects caused by the unstable state of the surface structure of the keratinous tissue of the skin.

In addition, the detection device includes an electret film 126 on the surface of each fine electrode 121 forming the detection electrode plane. The electret film 126 is composed of a tetrafluoroethylene film or the like, and holds charges semi-permanently. For this scheme, the bias voltage caused by the fixed polarization of the electret film 126 forms an electrostatic capacitance between the fine electrode 121 and the dermal tissue without externally applying a high-frequency bias voltage, thereby allowing the detection of the fine electrode 121, and allows non-invasive detection of deep skin structures covered with epidermal tissue of the skin, such as the dermis or the like.

With the detection device having the structure shown in FIG. 13 , a fine electrode 121 having an electret film 126 is arranged at the opening 122 a of the case 122 described above. At the time of measurement, the detection device is positioned such that the opening 122 a faces the tissue, thereby forming an electrostatic capacitance between the fine electrode 121 and the skin through the dielectric film 125 . Shell 122, on the other hand, acts as a counter electrode with respect to the skin and is grounded. On the other hand, the electrodes inside the opening 122a serve as detection electrodes. Therefore, the potential change caused by the epidermal tissue is common to both electrodes, and therefore, its components exhibit opposite polarities between the two electrodes, resulting in cancellation of each other.

On the other hand, a change in potential at the deep part of the skin causes electrostatic capacitance between the dermis layer having conductivity and the fine electrode 121 serving as a detection electrode, allowing detection of a change in potential at the deep part of the skin. On the other hand, no bias voltage caused by the electret film or the like is applied to the capacitance formed by the shell 122, so measuring the capacitance formed by the shell 122 caused by the electric charge on the skin surface does not detect the capacitance of the deep layer of the skin. change in potential. Thus, this solution allows the detection device to accurately detect the potential change in the deep layer of the skin alone, while counteracting the adverse effects caused by the electrostatic induction on the skin surface, the charge on it, and the like.

With the scheme of measuring the change in potential by extracting the change in electrostatic capacitance at each point on the tissue, different magnitudes due to the change in electrostatic capacitance depending on the thickness of the epidermis are detected for each point. FIG. 14 shows a scheme that has a structure in which the above-mentioned detection electrodes (fine electrodes 121) are two-dimensionally arranged in a matrix form, and a scheme that has a function in which the utilization is synchronized with the entire human body due to walking or the like. By varying the magnitude of the potential, a conductive layer structure beneath the epidermis is obtained.

As shown in Fig. 15, while walking, charge changes occur synchronously with the entire human body and in a single phase due to grounding and electrical floating between the feet and the ground. The electric charge change on the human body due to walking is described below. That is, the waveform formed on the skin by walking and detected by the capacitance sensor is formed according to the following two mechanisms.

The first mechanism is basically the same as a condenser microphone. Condenser microphones have a mechanism in which the gap between the diaphragm and the electret electrode changes due to the vibration of the diaphragm, the electrostatic capacitance (C) of the gap changes due to the vibration, and the electrostatic capacitance changes through the gate of the FET. The resulting signal is impedance converted, thereby detecting the vibration of the diaphragm. The detection device according to the present invention has the same structure as the condenser microphone, except that a dielectric thin film is contained therein instead of a vibrating membrane, wherein the dielectric thin film is pressed down to be in contact with human tissue at the time of measurement, thereby passing the dielectric thin film between the detection device and Charge coupling occurs between human tissues. Meanwhile, capacitance (electrostatic capacitance) is formed by the gap between the electret electrode and the dielectric film, and furthermore, the electrostatic capacitance of the human body and the electrostatic capacitance of the gap are combined due to charge coupling. In this state, similar to a condenser microphone, the detection device directly detects the change in electrostatic capacitance due to the interaction between the human body and the external environment (such as a grounded object), such as walking, etc., in the form of a waveform signal.

Here, the electrostatic capacitance (C) of the human body changes in a manner corresponding to the distance between the ground and the position of the foot in space. That is to say, when the feet are in contact with the ground, the capacitance of the human body is relatively large. On the other hand, with the foot off the ground, since the air layer between the palm (of the shoe) and the ground has a low dielectric constant, the electrostatic capacitance of the human body is very small. On the other hand, the larger the contact area between the pin and the ground, the larger the electrostatic capacitance. Note that the electrostatic capacitance C is represented by the following expression.

C=ε·S/d[F] (ε represents the dielectric constant of the medium filling the gap between the electrodes, S represents the area of the electrodes, and d represents the distance between the electrodes)

It can be understood from the above expression that the larger the contact area between the pin and the ground, that is, the larger the area of the electrode (S), the larger the electrostatic capacitance.

The second mechanism is that the electrodes themselves function as charge sensors. That is to say, the electrode stored in the metal shell of the detection device facing the tissue through the dielectric film detects the potential change induced on the dielectric film due to the charge of the human body in the form of a waveform.

It is assumed that the waveform detected on the human body is formed according to the two mechanisms as described above, that is, it is assumed that the waveform is basically formed based on charges rather than potential. That is, it is assumed that a phenomenon represented by the following expression occurs. Note that this hypothesis is confirmed by restoring the observed waveforms by means of simulations using the equivalent circuit method

Q (charge) = C (capacitance) V (electrode voltage)

Although the above-mentioned electric charge change generally exhibits the same waveform throughout the human body, the waveform exhibits different amplitudes corresponding to the fine structure of skin tissue, especially the relationship between the epidermis and dermis. The waveform due to the change in charge changes synchronously throughout the body. Therefore, for the present scheme, the amplitude of the waveform detected by each fine detection electrode arranged in the form of a two-dimensional matrix is compared, thereby measuring the distance between the electrode and the dermis for each electrode, and obtaining the structure.

As described above, with the present scheme, without active charge generating means such as electrodes for applying charges, etc., a charge change due to walking or other motion is detected by each fine electrode 121, wherein the following The fact that on the human body the charge changes due to the interaction between the foot and the ground as a result of the movement of the foot off and in contact with the ground during walking etc. Then, the amplitude difference between the waveforms due to the synchronous charge change caused by the user's motion on the whole body is converted into the distance between the skin surface and the tissue below the epidermis, thereby detecting the deep structure under the epidermis, such as the detection electrode The underlying dermis and so on.

In general, it is assumed that conventional electrostatic capacitance methods have been applied to grounded fixed authentication equipment. Therefore, when the user wears the wearable authentication device using this conventional method to perform user authentication, in the case where the user walks on a carpet in a low-humidity environment in winter, both the detection electrode and the ground portion are greatly charged, thereby making accurate detection difficult. The reason for this is that, for a wearable authentication device, the ground portion is located on the human body.

In order to solve the above-mentioned problems, a method etc. has been proposed in which an additional transmission device such as an electrode, a transducer, etc. is provided in addition to the detection electrode to be in contact with the human body, and a predetermined ultrasonic wave or high-frequency signal is actively provided through the transmission device to be in contact with the human body. Propagate on the human body, detect the propagation of the signal on the human body through the fine electrodes on the skin, and determine whether the surface of each fine electrode is in contact with the skin, so as to obtain the user's fingerprint pattern. However, this method leads to a complex structure and to limiting the tissue to be authenticated to a specific part such as a fingerprint, a part of the skin of the palm, and the like. For example, consider an authentication method that performs authentication using the skin under a finger ring containing a built-in authentication device. In this case, the pattern of the epidermis layer at portions such as wrinkles and the like tends to be formed differently from that of the dermis layer, and is orthogonal thereto in some cases. That is, for this method, epidermal patterns with poor stability are detected, leading to the problem of imprecise authentication.

On the other hand, for the solution according to the present invention, instead of detecting the epidermal pattern, the structure of the tissue below the epidermis (such as the concave-convex pattern of the dermis) is detected by measuring the electrostatic capacitance as described above, thereby solving all the above-mentioned problems.

That is, with the present invention, biometric authentication is performed by detecting the structure of tissue under the epidermis, and therefore, "biometric authentication" and "living tissue authentication" are integrated. Thus, even if the tissue is made alive by soaking in a physiological saline solution, the system is able to identify and reject tissue excised from the user's body by detecting the absence of blood flow. In addition, tissues to be certified need to exhibit normal pulmonary circulation, normal heartbeat, normal blood flow, and a normal ratio of hemoglobin in the blood. Therefore, if someone else surgically amputates the user's arm to "cheat", the arm's blood vessels would need to be connected to a heart-lung machine and the heartbeat waves accurately reproduced. Therefore, it is difficult to "spoof" in the current situation where mobile heart-lung machines are not available. Even if mobile heart-lung machines become available in the future, this "cheat" will still require advanced surgical techniques and surgical equipment to perform: amputation of the arm from the body; connection of arm vessels to the heart-lung machine; delicate vascular and nerve management; The changes in the tissue produced by the vital response to the tissue; the stability of the tissue after blood flow is restored; etc., are highly impractical. On the other hand, it would be more difficult to fake the exact same 3D structure of fine capillaries (resulting in the same scattering of light) than tissue excised from the user's body.

Furthermore, the present invention can be applied to wearable structures. For example, an arrangement may be made in which a wearable information device or a mobile information device contains detection means for detecting patterns of tissues, blood vessels, etc. under the epidermis, wherein when the user holds or wears the information device, the detection means On the surface in contact with the user's skin, it is difficult to perform visual observation under natural light. When the user holds or wears the information device, the skin tissue pattern under the epidermis is detected on the contact surface between the user's body and the information device, and the detected pattern will be Compared with the information device or the registered mode in the server computer connected to the information device through the network, the system is allowed to permit or restrict at least a part of the services provided from the information device or network system according to the detection results, which allows the so-called "access control" .

Consider a case where the present invention is applied to a wearable authentication device such as a watch-type authentication device or the like. Also, in this case, it is necessary to strictly fix the position and orientation of the authentication device when installed by the user. Furthermore, the authentication device needs to fit tightly to the user's body without loosening so as not to deviate from the wearing position even when the user is active. Specifically, the system needs to determine the portion of skin to be authenticated. On the other hand, an arrangement can be made in which the interferogram is registered for a wide skin area containing the target area. However, this scheme requires pattern matching processing for searching for a matching pattern in the above-mentioned wide area, resulting in a large processing load. Such a large load is undesirable for a mobile authentication device in terms of power consumption and the like.

For example, consider the special case of biometric authentication using skin patterns such as fingerprints and the like. In this case, the center of a swirl pattern, a horseshoe pattern, etc. can be easily detected, and in addition, the area of the surface of the finger having such a structure is narrow, thereby facilitating the search for a position to be authenticated. However, except for a limited special part, other common parts have a relatively large area compared to a fingertip, and have a swirl pattern different from a fingerprint, a fine skin pattern that does not have a geometry that is conducive to searching for a location to be authenticated, This makes it very difficult to search for an area to authenticate.

In order to solve the above-mentioned problem, an arrangement may be made in which the skin pattern is registered for a wide area in advance as described above, and the system determines whether the pattern detected at the time of authentication is included in the above-mentioned registered pattern. However, this solution leads to registration for a very large area (very cumbersome), and causes problems such as excessive processing load during authentication and excessively long processing time of the authentication device. For an ideal scenario, it would be best to register a skin pattern for the entire body. However, as mentioned above, this solution is not really desirable. Also, in this case, it is difficult to determine a "wide area". In an actual situation, the authentication device will deviate from the authentication area due to the flexibility of the human body or the difference in the position where the authentication device is worn for each authentication.

In order to solve the above-mentioned problems, skin including a bifurcated structure of subcutaneous blood vessels is preferably used as the skin to be authenticated. The direction of the above-mentioned main axis can be easily obtained by using the bifurcated structure. For example, an arrangement may be made in which the positional relationship regarding the bifurcation structure is determined and stored in advance at the time of user registration, thereby allowing the portion of the skin to be authenticated to be adjusted in a simple manner according to the position of the blood vessel bifurcation structure at the time of user authentication.

[Method of using temperature difference]

Tissue pattern detection and authentication using temperature differences are described below. The skin structure consists of epidermal tissue, which has no blood vessels and is passive to body temperature, and dermal tissue, which has blood vessels and actively affects temperature through blood flow. This results in a temperature of the dermal tissue that is relatively higher than that of the epidermal tissue, except in special cases where external heat is supplied, such as direct sunlight onto the body surface. The detecting device according to the present embodiment detects the structure of the tissue under the epidermis using the mechanism described above.

For example, the detection device according to the present embodiment has a structure in which fine devices such as thermistor bolometers, pyroelectric elements, and the like are arranged two-dimensionally for detecting temperature instead of the above-mentioned fine electrodes, and in each Measure the temperature at the point. In this case, the temperature difference between the fine devices corresponding to the thickness of the skin layer etc. under each fine device is detected. The detection device according to the present embodiment detects the concavo-convex structure of the dermis layer below the epidermis using the above mechanism. In particular, a pyroelectric element having a sensitive range corresponding to infrared rays emitted from a human body is preferably used as a fine device for detecting temperature, thereby allowing detection while preventing adverse effects caused by external heat sources such as sunlight.

In addition, an arrangement may be made in which infrared light detecting means as temperature detecting means are arranged in a matrix, and the detection surface thus formed is made close to the surface of the skin, thereby detecting the pattern of the dermis below the epidermal tissue, in which living tissue is used It is a characteristic that infrared rays of a unique wavelength (for example, a wavelength of about 10 μm) are emitted due to body temperature. With the present scheme, an infrared magnitude difference corresponding to the thickness of the epidermis or the distance between the sensor unit and the dermis serving as an infrared source is detected between the infrared detection sensor units forming a matrix shape. The detection device according to the solution detects the structure of the subcutaneous tissue, such as the concavo-convex pattern of the dermis, according to the distribution of infrared magnitudes.

Furthermore, an arrangement may be made in which the position of the blood vessel is detected using the characteristic that the portion containing the subcutaneous blood vessel exhibits a relatively high temperature compared to other portions, thereby allowing biometric authentication. Furthermore, an arrangement may be made in which the position or direction of the portion to be authenticated is determined from the detected image of the capillary. In addition, living tissue discrimination can also be performed based on detection images of capillaries.

Industrial Applicability

As can be clearly understood from the foregoing description, the present invention allows for universal biometric authentication not only with specific parts such as fingertips, etc., but with any desired part of the user's skin. Furthermore, such a part to be authenticated cannot be observed from the outside unlike a fingerprint, and therefore, it is difficult for other persons to recognize the user's body part used for authentication. Therefore, the present invention has the advantages of high privacy security and high anti-counterfeiting security.

Furthermore, the present invention provides a method of authentication utilizing a part having active blood flow or active body fluid circulation, such as dermal tissue. The nature of this part exhibits a high sensitivity to changes in blood flow or body fluid circulation, thereby providing the necessary and complete integration of biometric authentication means and identification of living tissue. Thus, the present invention provides biometric authentication while suppressing the risk of surgical hazards, ie improving user safety.

Furthermore, the present invention can be applied to a wearable detection device, and a wearable authentication device having a detection portion in contact with human skin, thereby allowing biometric authentication utilizing the user's daily actions without any special user operation. Furthermore, even in the case where a detection error or an authentication error occurs, retry processing can be performed without any specific user operation, so it is not troublesome.

Claims (17)

1. blood vessel authentication apparatus comprises:

Luminous component, be configured to along a part of emissive source light of predetermined direction to human body, the part of described human body has skin corium and the deep layer under described skin corium, described deep layer has the blood vessel that transmits blood, and described predetermined direction tilts with respect to the normal direction of the target part of described part;

Imaging moiety, be configured to detect scattered light, described scattered light is to penetrate described skin corium and by the part of the described source light of the tissue scatter in the described deep layer, described tissue scatter light in the described deep layer makes to be compared with other zones that do not have blood vessel, with the corresponding zone of blood vessel in detect less light; And

Authentication section is configured to authenticate the people's relevant with the part of this human body identity based on by the scattered light that described imaging moiety detected and the comparison of previously stored vessel information.

2. blood vessel authentication apparatus as claimed in claim 1, the part of wherein said human body are fingers.

3. blood vessel authentication apparatus as claimed in claim 1 or 2, wherein said imaging moiety detects the scattered light that arrives from the direction different with described predetermined direction.

4. the described blood vessel authentication apparatus of arbitrary as described above claim, wherein said vessel information comprises vessel position information.

5. the described blood vessel authentication apparatus of arbitrary as described above claim, wherein said vessel information comprises vascular pattern information.

6. the described blood vessel authentication apparatus of arbitrary as described above claim also comprises memory device, is configured to store described vessel information.

7. the described blood vessel authentication apparatus of arbitrary as described above claim also comprises interface, is used for being connected to the memory device that is used to preserve described vessel information via network.

8. the described blood vessel authentication apparatus of arbitrary as described above claim, wherein said source is near infrared light only.

9. it is relative with the described target part of described part that the described blood vessel authentication apparatus of arbitrary as described above claim, wherein said imaging moiety are placed with.

10. blood vessel authentication method may further comprise the steps:

The storage vessel information;

Along a part of emissive source light of predetermined direction to human body, described part has skin corium and the deep layer under described skin corium, and described deep layer has the blood vessel that transmits blood, and described predetermined direction tilts with respect to the normal direction of the target part of described part;

Detect scattered light, described scattered light is to penetrate described skin corium and by the part of the described source light of the tissue scatter in the described deep layer, described tissue scatter light in the described deep layer makes to be compared with other zones that do not have blood vessel, with the corresponding zone of blood vessel in detect less light; And

Authentication and the people's of this part correlation identity comprises the testing result and the described vessel information of more described detection step.

11. method as claimed in claim 10, the part of wherein said human body are fingers.

12. as claim 10 or 11 described methods, wherein said detection step detects the scattered light that arrives from the direction different with described predetermined direction.

13. the described method of arbitrary as described above claim, wherein the vessel information of storing in described storing step comprises vessel position information.

14. the described method of arbitrary as described above claim, wherein said vessel information comprises vascular pattern information.

15. the described method of arbitrary as described above claim, wherein said storing step are included in the described vessel information of storage in the device of carrying out described detection step.

16. the described method of arbitrary as described above claim, wherein said storing step are included in the described vessel information of storage in the memory device; And

Described authenticating step comprises via network retrieves described vessel information from described memory device.

17. the described method of arbitrary as described above claim, the step of wherein said emissive source light comprises the emission near infrared light.

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