JP6355371B2 - Personal authentication device and finger vein authentication device - Google Patents

Description

  The present invention relates to a personal authentication device and a finger vein authentication device using a living body, and more particularly to a technique for performing authentication using a blood vessel pattern obtained by imaging light transmitted through a living body.

  In recent years, security for personal information has been regarded as important. Biometric authentication is attracting attention as a personal authentication technology that protects security. Biometric authentication is a technology for authenticating using human biometric information, and is excellent in convenience and confidentiality.

  As a conventional biometrics authentication technique, authentication using a fingerprint, an iris, a voice, a face, a vein on the back of a hand, or a finger vein is known. Among these, biometric authentication using veins is excellent in forgery resistance because it uses internal information of the living body.

  Hereinafter, a personal authentication device using a finger vein will be described. When performing personal authentication using a finger vein authentication device, a user first presents a finger on the authentication device. The finger vein authentication device irradiates the finger with infrared light. Infrared light is scattered inside the finger and then transmitted to the outside. Then, the finger vein authentication device captures infrared light transmitted to the palm side of the finger. At this time, hemoglobin in the blood absorbs more infrared light than the surrounding tissue. Therefore, the light transmitted to the palm side of the finger has a contrast difference between the weak light attenuated because it has passed through the vein portion and the strong light that has not attenuated that has exited from the portion without the vein. Therefore, in the image captured by the finger vein authentication device, blood vessels (finger veins) distributed subcutaneously on the palm side of the finger are visualized as dark shadow patterns (finger vein patterns). The finger vein authentication device performs personal authentication by previously registering the characteristics of the finger vein pattern and obtaining the correlation between the user's finger vein pattern presented at the time of authentication and the characteristics registered in advance.

  As a conventional example of this type of finger vein authentication device, for example, an authentication device described in Patent Document 1 is known. This publication describes a method of performing personal authentication using an image taken with a microlens array in order to reduce the thickness of the authentication device.

  Patent Document 2 describes that a left and right finger placing table for placing the left and right fingers of a finger to be authenticated is provided, and an illumination light source is disposed in the left and right finger placing table. In addition, it is described that light source elements having two kinds of angles are arranged as light sources and are switched on for each finger.

JP 2008-036058 A JP 2010-097483 A

  As described above, a method of arranging light sources having different installation angles is known as a method of irradiating light of various sizes with an ideal angle in a biometric authentication device using transmitted light.

  However, Patent Document 1 and Patent Document 2 do not disclose a method for determining the installation angles of a plurality of light sources. In addition, only by changing the installation angle of the light source, there remains a problem that light that adversely affects photographing is irradiated on the living body, or that a sufficient amount of light cannot be irradiated for photographing the living body. For this reason, a clear vein image cannot be taken, and the authenticity level is lowered.

  The present invention is an invention for solving the above-described problems, and provides a personal authentication device and a finger vein authentication device that can shoot light suitable for authentication by irradiating light to an optimal position on a living body of various sizes. The purpose is to provide.

In order to achieve the object, the personal authentication device of the present invention is arranged in a casing (for example, a finger rest 5) having an opening on a mounting surface on which a finger is mounted, and in the casing in the longitudinal direction of the finger. Extracted from a plurality of light sources that illuminate the finger diagonally, an imaging unit that images light from the light source that has passed through the finger through the opening in the housing, and a finger vein image acquired by the imaging unit A processing unit (e.g., authentication processing unit 10) that collates the stored characteristics with biometric information stored in advance, and a light shielding unit that shields light from a plurality of light sources on the same surface as the placement surface. a distance between the light source and the light-shielding portion (e.g., a distance k1 shown in FIG. 9 (c), the distance k2 shown in FIG. 9 (d)) is varies, the light-shielding portion with respect to the width direction of the finger The light is shielded from the opening to the same distance, and the positions of the plurality of light sources are different with respect to the lateral width direction of the finger. Characterized in that it placed in the release.

  ADVANTAGE OF THE INVENTION According to this invention, the image suitable for authentication can be image | photographed by irradiating light to the optimal position with respect to the biological body of various sizes.

It is a figure which shows the finger vein authentication system which concerns on 1st Embodiment, (a) is a figure which shows the whole structure, (b) is the memory | storage part in a finger vein authentication system, and the inside of a memory | storage device It is a figure which shows a structure. It is a figure which shows the finger vein data acquisition apparatus which concerns on 1st Embodiment, (a) is a top view, (b) is a top view when a finger is shown (when mounted), (c) is A- It is A sectional drawing, (d) is BB sectional drawing. It is a figure which shows the relationship between a light source and a light-shielding part. It is a figure which shows irradiation when the installation angle of a light source is large, (a) is a case of a thick finger, (b) is a case of a thin finger. It is a figure which shows irradiation when the installation angle of a light source is small, (a) is a case of a thick finger, (b) is a case of a thin finger. It is a figure which shows the example of a narrow light-shielding light source unit (1st light source unit). It is a figure which shows the example of a wide light-shielding light source unit (2nd light source unit). It is a figure which shows the other example of a finger vein data acquisition apparatus, (a) has an opening part for every light source, (b) is a case where many light sources are arrange | positioned. It is a figure which shows the finger vein data acquisition apparatus which concerns on 2nd Embodiment, (a) is a top view, (b) is a top view at the time of mounting a finger, (c) is AA sectional drawing. (D) is BB sectional drawing. It is a figure which shows the other example of a finger vein data acquisition apparatus, (a) is a case where light shielding is not enough, (b) is a case where light shielding is enough. It is a figure which shows the finger vein data acquisition apparatus which concerns on 3rd Embodiment, (a) is a top view, (b) is a top view at the time of mounting a finger, (c) is AA sectional drawing. (D) is BB sectional drawing. It is a flowchart which shows a registration process. It is a flowchart which shows an authentication process. It is a flowchart which shows a light source selection process. It is a flowchart which shows the light quantity adjustment process which concerns on 1st Embodiment. It is a flowchart which shows the light quantity adjustment process which concerns on 4th Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<< first embodiment >>
FIG. 1 is a diagram illustrating a finger vein authentication system according to a first embodiment, (a) is a diagram illustrating an overall configuration, and (b) is a memory and a memory that are storage units in the finger vein authentication system. It is a figure which shows the internal structure of an apparatus. The finger vein authentication system 80 (personal authentication device) includes a finger vein data acquisition device 2, an image input unit 18, an authentication processing unit 10, a storage device 14, a display unit 17, and information input for acquiring an image necessary for personal authentication. Unit 19, audio output unit 6, and power supply unit 15.

  The finger vein data acquisition device 2 includes a light source 50 for photographing finger veins, an imaging unit 4, and a finger rest 5 (casing, finger rest) having a placement surface for presenting a finger. The light source 50 is, for example, an infrared light emitting diode (LED), and irradiates the finger 1 presented on the finger rest 5 with infrared light. The finger rest 5 has a light shielding portion 22 that shields infrared rays (described in detail in FIG. 2). The imaging unit 4 is a CMOS sensor, for example, and images the presented finger 1.

  The image input unit 18 inputs an image captured by the imaging unit 4 to the authentication processing unit 10 that functions as a processing unit. Note that the image input unit 18 may perform a process of extracting a blood vessel pattern image from an image captured by the imaging unit 4 and input the extracted blood vessel pattern image to the authentication processing unit 10.

  Further, the image input unit 18 and the finger vein data acquisition device 2 may be integrated as a vein image extraction device, or the image input unit 18 may be configured as an integral unit with the authentication processing unit 10. Needless to say.

  The authentication processing unit 10 includes a central processing unit (CPU) 11 (central processing unit), a memory 12, and various interfaces (IFs) 13. The CPU 11 performs various processes by executing programs stored in the memory 12 (for example, a registration program 100 (see FIG. 12) and an authentication program 120 (see FIG. 13)). The memory 12 temporarily stores a program executed by the CPU. The memory 12 stores the image input from the image input unit 18. The interface 13 is connected to a device external to the authentication processing unit 10. Specifically, the interface 13 is connected to the finger vein data acquisition device 2, the storage device 14, the display unit 17, the information input unit 19, the audio output unit 6, the image input unit 18, and the like.

  The storage device 14 stores user registration data 30, a registration program 100, and an authentication program 120 in advance. The registration data 30 is information for collating users, and is, for example, an image of a finger vein pattern. The finger vein pattern image is an image obtained by capturing blood vessels (finger veins) distributed under the skin on the palm side of the finger as dark shadow patterns.

  The display unit 17 is a liquid crystal display, for example, and displays information received from the authentication processing unit 10. The information input unit 19 is, for example, a keyboard, and transmits information input from the user to the authentication processing unit 10. The voice output unit 6 is a speaker or the like, and transmits information received from the authentication processing unit 10 by voice. The power supply unit 15 is a dry battery or an external power supply, and supplies power for driving the finger vein data acquisition device 2 and the authentication processing unit 10.

  In the finger vein authentication system 80, when the user presents the finger 1 to the finger vein data acquisition device 2, the light source 50 for vein imaging is turned on and a vein image of the finger is captured. The light source 50 irradiates the finger 1 with light. The irradiated light is scattered inside the finger 1 and the light transmitted through the finger 1 enters the imaging unit 4. The incident light is converted into an electrical signal by the imaging unit 4 and is taken into the authentication processing unit 10 as an image. The captured image is stored in the memory 12.

  Next, as illustrated in FIG. 1B, the registration data 30, the registration program 100, and the authentication program 120 stored in the storage device 14 are stored in the memory 12 from the storage device 14. Further, the CPU 11 creates authentication data 40 from the input image in accordance with the authentication program 120 stored in the memory 12 and collates with the registration data 30.

  In the verification process, the positional deviation between the registration data and the authentication data is corrected based on the result of the finger presentation position obtained by the authentication processing unit 10. Thereafter, the correlation between the registration data and the authentication data is obtained. It is determined whether the data matches the registered data according to the calculated correlation value. An individual is authenticated using this determination result. The authentication result is displayed on the display unit 17 or notified by voice from the voice output unit 6.

  2A and 2B are diagrams showing the finger vein data acquisition apparatus according to the first embodiment, in which FIG. 2A is a top view, FIG. 2B is a top view when a finger is presented (placed), and FIG. ) Is an AA cross-sectional view, and (d) is a BB cross-sectional view.

  The finger vein data acquisition device 2 is provided with a finger rest 5 for a user to present a finger to be authenticated. The finger rest 5 has an opening 20 for placing a finger at the center, and openings 26 for the light source 50 on both sides of the opening 20. A plurality of light sources 50 for finger vein imaging are installed in the opening 26.

  An infrared transmission filter (not shown) may be installed in the opening 20 so as to cover the opening 20. By providing the infrared transmission filter, unnecessary light other than infrared light can be prevented from entering the apparatus. In addition, foreign substances such as dust and dust can be prevented from entering the apparatus. The infrared transmission filter is preferably installed at a position several millimeters lower than the finger rest 5 so that the finger 1 and the infrared transmission filter do not come into contact with each other. Thereby, it is possible to prevent the blood vessel pattern from disappearing or deforming due to the pressing of the finger. Further, it is possible to prevent dirt from adhering to the infrared transmission filter.

  The imaging unit 4 is installed immediately below the opening 20. When the finger 1 is presented, a light source 50 including a plurality of light source elements irradiates the finger 1 with infrared light. The irradiated light scatters in all directions when it reaches the inside of the finger. A part of the light scattered inside the finger reaches near the upper part of the opening 20, and a part of the light travels from the inside of the finger toward the outside of the finger. This light passes through the opening 20 and the infrared transmission filter and is photographed by the imaging unit 4. Since this light is transmitted from the inside of the finger 1 through the palm side surface of the finger 1, weak light attenuated because it has passed through the vein portion and strong light that has not attenuated that has exited from the portion without the vein. Has a contrast difference. Therefore, when this light is imaged, a finger vein pattern image of a partial region located directly above the opening 20 is displayed in the video.

  In order to capture a clear image of the partial region of the finger 1 located above the opening 20, that is, the finger vein pattern of the imaged portion, the following optical conditions must be satisfied. First, the reflected light of the light irradiated on the skin surface of the imaged part from the outside of the finger is not imaged, that is, the scattered light that has not reached the depth at which the finger vein exists is not imaged. is there. When this condition is not satisfied, the light having no finger vein pattern information reduces the contrast between the finger vein portion and the other living tissue. Furthermore, unnecessary images such as wrinkles on the finger surface are clearly reflected, making it difficult to see the finger vein pattern. Therefore, in order to capture the vein pattern more clearly, the light source is arranged so that the light emitted from the light source 50 can be irradiated only to a high position of the living body to be imaged (for example, a position close to the back of the finger). It needs to be adjusted.

  In this embodiment, the installation position of the light source 50 for vein imaging is on the left and right sides of the region where the finger 1 is presented (in the long axis direction of the finger). The height to be installed is the same height as the upper surface of the finger rest 5 or a position lower than the finger rest 5. The installation angle α of the light source 50 is set to a range of 0 to 90 degrees, and light is irradiated obliquely upward (see FIG. 2C). Furthermore, as shown to Fig.2 (a), the site | part between the opening part 20 and the opening part 26 is created with the member which can interrupt | block the light of the light source 50 (henceforth the light-shielding part 22).

  As shown in FIG. 2A, in the light shielding part 22, the width of the light shielding part is narrow at the AA cross section, and the light shielding part is wide at the BB cross section. Although details will be described later, a narrow light-shielding light source unit 65 (first light source unit) for narrow light shielding is formed in FIG. 6, and a wide light-shielding light source unit 66 (second light source unit) for wide light shielding is formed in FIG. Has been.

  In the present embodiment, the apparatus can be thinned by lowering the installation position of the light source 50. For example, the size of the finger vein data acquisition device 2 is about 30 mm in width, 30 mm in length, and about 5 mm in height. Further, by placing the light source 50 obliquely upward, it is possible to irradiate strong light to a high finger position. Further, by installing the light shielding unit 22 between the light source 50 and the finger 1, light that travels in the lower direction among the light emitted from the light source 50 is shielded, and only light that travels in the higher direction is irradiated to the finger 1. Can do. Thereby, a clear vein image can be taken.

  FIG. 3 is a diagram illustrating a relationship between the light source and the light shielding unit. 4A and 4B are diagrams illustrating irradiation when the installation angle of the light source is large. FIG. 4A illustrates the case of a thick finger, and FIG. 4B illustrates the case of a thin finger. 5A and 5B are diagrams illustrating irradiation when the installation angle of the light source is small. FIG. 5A illustrates the case of a thick finger, and FIG. 5B illustrates the case of a thin finger.

In FIG. 3, hereinafter, the light source 50 and the light shielding unit 22 are collectively referred to as a light source unit 60. The installation angle α of the light source 50 is an angle formed by the optical axis 61 (irradiation axis) of the light source 50 and the upper surface (mounting surface) of the finger rest 5. Further, in FIG. 3, the viewing angle β of the light source 50 is set, and a portion where the light irradiated from the light source 50 is blocked by the light blocking unit 22 is generated. At this time, an angle formed between the light-shielded portion and the upper surface (mounting surface) of the finger rest 5 is referred to as a light-shielding angle θ. Note that a region having a viewing angle β is defined as a predetermined region. Further, the installation angles α of the plurality of light sources 50 may be the same angle, or may be α ± α ₀ as the predetermined value α ₀ .

  In order to capture a clearer image, the light shielding angle θ on the palm side of the finger is increased, and the irradiation position h (height from the placement surface) is irradiated to irradiate the back of the finger. (See FIGS. 4 and 5). However, there is no installation angle α at which a sufficient amount of light hits fingers of various thicknesses and the light irradiation position h can be kept high.

  For example, as shown in FIG. 4A, when the installation angle α is set to α1 (> α2) so that the light hits a sufficiently high position with respect to a thick finger and the installation angle α1 is increased, A clear image can be taken, but the picture quality decreases when a thin finger is taken. This is because light is irradiated further upward than the upper end of the thin finger (the back of the finger) (FIG. 4B), and a sufficient amount of light is not irradiated to the finger.

On the other hand, as shown in FIG. 5B, when the installation angle α is set to α2 and the installation angle α2 is reduced so that a sufficient amount of light is irradiated to the thin finger, FIG. As shown by, the light irradiation position h _LF for the thick finger is lowered, so that the vein image when the thick finger is photographed becomes unclear.

  As described above, in the finger vein data acquisition device 2 configured to irradiate light on the object to be imaged from an oblique direction, the image quality deteriorates when the installation angle α is increased, and when the installation angle α is decreased, the image quality is deteriorated when the installation angle α is decreased. The problem that the image quality deteriorates occurs.

  Therefore, the present embodiment is characterized in that a clear vein image can be taken with fingers of various sizes by providing two types of light source units with a fixed installation angle α and different light shielding angles θ. is there.

  FIG. 6 is a diagram illustrating an example of a narrow light-shielding light source unit (first light source unit). FIG. 7 is a diagram illustrating an example of a wide light-shielding light source unit (second light source unit). The positional relationship between the light source 50 and the light shielding unit 22 in the light source unit 60 will be described with reference to FIGS. 2 and 3 as appropriate with reference to FIGS. 6 is a cross-sectional view taken along the line AA in FIG. 2C, and FIG. 7 is a cross-sectional view taken along the line BB in FIG. Regarding the light source 50, the light source 50 of the narrow light-shielding light source unit 65 (first light source unit) is used as the light source 51 (first light source), and the light source 50 of the wide light-shielding light source unit 66 (second light source unit) is used as the light source 52. And

  The finger vein data acquisition apparatus 2 includes a narrow light-shielding light source unit 65 having a small light-shielding angle θ and a wide light-shielding light source unit 66 having a large light-shielding angle θ. The light source 51 of the narrow light-shielding light source unit 65 and the light source 52 of the wide light-shielding light source unit 66 are both installed at the same installation angle α. Further, the distances d1 and d2 of the light source 50 with respect to the central axis of the opening 20 are the same.

  On the other hand, the size of the light shielding unit 22 is different for each light source unit, and the width w1 of the light shielding unit 22 in the narrow light shielding light source unit 65 is smaller than the width w2 of the light shielding unit 22 in the wide light shielding light source unit 66. As a result, the distance k1 between the light shielding part 22 and the light source 50 in the narrow light shielding light source unit 65 is larger than the distance k2 between the light shielding part 22 and the light source 50 in the wide light shielding light source unit 66. Is smaller than the light-shielding angle θ2 of the wide light-shielding light source unit 66.

  As shown in FIGS. 6 and 7, by changing the size of the light-shielding portion 22, a narrow light-shielding light source unit 65 where the lower limit position of the irradiation light is irradiated to a position lower than the placement surface, and the placement Two types of light source units can be realized, which are the wide light-shielding light source unit 66 that emits light at a high position from the surface.

  As described above, the installation angle α of the light source 51 in the narrow light-shielding light source unit 65 and the light source 52 in the wide light-shielding light source unit 66 have the same value. Therefore, since the light sources 51 and 52 can be arranged on the same plane, members for supporting the light source can be shared, the number of parts in the finger vein data acquisition device 2 can be reduced, and the part shape can be made simpler. There are advantages.

Next, processing contents of the authentication processing unit 10 will be described.
FIG. 12 is a flowchart showing the registration process. A registration processing procedure executed by the registration program 100 executed by the CPU 11 will be described with reference to FIG. In the registration process, first, the CPU 11 performs a finger presentation detection process (S101) for determining whether or not a finger is presented (placed) on the device. Thereafter, the CPU 11 performs a light amount adjustment process (S103) for irradiating an appropriate light amount from the light source 50 to the finger to be imaged. After completing the adjustment of the light amount, the CPU 11 performs pattern extraction processing (S108) and feature data creation processing (S109). Finally, the feature data is stored in the storage device 14, and the registration process is completed.

Details of the registration process of FIG. 12 will be described next.
First, the finger presentation detection process (S101) will be described. The finger presentation detection process is a process for determining whether or not a finger is placed on the finger rest 5. As a determination method, a method using a touch sensor installed in the finger rest 5, a method using image processing, a method combining a touch sensor and image processing, or the like can be used.

  Here, an example of a method using image processing will be described. The image processing method has an advantage that the number of parts can be reduced and the cost can be reduced because a sensor dedicated to finger detection is not required. First, the above-described light source 50 used as illumination for finger vein pattern photography is blinked at a constant cycle. When the finger 1 is not presented on the finger rest 5, the light emitted from the light source 50 is reflected on the imaging unit 4 because there is no object that scatters light even when the light source 50 is turned on or off. I will not put it. Therefore, when the image of the imaging unit 4 is compared between the light source 50 being turned on and the light source 50 being turned off, the luminance value does not change significantly.

  On the other hand, when the finger 1 is presented on the apparatus, the light emitted from the light source 50 is scattered by the finger 1 and reflected on the imaging unit 4. Therefore, a large change occurs in the luminance value of the image when the light source 50 is turned on and when the light source 50 is turned off. Therefore, an image captured when the finger vein data acquisition device 2 is turned on and off is sent to the authentication processing unit 10 via the image input unit 18, and the CPU 11 calculates and holds the amount of change of the image, thereby presenting the finger. Can be detected.

  When the finger presentation detection process (S101) is completed, light for illumination for vein photography is output from the light source 50. At this time, the light source to be turned on at the time of vein imaging and the amount of light necessary for imaging differ depending on the thickness of the finger and the thickness of the skin presented on the finger rest 5. Therefore, a light source selection process is performed so as to obtain the clearest image (S102), and a process of adjusting the light amount of the selected light source (S103) is performed.

  First, an outline of the light source selection process (S102) will be described. As described above, when photographing a thick finger, it is desirable to turn on only the wide light shielding light source (the light source 52 of the wide light shielding light source unit 66). This is because by turning on the wide light-shielding light source, light is irradiated to a high position from the placement surface of the finger 1 and a clear image can be taken. On the other hand, when photographing a thin finger, it is desirable to select a narrow light-shielding light source (the light source 51 of the narrow light-shielding light source unit 65) because an image with sufficient brightness cannot be obtained only with the light from the wide light-shielding light source. That is, the light source selection process (S102) is a process of determining the size of the finger 1 presented on the finger rest 5 and selecting a light source that matches the size of the finger 1 to be imaged.

  In this embodiment, the thickness of the finger 1 is determined using an image taken when the wide light-shielding light source is turned on. This is because the luminance value of the image obtained when the wide light-shielding light source is turned on changes depending on the thickness of the finger presented. Specifically, the brightness increases when a thick finger is presented, and the brightness decreases when a thin finger is presented. Therefore, it is only necessary to determine whether or not the brightness value of the captured image is equal to or greater than a certain value.

  FIG. 14 is a flowchart showing the light source selection process. In the light source selection process (S102), first, the CPU 11 commands to turn on only the wide light-shielding light source (light source 52) at the maximum intensity (S1021). Thereafter, an image is taken by the imaging unit 4 (S1022). The CPU 11 calculates the average luminance value of the image (S1023). It is determined whether or not the average luminance value is greater than or equal to a predetermined threshold value (S1024). When the average luminance value is equal to or greater than the threshold value (S1024, Yes), the CPU 11 selects the wide light-shielding light source (light source 52) (S1025), and when the average luminance value is less than the threshold value (S1024, No), the narrowness A light-shielding light source (light source 51) is selected (S1026), and the light source selection process ends. With the above procedure, a light source suitable for the finger to be imaged is selected.

  Returning to FIG. 12, the light amount adjustment processing (S103) will be described next. In finger vein imaging, a clear vein image can be obtained when the average luminance value of the captured image is a value near the center of the luminance gradation.

  For example, when the average luminance value of the photographed image is too low, the contrast between the blood vessel and the rest of the image is poor, so it is not clear. On the other hand, when the average luminance value is too high, a saturated portion occurs and the blood vessel pattern cannot be extracted. That is, in the light amount adjustment process (S103), the median value of the luminance gradation is set as the target luminance value, and the light amount is adjusted so that the average luminance value of the captured image approaches the target value. In this embodiment, a method of constantly monitoring the average luminance value of the photographed image and bringing the light amount close to the target luminance value while performing feedback control according to the value is used as the light amount adjustment method.

  FIG. 15 is a flowchart illustrating the light amount adjustment processing according to the first embodiment. In the light amount adjustment process (S103), first, the CPU 11 issues a lighting command to the light source 50 (light source 51 or light source 52) selected in the light source selection process (S102) with a preset initial light amount value (L0) ( S1031). The initial light quantity value (L0) is set in advance by measuring a light quantity value at which a target luminance value image can be taken when a standard finger is placed. Next, an image is taken by the imaging unit 4 (S1032). The CPU 11 calculates the average luminance value (V0) of this image (S1033). It is determined whether the calculated average luminance value (V0) is a target luminance value (S1034). When the target luminance value has not been reached (S1034, No), the CPU 11 calculates and resets the next light amount value (S1035), and instructs the light source 50 to turn on (S1036). The next light quantity value is calculated using the feature that the light quantity value and the average luminance value of the captured image are in a proportional relationship. After resetting the light amount value, an image is taken (S1032), and the CPU 11 calculates the average luminance value (S1033) and performs the determination of the average luminance value (S1034) again. This flow is repeated to approach the target luminance value. When the target luminance value is reached in the determination of the average luminance value in S1034 (S1034, Yes), the light amount adjustment process is terminated.

  Returning to FIG. 12, next, blood vessel pattern extraction processing is performed (S108). The blood vessel pattern extraction process (S108) is a process that excludes information (such as noise and wrinkles) unnecessary for authentication from the image captured by the imaging unit 4 and detects only the blood vessel pattern portion. As a blood vessel pattern extraction method, a method using an edge enhancement filter or a matched filter that emphasizes a line segment, a method of extracting a line pattern by tracking a line component, and a local depression position of a luminance value in a cross-sectional profile of an image An extraction method or the like can be used.

  Thereafter, the CPU 11 performs a feature data creation process from the result of the extraction process (S109). As the feature data, a method using the image itself as a result of extraction processing as a feature amount, a method for detecting a branch point or an end point, or the like can be used. When the image itself is used as a feature amount, a reduction process may be applied to the extracted image in order to reduce the data size.

  In the feature data storage process (S110), the feature data generated in the feature data creation process (S109) and the finger presentation position information calculated in the finger presentation detection process (S101) are stored in the storage device 14. As the finger position information, the right contour position and the left contour position of the finger may be stored, or the center position of the finger calculated based on the contour position information may be stored. Further, the encryption processing may be performed on the feature data before saving.

  FIG. 13 is a flowchart showing the authentication process. An authentication processing procedure performed by the authentication program 120 will be described with reference to FIG. In the authentication process, a finger presentation detection process (S101), a light source selection process (S102), a light amount adjustment process (S103), a pattern extraction process (S108), and a feature data creation process (S109) are performed. Thereafter, a matching process (S112) with previously registered feature data is performed to determine whether or not the finger to be authenticated is a registered finger.

  Among the processing steps of the authentication process, five processes of a finger presentation detection process (S101), a light source selection process (S102), a light amount adjustment process (S103), a pattern extraction process (S108), and a feature data creation process (S109) Uses the same method as the registration process. Below, collation processing (S112) is explained.

  In the matching process (S112), the feature data generated in the feature data generation process (S109) during the authentication process is compared with the feature data created and stored at the time of registration. When the image itself is used as the feature data, the images are overlapped and the pixel values are compared to calculate the coincidence rate. When branch points and end points are used as feature data, the coincidence rate is calculated by comparing information such as the number of branches, the angle of the branch line, and the relative distance.

  The CPU 11 determines whether the fingers are the same finger or different fingers (whether the matching rate is high) using the matching rate obtained here (S113). The authentication threshold for determination can be statistically calculated in advance. When the coincidence rate is higher than the authentication threshold (S113, Yes), it is determined as a registrant and the process after authentication is performed (S114). If it is determined that the user is a registered person, for example, unlocking is performed as a process after authentication. If the matching rate is not higher than the authentication threshold (S113, No), it is considered that an unregistered finger has been presented and authentication is rejected.

  In the registration process of FIG. 12 and the authentication process of FIG. 13, in other words, the CPU 11 functions not only as a feature extraction unit and a feature verification unit, but also as a light source selection unit, a light amount control unit, and a unit for measuring a finger position. Part.

  In the present embodiment, the light source 51 (first light source) in the narrow light-shielding light source unit 65 and the light source 52 (second light source) in the wide light-shielding light source unit 66 are provided as the plurality of light sources. The authentication processing unit 10 may turn on the second light source when a finger is placed, and turn on the first light source when it is determined that the finger is a thin finger.

  In the present embodiment, the case where there are two types of light sources 50 has been described, but three or more types of light sources 50 having different installation angles may be used. Moreover, the light shielding part 22 and the finger rest 5 can be created as the same component using the same member. Producing as the same part has the effect of reducing the number of parts of the apparatus and reducing the cost of the apparatus.

  8A and 8B are diagrams showing another example of the finger vein data acquisition apparatus. FIG. 8A shows a case where an opening is provided for each light source, and FIG. 8B shows a case where a large number of light sources are arranged. In the case of FIG. 2A, the finger vein data acquisition device 2 has a plurality of light sources including four light sources 50 arranged in the opening 26 on both sides of the opening 20. On the other hand, in the case of FIG. 8A, the narrow light-shielding light source unit 65 (see FIG. 6) is arranged for the opening 26a, and the wide light-shielding light source unit 66 (see FIG. 7) is arranged for the opening 26b. did. Further, a light shielding member may be disposed between the narrow light shielding light source unit 65 and the wide light shielding light source unit 66, and the two types of light source units may be independent.

  In the case of FIG. 8B, it is also possible to arrange a plurality of light sources consisting of eight light sources 50 by combining two types of light source units in the opening 26 similar to FIG. A sufficient amount of light emission can be obtained from the light source 50 by the arrangement of the plurality of light sources shown in FIG.

<< Second Embodiment >>
FIG. 9 is a diagram illustrating a finger vein data acquisition apparatus according to the second embodiment, where (a) is a top view, (b) is a top view when a finger is placed, and (c) is AA. It is sectional drawing, (d) is BB sectional drawing. In the first embodiment, the size of the light shielding unit 22 is changed to change the light shielding angle θ. However, in the second embodiment, the position of the light source 50 is changed to change the light shielding angle θ. Yes. The finger vein data acquisition apparatus 2 of the second embodiment includes a narrow light shielding light source unit 65 (see FIG. 9C) with a small light shielding angle θ (θ1) and a wide light shielding light source unit 66 with a large light shielding angle θ (θ2). (See FIG. 9D).

  As shown in FIG. 9A, a light source 50 (light sources 51 and 52) is disposed in the opening 26c, and a light shielding part 71 is provided between the opening 20 and the opening 26c. FIG. 9C is a cross-sectional view taken along the line AA, and shows the narrow light-shielding light source unit 65. FIG. 9D is a cross-sectional view of the wide light-shielding light source unit 66 in the BB cross section. The light source 51 of the narrow light-shielding light source unit 65 and the light source 52 included in the wide light-shielding light source unit 66 are both installed at the same angle α. Further, the width w1 of the light shielding part 71 of the narrow light shielding light source unit 65 and the width w2 of the light shielding part 71 of the wide light shielding light source unit 66 are the same width. However, the distances d1 and d2 of the light source 50 with respect to the central axis of the opening 20 are different, and the distance d2 is smaller than the distance d1. As a result, the distance k1 between the light shielding part 71 and the light source 51 (first light source) in the narrow light shielding light source unit 65 is between the light shielding part 71 and the light source 52 (second light source) in the wide light shielding light source unit 66. Since the distance is larger than the distance k2, the light shielding angle θ1 of the narrow light shielding light source unit 65 is smaller than the light shielding angle θ2 of the wide light shielding light source unit 66. A plurality of light source units having different light blocking angles θ can be realized by changing the distances d1 and d2 of the light sources as in the present embodiment.

  In the second embodiment, the point that the light shielding from the light source 50 is excellent will be described with reference to FIG. 10A and 10B are diagrams showing another example of the finger vein data acquisition apparatus. FIG. 10A shows a case where light shielding is not sufficient, and FIG. 10B shows a case where light shielding is sufficient. As shown in FIG. 3, light emitted from a light source element such as an LED generally travels while spreading over a certain range at a viewing angle β.

  For this reason, when the light source 52 is disposed in the opening 26d shown in FIG. 10A, the light output from the light source 52 of the wide light-shielding light source unit 66 (see FIG. 7) is irradiated at the viewing angle β. Among them, the light traveling to the area indicated by the reference numeral 82 in FIG. 10A passes through the light shielding portion 22 in the wide light shielding light source unit 66 (see FIG. 7), so that a predetermined amount of light can be shielded. However, since the light in the region indicated by reference numeral 81 in FIG. 10A passes through the light shielding portion 22 in the narrow light shielding light source unit 65 (see FIG. 6), the light shielding is insufficient. Therefore, the lower limit irradiation position from the light placement surface to the finger is lowered, and the image quality when photographing a thick finger is deteriorated.

  On the other hand, in the case shown in FIG. 10B, the problem as shown in FIG. 10A does not occur. In the case of the second embodiment, as shown in FIG. 9, the width of the light shielding unit 22 (the light shielding unit 71 in FIG. 9) of the narrow light shielding light source unit 65 and the wide light shielding light source unit 66 is the same. It has an excellent feature that does not cause such problems.

<< Third Embodiment >>
11A and 11B are diagrams showing a finger vein data acquisition apparatus according to the third embodiment. FIG. 11A is a top view, FIG. 11B is a top view when a finger is placed, and FIG. It is sectional drawing, (d) is BB sectional drawing. In the second embodiment, the position of the light source 50 is changed in the finger width direction to change the light shielding angle θ. However, in the third embodiment, the position of the light source 50 is changed in the finger height direction. Thus, the light shielding angle θ is changed. The finger vein data acquisition apparatus 2 of the third embodiment includes a narrow light-shielding light source unit 65 (see FIG. 11C) with a small light-shielding angle θ and a wide light-shielding light source unit 66 with a large light-shielding angle θ (see FIG. 11D). See).

  As shown in FIG. 11A, the light source 50 is disposed in the opening 26e, and a light shielding part 72 is provided between the opening 20 and the opening 26e. FIG. 11C is a cross-sectional view taken along the line AA, and shows the narrow light-shielding light source unit 65. FIG. 11D is a cross-sectional view of the wide light-shielding light source unit 66 in the BB cross section. The light sources 50 included in the narrow light-shielding light source unit 65 and the wide light-shielding light source unit 66 are both installed at the same angle α. Further, the distances d1 and d2 of the light source 50 with respect to the central axis of the opening 20 (that is, W1 = W2, k1 = k2) are the same. However, the light source 50 shown in FIG. 11D is installed at a position lower than the placement surface of the finger rest 5 by d6 in the height direction on the finger. As a result, the light blocking angle θ1 of the narrow light blocking light source unit 65 is smaller than the light blocking angle θ2 of the wide light blocking light source unit 66. By changing the distance d6 in the height direction of the light source as in this embodiment, a plurality of light source units having different light shielding angles θ can be realized.

<< Fourth Embodiment >>
In the fourth embodiment, another embodiment of the light amount adjustment process (S103) will be described. In the light amount adjustment process (S103) of the first embodiment, the light amount adjustment process (S103) is performed after the light source selection process (S102). On the other hand, the light amount adjustment process (S103) of the fourth embodiment does not require the light source selection process (S102). Therefore, the processing time of the registration process and the authentication process can be shortened as compared with the light source selection process and the light quantity adjustment process of the first embodiment, and even when the finger presentation position moves during the light quantity adjustment process, the optimum light quantity It has the feature that it can continue to light up.

  Further, in the first embodiment, the light amount of only one of the light source 52 of the wide light-shielding light source unit 66 or the light source 51 of the narrow light-shielding light source unit 65 is adjusted in the light amount adjustment process (S103). On the other hand, since the process of the fourth embodiment can simultaneously adjust the light amounts of the two types of light sources 51 and 52, a more optimal light amount can be calculated for the finger to be imaged.

  For example, when the light amount adjustment (S103) of the first embodiment is applied when photographing a finger with a medium thickness, if only the light source 51 is turned on, the image quality becomes unclear due to insufficient light shielding, and the light source 52 It can be assumed that an image with sufficient brightness cannot be obtained with only the amount of light shielding. When shooting such a finger, rather than turning on only one of them, first, the light source 52 is turned on with the maximum light amount, and only the amount of insufficient brightness is compensated with the light amount of the light source 51. Light directed to a low position from the finger placement surface can be reduced, and a clear image can be taken. The light amount adjustment of the fourth embodiment is a technique for capturing a clearer image by controlling by combining two types of light sources.

  Note that the light amount adjustment process (S103) is specifically a process for controlling the amount of current flowing through the light sources 51 and 52, and therefore, in addition to the above-described influence on the sharpness of the image, the power consumption of the authentication apparatus. It is also necessary to consider the impact on

  Here, the requirements of the light amount adjustment process (S103) will be reorganized. It is important that the process for controlling the light source for illumination satisfies the following three requirements.

  Requirement 1 is to make power consumption below a certain value. The small finger vein authentication system 80 (personal authentication device) described in the present invention is used for personal identification purposes for information terminals such as tablet terminals and smartphones. Since a small information terminal needs to reduce power consumption, it is also necessary to suppress power consumption of the authentication device, and the amount of current that flows to the light source of the authentication device is also limited.

Requirement 2 is to adjust the amount of light so that an image suitable for authentication can be taken. There are two conditions for an image suitable for authentication.
Requirement 2-1: The first condition is a condition that the average luminance of the image is the median value of the luminance gradation.
Requirement 2-2: The second condition is that a light-shielding light source (second light source) used for a light-shielding light source unit 66 wider than a light-shielding light source (first light source) used for a light-shielding light source unit 65 (see FIG. 6). This is a condition that shooting is performed with priority. If the wide light-shielding light source is turned on preferentially, light is emitted above the finger, so that the contrast of the vein image is increased and the authentication accuracy is improved.

  Of these two conditions, requirement 2-1 is more effective in improving authentication accuracy than requirement 2-2. Therefore, priority is given to satisfying the requirement 2-1, and the goal is to satisfy the requirement 2-2 only when there are a plurality of combinations of light quantities that satisfy the requirement 2-1.

  Requirement 3 is that an optimal light amount value can be calculated even when the finger position changes. As shown in the flow of FIG. 15, the light amount adjustment process captures an image of several frames. Since the position of the finger presented by the user may change during that time, it is necessary to continue to capture an image optimal for authentication even in such a situation.

These requirements are formulated as follows.
First, the light quantity values of the wide light-shielding light source (light source 52 (second light source)) and the narrow light-shielding light source (light source 51 (first light source)) are P _h and P _l , respectively, and the light quantity determined by the LED rating of the light source element. When the maximum value is Pmax, P _h and P _l satisfy the following conditional expressions.

0 ≦ P ₁ ≦ Pmax, 0 ≦ P _h ≦ Pmax (1)

When the maximum amount of combined light intensity values determined by using current limit of the wide light shielding source and the narrow light shielding light source shown in requirement 1 and P _S, requirement 1

P _h + P _l ≦ P _S (2)
It becomes.

Since the average luminance value of the image is determined by the light amount value, this is defined as a function I (P _h , P _l ). Here, the _{I t, I (P h,} P l) when the target value of,

Requirement 2-1 is δI = | I (P _h , P _l ) −I _t | (3)
This corresponds to obtaining P _h and P _l that minimize δI defined by equation (3). Furthermore, since the requirements 2-2 P _h is desirably as large as possible, it should be adjusted to the maximum in the range that satisfies the above-mentioned conditions.

Here, if the function form of I (P _h , P _l ) is known, P _h and P _l can be easily determined. However, actually, this function form cannot be obtained before the start of authentication. This is because the function form of I (P _h , P _l ) varies depending on the finger shape, light transmittance, and position where the finger is placed. In other words, the light amount adjustment processing uses the information measured at the time of authentication to estimate the function form of I (P _h , P _l ) and satisfies the expressions (1) and (2) while satisfying the expression (3). It is defined that the optimum light quantity values P _h and P _l that are defined in the above are minimized.

FIG. 16 is a flowchart illustrating light amount adjustment processing according to the fourth embodiment. The light amount adjustment process (S103) executed by the CPU 11 will be described with reference to FIG. In the light amount adjustment process, the CPU 11 first issues a light source lighting command with an arbitrary initial light amount value (L0) (S1031), and takes an image (S1032). As the initial light amount value, a value evaluated in advance so that the average luminance becomes a target value and the light amount value of the wide light-shielding light source becomes high can be used as an optimum value for a finger having an average thickness. Next, the CPU 11 calculates an average luminance value (V0) of the photographed image (S1033). Subsequently, when the average luminance value does not reach the target value (S1034, No), the CPU 11 executes processing for calculating the optimum light amount value (S1040). This process is a process for determining the light quantity value when photographing the next frame using the average luminance value for the past several frames and the light quantity value at the time of photographing. Next, the CPU 11 instructs to turn on the light source with the light amount value calculated by the optimal light amount calculation processing (S1040) (S1036), and then returns to the processing of S1032. By repeating this flow, it is possible to average luminance value of the image to be captured to continue a state close to the target luminance value I _t. That is, in S1034, when the average luminance value reaches the target value (S1034, Yes), the light amount adjustment is terminated. Hereinafter, the optimal light quantity value calculation process (S1040) in the flow shown in FIG. 16 will be described.

The average luminance value of the image captured when the light amount values P _h and P _l are both 0 is constant regardless of the finger to be imaged. In this device, the average brightness value when the light amount value is 0 is 0.
I (0,0) = 0
It becomes.

In addition, the luminance value of an image captured when the light amount values P _h and P _l of each light source are increased is higher than before the light amount value is increased. Therefore, it is considered that the average luminance I (P _h , P _l ) is a monotonically increasing function with respect to the light amount values P _h and P _l . In this embodiment, the luminance value is proportional to each light amount value, that is, I (P _h , 0) = aP _h , I (0, P _l ) = bP _l
Assume that Here, a and b are respective proportionality coefficients. Moreover, it is assumed that the contribution to the luminance by the light quantity value of each light source is additive. That is,

I (P _h , P _l ) = I (P _h , 0) + I (0, P _l ) (4)
Can be written.

From the _{above, I (P h, P l} ) function form of _{I (P h, P l)} = aP h + bP l (5)
It becomes.

  Here, when the light shielding angle θ1 is small, almost all of the light output from the narrow light shielding light source unit 65 shown in FIG. Since the light output from the light has a large light shielding angle θ2, the contribution ratio to the luminance value of the image is low. Therefore, the increase rate of the luminance value due to the increase in the light amount value of the wide light-shielding light source (light source 52 (second light source)) is lower than the increase rate of the luminance value due to the narrow light-shielding light source (light source 51 (first light source)). Therefore, the following relationship is established between the coefficients a and b.

      a <b (6)

The method for calculating the optimum luminance in the present embodiment is a method for estimating the luminance value I (P _h , P _l ) when the light amount values P _h , P _l are changed within a range that satisfies the above-described constraint equation. By estimating the coefficients a and b in the above equation (5) from the light quantity value irradiated in the past and the average brightness value at that time, the average brightness I (P _h , P corresponding to the arbitrary light quantity value P _h , P _l is obtained. _l ) can be obtained. This approach, coefficients a, using the estimated result of b, is a process of obtaining _{I (P h, P l)} = I t become _{P h,} a combination of _{P l.}

As a method for determining the coefficients a and b, for example, a least square method can be used. The least square method is a technique widely used as an optimization technique for minimizing an error between a model function and a measurement result. Hereinafter, as an example of a coefficient determination method, a method for obtaining the coefficients a and b using the least square method will be described. Average luminance value of the past N frames _{I 1, I 2, ...,} and _{I N,} the amount of time
(P _{h, 1} , P _{l, 1} ), (P _{h, 2} , P _{l, 2} ), ..., (P _{h, N} , P _{l, N} )
The square error s ² is

となる。最小二乗法ではこのｓ^２が最小となるａ，ｂを求める。求めた結果は、以下のようになる。

It becomes. In the least square method, a and b that minimize s ² are obtained. The results obtained are as follows.

Here, <> means an average value. By using the values of a and b thus obtained, it is possible to estimate the average luminance I (P _h , P _l ) corresponding to the arbitrary light quantity values P _h and P _l . Next, optimal light quantity values P _h and P _l are determined using the above a and b.

Optimum light intensity _{values, I (P h, P l} ) = satisfy _{I t P h,} is a _{P l, I (P h,} P l) for is a two-variable function I _{(P h, P l)} There are a plurality of combinations of P _h and P _l that satisfy = I _t . Here, P _h, the value of P _l is uniquely determined considering the condition that P _h shown is maximum requirements 2-2. That, I _{(P h, P l)} = satisfy _{I t P h,} in the combination of _{P l,} formula (1), satisfies the condition of formula (2), and _{P h} is maximized _{P h} , _Pl is the optimum light amount value.

  Thus, the above-mentioned requirements can be satisfied by calculating the optimum light amount. Further, in this method, when calculating the optimum light amount, the processing can be executed if there is data for two frames immediately before the optimum light amount value calculation processing (S1040). However, the correct light quantity value can be calculated simply by taking data for two frames thereafter.

  According to this embodiment, a highly accurate and small personal authentication device can be realized. The personal authentication device can shoot light suitable for authentication by irradiating light at an optimal position with respect to living bodies of various sizes. In addition, the personal authentication device can capture a clear vein image regardless of the size of the living body to be imaged and the presentation position. This enables highly accurate authentication.

  In the personal authentication device of the present embodiment, it has been described that a vein image is captured, but the present invention is not limited to this. For example, a blood vessel image including an artery may be taken. In addition, the light shielding unit 22 may be configured by the inner wall of the finger rest 5 and the inner wall of the housing.

1 finger 2 finger vein data acquisition device 4 imaging unit 5 finger rest (housing, finger rest)
6 voice output unit 10 authentication processing unit 11 CPU (central processing unit)
12 Memory 13 Interface (IF)
DESCRIPTION OF SYMBOLS 14 Memory | storage device 15 Power supply part 17 Display part 18 Image input part 19 Information input part 20, 26 Opening part 22, 71, 72 Light-shielding part (light-shielding means)
30 registration data 40 authentication data 50 light source 51 light source (first light source, narrow light source)
52 Light source (second light source, wide light blocking light source)
60 Light source unit 61 Optical axis (irradiation axis)
65 Narrow light-shielding light source unit (first light source unit)
66 Wide light-shielding light source unit (second light source unit)
80 finger vein authentication system (personal authentication device)
100 registration program 120 authentication program

Claims (5)

A housing having an opening on a placement surface on which a finger is placed;
In the housing, a plurality of light sources arranged in the longitudinal direction of the finger and irradiating the finger obliquely,
In the housing, an imaging unit that images the light from the light source that has passed through the finger through the opening;
A processing unit that performs matching between the feature extracted from the finger vein image acquired by the imaging unit and biometric information stored in advance,
On the same surface as the placement surface, a light-shielding portion that shields light from the plurality of light sources, and the distance between each light source and the light-shielding portion is different.
The light shielding portion is shielded from the opening to the same distance with respect to the width direction of the finger,
Wherein the positions of a plurality of light sources with respect to the width direction of the finger, characterized in that arranged at different distances personal authentication device. The personal authentication apparatus according to claim 1, wherein the optical axes of the plurality of light sources are at the same angle with respect to the placement surface. The plurality of light sources are
A first light source having a long distance between the light source and the light shielding portion;
A second light source having a short distance between the light source and the light shielding portion;
The processing unit turns on the second light source when the finger is placed,
The personal authentication device according to claim 1, wherein when it is determined that the finger is a thin finger, the first light source is turned on. The personal authentication device has a light amount control means for controlling the light amount of the light source,
The light amount control means calculates an average luminance value of the captured vein image,
When the average luminance value does not reach a predetermined target value, the first light source and the second light source are turned on, and the first light source and the second light source satisfy the predetermined target value. The personal authentication apparatus according to claim 3 , wherein the light quantity value of the light source is calculated.   A housing having an opening on the placement surface on which the finger to be authenticated is placed;
  In the housing, a plurality of light sources arranged in the longitudinal direction of the finger and irradiating the finger obliquely,
  In the housing, an imaging unit that captures an image of the finger vein of the authentication target through the opening with light from the light source that has passed through the finger;
  A processing unit that performs matching between the feature extracted from the finger vein image acquired by the imaging unit and biometric information stored in advance,
  On the same surface as the placement surface, a light-shielding portion that shields light from the plurality of light sources, and the distance between each light source and the light-shielding portion is different.
  The light shielding portion is shielded from the opening to the same distance with respect to the width direction of the finger,
  The positions of the plurality of light sources are arranged at different distances with respect to the width direction of the finger.
  A finger vein authentication device characterized by that.

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