Biometric image acquisition apparatus, biometric image acquisition method, and biometric authentication system

Abstract

To provide a biometric image acquisition apparatus, a biometric image acquisition method, and a biometric authentication system for acquiring a captured image more suitable for biometric authentication.SOLUTION: An authentication apparatus for acquiring a biometric image, comprises: an imaging unit 40 for imaging at least a part of a hand UH of a person to be authenticated; an illumination unit 30 having an illumination 32 that illuminates the hand of the person to be authenticated; an exposure control unit 20 for controlling the imaging unit 40 and the illumination 32 based on an exposure control parameter that controls at least one of the imaging unit and the illumination; and a control unit 10 having a processor 11 that detects fingertips from a captured image captured by the imaging unit 40, evaluates brightness of the detected fingertips, and selects and acquires at least one captured image from among a plurality of captured images based on the brightness of the fingertips.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a biometric image acquisition device, a biometric image acquisition method, and a biometric authentication system. [Background technology]

[0002] Patent Document 1 discloses a biometric authentication device that acquires multiple sets of palm images using light irradiated from a light source under multiple different lighting conditions, adjusts the time interval between each of the multiple image sets when acquiring the multiple image sets depending on the shooting conditions, extracts biometric features from each of the multiple image sets, and compares each extracted biometric feature with a registered biometric feature that has been registered in advance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-162302 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable that an image used for biometric authentication is captured under more appropriate lighting conditions in order to suppress a decrease in the accuracy of extracting biometric information and the accuracy of biometric authentication using the biometric information. However, in the configuration of Patent Document 1, biometric authentication is performed using a set of images captured at an adjusted time interval and under a plurality of different lighting conditions. Therefore, depending on the adjusted time interval, the speed at which the user moves the palm, etc., the biometric authentication device may not be able to obtain a set of images captured under all lighting conditions. In addition, in the past, in synchronous control of lighting and a camera during high-speed shooting, it was difficult to control the ON / OFF of lighting in accordance with the shooting timing of the camera.

[0005] The present disclosure has been devised in view of the above-mentioned conventional circumstances, and aims to provide a biometric image acquisition device, a biometric image acquisition method, and a biometric authentication system that acquire a captured image more suitable for biometric authentication. [Means for solving the problem]

[0006] The present disclosure provides a biometric image acquisition device comprising an imaging unit that images at least a portion of the hand of a person to be authenticated, a light that illuminates the hand of the person to be authenticated, a control unit that controls the imaging unit and the light based on an exposure control parameter that controls at least one of the imaging unit and the light, a detection unit that detects the fingertips of the hand from an image captured by the imaging unit, an evaluation unit that evaluates the brightness of the detected fingertips, and an acquisition unit that selects and acquires at least one of a plurality of image images based on the brightness of the fingertips.

[0007] The present disclosure also provides a biometric image acquisition method performed by a computer, which includes illuminating and capturing an image of a person's hand based on an exposure control parameter, detecting fingertips of the person's hand from the captured image, evaluating brightness of the detected fingertips, and selecting and acquiring at least one of the captured images based on the brightness of the fingertips.

[0008] The present disclosure also provides a biometric authentication system including a biometric image acquisition device that acquires an image of at least a part of a hand of a person to be authenticated, and an authentication device capable of communicating with the biometric image acquisition device, in which the biometric image acquisition device illuminates and captures the hand of the person to be authenticated based on an exposure control parameter, detects the fingertips of the hand of the person to be authenticated from the captured image, evaluates the brightness of the detected fingertips, selects and acquires at least one of the captured images based on the brightness of the fingertips, and transmits it to the authentication device, and the authentication device authenticates the person to be authenticated based on the captured image transmitted from the biometric image acquisition device. Effect of the Invention

[0009] According to the present disclosure, a captured image suitable for biometric authentication can be acquired. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram for explaining a use case example of a biometric authentication system according to the first embodiment and a modified example of the first embodiment. [Diagram 2] FIG. 1 is a perspective view showing a first illumination arrangement example of an authentication device according to the first embodiment and a biometric information acquisition device according to a modified example of the first embodiment. [Diagram 3] FIG. 1 is a block diagram showing an example of an internal configuration of an authentication device according to a first embodiment. [Figure 4] Diagram for explaining an example of finger detection and identification [Diagram 5] A flowchart for explaining the operation procedure of the biometric authentication system according to the first embodiment. [Figure 6] A flowchart for explaining the operation procedure of the biometric authentication system according to the first embodiment. [Figure 7] Diagram explaining examples of using biometric authentication systems [Figure 8] FIG. 1 is a diagram for explaining an example of exposure control in an authentication device. [Figure 9] Timing chart showing example 1 of illumination control and exposure control of an image sensor [Figure 10] Timing chart showing example 2 of illumination control and exposure control of an image sensor [Figure 11] Table showing the state of each frame in Example 3 of illumination control and exposure control of the image sensor [Figure 12] A table showing the state of each frame in a modification of the third example of illumination control and exposure control of the image sensor. [Figure 13] Table showing the state of each frame in Example 4 of illumination control and exposure control of the image sensor [Figure 14] FIG. 1 is a block diagram showing an example of an internal configuration of a biometric information acquiring device according to a modification of the first embodiment. [Figure 15]FIG. 1 is a block diagram showing an example of an internal configuration of an authentication device according to a modification of the first embodiment. [Figure 16] A table showing the correspondence between the operation procedures shown in FIG. 5 and FIG. 6 and the operation procedures of the biometric authentication system according to each embodiment. [Figure 17] FIG. 1 is a diagram illustrating an example of exposure control in a conventional authentication device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Background to this disclosure) Here, as a comparative example of each embodiment described later, an example of capturing an image when conventional exposure control is executed will be described with reference to Fig. 17. Fig. 17 is a diagram for explaining an example of exposure control in a conventional authentication device B1. The authentication device B1 shown in Fig. 17 has the same configuration as the authentication device B1 described later.

[0012] The authentication device B1 illuminates a user's hand UH, which is a biometric authentication target, with at least one illumination unit 30 (see FIG. 3), and captures an image of the user's hand UH with an imaging unit 40 (see FIG. 3). The authentication device B1 executes biometric authentication (user authentication) using the captured image.

[0013] Here, authentication device B1 captures an image of a moving user's hand UH by controlling each of illumination unit 30 and imaging unit 40 under predetermined exposure conditions. Each of captured images IMG01, IMG02, and IMG03 is an image of the hand UH captured by authentication device B1.

[0014] The captured image IMG01 is an image captured when the distance (hereinafter referred to as "imaging distance") between the user's hand UH and the glass surface 16 (see FIG. 1) of the authentication device B1 is short. The user's hand UH captured in the captured image IMG01 is blown out due to the short imaging distance, resulting in degraded image quality. The luminance graph LG01 indicates the luminance value (hereinafter referred to as "biometric luminance value") of the area of ​​the user's hand UH captured in the captured image IMG01 from which biometric information used for biometric authentication is extracted. The biometric luminance value indicated by the luminance graph LG01 is greater than the biometric luminance value Lm11 suitable for acquiring (extracting) biometric information used for biometric authentication. Therefore, the captured image IMG01 is an image that is not suitable for acquiring biometric information.

[0015] Captured image IMG02 is an image captured when the imaging distance is appropriate. Brightness graph LG02 shows the biometric brightness value of captured image IMG02. The biometric brightness value shown by brightness graph LG02 is approximately equal to biometric brightness value Lm11 suitable for acquiring (extracting) biometric information used for biometric authentication. Therefore, captured image IMG02 is a captured image suitable for acquiring biometric information.

[0016] Captured image IMG03 is an image captured at a long imaging distance. Brightness graph LG03 shows the biometric brightness value of captured image IMG03. The user's hand UH shown in captured image IMG03 is dark due to the long imaging distance, and image quality is degraded. The biometric brightness value shown by brightness graph LG03 is smaller than the biometric brightness value Lm11 suitable for acquiring (extracting) biometric information used for biometric authentication. Therefore, captured image IMG03 is not suitable for acquiring biometric information.

[0017] As described above, the authentication device B1 that executes conventional exposure control may have difficulty in acquiring biometric information suitable for biometric authentication or in realizing more accurate biometric authentication, depending on the height at which the user holds his / her hand UH (i.e., the imaging distance), the angle at which the user holds his / her hand UH, the shape of each user's hand UH, etc. In addition, the user must repeatedly retake the image in order to capture an image from which biometric information suitable for biometric authentication can be acquired, which is very troublesome.

[0018] Therefore, in each of the embodiments described below, examples of a biometric image acquisition device, a biometric image acquisition method, and a biometric authentication system that acquire a captured image more suitable for biometric authentication will be described.

[0019] Hereinafter, with reference to the drawings as appropriate, detailed descriptions will be given of the embodiments that specifically disclose the configurations and operations of the biometric image acquisition device, biometric image acquisition method, and biometric authentication system according to the present disclosure. However, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of already well-known matters and duplicate descriptions of substantially identical configurations may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the attached drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0020] (Embodiment 1) A use case of the biometric authentication system 100 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram for explaining an example of a use case of the biometric authentication systems 100 and 200 according to the first embodiment and the modified example of the first embodiment. Note that the biometric authentication system 100 according to the first embodiment will be described here, and the biometric authentication system 200 according to the modified example of the first embodiment will be described later.

[0021] In the following description, biometric authentication using a fingerprint as biometric information will be described, but the biometric information is not limited to this. The biometric information may be a fingerprint, a palm vein, or the like of a user.

[0022] The biometric authentication system 100 according to the first embodiment includes an authentication device B1 and a monitor MN. The biometric authentication system 100 captures an image of at least a part of a hand UH of a user who is to be authenticated (specifically, an area from which biometric information used for biometric authentication can be extracted) by the authentication device B1, and acquires the biometric information of the user appearing in the captured image. The biometric authentication system 100 also performs biometric authentication by matching the biometric information of the user with each of a plurality of pieces of biometric information registered in advance by the authentication device B1, and outputs and displays the biometric authentication result on the monitor MN.

[0023] In the following description, a case where the user's hand UH is captured while moving and not in contact with the glass surface 16 (i.e., a predetermined image capturing surface) will be mainly described as an example, but the present invention is not limited to this. The user's hand UH may be captured while stationary (still).

[0024] The monitor MN is configured using, for example, a Liquid Crystal Display (LCD) or an organic electroluminescence (EL). The monitor MN displays the matching result output from the authentication device B1, or outputs the result by voice through a speaker (not shown). The monitor MN may be configured integrally with the authentication device B1.

[0025] Although the biometric authentication system 100 will be described with reference to an example in which the authentication device B1 and the monitor MN are separate entities, they may be integrated into one body.

[0026] The structure and internal configuration of authentication device B1 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a perspective view showing an example of a first illumination arrangement of authentication device B1 in embodiment 1 and biometric information acquisition device B1A in a modified example of embodiment 1. Fig. 3 is a block diagram showing an example of the internal configuration of authentication device B1 according to embodiment 1.

[0027] The authentication device B1, which is an example of a biometric image acquisition device, is made of metal or resin. The authentication device B1 includes a control unit 10, a glass surface 16 (see FIG. 1), a housing 18, an exposure control unit 20, an illumination unit 30, an imaging unit 40, a sensor unit 50, and a display control unit 60.

[0028] The control unit 10 includes a processor 11, a memory 12, and a biological information database DB.

[0029] The processor 11, which is an example of an evaluation unit and an acquisition unit, is configured using, for example, a Central Processing Unit (hereinafter referred to as "CPU"), a System-on-Chip (SOC) or a Field Programmable Gate Array (hereinafter referred to as "FPGA"), and performs various processes and controls in cooperation with the memory 12. Specifically, the processor 11 refers to the programs and data stored in the memory 12 and executes the programs to realize the functions of each unit, such as the control unit 10, the exposure control unit 20, the sensor unit 50, and the display control unit 60.

[0030] The processor 11 causes the exposure control unit 20 to start controlling the illumination unit 30 and the imaging unit 40, based on a first detection signal output from the sensor unit 50 notifying detection of the user's hand UH.

[0031] The processor 11 causes the exposure control unit 20 to end the control of the illumination unit 30 and the imaging unit 40, based on the second detection signal output from the sensor unit 50 notifying the detection of the user's hand UH.

[0032] The processor 11 also detects the user's fingertip from the captured image captured by the imaging unit 40. The processor 11 generates a fingertip image by cutting out an area including at least the detected fingertip (for example, the first joint). The processor 11 adjusts the exposure control conditions for capturing images of each finger based on information on the biometric luminance value of the generated fingertip image. The processor 11 determines the priority order of the fingertip images to be used for biometric authentication based on information on the biometric luminance value of the captured fingertip image. Based on the determined priority order, the processor 11 stores (registers) the user's biometric information in the biometric information database DB, and performs user authentication (i.e., biometric authentication) by comparing the biometric information of each of a plurality of users stored (registered) in advance in the biometric information database DB. The processor 11 outputs the biometric authentication result to the display control unit 60 and displays it on the monitor MN.

[0033] The biometric information referred to here may be the fingertip image itself, or may be a feature value that indicates the individuality of the user extracted from the fingertip image. The feature value is extracted using a known technique (for example, the minutia method or the frequency feature analysis method). The minutia method is a method for extracting fingerprint feature values ​​by detecting end points or branch points (divisions) that indicate breaks in fingerprint lines among the ridges of the fingerprint. The frequency feature analysis method is a method for extracting fingerprint feature values ​​from a waveform of a frequency that is converted into a frequency based on the edges, bending points, etc. of the fingerprint unevenness. The vein feature value is extracted by extracting the vein pattern of the user's finger from an image of the user's finger captured using near-infrared light, for example.

[0034] The memory 12 has, for example, a random access memory (hereinafter referred to as "RAM") as a working memory used when executing each process of the processor 11 and the exposure control circuit 21, and a flash memory for storing programs and data that define the operation of the processor 11 and the exposure control circuit 21. The RAM temporarily stores data or information generated or acquired by the processor 11 or the exposure control circuit 21. The flash memory has written therein programs that define the operation of the processor 11 and the exposure control circuit 21.

[0035] The memory 12 stores exposure control condition tables TB1, TB2, and TB3 for the illumination unit 30 and the imaging unit 40, which are executed by the exposure control unit 20. Here, the exposure control conditions are illumination parameters of the illumination 32 (e.g., ON time or OFF time of the illumination 32, lighting pattern, illuminance, etc.) or imaging parameters of the imaging unit 40 (e.g., shutter speed, shutter opening / closing pattern, shutter cycle, etc.), which are conditions (parameters) for controlling the illumination 32 or the imaging unit 40.

[0036] The biometric information database DB, as an example of a database, is a storage medium device such as a hard disk drive (hereinafter referred to as "HDD") or a solid state drive (hereinafter referred to as "SSD"), and stores the biometric information of multiple users registered in advance by an administrator. The biometric information stored in the biometric information database DB is stored in association with user information (e.g., name, date of birth, identification number capable of identifying the user, employee number, or facial photograph, etc.). Note that when user authentication is performed using the fingerprints or veins of multiple fingers, the biometric information database DB may also store finger information (e.g., middle finger or index finger, etc.) corresponding to the biometric information in further association with the biometric information.

[0037] 3 shows an example in which the biometric information database DB is configured integrally with the authentication device B1, it may be configured as an external storage device separate from the authentication device B1 and connected to be able to transmit and receive data via wireless or wired communication. The wireless communication here refers to communication via a wireless Local Area Network (LAN) such as Wi-Fi (registered trademark).

[0038] Glass surface 16 (see FIG. 1) is disposed adjacent to at least one sensor (first approach sensor 51 or second approach sensor 52, see FIG. 1) on the top surface of housing 18. Glass surface 16 is provided so that a user's hand UH passing over housing top surface 18A (see FIG. 1) of housing 18 can be illuminated by illumination unit 30 and imaged by imaging unit 40.

[0039] The cover guide 17 is made of metal or resin and is formed in a substantially L-shape. One end of the substantially L-shape of the cover guide 17 is fixed to one side of the rectangular housing top surface 18A. The other end of the substantially L-shape of the cover guide 17 is provided so as to cover the housing top surface 18A, and blocks the illumination light from the illumination unit 30 that passes through the glass surface 16 of the housing top surface 18A at the other end side.

[0040] The other end side of the cover guide 17 is formed so that the distance (i.e., height) between the lower surface of the cover guide 17 and the housing top surface 18A increases (is higher) from the side where one end of the four sides of the housing top surface 18A is fixed toward the opposing side. This allows the authentication device B1 to increase the distance (i.e., height) between the cover guide 17 and the housing top surface 18A in the direction where the user is located. Therefore, the user can easily insert his / her hand between the cover guide 17 and the housing top surface 18A and pass it through, since the distance (height) between the cover guide 17 and the housing top surface 18A is the highest toward the side where the user is located.

[0041] Also, the cover guide 17 has openings between two sides adjacent to the side to which one end of the cover guide 17 is fixed (i.e., the side corresponding to the direction in which the user's finger enters and the side corresponding to the direction in which the user's finger leaves) and the other end side of the cover guide 17. This allows the user to intuitively grasp the direction in which the user's finger should pass (i.e., either the passing direction X or the direction opposite to the passing direction X).

[0042] By using the cover guide 17, the authentication device B1 can also limit the height of the user's hand UH, i.e., the imaging distance between the imaging unit 40 and the user's hand UH, to the distance between the cover guide 17 and the glass surface 16. Note that the cover guide 17 is not an essential component in the authentication device B1 according to the first embodiment and may be omitted.

[0043] The exposure control unit 20, which is an example of a control unit, is configured using, for example, a CPU, SOC, or FPGA, and performs various processes and controls in cooperation with the memory 12. Specifically, the exposure control unit 20 refers to the programs and data stored in the memory 12 and executes the programs, thereby realizing the functions of the exposure control circuit 21.

[0044] When the exposure control unit 20 acquires a control command output from the processor 11, it executes illumination control of the illumination unit 30 and exposure control of the imaging unit 40 based on the exposure control conditions stored in the exposure control condition tables TB1 to TB3 stored in the memory 12. The exposure control circuit 21 outputs an illumination light emission signal generated based on the exposure control conditions to the illumination driver circuit 31. The exposure control circuit 21 also outputs a shutter control signal generated based on the exposure control conditions to the imaging sensor 42.

[0045] The exposure control circuit 21 repeatedly executes the illumination control of the illumination unit 30 and the exposure control of the imaging unit 40 while the sensor unit 50 continues to detect the user's hand UH from within the imaging area that can be imaged by the imaging unit 40. The exposure control circuit 21 terminates the illumination control of the illumination unit 30 and the exposure control of the imaging unit 40 when the sensor unit 50 does not detect the user's hand UH from within the imaging area that can be imaged by the imaging unit 40, as output from the processor 11.

[0046] The illumination unit 30 is stored inside the housing 18 of the authentication device B1, and illuminates the user's hand UH which is the image capture target of the imaging unit 40. The illumination unit 30 includes an illumination driver circuit 31 and at least one illumination 32.

[0047] The lighting driver circuit 31 executes ON / OFF control of the lighting 32 based on a control command output from the exposure control circuit 21 .

[0048] The illumination 32 is configured to have one or more illuminations such as a Light Emittimg Diode (LED), a Laser Diode (LD), an InfraRed (IR) illumination, etc. The illumination 32 may have a plurality of illumination regions (one example of a light emitting region) that can be controlled to be turned on and off. Note that FIG. 2 shows the illumination unit 30 formed in a circular ring shape as an example, but is not limited to this. For example, the illumination 32 and each illumination region may be configured to be a surface light source, a point light source, or a line light source, or may be configured to be a combination of a plurality of different light sources among a surface light source, a point light source, or a line light source. The illumination 32 may be configured to have a configuration in which each of the plurality of illuminations is arranged to be polygonal, approximately rectangular, approximately annular, approximately U-shaped, or rhombic, or may be arranged approximately parallel to each other.

[0049] The imaging unit 40 is stored inside the housing 18 of the authentication device B1, and captures an image of the user's hand UH held over the glass surface 16. The imaging unit 40 includes a lens 41, an imaging sensor 42, and an imaging signal processing unit 43.

[0050] The lens 41 forms an image on the imaging sensor 42 from light incident on a lens barrel (not shown).

[0051] The imaging sensor 42 is a so-called image sensor, and is, for example, a solid-state imaging element such as a Charged-Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS). The imaging sensor 42 executes start / end control of an electronic shutter (not shown) (i.e., start / end control of exposure) based on a shutter control signal output from the exposure control circuit 21. The imaging sensor 42 also converts an optical image formed on the imaging surface by the lens 41 into an electrical signal at a frame rate set in advance by an administrator, and outputs the electrical signal to the imaging signal processing unit 43.

[0052] The imaging signal processing unit 43 processes the electrical signal output from the imaging sensor 42 and outputs the processed signal to the processor 11 .

[0053] The sensor unit 50 includes a first approach sensor 51 and a second approach sensor 52 (see FIG. 1) as an example of a detection unit, and a sensor control circuit 53.

[0054] Specifically, each of the first approach sensor 51 and the second approach sensor 52 is realized by a reflective Time Of Flight (TOF) sensor, an infrared sensor, a transmissive laser sensor, a light receiving sensor, etc. Each of the first approach sensor 51 and the second approach sensor 52 is arranged in a passing direction X in which the user's finger passes across the glass surface 16, and detects whether or not the user's hand UH is present within an imaging area (not shown) of the imaging unit 40. When each of the first approach sensor 51 and the second approach sensor 52 detects the user's hand UH within the imaging area of ​​the imaging unit 40, it generates a detection signal and outputs it to the processor 11.

[0055] Next, an example of finger detection and identification will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining an example of finger detection and identification. Note that Fig. 4 describes an example of detecting and identifying three fingers of a user, that is, an index finger, a middle finger, and a ring finger, but it goes without saying that the number of fingers to be detected is not limited to this.

[0056] Each of the captured images IMG1, IMG2, IMG3, IMG4, IMG5, IMG6, IMG7, IMG8, ​​IMG9, and IMG10 shown in Figure 4 is an image of a user's hand UH passing over the glass surface 16, and is an image captured at a predetermined time interval.

[0057] The processor 11 acquires a captured image IMG1 captured at time T10 and detects a user's finger from the captured image IMG1. In the example shown in Fig. 4, the processor 11 determines that a user's finger is not detected from the captured image IMG1 and omits the finger identification process.

[0058] The processor 11 acquires a captured image IMG2 captured at time T11, detects the user's finger FNG1 from the captured image IMG2, and identifies which finger the detected finger FNG1 is. Based on the identification result, the processor 11 assigns to the detected finger FNG1 a tag "FID:1" indicating that the finger FNG1 is an index finger.

[0059] The processor 11 acquires a captured image IMG3 captured at time T12, detects the user's fingers FNG1 and FNG2 from the captured image IMG3, and identifies which fingers the detected fingers FNG1 and FNG2 belong to. Based on the identification result, the processor 11 assigns to the finger FNG1 a tag "FID:1" indicating that the finger FNG1 is an index finger, and to the finger FNG2 a tag "FID:2" indicating that the finger FNG2 is a middle finger.

[0060] The processor 11 acquires a captured image IMG4 captured at time T13, detects the user's fingers FNG1, FNG2, and FNG3 from the captured image IMG4, and identifies which finger each of the detected fingers FNG1 to FNG3 belongs to. Based on the identification result, the processor 11 assigns to the finger FNG1 a tag "FID:1" indicating that the finger FNG1 is an index finger, to the finger FNG2 a tag "FID:2" indicating that the finger FNG2 is a middle finger, and to the finger FNG3 a tag "FID:3" indicating that the finger FNG3 is a ring finger.

[0061] The processor 11 similarly executes the finger detection process, the identification process, and the tagging process on each of the captured image IMG5 captured at time T14 and the captured image IMG6 captured at time T15.

[0062] The processor 11 acquires the captured image IMG7 captured at time T16, detects the user's fingers FNG2 and FNG3 from the captured image IMG7, and identifies which fingers the detected fingers FNG2 and FNG3 belong to. Based on the identification result, the processor 11 assigns to the finger FNG2 a tag "FID:2" indicating that the finger FNG2 is a middle finger, and to the finger FNG3 a tag "FID:3" indicating that the finger FNG3 is a ring finger.

[0063] The processor 11 acquires a captured image IMG8 captured at time T17, detects the user's fingers FNG3 from the captured image IMG8, ​​and identifies which finger the detected fingers FNG3 belong to. Based on the identification result, the processor 11 assigns the finger FNG3 a tag "FID:3" indicating that the finger FNG3 is a ring finger.

[0064] The processor 11 similarly performs finger detection processing or finger identification processing on each of the captured image IMG9 captured at time T18 and the captured image IMG10 captured at time T19. In the example shown in Fig. 4, the processor 11 determines that the user's finger is not detected from the captured images IMG9 and IMG10, and omits the finger identification processing or the tagging processing.

[0065] 4, when the finger to be detected is set in advance as, for example, the index finger, middle finger, or ring finger, the processor 11 may identify the finger FNG4 detected from the captured images IMG5 to IMG9, and may omit the tagging process if it is determined to be the ring finger through the identification. Also, when the number of fingers to be detected is set in advance as three, the processor 11 may determine that the finger FNG4 detected from the captured images IMG5 to IMG9 is the fourth finger, and may omit the identification process or tagging process for this finger FNG4.

[0066] Next, the operation procedure of the biometric authentication system 100 according to the first embodiment will be described with reference to Fig. 5 to Fig. 7. Fig. 5 is a flowchart for explaining an example of the operation procedure of the biometric authentication system 100 according to the first embodiment. Fig. 6 is a flowchart for explaining an example of the operation procedure of the biometric authentication system 100 according to the first embodiment. Fig. 7 is a diagram for explaining an example of use of the biometric authentication system 100.

[0067] 5 and 6, an example of changing only the exposure condition (condition related to the shutter speed of the imaging unit 40) will be described as an example of the exposure control condition, but it goes without saying that the illumination control and the exposure control may be executed simultaneously. As an example of the use of the biometric authentication system 100 shown in FIG. 7, an example of capturing an image of a user's hand UH moving in the X direction on the glass surface 16 will be described, but the present invention is not limited to this.

[0068] Moreover, the correspondence between each process executed by the authentication device B1 shown in FIG. 5 and FIG. 6 and each process executed by the monitor MN is shown in a table TB4 in FIG. 16, which will be described later.

[0069] The authentication device B1 detects, by the first approach sensor 51 or the second approach sensor 52, the approach or insertion of the user's hand UH into an imaging area between the cover guide 17 and the glass surface 16 that can be imaged by the imaging unit 40 (St1-1).

[0070] When the first approach sensor 51 or the second approach sensor 52 detects the approach or insertion of the user's hand UH, the authentication device B1 starts the exposure control of the imaging unit 40 (St2-1), resets the number of fingertip detections m (m: an integer equal to or greater than 0) in the captured image to m=0 (zero), resets the exposure control count number n (n: an integer equal to or greater than 0) that counts the number of exposure controls that have been performed to n=0 (zero), and sets the number of set exposure conditions k (k: an integer equal to or greater than 1) that is set as the exposure control condition to be performed to k=1 (St2-2). The authentication device B1 starts strobe emission of the illumination 32 (St2-3).

[0071] When the current fingertip detection number m and exposure control count number n are (m, n)=(0, 0), the authentication device B1 refers to the exposure control conditions recorded as the initial settings. The authentication device B1 controls the shutter speed of the imaging unit 40 based on the exposure control conditions (initial settings) and captures the user's hand UH (St3-1). When the current fingertip detection number m and exposure control count number n are (m, n)≠(0, 0), the authentication device B1 controls the shutter speed of the imaging unit 40 under the shutter speed conditions (m, n) based on the shutter control table (for example, exposure control condition tables TB1, TB2, TB3, etc. shown in FIG. 11 to FIG. 13) and the current fingertip detection number m and exposure control count number n, and captures the user's hand UH (St3-1).

[0072] The authentication device B1 ends the strobe emission of the lighting 32 (St3-2). The authentication device B1 determines whether or not the set exposure condition number k and the exposure control count number n are equal (that is, whether or not k=n) (St3-3).

[0073] When it is determined in the process of step St3-3 that the set exposure condition number k and the exposure control count number n are equal (that is, k=n) (St3-3, YES), the authentication device B1 resets the exposure control count number n to n=0 (zero) (St3-4).

[0074] On the other hand, if the authentication device B1 determines in the process of step St3-3 that the set exposure condition number k and the exposure control count number n are not equal (that is, k≠n) (St3-3, NO), it increments the exposure control count number n (n+1) (St3-5).

[0075] The authentication device B1 detects fingertips from the captured image captured in step St3-1, and determines whether or not at least one fingertip is captured in the captured image (St3-6). When performing vein authentication, the authentication device B1 detects at least one finger joint (e.g., the second joint).

[0076] When the authentication device B1 determines in the process of step St3-6 that at least one fingertip is captured in the captured image (St3-6, YES), it sets the fingertip detection number m to the number of detected fingertips and sets the set exposure condition number k=m (St3-7). Furthermore, the authentication device B1 identifies which finger each of the detected fingertips belongs to. The authentication device B1 generates and assigns a tag for identifying each fingertip, corresponding to the identification result, to each of the detected fingertips.

[0077] On the other hand, if the authentication device B1 determines in the processing of step St3-6 that at least one fingertip is not captured in the captured image (St3-6, NO), it determines whether or not the user's hand UH is detected in the imaging area that can be captured by the imaging unit 40 by either one of the sensors (the first approach sensor 51 or the second approach sensor 52) (St4-1).

[0078] The authentication device B1 generates a fingertip image by cutting out an area including at least the first joint of the detected fingertip (St3-8). The authentication device B1 calculates a biometric luminance value of the fingertip shown in the generated fingertip image (St3-9). When performing vein authentication, the authentication device B1 generates a vein image by cutting out an area including at least one finger joint (e.g., the second joint).

[0079] The authentication device B1 calculates a biometric luminance value of the surface of the fingertip based on the luminance values ​​of pixels included in the generated fingertip image. The authentication device B1 determines whether the calculated biometric luminance value of the fingertip is equal to or less than a first threshold and equal to or more than a second threshold, which indicate a biometric luminance value suitable for biometric authentication (fingerprint authentication) (St3-10).

[0080] Here, a method for calculating the biometric luminance value of a fingertip will be described. The authentication device B1 may calculate an average value of luminance values ​​of pixels included in a fingertip region (i.e., a region including at least a first joint of a fingertip), and acquire the calculated average value of luminance values ​​as the biometric luminance value of the fingertip shown in the fingertip image. The authentication device B1 may also acquire the maximum value of the luminance values ​​of pixels included in the fingertip region as the biometric luminance value of the fingertip shown in the fingertip image. The authentication device B1 may also extract the luminance values ​​of the top p (p: an integer equal to or greater than 2) pixels from the luminance values ​​of pixels included in the fingertip region, calculate an average value of the luminance values ​​of the extracted p pixels, and acquire the calculated average value of luminance values ​​as the biometric luminance value of the fingertip shown in the fingertip image.

[0081] When the authentication device B1 determines in the process of step St3-10 that the biometric luminance value of the fingertip is equal to or less than the first threshold value and equal to or greater than the second threshold value (St3-10, YES), it retains the shutter speed condition (m, n) stored in the shutter control table (for example, the exposure control condition tables TB1 to TB3 shown in FIGS. 11 to 13) (St3-11). Note that "retaining" the exposure control condition here means that the exposure control condition will be the same when the next image of a finger with the same tag (i.e., the same finger) is captured.

[0082] Based on the calculated biometric luminance value of the fingertip, the authentication device B1 determines, for each finger, a priority order of the fingertip image to be registered in the biometric information database DB or the fingertip image to be used for biometric authentication. The authentication device B1 associates the determined information of the priority order with the fingertip image for each finger, and temporarily records them in the memory 12 (St3-12).

[0083] Here, a method for determining the priority of fingertip images will be described.

[0084] In step St4-1, the authentication device B1 further calculates the absolute value of the difference between the average value of the biometric luminance value for each pixel in the detected fingertip region and the optimal biometric luminance value of the fingertip suitable for biometric authentication (fingerprint authentication). The authentication device B1 may determine the priority order of the fingertip images to be used for biometric authentication based on the absolute value of the calculated difference.

[0085] In step St4-1, the authentication device B1 further calculates the absolute value of the difference between the peak value of the biometric luminance value in the detected fingertip region and the optimal value of the biometric luminance value of the fingertip suitable for biometric authentication (fingerprint authentication). The authentication device B1 may determine the priority order of the fingertip images to be used for biometric authentication based on the absolute value of the calculated difference.

[0086] In step St4-1, the authentication device B1 extracts the biometric luminance values ​​of the top V (V: an integer of 2 or more) pixels having the largest biometric luminance value in the detected fingertip region, and further calculates the absolute value of the difference between the average value of the extracted V pixels and the optimal biometric luminance value of the fingertip suitable for biometric authentication (fingerprint authentication). The authentication device B1 may determine the priority order of the fingertip images to be used for biometric authentication based on the absolute value of the calculated difference.

[0087] On the other hand, when the authentication device B1 determines in the process of step St3-10 that the biometric luminance value of the fingertip is equal to or less than the first threshold value and is not equal to or greater than the second threshold value (St3-10, NO), the authentication device B1 corrects the shutter speed condition (m, n) stored in the shutter control table (for example, the exposure control condition tables TB1-TB3 shown in Figs. 11-13) based on the calculated biometric luminance value of the fingertip (St3-11). The authentication device B1 corrects the shutter speed condition (i.e., the exposure control condition) so that the difference between the calculated biometric luminance value of the fingertip region and the target value of the biometric luminance value of the fingertip suitable for biometric authentication (fingerprint authentication) approaches 0 (zero). The method of correcting the shutter speed condition (i.e., the exposure control condition) will be described later.

[0088] The authentication device B1 determines whether the first approach sensor 51 or the second approach sensor 52 detects the insertion of the user's hand UH between the cover guide 17 and the glass surface 16 in an imaging area that can be imaged by the imaging unit 40 (St4-1).

[0089] When the authentication device B1 determines in the process of step St4-1 that the first approach sensor 51 or the second approach sensor 52 has not detected the user's hand UH from the imaging area (St4-1, NO), the authentication device B1 ends the lighting control (St5-1).

[0090] On the other hand, if the authentication device B1 determines in the process of step St4-1 that the first approach sensor 51 or the second approach sensor 52 has detected the user's hand UH from the imaging area (St4-1, YES), it proceeds to the process of step St2-3.

[0091] The authentication device B1 determines whether to perform the operation of enrolling biometric information or authenticating biometric information according to a pre-set enrollment / authentication mode (St6-1).

[0092] When the authentication device B1 determines to register biometric information in the process of step St6-1 (St6-1, registration), it registers the biometric information of the user in the biometric information database DB based on at least one temporarily stored fingertip image (St6-3). Specifically, the authentication device B1 selects a fingertip image from the at least one temporarily stored fingertip image in descending order of priority, and stores (registers) the biometric information of the user corresponding to the fingertip image (fingertip image or feature amount) in the biometric information database DB in association with user information (e.g., name, date of birth, identification number that can identify the user, employee number, or face photo, etc.) (St6-3). Note that the authentication device B1 may store (register) the biometric information of the user, the user information, and finger information corresponding to the fingertip image (e.g., middle finger of the right hand or index finger of the left hand, etc.) in association with each other in the biometric information database DB.

[0093] The authentication device B1 generates a registration result screen notifying that the registration result (user registration result) is "OK" and displays it on the monitor MN (St7-3).

[0094] When the authentication device B1 determines in the processing of step St6-1 to perform authentication of biometric information (St6-1, authentication), it selects a fingertip image from the at least one temporarily stored fingertip image in order of highest priority, and performs biometric authentication by comparing the user's biometric information corresponding to the fingertip image with the biometric information of at least one user registered in the biometric information database DB (St6-2).

[0095] The authentication device B1 determines, in order of priority, whether or not biometric information identical to or similar to the user's biometric information has been registered in the biometric information database DB, based on the user's biometric information or user information and various information registered in advance in the biometric information database DB (St6-4). Note that the authentication device B1 executes the process of step St6-4 for each finger.

[0096] In the process of step St6-4, when the authentication device B1 determines that the same or similar biometric information as the user's biometric information is already registered in the biometric information database DB for any one of the temporarily stored fingertip images (St6-4, YES), the authentication device B1 ends the process of step St6-4. The authentication device B1 generates an authentication result screen notifying that the biometric authentication result (user authentication result) is "OK" and displays it on the monitor MN (St7-1). Note that the authentication device B1 may perform biometric authentication for each of multiple fingers.

[0097] On the other hand, if the authentication device B1 determines in the processing of step St6-4 that the same or similar biometric information as the user's biometric information is not registered in the biometric information database DB for all the temporarily stored fingertip images (St6-4, NO), it generates an authentication result screen notifying that the biometric authentication result (user authentication result) is "NG" and displays it on the monitor MN (St7-2).

[0098] As described above, the biometric authentication system 100 can more efficiently obtain an image captured at a brightness (biometric luminance value) suitable for extracting biometric information, that is, for biometric authentication, by correcting the exposure control conditions for each finger so that the biometric luminance value of the fingertip area shown in the captured fingertip image approaches a biometric luminance value (target value) suitable for extracting biometric information.

[0099] Next, an example of exposure control performed by the authentication device B1 and an example of a captured image acquired by the exposure control will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining an example of exposure control in the authentication device B1.

[0100] The authentication device B1 shown in Fig. 8 captures images of the fingertips based on the exposure control conditions corresponding to each finger in the order of the index finger FNG11, ring finger FNG13, and middle finger FNG12. Also, an example is shown in which the imaging distances between the imaging unit 40 and each of the index finger FNG11, ring finger FNG13, and middle finger FNG12 shown in Fig. 8 are index finger FNG11<ring finger FNG13<middle finger FNG12.

[0101] The authentication device B1 captures an image of the index finger FNG11 under exposure control conditions corresponding to the index finger FNG11 at time T21 and time T24. The authentication device B1 captures an image of the ring finger FNG13 under exposure control conditions corresponding to the ring finger FNG13 at time T22. The authentication device B1 captures an image of the middle finger FNG12 under exposure control conditions corresponding to the middle finger FNG12 at time T23.

[0102] Each of the luminance graphs LG11 to LG13 indicates the biometric luminance value of the fingertip image captured at each time. That is, each of the luminance graphs LG11 to LG13 indicates the biometric luminance value of the index finger FNG11 in the captured image at time T21 and time T24, the biometric luminance value of the ring finger FNG13 at time T22, and the biometric luminance value of the middle finger FNG12 at time T23.

[0103] Captured image IMG11 is an image captured at time T23. The biometric luminance value of middle finger FNG12 captured in captured image IMG11 is approximately equal to the target biometric luminance value (=biometric luminance value Lm20). In addition, the other fingers captured in captured image IMG11, index finger FNG11 and ring finger FNG13, are not suitable for biometric authentication because their biometric luminance values ​​are larger (brighter) than the target biometric luminance value.

[0104] Captured image IMG12 is an image captured at time T22. The biometric luminance value of ring finger FNG13 in captured image IMG12 is approximately equal to the target biometric luminance value (=biometric luminance value Lm20). In addition, the other fingers in captured image IMG11 are not suitable for biometric authentication because the biometric luminance value of index finger FNG11 is larger (brighter) than the target biometric luminance value and the biometric luminance value of middle finger FNG12 is smaller (darker) than the target biometric luminance value.

[0105] Captured image IMG13 is an image captured at time T21. The biometric luminance value of index finger FNG11 captured in captured image IMG13 is approximately equal to the target biometric luminance value (=biometric luminance value Lm20). In addition, the biometric luminance values ​​of other fingers captured in captured image IMG11, namely middle finger FNG12 and ring finger FNG13, are smaller (darker) than the target biometric luminance value, and therefore are not suitable for biometric authentication.

[0106] As described above, even if the heights of the fingers of the held-out hand UH are different and therefore the imaging distances between the imaging unit 40 and each finger are different, the biometric authentication system 100 adjusts the exposure control conditions for each finger. This allows the biometric authentication system 100 to acquire fingertip images in which the biometric luminance value of the fingertip region of each finger is a biometric luminance value (target value) suitable for biometric authentication.

[0107] Next, an example of exposure control executed by the authentication device B1 will be described with reference to Fig. 9. Fig. 9 is a timing chart showing an example 1 of illumination control of the illumination 32 and exposure control of the imaging sensor .

[0108] The timing chart shown in Fig. 9 shows an example of exposure control after capturing an image of the user's hand UH under initially set exposure control conditions, detecting three fingers (index finger, middle finger, and ring finger) from the captured captured image, and setting (correcting) exposure control conditions corresponding to each finger based on the bioluminance value of the fingertip area of ​​each finger. It goes without saying that the timing chart shown in Fig. 9 is an example and is not limited thereto.

[0109] The exposure control unit 20 switches the exposure control corresponding to each of the three fingers in a time-division manner to capture an image of each of the three fingers. For example, the exposure control unit 20 refers to the exposure control condition table and executes exposure control under a first exposure control condition corresponding to the first finger (k=1, index finger) in time period T31, executes exposure control under a first exposure control condition corresponding to the second finger (k=2, middle finger) in time period T32, and executes exposure control under a first exposure control condition corresponding to the first finger (k=3, ring finger) in time period T33.

[0110] The processor 11 calculates a biometric luminance value of the first finger appearing in the captured image captured in the time period T31. Based on the calculated biometric luminance value, the processor 11 corrects the first exposure control condition so that the biometric luminance value of the fingertip region appearing in the fingertip image approaches the biometric luminance value Lm20 (target value), that is, so that the biometric luminance value of the fingertip region appearing in the fingertip image becomes smaller. The processor 11 generates a second exposure control condition corresponding to the first finger and stores it in the exposure control condition table.

[0111] Similarly, the processor 11 calculates a biometric luminance value of the second finger appearing in the captured image captured in time period T32. Based on the calculated biometric luminance value, the processor 11 corrects the first exposure control condition so that the biometric luminance value of the fingertip region appearing in the fingertip image approaches the biometric luminance value Lm20 (target value), that is, so that the biometric luminance value of the fingertip region appearing in the fingertip image becomes smaller. The processor 11 generates a second exposure control condition corresponding to the second finger, and stores it in the exposure control condition table.

[0112] Furthermore, the processor 11 calculates a biometric luminance value of the third finger appearing in the captured image captured in the time period T33. Based on the calculated biometric luminance value, the processor 11 corrects the first exposure control condition so that the biometric luminance value of the fingertip region appearing in the fingertip image approaches the biometric luminance value Lm20 (target value), that is, so that the biometric luminance value of the fingertip region appearing in the fingertip image becomes larger. The processor 11 generates a second exposure control condition corresponding to the third finger, and stores it in the exposure control condition table.

[0113] The exposure control unit 20 refers to the exposure control condition table and performs exposure control under the second exposure control condition corresponding to the first finger (k=1, index finger) in time period T34, performs exposure control under the second exposure control condition corresponding to the second finger (k=2, middle finger) in time period T35, and performs exposure control under the second exposure control condition corresponding to the first finger (k=3, ring finger) in time period T36.

[0114] The processor 11 calculates a biometric luminance value of the first finger appearing in the captured image captured in the time period T34. The processor 11 corrects the second exposure control condition that brings the calculated biometric luminance value closer to the biometric luminance value Lm20 (target value), generates a third exposure control condition corresponding to the first finger, and stores the third exposure control condition in the exposure control condition table.

[0115] Similarly, based on the captured image captured during time period T35, processor 11 corrects the second exposure control condition so as to bring the biometric luminance value of the second finger closer to the biometric luminance value Lm20 (target value), generates a third exposure control condition corresponding to the second finger, and stores it in the exposure control condition table.

[0116] In addition, based on the captured image captured during time period T36, the processor 11 corrects the second exposure control condition so as to bring the biometric luminance value of the third finger closer to the biometric luminance value Lm20 (target value), generates a third exposure control condition corresponding to the third finger, and stores it in the exposure control condition table.

[0117] The exposure control unit 20 refers to the exposure control condition table and performs exposure control under the third exposure control condition corresponding to the first finger (k=1, index finger) in time period T37, performs exposure control under the third exposure control condition corresponding to the second finger (k=2, middle finger) in time period T38, and performs exposure control under the third exposure control condition corresponding to the first finger (k=3, ring finger) in time period T39.

[0118] The processor 11 calculates a biometric luminance value of the first finger appearing in the captured image captured in the time period T37. The processor 11 corrects the third exposure control condition that brings the calculated biometric luminance value closer to the biometric luminance value Lm20 (target value), generates a fourth exposure control condition corresponding to the first finger, and stores the fourth exposure control condition in the exposure control condition table.

[0119] Similarly, based on the captured image captured during time period T38, the processor 11 corrects the third exposure control condition so as to bring the biometric luminance value of the second finger closer to the biometric luminance value Lm20 (target value), generates a fourth exposure control condition corresponding to the second finger, and stores it in the exposure control condition table.

[0120] In addition, based on the captured image captured during time period T39, the processor 11 corrects the third exposure control condition so as to bring the biometric luminance value of the third finger closer to the biometric luminance value Lm20 (target value), generates a fourth exposure control condition corresponding to the third finger, and stores it in the exposure control condition table.

[0121] The exposure control unit 20 refers to the exposure control condition table and performs exposure control under the fourth exposure control condition corresponding to the first finger (k=1, index finger) in time period T40, performs exposure control under the fourth exposure control condition corresponding to the second finger (k=2, middle finger) in time period T41, and performs exposure control under the fourth exposure control condition corresponding to the first finger (k=3, ring finger) in time period T42.

[0122] The processor 11 calculates a biometric luminance value of the first finger appearing in the captured image captured in the time period T40. The processor 11 determines that the calculated biometric luminance value is the biometric luminance value Lm20 (target value), and holds the fourth exposure control condition corresponding to the first finger without correcting it.

[0123] Similarly, the processor 11 calculates the biometric luminance value of the second finger appearing in the captured image captured in the time period T41. The processor 11 determines that the calculated biometric luminance value is the biometric luminance value Lm20 (target value), and holds the fourth exposure control condition corresponding to the second finger without correcting it.

[0124] Furthermore, the processor 11 calculates a biometric luminance value of a third finger appearing in an image captured in time period T42. The processor 11 determines that the calculated biometric luminance value is the biometric luminance value Lm20 (target value), and holds the fourth exposure control condition corresponding to the third finger without correcting it.

[0125] The exposure control unit 20 causes each finger to be imaged under the fourth exposure control condition corresponding to each finger until the user's hand UH leaves the imaging area of ​​the imaging unit 40.

[0126] As described above, even if the heights of the fingers of the held-out hand UH are different and therefore the imaging distances between the imaging unit 40 and each finger are different, the biometric authentication system 100 can adjust the exposure control conditions for each finger. This allows the biometric authentication system 100 to acquire fingertip images in which the biometric luminance value of the fingertip region of each finger is a biometric luminance value (target value) suitable for biometric authentication.

[0127] Next, an example of exposure control executed by the authentication device B1 will be described with reference to Fig. 10. Fig. 10 is a timing chart showing an example 2 of illumination control of the illumination 32 and exposure control of the imaging sensor .

[0128] 10, an example of adjusting the bioluminance value of the fingertip of each finger at which an image is captured will be described by controlling the ON time and OFF time of the illumination 32. Also, an example of an exposure control condition that is an initial setting will be described in which the time ratio of the ON time and the OFF time of the illumination 32 to a fixed exposure time is "ON time:OFF time=1:1".

[0129] The exposure control unit 20 causes the three fingers to be imaged in a time-division manner based on the exposure control conditions (initial settings). Specifically, the exposure control unit 20 refers to the exposure control condition table, executes exposure control corresponding to the exposure control conditions (initial settings), and causes the first finger (k=1, index finger) to be imaged in time zone T51, the second finger (k=2, middle finger) to be imaged in time zone T52, and the third finger (k=3, ring finger) to be imaged in time zone T53.

[0130] The processor 11 determines that the bioluminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the exposure control condition (initial setting). The processor 11 corrects the initial setting exposure control condition (ON time:OFF time=1:1) to increase the calculated bioluminance value of the fingertip region, and generates a first exposure control condition (ON time:OFF time=8:2) corresponding to the first finger. The processor 11 stores it in the exposure control condition table.

[0131] Similarly, the processor 11 determines that the bioluminance value of the fingertip region of the second finger is larger (brighter) than the target value based on the captured image captured under the exposure control condition (initial setting). The processor 11 corrects the initial setting exposure control condition (ON time:OFF time=1:1) to reduce the calculated bioluminance value of the fingertip region, generates a first exposure control condition (ON time:OFF time=2:8) corresponding to the second finger, and stores it in the exposure control condition table.

[0132] Furthermore, the processor 11 determines that the bioluminance value of the fingertip region of the third finger is appropriate based on the captured image captured under the exposure control condition (initial setting). The processor 11 holds the initial setting exposure control condition (ON time:OFF time=1:1) as the exposure control condition corresponding to the third finger.

[0133] The exposure control unit 20 refers to the exposure control condition table and causes the first finger (k=1, index finger) to be imaged under the first exposure control condition (ON time:OFF time=8:2) corresponding to the first finger in time period T51. The exposure control unit 20 also causes the second finger (k=2, middle finger) to be imaged under the first exposure control condition (ON time:OFF time=2:8) corresponding to the second finger in time period T52. The exposure control unit 20 causes the third finger (k=3, ring finger) to be imaged under the exposure control condition (initial setting, ON time:OFF time=1:1) corresponding to the third finger in time period T53.

[0134] Next, an example of exposure control executed by the authentication device B1 will be described with reference to Fig. 11. Fig. 11 is a table showing the state of the illumination control of the illumination 32 and the state of the imaging sensor 42 for each frame in the third example of exposure control.

[0135] 11, an example of adjusting bioluminance values ​​of fingertips of three detected fingers will be described by controlling the open time and the closed time of the shutter of the image sensor 42 relative to the ON time (constant) of the illumination 32. Also, an example of an exposure control condition that is an initial setting will be described in which the duty ratio of the open time and the closed time of the shutter of the image sensor 42 relative to the ON time (constant) of the illumination 32 is "open time:closed time=50:50".

[0136] The exposure control condition table TB1 stores the exposure control condition for each finger. For ease of explanation, the exposure control condition table TB1 shown in FIG. 11 indicates the exposure control condition for each finger and the bioluminance value of the fingertip area in the fingertip image captured under the exposure control condition (i.e., the imaging result). However, the exposure control condition table TB1 does not need to store the exposure control condition for each finger in association with the bioluminance value of the fingertip area in the fingertip image captured under the exposure control condition, and may store only the latest exposure control condition.

[0137] The exposure control unit 20 captures images of the three fingers in a time-division manner based on the exposure control conditions (initial settings) stored in an exposure control condition table TB1.

[0138] Processor 11 determines that the bioluminance value of the fingertip region of the first finger (exposure control count number n=0, index finger) is smaller (darker) than the target value based on the captured image captured under the exposure control condition (initial setting). Processor 11 executes a correction to increase the open time of the initial setting exposure control condition "open time:close time=50:50" by 10% in order to increase the calculated bioluminance value of the fingertip region. Processor 11 generates a first exposure control condition "open time:close time=60:40" corresponding to the first finger through the correction, and stores it in exposure control condition table TB1.

[0139] Similarly, processor 11 determines that the bioluminance value of the fingertip region of the second finger (exposure control count number n=1, middle finger) is larger (brighter) than the target value based on the captured image captured under the exposure control condition (initial setting). Processor 11 executes a correction to reduce the open time of the initial setting exposure control condition "open time:close time=50:50" by 10% in order to reduce the calculated bioluminance value of the fingertip region. Processor 11 generates a first exposure control condition "open time:close time=40:60" corresponding to the second finger through the correction, and stores it in exposure control condition table TB1.

[0140] Furthermore, the processor 11 determines that the bioluminance value of the fingertip region of the third finger (exposure control count number n=2, ring finger) is appropriate based on the captured image captured under the exposure control condition (initial setting). The processor 11 holds the initial setting exposure control condition "open time:close time=50:50" as the exposure control condition corresponding to the third finger.

[0141] The exposure control unit 20 captures images of the three fingers in a time-division manner (first image capture) based on the first exposure control condition stored in the exposure control condition table TB1.

[0142] Processor 11 determines that the bioluminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the first exposure control condition. Processor 11 executes a correction to increase the open time of the first exposure control condition "open time:close time=60:40" by 10% in order to increase the calculated bioluminance value of the fingertip region. Processor 11 generates a second exposure control condition "open time:close time=70:30" corresponding to the first finger through the correction, and stores it in exposure control condition table TB1.

[0143] Similarly, the processor 11 determines that the bioluminance value of the fingertip region of the second finger is greater (brighter) than the target value based on the captured image captured under the first exposure control condition. In order to increase the calculated bioluminance value of the fingertip region, the processor 11 executes a correction to reduce the open time of the first exposure control condition "open time:close time=40:60" by 10%, generates a second exposure control condition "open time:close time=30:70", and stores it in the exposure control condition table TB1.

[0144] Moreover, since the adjustment of the exposure control condition corresponding to the third finger has been completed, the processor 11 omits the correction of the exposure control condition corresponding to the third finger. The processor 11 may determine whether the biometric luminance value of the fingertip region continues to be appropriate based on the captured image captured under the currently set exposure control condition. When the processor 11 determines that the biometric luminance value of the fingertip region is no longer appropriate, the processor 11 may correct the currently set exposure control condition based on the calculated biometric luminance value.

[0145] The exposure control unit 20 captures images of the three fingers in a time-division manner (second imaging) based on the second exposure control condition stored in the exposure control condition table TB1.

[0146] The processor 11 determines that the bioluminance value of the fingertip region of the first finger is appropriate based on the captured image captured under the second exposure control condition. The processor 11 stores the second exposure control condition "open time:close time=70:30" as the exposure control condition corresponding to the first finger.

[0147] Similarly, the processor 11 determines that the bioluminance value of the fingertip region of the second finger is greater (brighter) than the target value based on the captured image captured under the second exposure control condition. In order to increase the calculated bioluminance value of the fingertip region, the processor 11 executes a correction to reduce the open time of the second exposure control condition "open time:close time=30:70" by 10%, generates a third exposure control condition "open time:close time=20:80", and stores it in the exposure control condition table TB1.

[0148] Furthermore, since the adjustment of the exposure control condition corresponding to the third finger has been completed, the processor 11 omits correction of the exposure control condition corresponding to the third finger.

[0149] The exposure control unit 20 captures images of the three fingers in a time-division manner (third image capture) based on the third exposure control condition stored in the exposure control condition table TB1.

[0150] The processor 11 determines that the bioluminance value of the fingertip region of the second finger is appropriate based on the captured image captured under the third exposure control condition. The processor 11 stores the third exposure control condition "open time:close time=20:80" as the exposure control condition corresponding to the second finger.

[0151] The exposure control unit 20 repeatedly captures images of each of the three fingers under the exposure control conditions corresponding to each finger until the user's hand UH leaves the imaging area of ​​the imaging unit 40.

[0152] Next, an example of exposure control executed by the authentication device B1 will be described with reference to Fig. 12. Fig. 12 is a table showing the state of each frame in a modification of the illumination control of the illumination 32 and the exposure control example 3 of the imaging sensor 42.

[0153] 12, an example of adjusting bioluminance values ​​of fingertips of four detected fingers will be described by controlling the open time and the closed time of the shutter of the image sensor 42 relative to the ON time (constant) of the illumination 32. Also, an example of an exposure control condition that is the initial setting will be described in which the duty ratio of the open time and the closed time of the shutter of the image sensor 42 relative to the ON time (constant) of the illumination 32 is "open time:closed time=50:50".

[0154] The exposure control condition table TB2 stores the exposure control condition for each finger. For ease of explanation, the exposure control condition table TB2 shown in FIG. 12 indicates the exposure control condition for each finger and the bioluminance value of the fingertip area in the fingertip image captured under this exposure control condition (i.e., the imaging result). However, the exposure control condition table TB2 does not need to store the exposure control condition for each finger in association with the bioluminance value of the fingertip area in the fingertip image captured under this exposure control condition, and may store only the latest exposure control condition.

[0155] The exposure control unit 20 captures images of each of the four fingers in a time-division manner based on the exposure control conditions (initial settings) stored in an exposure control condition table TB2.

[0156] Processor 11 determines that the bioluminance value of the fingertip region of the first finger (exposure control count number n=0, index finger) is smaller (darker) than the target value based on the captured image captured under the exposure control condition (initial setting), and executes a correction to increase the open time of the initial setting exposure control condition "open time:close time=50:50" by 10%. Processor 11 generates a first exposure control condition "open time:close time=60:40" corresponding to the first finger through the correction, and stores it in exposure control condition table TB2.

[0157] Similarly, based on the captured images captured under the exposure control conditions (initial settings), the processor 11 determines that the bioluminance values ​​of the fingertip regions of the second finger (exposure control count number n=1, middle finger) and the fourth finger (exposure control count number n=3, little finger) are greater (brighter) than the target value, and executes a correction to reduce the open time of the initial setting exposure control condition "open time:close time=50:50" by 10%. The processor 11 generates a first exposure control condition "open time:close time=40:60" corresponding to the second finger and the fourth finger through the correction, and stores it in the exposure control condition table TB2.

[0158] In addition, based on the captured image under the exposure control conditions (initial settings), the processor 11 determines that the bioluminance value of the fingertip area for the third finger (exposure control count number n=2, ring finger) is appropriate, and retains the initial setting exposure control condition of "open time:closed time=50:50" as the exposure control condition corresponding to the third finger.

[0159] The exposure control unit 20 captures images of each of the four fingers in a time-division manner (first image capture) based on the first exposure control condition stored in the exposure control condition table TB2.

[0160] Processor 11 determines that the bioluminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the first exposure control condition, and executes a correction to increase the open time of the first exposure control condition "open time:close time=60:40" by 10%. Processor 11 generates a second exposure control condition "open time:close time=70:30" corresponding to the first finger through the correction, and stores it in exposure control condition table TB2.

[0161] Similarly, based on the captured image captured under the first exposure control condition, the processor 11 determines that the bioluminance value of the fingertip region for the second finger is greater (brighter) than the target value, and executes a correction to reduce the open time of the initial exposure control condition "open time:close time=40:60" by 10%. The processor 11 generates a second exposure control condition "open time:close time=30:70" corresponding to the second finger through the correction, and stores it in the exposure control condition table TB2.

[0162] Furthermore, since the adjustment of the exposure control condition corresponding to the third finger has been completed, the processor 11 omits correction of the exposure control condition corresponding to the third finger.

[0163] In addition, based on the captured image captured under the first exposure control condition, the processor 11 determines that the bioluminance value of the fingertip area for the fourth finger is appropriate, and retains the first exposure control condition "open time:closed time=40:60" as the exposure control condition corresponding to the fourth finger.

[0164] The exposure control unit 20 captures images of each of the four fingers in a time-division manner (second imaging) based on the second exposure control condition stored in the exposure control condition table TB2.

[0165] Based on the captured image taken under the second exposure control condition, the processor 11 determines that the bioluminance value of the fingertip area for the first finger is appropriate, and retains the second exposure control condition "open time:closed time=70:30" as the exposure control condition corresponding to the first finger.

[0166] Similarly, based on the captured image captured under the second exposure control condition, the processor 11 determines that the bioluminance value of the fingertip region for the second finger is greater (brighter) than the target value, and executes a correction to reduce the open time of the initial setting exposure control condition "open time:close time=30:70" by 10%. The processor 11 generates a third exposure control condition "open time:close time=20:80" corresponding to the second finger through the correction, and stores it in the exposure control condition table TB2.

[0167] Furthermore, since the adjustment of the exposure control conditions corresponding to the third and fourth fingers has been completed, the processor 11 omits correction of the exposure control conditions corresponding to the third and fourth fingers.

[0168] The exposure control unit 20 captures images of each of the four fingers in a time-division manner (third image capture) based on the third exposure control condition stored in the exposure control condition table TB2.

[0169] Based on the captured image under the third exposure control condition, the processor 11 determines that the bioluminance value of the fingertip area for the third finger is appropriate, and retains the third exposure control condition "open time:closed time=20:80" as the exposure control condition corresponding to the second finger.

[0170] Furthermore, since the processor 11 has completed adjustment of the exposure control conditions corresponding to the first, third, and fourth fingers, it omits correcting the exposure control conditions corresponding to the first, third, and fourth fingers.

[0171] As a result, the biometric authentication system 100 can adjust the exposure control condition for each predetermined value based on the magnitude relationship between the calculated biometric luminance value and the target value. This allows the biometric authentication system 100 to acquire a fingertip image in which the biometric luminance value of the fingertip region of each finger is a biometric luminance value (target value) suitable for biometric authentication.

[0172] Next, an example of exposure control executed by the authentication device B1 will be described with reference to Fig. 13. Fig. 13 is a table showing the state of the illumination control of the illumination 32 and the state of the imaging sensor 42 for each frame in the exposure control example 4.

[0173] 13, an example of adjusting bioluminance values ​​of fingertips of three detected fingers by controlling the shutter speed will be described. Also, an example of an exposure control condition that is the initial setting is a shutter speed of 40 μs.

[0174] The exposure control condition table TB3 stores the exposure control conditions for each finger. For ease of understanding, the exposure control condition table TB3 shown in FIG. 13 only shows a correction example of the exposure control conditions for the first finger (exposure control count number n=0, index finger).

[0175] The exposure control unit 20 captures images of the three fingers in a time-division manner based on the exposure control conditions (initial settings) stored in an exposure control condition table TB3.

[0176] The processor 11 determines that the bioluminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the exposure control condition (initial setting). The processor 11 determines the correction value of the shutter speed (i.e., the exposure control condition) based on the magnitude of the difference between the calculated bioluminance value and the target value.

[0177] The processor 11 shown in Figure 13 determines that the difference between the biometric luminance value and the target value is "large", and corrects the initial setting exposure control condition "shutter speed = 40 μs" based on the correction value "20 μs" corresponding to the difference "large", generates a first exposure control condition "shutter speed = 60 μs", and stores it in the exposure control condition table TB3.

[0178] The exposure control unit 20 captures images of the three fingers in a time-division manner (first image capture) based on the first exposure control condition "shutter speed=60 μs" stored in the exposure control condition table TB3.

[0179] The processor 11 determines that the biometric luminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the first exposure control condition, and determines a correction value for the shutter speed (i.e., exposure control condition) based on the magnitude of the difference between the biometric luminance value and the target value. The processor 11 shown in Fig. 13 determines that the magnitude of the difference between the biometric luminance value and the target value is "medium", corrects the first exposure control condition "shutter speed = 60 μs" based on the correction value "10 μs" corresponding to the magnitude of this difference "medium", generates a second exposure control condition "shutter speed = 70 μs", and stores it in the exposure control condition table TB3.

[0180] The exposure control unit 20 captures images of the three fingers in a time-division manner (second imaging) based on the second exposure control condition "shutter speed=70 μs" stored in the exposure control condition table TB3.

[0181] The processor 11 determines that the biometric luminance value of the fingertip region of the first finger is smaller (darker) than the target value based on the captured image captured under the second exposure control condition, and determines a correction value for the shutter speed (i.e., exposure control condition) based on the magnitude of the difference between the biometric luminance value and the target value. The processor 11 shown in Fig. 13 determines that the magnitude of the difference between the biometric luminance value and the target value is "small", corrects the initial setting exposure control condition "shutter speed = 70 μs" based on the correction value "5 μs" corresponding to the magnitude of this difference "small", generates a second exposure control condition "shutter speed = 75 μs", and stores it in the exposure control condition table TB3.

[0182] The exposure control unit 20 captures images of the three fingers in a time-division manner (third image capture) based on the third exposure control condition "shutter speed=75 μs" stored in the exposure control condition table TB3.

[0183] Based on the captured image taken under the third exposure control condition, the processor 11 determines that the bioluminance value of the fingertip area for the first finger is appropriate, and retains the third exposure control condition "shutter speed = 75 μs" as the exposure control condition corresponding to the first finger.

[0184] Here, an example of adjusting (changing) the exposure control conditions shown in FIG. 13 will be specifically described.

[0185] The processor 11 corrects the parameters specified in the current exposure control conditions Cur (e.g., the lighting parameters of the lighting 32 or the imaging parameters of the imaging unit 40) based on whether the difference DifB (=Bri-TarB) between the biometric luminance value Bri and the target value TarB is negative or positive, and the magnitude of the difference DifB.

[0186] When the processor 11 determines that the difference DifB is a negative number, the processor 11 determines whether the magnitude of the difference DifB is less than the first difference Ref1, is equal to or greater than the first difference Ref1 and less than the second difference Ref2, or is equal to or greater than the second difference Ref2, where the first difference Ref1 is smaller than the second difference Ref2.

[0187] When the processor 11 determines that the magnitude of the difference DifB is less than the first difference Ref1, it determines that the magnitude of the difference DifB is "small" and acquires a correction coefficient ks1 corresponding to the magnitude of the difference DifB being "small". The processor 11 multiplies the acquired correction coefficient ks1 by the correction unit Cor of the parameter of the exposure control condition to calculate a correction value (=parameter correction unit Cor×correction coefficient ks1). The processor 11 corrects the current exposure control condition Cur based on the calculated correction value, and sets a new exposure control condition Cont (=current exposure control condition Cur+(parameter correction unit Cor×correction coefficient ks1)).

[0188] When the processor 11 determines that the magnitude of the difference DifB is greater than or equal to the first difference Ref1 and less than the second difference Ref2, it determines that the magnitude of the difference DifB is "medium", and obtains a correction coefficient km1 corresponding to the "medium" magnitude of the difference DifB. The processor 11 multiplies the correction coefficient km1 obtained by the correction unit Cor of the exposure control condition parameter to calculate a correction value (= correction unit Cor of the parameter × correction coefficient km1). Based on the calculated correction value, the processor 11 corrects the current exposure control condition Cur and sets a new exposure control condition Cont (= current exposure control condition Cur + (correction unit Cor of the parameter × correction coefficient km1)).

[0189] When the processor 11 determines that the magnitude of the difference DifB is greater than or equal to the second difference Ref2, it determines that the magnitude of the difference DifB is "large", and obtains a correction coefficient kl1 corresponding to the "large" magnitude of the difference DifB. The processor 11 multiplies the correction coefficient kl1 obtained by the correction unit Cor of the exposure control condition parameter to calculate a correction value (= correction unit Cor of the parameter × correction coefficient kl1). Based on the calculated correction value, the processor 11 corrects the current exposure control condition Cur and sets a new exposure control condition Cont (= current exposure control condition Cur + (correction unit Cor of the parameter × correction coefficient kl1)).

[0190] As described above, when the processor 11 determines that the difference DifB is a negative number (<0 (zero)), it corrects the exposure control condition for each finger by setting a new exposure control condition Cont as follows based on the magnitude of the difference DifB. Here, the magnitude relationship of the correction coefficients is ks1 < km1 < kl1. When DifB < Ref1, Cont = Cur + (Cor × ks1) When Ref1 ≤ DifB < Ref2, Cont = Cur + (Cor × km1) When DifB ≥ Ref2, Cont = Cur + (Cor × kl1)

[0191] When the processor 11 determines that the difference DifB is a positive number, the processor 11 determines whether the magnitude of the difference DifB is less than the third difference Ref3, is equal to or greater than the third difference Ref3 and less than the fourth difference Ref4, or is equal to or greater than the fourth difference Ref4, where the third difference Ref3<the fourth difference Ref4.

[0192] When the processor 11 determines that the magnitude of the difference DifB is less than the third difference Ref3, it determines that the magnitude of the difference DifB is "small" and acquires a correction coefficient ks2 corresponding to the magnitude of the difference DifB being "small". The processor 11 multiplies the acquired correction coefficient ks2 by the correction unit Cor of the parameter of the exposure control condition to calculate a correction value (=parameter correction unit Cor×correction coefficient ks2). The processor 11 corrects the current exposure control condition Cur based on the calculated correction value, and sets a new exposure control condition Cont (=current exposure control condition Cur+(parameter correction unit Cor×correction coefficient ks2)).

[0193] When the processor 11 determines that the magnitude of the difference DifB is equal to or larger than the third difference Ref3 and smaller than the fourth difference Ref4, the processor 11 determines that the magnitude of the difference DifB is "medium" and acquires a correction coefficient km2 corresponding to the magnitude of the difference DifB being "medium". The processor 11 multiplies the acquired correction coefficient km2 by the correction unit Cor of the parameter of the exposure control condition to calculate a correction value (=parameter correction unit Cor×correction coefficient km2). The processor 11 corrects the current exposure control condition Cur based on the calculated correction value, and sets a new exposure control condition Cont (=current exposure control condition Cur+(parameter correction unit Cor×correction coefficient km2)).

[0194] When the processor 11 determines that the magnitude of the difference DifB is greater than or equal to the fourth difference Ref4, it determines that the magnitude of the difference DifB is "large", and obtains a correction coefficient kl2 corresponding to the "large" magnitude of the difference DifB. The processor 11 multiplies the obtained correction coefficient kl2 by the correction unit Cor of the parameter of the exposure control condition to calculate a correction value (= correction unit Cor of the parameter × correction coefficient kl2). The processor 11 corrects the current exposure control condition Cur based on the calculated correction value, and sets a new exposure control condition Cont (= current exposure control condition Cur + (correction unit Cor of the parameter × correction coefficient kl2)).

[0195] As described above, when the processor 11 determines that the difference DifB is a positive number (≧0 (zero)), it corrects the exposure control condition for each finger by setting a new exposure control condition Cont as follows based on the magnitude of the difference DifB. Here, the magnitude relationship of the correction coefficients is ks2 < km2 < kl2. When DifB < Ref3, Cont = Cur + (Cor × ks2) When Ref3 ≦ DifB < Ref4, Cont = Cur + (Cor × km2) When DifB ≧ Ref4, Cont = Cur + (Cor × kl2)

[0196] As described above, the biometric authentication system 100 can adjust the exposure control condition based on the magnitude and magnitude relationship of the difference between the calculated biometric luminance value and the target value. That is, when the difference between the biometric luminance value and the target value is large, the biometric authentication system 100 increases the adjustment (change) amount of the exposure control condition, and when the difference between the biometric luminance value and the target value is small, the biometric authentication system 100 decreases the adjustment (change) amount of the exposure control condition, so that the exposure control condition can be adjusted more efficiently. Thereby, the biometric authentication system 100 can obtain a fingertip image in which the biometric luminance value of the fingertip region of each finger is a biometric luminance value (target value) suitable for biometric authentication.

[0197] 7, when capturing an image of a user's hand UH moving on the glass surface 16, the image capturing distance, position, and image capturing angle of the user's hand UH relative to the image capturing unit 40 change over time. Therefore, the biometric authentication system 100 in the first embodiment detects fingers from the captured image, identifies each detected finger, and adjusts the exposure control conditions corresponding to each finger. As a result, the biometric authentication system 100 can obtain a fingertip image suitable for biometric authentication for each finger, even if the image capturing distance, position, and image capturing angle relative to the image capturing unit 40 change.

[0198] (Modification of the first embodiment) The biometric authentication system 100 according to the above-mentioned first embodiment has been described as an example in which the authentication device B1 captures an image of the user's hand UH, performs biometric authentication, and displays the biometric authentication result on the monitor MN. The biometric authentication system 200 according to the modified example of the first embodiment will be described as an example in which the biometric information acquisition device B1A captures an image of the user's hand UH, the authentication device P1 performs biometric authentication, and displays the biometric authentication result on the monitor MN. In the following description, the same reference numerals are assigned to components similar to those of the devices constituting the biometric authentication system 100 according to the first embodiment, and description thereof will be omitted.

[0199] A biometric authentication system 200 according to a modification of the first embodiment will be described with reference to Fig. 1. The biometric authentication system 200 includes a biometric information acquisition device B1A (an example of a biometric image acquisition device), an authentication device P1, and a monitor MN.

[0200] The biometric authentication system 200 captures an image of a user's hand or a part of the hand UH using the biometric information acquisition device B1A, acquires the biometric information of the user shown in the captured image, and transmits it to the authentication device P1 connected to the biometric information acquisition device B1A so as to be capable of transmitting and receiving data. The biometric authentication system 200 also performs biometric authentication by using the authentication device P1 to match the user's biometric information with each of a plurality of pieces of biometric information registered in advance, and transmits the biometric authentication result to the biometric information acquisition device B1A. The biometric authentication system 200 generates an authentication result screen notifying the user of the biometric authentication result using the biometric information acquisition device B1A, and outputs and displays it on the monitor MN.

[0201] Although the biometric authentication system 200 will be described as an example in which the biometric information acquisition device B1A and the monitor MN are configured as separate entities, they may be configured as an integrated unit.

[0202] In the biometric authentication system 200, the biometric information acquisition device B1A and the authentication device P1 may be connected to each other via a network (not shown) so as to be able to transmit and receive data therebetween, or may be connected to each other via, for example, a wired cable or the like so as to be able to transmit and receive data therebetween.

[0203] The internal configuration of biometric information acquisition device B1A will be described with reference to Fig. 14. Fig. 14 is a block diagram showing an example of the internal configuration of biometric information acquisition device B1A according to a modified example of embodiment 1. Note that the inside of housing 18 of biometric information acquisition device B1A is similar to the inside of housing 18 of authentication device B1 shown in Fig. 2, and therefore description thereof will be omitted.

[0204] The biometric information acquisition device B1A is made of metal or resin and includes a control unit 10A, a glass surface 16, a housing 18, an exposure control unit 20, an illumination unit 30, an imaging unit 40, a sensor unit 50, a display control unit 60, and a communication unit 70.

[0205] The control unit 10A includes a processor 11A and a memory 12.

[0206] The processor 11A is configured using, for example, a CPU, SOC, or FPGA, and performs various processes and controls in cooperation with the memory 12. Specifically, the processor 11A refers to the programs and data stored in the memory 12 and executes the programs to realize the functions of each unit, such as the control unit 10A, the exposure control unit 20, the sensor unit 50, or the display control unit 60.

[0207] The processor 11A causes the exposure control unit 20 to start controlling the illumination unit 30 and the imaging unit 40, based on a detection signal notifying the detection of the user's hand UH output from the sensor unit 50. When the user's hand UH output from the sensor unit 50 is not detected, the processor 11A causes the exposure control unit 20 to end controlling the illumination unit 30 and the imaging unit 40.

[0208] The processor 11A also detects the user's fingertip from the captured image captured by the imaging unit 40. The processor 11A generates a fingertip image by cutting out an area including at least the detected fingertip (for example, the first joint). The processor 11A determines the priority order of the fingertip image to be used for biometric authentication based on the biometric luminance value of the generated fingertip image. Based on the determined priority order, the processor 11A outputs the user's biometric information to the communication unit 70 and transmits it to the authentication device P1.

[0209] The processor 11A may select one of the temporarily stored fingertip images based on a priority order, extract biometric information corresponding to the selected fingertip image, and transmit it to the authentication device P1. In this case, when the authentication device P1 transmits a registration or authentication result of "NG", the processor 11A selects one of the temporarily stored fingertip images whose biometric information has not been transmitted to the authentication device P1 based on a priority order, and transmits it to the authentication device P1. The processor 11A repeatedly executes the above-mentioned process until there are no fingertip images whose biometric information has not been transmitted to the authentication device P1. The processor 11A may terminate the transmission of the biometric information corresponding to the fingertip image when the authentication device P1 transmits a registration or authentication result of "OK".

[0210] Furthermore, the processor 11A may associate all the temporarily stored fingertip images with information on the priority order corresponding to these fingertip images, and transmit them to the authentication device P1.

[0211] The processor 11A acquires the biometric authentication result (user authentication result) transmitted from the authentication device P1. Based on the acquired information of the biometric authentication result, the processor 11A generates an authentication result screen for notifying the user of the biometric authentication result, outputs the screen to the display control unit 60, and causes the monitor MN to display the screen.

[0212] The communication unit 70 is connected to the communication unit 80 in the authentication device P1 so as to be able to communicate data with it. The communication unit 70 may be connected to the communication unit 80 in the authentication device P1 so as to be able to communicate wirelessly or wired with it. The communication unit 70 transmits the biometric information of the user output from the processor 11A to the authentication device P1. The communication unit 70 also outputs the biometric authentication result transmitted from the authentication device P1 to the processor 11A.

[0213] The user's biometric information and the biometric authentication result information transmitted and received by the communication unit 70 may be encrypted by the processors 11A and 81, respectively.

[0214] Next, the internal configuration of the authentication device P1 will be described with reference to Fig. 15. Fig. 15 is a block diagram showing an example of the internal configuration of the authentication device P1 according to a modification of the first embodiment.

[0215] The authentication device P1 includes a communication unit 80, a processor 81, a memory 82, and a biometric information database DBA. The biometric information database DBA may be configured separately from the authentication device P1 and connected to the authentication device P1 so as to be able to transmit and receive data therebetween.

[0216] The communication unit 80 is connected to the communication unit 70 in the biometric information acquisition device B1A so as to be capable of wireless or wired communication and transmits and receives data. The communication unit 80 acquires the user's biometric information transmitted from the biometric information acquisition device B1A and outputs it to the processor 81. The communication unit 80 also transmits information on the biometric authentication result output from the processor 81 to the biometric information acquisition device B1A.

[0217] The processor 81 is configured using, for example, a CPU, SOC, or FPGA, and performs various processes and controls in cooperation with the memory 82. Specifically, the processor 81 refers to the programs and data stored in the memory 82 and executes the programs to realize the functions of each unit.

[0218] The processor 81 executes user authentication using biometric information (i.e., biometric authentication) based on the biometric information of the user and the biometric information of each of a plurality of users registered (stored) in advance in the biometric information database DBA. The processor 81 generates a biometric authentication result, outputs information on the biometric authentication result to the communication unit 80, and transmits it to the biometric information acquisition device B1A.

[0219] The memory 82 has, for example, a RAM as a work memory used when executing each process of the processor 81, and a flash memory for storing programs and data that define the operation of the processor 81. The RAM temporarily stores data or information generated or acquired by the processor 81. The flash memory has written therein programs that define the operation of the processor 81.

[0220] The biometric information database DBA is a storage medium device such as an HDD or SSD, and stores biometric information of multiple users registered in advance by an administrator. The biometric information stored in the biometric information database DBA is stored in association with user information (e.g., name, date of birth, identification number for identifying the user, employee number, or facial photograph, etc.). When user authentication is performed using fingerprints or veins of multiple fingers, the biometric information database DBA may also store finger information (e.g., middle finger or index finger, etc.) corresponding to the biometric information in further association with the biometric information.

[0221] Next, the correspondence between the operation procedures shown in Fig. 5 and Fig. 6 and the operation procedures of the biometric authentication systems 100 and 200 according to each embodiment will be described with reference to Fig. 16. Fig. 16 is a table TB4 showing the correspondence between the operation procedures shown in Fig. 5 and Fig. 6 and the operation procedures of the biometric authentication systems 100 and 200 according to each embodiment.

[0222] In the biometric authentication system 100 according to the first embodiment, the authentication device B1 executes the processes of steps St1-1 to St6-4, and the monitor MN executes the processes of steps St7-1 to St7-3.

[0223] In addition, in the biometric authentication system 200 according to the variation of the first embodiment, the biometric information acquisition device B1A executes the processes of steps St1-1 to St5-1, the authentication device P1 executes the processes of steps St6-1 to St6-4, and the monitor MN executes the processes of steps St7-1 to St7-3.

[0224] (Additional Note) The above description of each embodiment discloses the following techniques.

[0225] (Technology 1) An imaging unit 40 that images at least a part of the hand of a person to be authenticated (user); A light 32 for illuminating the hand of the person to be authenticated; A control unit (processor 11, 11A) that controls the imaging unit 40 and the illumination 32 based on an exposure control parameter (exposure control condition) that controls at least one of the imaging unit 40 and the illumination 32; A detection unit (processor 11, 11A) that detects the fingertips of the hand from the captured image captured by the imaging unit 40; An evaluation unit (processor 11, 11A) that evaluates the brightness (biometric luminance value) of the detected fingertip; and an acquisition unit (processor 11, 11A) that selects and acquires at least one captured image from the plurality of captured images based on the brightness of the fingertip. Biometric image acquisition device (authentication device B1, biometric information acquisition device B1A). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can acquire a captured image more suitable for biometric authentication.

[0226] (Technology 2) The evaluation unit (processor 11, 11A) corrects the exposure control parameters (exposure control conditions) so that the brightness of the fingertip falls within a predetermined range (not more than a first threshold value and not less than a second threshold value); The control unit (processor 11, 11A) controls the imaging unit 40 and the illumination 32 based on the corrected exposure control parameters (exposure control conditions) to capture an image of the hand of the person to be authenticated again. A biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to (Technology 1). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can adjust the exposure control conditions so that the biometric luminance value of the fingertip shown in the captured image becomes a biometric luminance value (target value) that is more suitable for biometric authentication, thereby making it possible to acquire an image that is more suitable for biometric authentication.

[0227] (Technology 3) The evaluation unit (processor 11, 11A) corrects the exposure control parameters (exposure control conditions) based on a difference between the brightness of the fingertip and a target value of the brightness of the fingertip, The control unit (processor 11, 11A) controls the imaging unit 40 and the illumination 32 based on the corrected exposure control parameters (exposure control conditions) to capture an image of the hand of the person to be authenticated again. A biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to (Technology 1) or (Technology 2). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can adjust the exposure control conditions so that the biometric luminance value of the fingertip shown in the captured image becomes a biometric luminance value (target value) that is more suitable for biometric authentication, thereby making it possible to acquire an image that is more suitable for biometric authentication.

[0228] (Technology 4) The detection unit (processor 11, 11A) identifies which finger the detected fingertip belongs to, The acquisition unit (processor 11, 11A) selects and acquires the captured image for each finger based on the brightness of the fingertip. The biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to any one of (Technology 1) to (Technology 3). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can acquire a captured image more suitable for biometric authentication for each finger used for biometric authentication.

[0229] (Technology 5) The detection unit (processor 11, 11A) determines the number of times to capture an image of the hand of the person to be authenticated based on the number of the detected fingertips, The imaging unit 40 images the hand of the person to be authenticated the determined number of times. The biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to any one of (Technology 1) to (Technology 4). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can acquire a captured image for each finger that is more suitable for biometric authentication.

[0230] (Technology 6) the evaluation unit (processor 11, 11A) corrects the exposure control parameters (exposure control conditions) for each finger based on the brightness of the fingertip for each finger detected from the captured image captured with the exposure control parameters (exposure control conditions); The control unit (processor 11, 11A) controls the imaging unit 40 and the illumination 32 in a time-division manner using the corrected exposure control parameters (exposure control conditions) for each finger to capture an image of the hand of the person to be authenticated. The biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to any one of (Technology 1) to (Technology 5). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can adjust the exposure control condition for each finger, and can therefore acquire a captured image for each finger that is more suitable for biometric authentication.

[0231] (Technology 7) The evaluation unit (processor 11, 11A) correcting the exposure control parameters (exposure control conditions) based on the brightness of the fingertip for each finger detected from the captured image, and capturing an image of the hand of the person to be authenticated based on the corrected exposure control parameters (exposure control conditions) for each finger; when it is determined that the brightness of the fingertip detected from the captured image is within a predetermined range (less than a first threshold and more than a second threshold), correction of the exposure control parameters (exposure control conditions) corresponding to the finger whose brightness of the fingertip is within the predetermined range (less than a first threshold and more than a second threshold) is omitted; The biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) according to any one of (Technology 1) to (Technology 6). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can adjust the exposure control condition for each finger, and can therefore acquire a captured image for each finger that is more suitable for biometric authentication.

[0232] (Technology 8) The authentication device further includes a sensor (sensor unit 50) for detecting a hand of the person to be authenticated from an imaging area that can be imaged by the imaging unit 40, While the hand of the person to be authenticated is detected within the imaging area, the control unit (processor 11, 11A) repeatedly corrects the exposure control parameters (exposure control conditions) based on the brightness of the fingertip of each of the fingers detected from the captured image, and captures an image of the hand of the person to be authenticated based on the corrected exposure control parameters (exposure control conditions) for each of the fingers. A biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) described in (Technology 7). With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can adjust the exposure control condition for each finger, and can therefore acquire a captured image for each finger that is more suitable for biometric authentication.

[0233] (Technology 9) A biometric image acquisition method performed by a computer (authentication device B1, biometric information acquisition device B1A), Based on the exposure control parameters (exposure control conditions), the hand of the person to be authenticated (user) is illuminated with light 32 and an image is taken. Detecting fingertips of the hand of the person to be authenticated from the captured image, and evaluating brightness of the detected fingertips; Selecting and acquiring at least one captured image from the captured images based on the brightness of the fingertip. Biometric image acquisition method. With this configuration, the biometric image acquisition device (authentication device B1, biometric information acquisition device B1A) can acquire a captured image more suitable for biometric authentication.

[0234] (Technology 10) a biometric image acquisition device (biometric information acquisition device B1A) that acquires an image of at least a part of a hand of a person to be authenticated (user); A biometric authentication system 200 including an authentication device P1 capable of communicating with the biometric image acquisition device (biometric information acquisition device B1A), The biometric image acquisition device (biometric information acquisition device B1A) includes: Based on the exposure control parameters (exposure control conditions), the hand of the person to be authenticated is illuminated with light 32 and an image is taken. Detecting fingertips of the hand of the person to be authenticated from the captured image, and evaluating brightness of the detected fingertips; Selecting and acquiring at least one captured image from the captured images based on the brightness of the fingertip, and transmitting the selected image to the authentication device P1; The authentication device P1 authenticating the person to be authenticated based on the captured image transmitted from the biometric image acquisition device (biometric information acquisition device B1A); Biometric authentication system. With this configuration, the biometric authentication system 200 can obtain a captured image that is more suitable for biometric authentication.

[0235] Although various embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the components in the various embodiments described above may be arbitrarily combined within the scope of the invention. [Industrial Applicability]

[0236] The present disclosure is useful as providing a biometric image acquisition device, a biometric image acquisition method, and a biometric authentication system that acquire a captured image more suitable for biometric authentication. [Explanation of symbols]

[0237] 10, 10A, 80 Control unit 11,11A,81 Processor 12,82 Memory 16 Glass Surface 17 Cover Guide 18. Cabinet 20 Exposure control section 32 Lighting 40 Imaging unit 50 Sensor section 100,200 Biometric authentication systems B1,P1 authentication device B1A Biometric information acquisition device DB,DBA Biometric information database MN Monitor TB1,TB2,TB3 Exposure control condition table

Claims

1. an imaging unit that images at least a part of a hand of a person to be authenticated; a light for illuminating the hand of the person to be authenticated; a control unit that controls the imaging unit and the illumination based on an exposure control parameter that controls at least one of the imaging unit and the illumination; a detection unit that detects fingertips of the hand from an image captured by the imaging unit; an evaluation unit for evaluating the brightness of the detected fingertip; and an acquisition unit that selects and acquires at least one captured image from the plurality of captured images based on the brightness of the fingertip. Biometric image acquisition device.

2. The evaluation unit corrects the exposure control parameter so that the brightness of the fingertip falls within a predetermined range; the control unit controls the imaging unit and the illumination based on the corrected exposure control parameters, and causes the imaging unit to capture an image of the hand of the person to be authenticated again. The biometric image acquisition device according to claim 1 .

3. the evaluation unit corrects the exposure control parameter based on a difference between the brightness of the fingertip and a target value of the brightness of the fingertip; the control unit controls the imaging unit and the illumination based on the corrected exposure control parameters, and causes the imaging unit to capture an image of the hand of the person to be authenticated again. The biometric image acquisition device according to claim 1 .

4. The detection unit identifies which finger each of the detected fingertips belongs to, the acquiring unit selects and acquires the captured image for each of the fingers based on the brightness of the fingertip. The biometric image acquisition device according to claim 1 .

5. the detection unit determines the number of times to capture an image of the hand of the person to be authenticated based on the number of the detected fingertips; the imaging unit images the hand of the person to be authenticated the determined number of times; The biometric image acquisition device according to claim 1 .

6. the evaluation unit corrects the exposure control parameters for each finger based on brightness of the fingertip for each finger detected from the captured image captured using the exposure control parameters; the control unit controls the imaging unit and the illumination in a time-division manner using the corrected exposure control parameters for each finger to image the hand of the person to be authenticated. The biometric image acquisition device according to claim 1 .

7. The evaluation unit is correcting the exposure control parameters based on the brightness of the fingertip for each finger detected from the captured image, and capturing an image of the hand of the person to be authenticated based on the corrected exposure control parameters for each finger; when it is determined that the brightness of the fingertip detected from the captured image is within a predetermined range, correction of the exposure control parameter corresponding to a finger whose fingertip brightness is within the predetermined range is omitted. The biometric image acquisition device according to claim 1 .

8. a sensor for detecting a hand of the person to be authenticated from an imaging area that can be imaged by the imaging unit, the control unit, while the hand of the person to be authenticated is detected within the imaging area, repeatedly corrects the exposure control parameters based on the brightness of the fingertip of each of the fingers detected from the captured image, and captures an image of the hand of the person to be authenticated based on the corrected exposure control parameters for each of the fingers. The biometric image acquisition device according to claim 7 .

9. 1. A computer-implemented method for acquiring a biometric image, comprising: Illuminating and capturing an image of the subject's hand based on the exposure control parameters; Detecting fingertips of the hand of the person to be authenticated from the captured image, and evaluating brightness of the detected fingertips; selecting and acquiring at least one captured image from the captured images based on the brightness of the fingertip; Biometric image acquisition method.

10. a biometric image capture device for capturing an image of at least a part of a hand of a person to be authenticated; A biometric authentication system including an authentication device capable of communicating with the biometric image acquisition device, The biological image acquisition device includes: Illuminating and capturing an image of the subject's hand based on the exposure control parameters; Detecting fingertips of the hand of the person to be authenticated from the captured image, and evaluating brightness of the detected fingertips; Selecting and acquiring at least one captured image from the captured images based on the brightness of the fingertip, and transmitting the selected captured image to the authentication device; The authentication device includes: authenticating the person to be authenticated based on the captured image transmitted from the biometric image acquisition device; Biometric authentication system.

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