A biometric capture device includes: a first light source configured to emit a light of a first wavelength to a biometric body; a second light source configured to emit a light of a second wavelength different from the first wavelength to the biometric body; a camera configured to capture a reflected light from the biometric body; a memory; and a processor coupled to the memory and the processor configured to execute a process, the process including: acquiring a biometric image based on a component of the first wavelength from an image captured by the camera; acquiring distance information between the biometric body and the camera based on a component of the second wavelength from the image captured by the camera; and correcting the biometric image based on the distance information.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-048724, flied on Mar. 11, 2016, the entire contents of which are incorporated herein by reference.

FIELD

A certain aspect of embodiments described herein relates to a biometric capture device, a biometric capture method, and a computer-readable non-transitory medium.

BACKGROUND

In a biometric authentication, a light source emits a light to a biometric body, and biometric information is acquired with use a reflection light from the biometric body (for example, see Japanese Patent Application Publication No. 2013-257609, Japanese Patent Application Publication No. 2008-246011, and Japanese Patent Application Publication No. 2010-240215).

SUMMARY

In a biometric authentication, there may be a case where an illumination light source for emitting a light to a whole of a biometric body and a distance detection light source for acquiring a distance between the biometric body and an image capture device are provided. The illumination light source and the distance detection light source alternately emit a light. The image capture device captures an image of the biometric body at a light emission timing of the illumination light source and the distance detection light source. Thus, a biometric image is captured and a distance is acquired. A size of the biometric image is corrected according to the detected distance. However, when the biometric body moves, a gap occurs between a position of the biometric body at the light emission timing of the illumination light source and a position of the biometric body at the light emission timing of the distance detection light source. Therefore, it is difficult to calculate a concise correction amount.

According to an aspect of the present invention, there is provided a biometric capture device including: a first light source configured to emit a light of a first wavelength to a biometric body; a second light source configured to emit a light of a second wavelength different from the first wavelength to the biometric body; a camera configured to capture a reflected light from the biometric body; a memory; and a processor coupled to the memory and the processor configured to execute a process, the process including: acquiring a biometric image based on a component of the first wavelength from an image captured by the camera; acquiring distance information between the biometric body and the camera based on a component of the second wavelength from the image captured by the camera; and correcting the biometric image based on the distance information.

DESCRIPTION OF EMBODIMENTS

A description will be given of a comparative example before describing embodiments.FIG. 1Aillustrates a plan view of a biometric capture device200in accordance with the comparative example. As illustrated inFIG. 1A, the biometric capture device200has a camera201, a plurality of illumination light sources202, a plurality of distance detection light sources203and so on. The plurality of illumination light sources202has a large irradiation angle and emit a light to a whole of a biometric body. The plurality of illumination light sources202are arranged around the camera201.

FIG. 1Billustrates a side view of the distance detection light source203. As illustrated inFIG. 1B, the distance detection light source203has a light-emitting element204and a condenser lens205. The condenser lens205condenses a light emitted by the light-emitting element204. Therefore, an irradiation angle of the distance detection light source203is small. Accordingly, a light irradiation range to a biometric body by each distance detection light source203is spaced from each other. That is, the distance detection light source203emits a spot light to the biometric body.

The illumination light source202and the distance detection light source203alternately emits a light. When the illumination light source202emits a light, the light is emitted to whole of the biometric body. Thus, the camera201captures an image of the whole of the biometric body. When the distance detection light source203emits a light, the spot light is emitted to a part of the biometric body.

FIG. 1Cillustrates a positional relationship between the camera201and a biometric body206.FIG. 1Cillustrates a case where the biometric body206is near the camera201and a case where the biometric body20is far from the camera201.FIG. 1Dillustrates a biometric image captured by the camera201at an emission timing of the illumination light source202and a spot light image captured by the camera201at an emission timing of the distance detection light source203, in a case where the biometric body206is far from the camera201.FIG. 1Eillustrates a biometric image captured by the camera201at an emission timing of the illumination light source202and a spot light image captured by the camera201at an emission timing attic distance detection light source203, in a case where the biometric body206is near the camera201.

As illustrated inFIG. 1D, when the biometric body206is far from the camera201, the biometric body206is small in the biometric image, in this case, the spot light is small, and a distance between spot lights is small. As illustrated inFIG. 1E, when the biometric body206is near the camera201, the biometric body206is large in the biometric image. In this case, the spot light is large, and the distance between spot lights is large, in this manner, there is a correlation between the distance between the camera201and the biometric body206and a size of the spot light or a distance between spot lights.FIG. 1Fillustrates a relationship between the distance between spot lights and the distance between the camera201and the biometric body206. As illustrated inFIG. 1F, when the distance between spot lights is acquired, distance information between the camera201and the biometric body206can be acquired. When the distance information is corrected and stored, it is possible to correct a size of the biometric body in the biometric image with use of the stored distance information.

When the illumination light source202and the distance detection light source203alternately emit a light, there is a timing gap of light emission between the illumination light source202and the distance detection light source203. In this case, when the biometric body moves with respect to the camera201, a correction accuracy of the biometric body size in the biometric image may be degraded. For example, a description will be given of a case where the biometric body gets closer to the camera201.FIG. 2Aillustrates a case where the biometric body206gradually gets closer to the camera201from a time t1to a time t6. At a time t1, a time t3and a time t5, the illumination light source202emits a light. At a time t2, a time t4and a time t6, the distance detection light source203emits a light.

FIG. 2Billustrates an image captured in a case where a switching of light emission of the illumination light source202and the distance detection light source203is sufficiently faster than a movement of the biometric body206. When the switching is sufficiently fast, the difference between the capture timing of the biometric body206and the capture timing of the spot light is small as illustrated inFIG. 2B,FIG. 2Cillustrates an image capture in a case where the switching of light emission of the illumination light source202and the distance detection light source203is sufficiently slower than the movement of the biometric body206. As illustrated inFIG. 2C, the difference between the capture timing of the biometric body206and the capture timing of the spot light is large. In this case, even if the biometric image is corrected in accordance with the distance between the spot lights, correction accuracy may be low.

And so, it is thought that a light of each optical device is received at the same timing. However, in this case, it is necessary to provide an optical device for detecting biometric information and an optical device for detecting a distance. In this case, component cost may be large. In the following embodiments, a description will be given of a biometric capture device, a biometric capture method and a biometric capture program that are capable of suppressing a component cost and achieving high correction accuracy.

First Embodiment

FIG. 3Aillustrates a biometric authentication device100in accordance with a first embodiment. As illustrated inFIG. 3A, the biometric authentication device100has a capture device10, a process unit20, an authentication unit30and so on. The capture device10has a camera11, a plurality of illumination light sources12, a plurality of distance detection light sources13and so on. Each component of the capture device10is provided on a rectangular substrate.

For example, the camera11is provided on a center of the substrate. The plurality of illumination light sources12surrounds the camera11around the camera11. InFIG. 3A, the number of the illumination light sources12is eight. The illumination light source12has a large irradiation angle and emits a light to the whole of the biometric body. The illumination light source12emits a light of a first wavelength or a predetermined wavelength range including the first wavelength. In the embodiment, the illumination light source12emits a near-infrared light. The first wavelength is 750 nm to 1400 nm.

FIG. 3Billustrates a side view of the distance detection tight source13. As illustrated inFIG. 3B, the distance detection light source13has a light-emitting element14and a condenser lens15. A light emitted by the light-emitting element14is condensed by the condenser lens15. Therefore, an irradiation angle of the distance detection light source13toward the biometric body is small. Accordingly, each irradiation range of each distance detection light source13is spaced from each other. That is, the distance detection light source13emits a spot light to the biometric body. In an example ofFIG. 3A, four distance detection light sources13are arranged on four corners of the substrate. The plurality of distance detection light sources13emit a light of a second wavelength different from the first wavelength or a predetermined wavelength range including the second wavelength. In the embodiment, the plurality of distance detection light sources13emit a blue light. And the second wavelength is 465 nm to 485 nm. When the wavelength range of the illumination light source12and the distance detection light source13has a range, the wavelength range of the illumination light source12does not include the second wavelength and the wavelength range of the distance detection light source13does not include the first wavelength.

FIG. 3Cillustrates a relationship between a wavelength of an emitted light to the biometric body and a reflection position of the biometric body. As illustrated inFIG. 3C, the reflection position of the biometric body fluctuates according to the wavelength of the emitted light. In concrete, the reflection position gets deeper from a skin surface, as the wavelength gets longer. For example, the blue light is reflected by an epidermis. A near-infrared light is reflected by a hypodermis. Therefore, when emitted lights having a different wavelength are used, it is possible to acquire a plurality of different information from the biometric body. In the embodiment, when a near-infrared light is used, it is possible to acquire information of a hypodermis such as a vein pattern. When a blue light is used, it is possible to acquire information of an epidermis near the skin surface of the biometric body. The blue light is reflected at a skin surface or a position near the skin surface of the biometric body. Therefore, blurring and scattering are small, compared to a near-infrared light wavelength, and an outline of the spot light is sharp. Therefore, distance detection accuracy is improved.

The camera11is a capture device having a sensitivity with respect to at least on of the first wavelength and the second wavelength. In the embodiment, the camera11is a color image sensor.FIG. 3Dillustrates an image of a B (blue) pixel captured by the camera11, an image of a (green) pixel captured by the camera11, and an R (red) pixel captured by the camera11. The distance detection light source13emits a blue light. Therefore, a spot light appears in the image of the B pixel. The illumination light source12emits a near-infrared light. Therefore, a whole of the biometric body appears in the image of the R pixel.

FIG. 4Aillustrates a block diagram of the process unit20and the authentication unit30. As illustrated inFIG. 4A, the process unit20acts as a light source controller21, an image acquirer22, a distance information detector23, a distance information storage24, a biometric information detector25, a corrector26and so on. The authentication unit30acts as a biometric information storage31, a comparer32, an output unit33and so on.

FIG. 4Billustrates a hardware structure of the process unit20and the authentication unit30. As illustrated inFIG. 4B, the process unit20and the authentication unit30have a CPU101, a RAM (Random Access Memory)102, a memory device103, a display device104and so on. These components are coupled to each other with a bus or the like.

The CPU101is a central processing unit. The CPU101includes one or more core. The RAM102is a volatile memory temporally storing a program executed by the CPU101, a data processed by the CPU101, and so on.

The memory device103is a nonvolatile memory device. The memory device103may be a SSD (Solid State Drive) such as a ROM (Read Only Memory) or a flash memory, or a hard disk driven by a hard disk drive. The memory device103stores a biometric capture program and a biometric authentication program in accordance with the first embodiment. The display device104is such as a liquid crystal device.

The biometric capture program and the biometric authentication program stored in the memory device103are developed to the RAM102. The CPU101executes the biometric capture program and the biometric authentication program developed to the RAM102. When the biometric capture program is executed, each unit of the process unit20is achieved. When the biometric authentication program is executed, each unit of the authentication unit30is achieved.

(Enrollment Process) A description will be given of an enrollment process based onFIG. 5.FIG. 5illustrates a flowchart of the enrollment process. In the enrollment process, biometric information of a user is stored in the biometric information storage31as a biometric template in advance, and distance information between a biometric body of the user and the camera11is stored in the distance information storage24in advance.

As illustrated inFIG. 5, the light source controller21makes the illumination light source12and the distance detection light source13emit a light simultaneously (Step S1). This means that a light emission period of the illumination light source12entirely or partially overlaps with a light emission period of the distance detection light source13. Therefore, a start timing and an end timing of the light emission of the illumination light source12may be different from those of the distance detection light source13.

Next, the image acquirer22acquires an image from the camera11at a timing when both of the light source12and the distance detection light source13emit a light (Step S2). Next, the distance information detector23detects distance information between the biometric body and the camera11with use of B pixel image of the image captured by the camera11(Step S3). The distance information has a correlation with a distance between the camera11and the biometric body. For example, the distance information is such as a size of a spot light, a shape of a spotlight, a distance between spot lights or the like. In the embodiment, the distance between spot lights is used as the distance information. Next, the distance information storage24stores the distance information detected by the distance information detector23(Step S4).

Next, the biometric information detector25detects biometric information with use of the R pixel image of the image captured by the camera11(Step S5). For example, the biometric information detector25detects a palm shape, a palm print, a vein pattern or the like as the biometric information. Next, the biometric information storage31stores the biometric information detected by the biometric information detector25. With the processes, the enrollment process is terminated.

(Authentication process) A description will be given of an authentication process based onFIG. 6.FIG. 6illustrates a flowchart of the authentication process. As illustrated inFIG. 6, the light source controller21makes the illumination light source12and the distance detection light source13emit a light simultaneously (Step S11). Next, the image acquirer22acquires an image from the camera11(Step S12). Next, the distance information detector23detects a distance between spot lights as the distance information with use of a B pixel image of the image captured by the camera11(Step S13).

Next, the biometric information detector25detects biometric information with use of an R pixel image of the image captured by the camera11(Step S14). Next, the corrector26corrects the biometric information detected in Step S14so that the distance information detected in Step S13gets closer to the distance information stored in the distance information storage24(Step S15).

For example, when a spot light size, a spot light shape, a distance between two spot lights or the like is used as the distance information, a distance between the camera11and the biometric body is acquired. Thus, it is possible to reduce a difference of a magnification ratio between the biometric information acquired in the authentication process and the biometric information acquired in the enrollment process. When three or more distances among spot lights is used as the distance information, it is possible to acquire an inclination angle of the biometric body in addition to the distance between the camera11and the biometric body. In this case, it is possible to reduce the difference of the magnification ratio between the biometric information acquired in the authentication process and the biometric information acquired in the enrollment process. Moreover, it is possible to reduce a difference of the inclination angle between the biometric body in the authentication process and the biometric body in the enrollment process. That is, it is possible to reduce a difference of a posture between the biometric body in the authentication process and the biometric body in the enrollment process.

Next, the comparer32compares the corrected biometric information with the biometric information stored in the biometric information storage31(Step S16). For example, the comparer32determines whether a similarity between the corrected biometric information and the biometric information stored in the biometric information storage31is equal to or more than a threshold. Next, the output unit33makes the display device104show the comparison result of the comparer32(Step S17). With the processes, the authentication process is terminated.

In the embodiment, a first wavelength light is emitted to a biometric body, and a second wavelength light is emitted to the biometric body. A biometric image is acquired based on the first wavelength component from an image captured by a camera. And, distance information between the camera and the biometric body is acquired based on the second wavelength component. In this manner, when wavelength components having a different wavelength are used, it is possible to acquire the biometric image and the distance information from the image captured by the camera without a plurality of image capture devices even if both of the first wavelength light and the second wavelength light are emitted. When the biometric image is corrected with use of the distance information, it is possible to improve authentication accuracy using a biometric image.

As illustrated inFIG. 3C, when the wavelength is shorter, the light is reflected at a position nearer the skin surface. When the light is reflected at a position near the skin surface, the blurring, the scattering and so on of the reflection light can be suppressed. It is therefore preferable that a wavelength shorter than the first wavelength is used as the second wavelength. For example, it is preferable that the second wavelength is a visible light range wavelength, and the first wavelength is a near-infrared range wavelength.

It is easier to detect a brightness value center of a spot light than to detect an outer edge of the spot light. Therefore, when a distance between a plurality of spot lights is detected with use of the plurality of spot lights, the accuracy of detecting the distance between the biometric body and the camera11is improved. When three or more spot lights are used, it is possible to acquire an inclination angle of the biometric body. In this case, it is possible to correct a posture of the biometric body, and the authentication accuracy is improved.

Although the biometric information detected in Step S14is corrected in the embodiment, the structure is not limited. For example, the biometric image may be corrected, and biometric information may be detected from the corrected biometric image. In any cases, the biometric information acquired from the biometric image is corrected. The biometric information stored in the biometric information storage31may be corrected. For example, the biometric information stored in the biometric information storage31may be corrected so that the distance information acquired in the enrollment process gets closer to the distance information acquired in the authentication process.

Second Embodiment

FIG. 7Aillustrates a plan view of a capture device10ain accordance with a second embodiment.FIG. 7Billustrates a cross sectional view ofFIG. 7A. As illustrated inFIG. 7AandFIG. 7B, the capture device10ahas an optical conductor16for equalizing distribution of the emitted light of the illumination light source12. The optical conductor16is arranged on the plurality of illumination light sources12. The optical conductor16is arranged so that the emitted light of the distance detection light source13does not enter the optical conductor16and the emitted light of the illumination light source12enters the optical conductor16.

As illustrated inFIG. 7B, the optical conductor16has a wedge-shaped cross section. As illustrated inFIG. 7A, the optical conductor16has a doughnut shape having a center through which an optical axis of the camera11passes. Moreover, the optical conductor16has an asperity for scattering a light toward an input side of the optical conductor16or an output side of the optical conductor16. For example, the optical conductor16has a structure such as a surface textured shape, a sandblast, or a prism groove that are structured with an asperity on the input side or the output side of the optical conductor16. With the asperity structure, it is possible to emit an illumination light of the illumination light source12to the biometric body evenly. It is therefore possible to improve the authentication accuracy. The optical conductor16may have a square shape or, a rectangular shape. Each of condenser lenses for generating a spot light may be simultaneously formed at four corners. An optical conductor for emitting a light to a biometric body and a condenser lens for a spot light may be structured with a single member. In this case, it is possible to reduce a cost. The optical conductor16may be made of a plastic such as acrylic or polycarbonate, or a glass. When plastic is used, the cost can be reduced more.

Third Embodiment

FIG. 8Aillustrates a plan view of a capture device10bin accordance with a third embodiment.FIG. 8Billustrates a cross sectional view ofFIG. 8A. As illustrated inFIG. 8AandFIG. 8B, the capture device10bhas a lens array17instead of the optical conductor16. The lens array17has a lens on the light emission side of each illumination light source12. The lens array17is arranged so that the emitted light of the distance detection light source13does not enter the lens array17and the emitted light of the illumination light source12enters the lens array17.

As illustrated inFIG. 8A, the lens array17has a doughnut shape having a center through which an optical axis of the camera11passes. Moreover, the lens array17has an asperity for scattering a light toward an input side of the lens array17or an output side of the lens array17. For example, the lens array17has a structure such as a surface textured shape, a sandblast, or a prism groove that are structured with an asperity on the input side or the output side of the lens array17. With the asperity structure, it is possible to emit an illumination light of the illumination light source12to the biometric body evenly. It is therefore possible to improve the authentication accuracy. The lens array17may have a square shape or a rectangular shape. Each of condenser lenses for generating a spot light may be simultaneously formed at four corners. A lens array for emitting a light to a biometric body and a condenser lens for a spot light may be structured with a single member. In this case, it is possible to reduce a cost. The lens array17may be made of a plastic such as acrylic or polycarbonate, or a glass. When plastic is used, the cost can be reduced more.

Fourth Embodiment

FIG. 9Aillustrates a plan view of a capture device10cin accordance with a fourth embodiment.FIG. 9Billustrates a cross sectional view ofFIG. 9A. As illustrated inFIG. 9AandFIG. 9B, the capture device10chas a diffraction optical element array18instead of the optical conductor16. The diffraction optical element array18has a diffraction optical element on the light emission side of each illumination light source12. The diffraction optical element array18is arranged so that the emitted light of the distance detection light source13does not enter the diffraction optical element array18and the emitted light of the illumination light source12enters the diffraction optical element array18.

As illustrated inFIG. 9A, the diffraction optical element array18has a doughnut shape having a center through which an optical axis of the camera11passes. The illumination light source12can emit a light to a necessary region of a biometric body with distribution, because each diffraction optical element is arranged on the illumination light source12. Thus, the authentication accuracy can be improved.

FIG. 9Cillustrates details of the diffraction optical element. As illustrated inFIG. 9C, the diffraction optical element is an ensemble of diffractions, in the diffraction optical element, a desirable pixel number of micro diffractions of which pitch and rotation direction are different from each other are arrayed. As an example, the biometric size is 110 mm×110 mm. A size of a light-emitting portion of the illumination light source12is 3 mm×3 mm. An emitted wavelength is 545 nm. An interval between the illumination portion of the illumination light source12and the diffraction optical element is 5 mm. A substrate of the diffraction optical element array is synthetic silica and has a thickness of 2 mm. In this case, as illustrated inFIG. 9D, when the diffraction optical element array (size is 5 mm) is structured with 250 pixels×250 (total is 62,500) number of diffraction optical elements having a Cell size of 0.02 mm, an effective square even distribution can be achieved in the illumination to the biometric body. The number of the pitch and the rotation direction of each diffraction is enormous. Therefore, for simplicity, details are omitted. The diffraction optical element array18may be made of a plastic such as acrylic or polycarbonate, or a glass. When plastic is used, the cost can be reduced more.

Fifth Embodiment

FIG. 10Aillustrates a plan view of a capture device10din accordance with a fifth embodimentFIG. 10Billustrates a cross sectional view ofFIG. 10A. As illustrated inFIG. 10AandFIG. 10B, the capture device10dhas a diffraction optical element array19instead of the diffraction optical element array18. The diffraction optical element array19has a diffraction optical element on the light emission side of each illumination light source12and each distance detection light source13. The lens of the illumination light source12and the distance detection light source13can be structured by a single member. It is therefore possible to reduce the number of components.

FIG. 10Cillustrates details of the diffraction optical element for the distance detection light source13. As illustrated inFIG. 10C, the diffraction optical element is an ensemble of diffractions. In the diffraction optical element, a desirable pixel number of micro diffractions of which pitch and rotation direction are different from each other are arrayed. Outwardly, the diffraction optical element is similar to the diffraction optical element for the illumination source12illustrated inFIG. 9C. However, as described later, the Cell size, the pixel number (PIX), the pitch of each diffraction and a rotation direction of each diffraction are different from those of the diffraction optical element ofFIG. 9C. As an example, the biometric size is 110 mm×110 mm. A size of a light-emitting portion of the distance detection light source13is 3 mm×3 mm. An emitted wavelength is 465 nm. An interval between the illumination portion of the distance detection light source13and the diffraction optical element is 5 mm. A substrate of the diffraction optical element is synthetic silica and has a thickness of 2 mm. In this case, as illustrated inFIG. 10D, when the diffraction optical element array (size is 3 mm) is structured with 120 pixels×120 (total is 14,400) number of diffraction optical elements having a Cell size of 0.025 mm, are effective square even distribution can be achieved in the illumination to the biometric body. The number of the pitch and the rotation direction of each diffraction is enormous. Therefore, for simplicity, details are omitted. The diffraction optical element array19may be made of an plastic such as acrylic or polycarbonate, or a glass. When plastic is used, the cost can be reduced more.

In the above-mentioned embodiments, the illumination light source12acts as an example of a first light source configured to emit a light of a first wavelength to a biometric body. The distance detection light source13acts as an example of a second light source configured to emit a light of a second wavelength different from the first wavelength to the biometric body. The camera11acts as an example of a camera configured to capture a reflected light from the biometric body. The biometric information detector25acts as an example of a biometric information acquirer configured to acquire a biometric image based on a component of the first wavelength from an image captured by the camera. The distance information detector23acts as an example of a distance information acquirer configured to acquire distance information between the biometric body and the camera based on a component of the second wavelength from the image captured by the camera. The corrector26acts as an example of a corrector configured to correct the biometric image based on the distance information. The capture device10and the process unit20act as an example of a biometric capture device.