Biometric authentication device

Abstract

To provide a biometric authentication device capable of intuitively grasping the position of an authentication object such as a hand and a finger.SOLUTION: According to the present invention, a biometric authentication device 100 includes a light guide layer 130 in which a light diffusion part 136 for displaying an aerial image P1 representing a biological design at height D is formed, a light source 110 for applying light to the light guide layer 130, a polarization beam splitter 150 arranged at an upper surface side of the light guide layer 130, a retroreflective layer 140 arranged on a bottom surface side of the light guide layer 130, and an imaging camera 160 for imaging a living body superimposed on the aerial image P1 through an opening 142 formed in the retroreflective layer 140, and performs biometric authentication on the basis of an image picked up by the imaging camera 160.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a biometric authentication device having a function of displaying an image in the air using retroreflection. [Background technology]

[0002] Aerial imaging by retroreflection (AIRR) is known. For example, the display device disclosed in Patent Document 1 uses two retroreflection members, one of which is positioned on the emission axis of the light source, to enable the image formed in the air to be viewed from a wider angle. The display device disclosed in Patent Document 2 arranges a half mirror, a retroreflection member, and an image output device in parallel to facilitate adjustment of the image formation position. The display device disclosed in Patent Document 3 reduces the number of times light passes through a phase difference member (λ / 4 plate) to prevent a decrease in image visibility. The display device disclosed in Patent Document 4 arranges a display and a retroreflection member in parallel to a beam splitter, and a polarizing optical element is placed on the display to reduce the device's thickness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-107165 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-81138 [Patent Document 3] Japanese Patent Application Publication No. 2019-66833 [Patent Document 4] Japanese Patent Application Publication No. 2019-101055 Summary of the Invention [Problem to be solved by the invention]

[0004] In various electronic devices and systems, personal authentication using biometrics such as fingerprints and veins is being developed. For example, in palm vein authentication, a person places their hand on the surface of a transparent acrylic plate, and then a camera captures an image of the palm veins from behind the acrylic plate, and the person is authenticated based on the captured image.

[0005] Conventional biometric authentication is mainly a contact type where the hand is placed on an acrylic plate, but at the same time, contactless biometric authentication is also being promoted. With contact type biometric authentication, the hand is placed on an acrylic plate, which allows the camera to take a stable image of the veins, but with contactless biometric authentication, the height of the hand is unstable in the air, which causes issues such as the camera being unable to focus properly or taking a long time (time-consuming) to focus.

[0006] For this reason, for example, it has been proposed to indicate the correct position of the hand with the color of lighting. Figure 1 shows the schematic configuration of a biometric authentication device equipped with such a function. As shown in Figure 1(A), an image P of a hand is displayed on the surface or inside of the authentication device 10, and the user holds their palm H in the air so that it is aligned with the position of the image P. Then, an image of the palm H is captured by the built-in camera of the biometric authentication device 10.

[0007] 1(B) is a block diagram showing the internal configuration of the biometric authentication device 10. The biometric authentication device 10 includes a sensor 20 that measures the distance to the palm H, an illumination unit 30 that illuminates an image P with a color according to the measured distance, a camera 40 that captures an image of the palm H, and a control unit 50 that controls each unit.

[0008] As shown in FIG. 1(C), when the palm H is close to the biometric authentication device 10 (however, the height D1 is greater than the focal length of the camera 40), the control unit 50 illuminates the image P in blue via the illumination unit 30, informing the user that the palm H is too far from the correct position. As shown in FIG. 1(D), when the height D2 to the palm H is in the correct position (approximately equal to the focal length), the control unit 50 illuminates the image P in green via the illumination unit 30, informing the user that the palm H is at the correct height. At this time, the camera 40 captures the palm H. As shown in FIG. 1(E), when the height D3 to the palm H is too close, the control unit 50 illuminates the image P in red, informing the user that the palm H is too close.

[0009] As described above, conventional biometric authentication devices can inform the user whether the hand height is appropriate or not by changing the color that lights up the image P. However, since the user cannot intuitively know the appropriate hand height, they still have to adjust the height of the palm H while checking the color that lights up the image P, which is cumbersome.

[0010] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a biometric authentication device that can intuitively grasp the position of an object to be authenticated, such as a hand or a finger. [Means for solving the problem]

[0011] The biometric authentication device of the present invention has the function of displaying an aerial image using retroreflection, and includes a light-guiding layer on which a design for the aerial image is formed, a light source that irradiates light onto the light-guiding layer, a polarizing beam splitter arranged on one main surface side of the light-guiding layer, a retroreflective layer arranged on the other main surface side opposite the one main surface of the light-guiding layer, and an imaging means that images a living body near the area where the aerial image is displayed through an opening formed in the retroreflective layer, and performs biometric authentication based on the image captured by the imaging means.

[0012] In one aspect, a polarizing filter having a polarization direction different from that of the polarizing beam splitter is provided at a position aligned with the opening. In one aspect, the polarization direction of the polarizing filter is perpendicular to the polarization direction of the polarizing beam splitter. In one aspect, the imaging means images the biometric subject when the light source is off. In one aspect, the display of the aerial image and the imaging by the imaging means are controlled in a time-division manner. In one aspect, the imaging means includes an infrared camera, and a visible light filter that blocks visible light is provided at a position aligned with the opening. In one aspect, the aerial image is generated at a position symmetrical to the design with respect to the plane of the polarizing beam splitter, and the imaging means is focused on the position of the aerial image. In one aspect, the biometric authentication device further includes output means for notifying a user that imaging by the imaging means has ended. In one aspect, the biometric subject is a fingerprint or vein. [Effects of the Invention]

[0013] According to the present invention, an aerial image is displayed to guide the user as to where to place the biometric device in the air, and an image of the biometric device placed in that position is then captured, allowing the user to intuitively recognize the position where to hold the biometric device, eliminating the hassle of contactless biometric authentication. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a conventional biometric authentication device. [Figure 2] FIG. 2(A) is an external perspective view of a biometric authentication device according to a first embodiment of the present invention, and FIG. 2(B) is a side view thereof. [Figure 3] 3 is a schematic cross-sectional view of the biometric authentication device shown in FIG. 2 taken along line XX. [Figure 4] FIG. 10 is a schematic cross-sectional view of a biometric authentication device according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a block diagram showing the electrical configuration of a biometric authentication device according to a third embodiment of the present invention. [Figure 6]FIG. 10 is a block diagram showing the electrical configuration of a biometric authentication device according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, an embodiment of the present invention will be described. The biometric authentication device of the present invention relates to a thin aerial image authentication device that has the function of displaying aerial images in three-dimensional space without the need for special glasses or the like. The user holds their biometric device in a position guided by the aerial image, and the biometric device at that position is captured by an imaging camera, thereby performing biometric authentication. It should be noted that the drawings referred to in the following description of the embodiments include exaggerated or emphasized portions to facilitate understanding of the invention, and do not directly represent the shape or scale of the actual product. [Example]

[0016] Next, an embodiment of the present invention will be described in detail. FIG. 2(A) is a schematic perspective view of a biometric authentication device according to a first embodiment of the present invention, and FIG. 2(B) is a side view thereof. The biometric authentication device 100 of this embodiment displays an aerial image P1 at a height D from the surface of a casing such as a housing. A user holds their palm H over the aerial image P1 at the height D, and an image of the palm H at the height D is captured by a built-in imaging camera, thereby authenticating the user. The user can intuitively hold their palm H over the aerial image P1 by visually recognizing the aerial image P1. The height D is the distance at which the imaging camera can clearly capture the palm H. The biometric information to be authenticated is not particularly limited, but may be, for example, a fingerprint or vein pattern on the palm or fingers.

[0017] 3 is a schematic cross-sectional view showing the configuration of the XX line of the biometric authentication device 100 shown in Fig. 2(A). As shown in the figure, the biometric authentication device 100 includes a light source 110, a polarizing filter 120, a light guide layer 130, a retroreflective layer 140, a polarizing beam splitter 150, and an imaging camera 160.

[0018] The light source 110 is disposed near the side portion 132 of the light guide layer 130, and emits light with a certain emission angle (or radiation angle) toward the light guide layer 130, uniformly irradiating the inside of the light guide layer 130. The light source 110 is not particularly limited, but a light emitting element such as a light emitting diode or a laser diode can be used. The number of light emitting elements is also not particularly limited.

[0019] A polarizing filter 120 is provided between the light source 110 and the incident surface (side) 132 of the light guide layer 130. The polarizing filter 120 is, for example, a polarizing film or a DBEF (reflective polarizing element), and converts the light from the light source 110 into a certain polarization state (for example, linearly polarized light). The polarizing filter 120 is particularly useful when the light from the light source 110 is unpolarized, but may be omitted when the light from the light source 110 is polarized.

[0020] The light guide layer 130 is a plate- or film-like transparent optical member having a flat top surface, a flat bottom surface, and side surfaces connecting the top and bottom surfaces. The planar shape of the light guide layer 130 is not particularly limited, but may be rectangular, for example. The light guide layer 130 may be made of any known material, such as glass, acrylic plastic, polycarbonate resin, or cycloolefin resin.

[0021] A light diffusion section 136 for diffusing or scattering light in the vertical direction is formed on the bottom or bottom surface 134 of the light guide layer 130. The light diffusion section 136 generates a design (original image) of the aerial image P1, and in this example, the light diffusion section 136 generates a design of a palm, which is the living body to be authenticated. The light diffusion section 136 is formed, for example, by processing a fine structure such as a dot pattern on the bottom surface of the light guide layer 130 by laser processing or printing.

[0022] A retroreflective layer 140 is formed on the bottom side of the light guide layer 130. The retroreflective layer 140 is an optical element that reflects light in the same direction as the incident light, and its configuration is not particularly limited, but it may be composed of, for example, prism-type retroreflective elements such as triangular pyramid-type retroreflective elements and full cube-corner-type retroreflective elements, or bead-type retroreflective elements. A protective film, a retardation film (e.g., a λ / 4 film), or the like may be interposed between the light guide layer 130 and the retroreflective layer 140.

[0023] A polarizing beam splitter 150 is disposed on the upper surface side of the light guide layer 130. The polarizing beam splitter 150 is an optical element that transmits part of incident light and reflects part of it, and is a polarization separation element that splits incident light into p-polarized and s-polarized components. For example, the polarizing beam splitter 150 transmits part of light of a certain polarization state and reflects part of it.

[0024] Light L1 incident from side portion 132 of light guide layer 130 travels inside while being totally reflected, for example, by the top and bottom surfaces of light guide layer 130, and a portion of this light L2 is diffused and scattered in the vertical direction by light diffusion portion 136. This diffused and scattered light L2 passes through the top surface of light guide layer 130 and is reflected by polarizing beam splitter 150. A portion L3 of the light reflected by polarizing beam splitter 150 is reflected by retroreflective layer 140 in the same direction as the incident light, and a portion of light L4 reflected by retroreflective layer 140 passes through polarizing beam splitter 150 to generate an aerial image P1. The aerial image P1 is the design (original image) generated by the light diffusion section 136, floating in the air in the same position. The aerial image P1 is generated at a height D from the polarizing beam splitter 150, and the height D is a position symmetrical to the light diffusion section 136 with respect to the plane of the polarizing beam splitter 150.

[0025] The biometric authentication device 100 of this embodiment has the function of displaying an aerial image P1 at a height D, as well as the function of capturing an image of a user's palm H superimposed at the height of the aerial image P1, as shown in FIG. 2. To achieve the imaging function, a through opening 142 is formed in the retroreflective layer 140, and the imaging camera 160 captures an image of the palm H through the opening 142. The position and size of the opening 142 are selected so that the imaging camera 160 can capture an image of the entire palm H. The focus of the imaging camera 160 is adjusted to be near the height D of the aerial image P1. For example, if the height of the aerial image P1 is D, the focal length F of the imaging camera 160 is adjusted to F≈2D.

[0026] When the user places the palm H of their hand in the air so that it overlaps the aerial image P1, the imaging camera 160 captures an image of the palm H. The timing of capturing the image is not particularly limited, but for example, the image may be captured automatically within a certain period of time after the aerial image P1 is displayed, or the user may issue an instruction for the imaging camera 160 to capture an image. Alternatively, if the biometric authentication device is equipped with a distance sensor or a proximity sensor, the imaging camera 160 may capture an image in response to the sensor detecting a living body. Image data captured by the imaging camera 160 is used for authenticating the user.

[0027] According to this embodiment, an aerial image P1 representing the design to be biometrically authenticated is displayed in the air to guide the position where the biometric device should be held, so that the user can intuitively place a biometric device such as the palm of their hand or fingers at height D of the aerial image P1.

[0028] Next, a second embodiment of the present invention will be described. Fig. 4 is a schematic cross-sectional view of a biometric authentication device 100A according to the second embodiment of the present invention, and the same components as those in the first embodiment are assigned the same reference numerals.

[0029] As explained in the first embodiment, the imaging camera 160 captures an image of the palm H through the opening 142, but a portion of the light L5 reflected by the polarizing beam splitter 150 becomes stray light through the opening 142 and is captured by the imaging camera 160. When this stray light is captured, the signal-to-noise ratio decreases, the image data is adversely affected, and the accuracy of biometric authentication decreases.

[0030] Therefore, in the second embodiment, a polarizing filter 170 is interposed between the opening 142 and the imaging camera 160 to prevent the reflected light L5 from the polarizing beam splitter 150 from being captured by the imaging camera 160. The polarizing filter 170 has a polarization state that suppresses transmission of the reflected light L5 from the polarizing beam splitter 150. For example, the polarization direction of the polarizing filter 170 differs from the polarization direction of the polarizing beam splitter 150, and for example, the polarization direction of the polarizing filter 170 is orthogonal to the polarization direction of the polarizing beam splitter 150. This prevents the unnecessary reflected light L5 from the polarizing beam splitter 150 from being captured by the imaging camera 160, preventing a decrease in the quality of image data of the living body captured by the imaging camera 160.

[0031] Next, a third embodiment of the present invention will be described. Fig. 5(A) is a block diagram showing the electrical configuration of a biometric authentication device 100B according to the third embodiment. The biometric authentication device 100B includes a light source driving unit 200 that drives a light source 110, an imaging camera 210 (imaging camera 160 in Figs. 3 and 4) that captures an image of a living body near an aerial image P1, and a control unit 220 that controls each unit.

[0032] 5(B), the control unit 220 causes the light source 110 to be repeatedly turned on and off at a constant cycle via the light source driving unit 200, and causes the imaging camera 200 to capture an image of the living body while the light source 110 is turned off. For example, the imaging camera 210 captures an image of the living body while the light source 110 is turned off between time t1 and time t2.

[0033] In this way, by controlling the display of the aerial image P1 and the imaging by the imaging camera in a time-division manner and imaging the living body during a period when no reflected light L5 is generated from the polarizing beam splitter 150, it is possible to prevent stray light from being incorporated into the captured image data. Note that in the third embodiment, the polarizing filter 170 used in the second embodiment is not necessarily required, but a polarizing filter 170 may be interposed.

[0034] Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, when an infrared camera is used to capture an image of veins in the palm of a hand or the like, a visible light filter is used in addition to or instead of the polarizing filter 170 used in the second embodiment. The visible light filter cuts visible light, preventing visible light from entering the infrared camera, and transmits infrared light and other light of wavelengths other than visible light.

[0035] According to this embodiment, by placing a visible light filter at a position that matches the opening 142, it is possible to prevent visible light from being reflected by the infrared camera, and by cutting out visible light noise, it is possible to increase the S / N ratio of the infrared image data and improve the accuracy of biometric authentication.

[0036] Next, a fifth embodiment of the present invention will be described. As shown in Fig. 6, biometric authentication device 100C of this embodiment includes, in addition to the configuration of Fig. 5, a sensor 230 that detects the approach or distance of a biometric subject, and an output unit 240. In response to the sensor 230 detecting that the biometric subject has approached height D of aerial image P1, control unit 220 causes imaging camera 210 to capture an image of the biometric subject. Then, in response to the completion of imaging of the biometric subject by imaging camera 210, output unit 240 outputs a sound (e.g., a beep) indicating the completion of imaging. This allows the user to know that an image for biometric authentication has been captured, and allows the user to return palm H to its original position.

[0037] In another embodiment, control unit 220 may cause light source 110 to blink or light up at a brightness or color different from normal via light source driving unit 200 to notify the user that imaging by imaging camera 210 has finished. For example, to prompt the user to capture an image of a living body, aerial image P1 may be displayed in blue, and when imaging has finished, aerial image P1 may be displayed in green.

[0038] The biometric authentication device of this embodiment can be applied to user input in any device, such as a computer device, an in-vehicle electronic device, an ATM at a bank, a ticket vending machine at a station, or an elevator input button.

[0039] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention described in the claims. [Explanation of symbols]

[0040] 100, 100A, 100B, 100C: Biometric authentication device 110: Light source 120: Polarizing filter 130: Light guide layer 136: Light diffusion section 140: Retroreflective layer 150: Polarizing beam splitter 160: Imaging camera 170: Polarizing filter P1: Aerial image

Claims

1. A biometric authentication device having a function of displaying an aerial image using retroreflection, a light guiding layer on which a design for an aerial image is formed; a light source that irradiates the light guide layer with light; a polarizing beam splitter disposed on one main surface side of the light guide layer; a retroreflective layer disposed on the other principal surface side of the light guide layer opposite to the one principal surface; an imaging means for imaging a living body near an area where an aerial image is displayed through an opening formed in the retroreflective layer, A biometric authentication device that performs biometric authentication based on the image captured by the imaging means.

2. The biometric authentication device according to claim 1 , further comprising a polarizing filter having a polarization direction different from that of the polarizing beam splitter, provided at a position aligned with the opening.

3. The biometric authentication device according to claim 2 , wherein the polarization direction of the polarizing filter is orthogonal to the polarization direction of the polarizing beam splitter.

4. The biometric authentication device according to claim 1 , wherein the image capturing unit captures an image of the living body when the light source is turned off.

5. The biometric authentication device according to claim 4 , wherein the display of the aerial image and the image capture by the image capture means are controlled in a time-division manner.

6. The biometric authentication device according to claim 1 , wherein the imaging means includes an infrared camera, and a visible light filter that blocks visible light is provided at a position aligned with the opening.

7. The biometric authentication device according to claim 1 , wherein the aerial image is generated at a position symmetrical to the design with respect to the plane of the polarizing beam splitter, and the focal point of the imaging means is adjusted to the position of the aerial image.

8. The biometric authentication device according to claim 1 , further comprising an output unit that notifies the user that the image capturing unit has finished capturing an image.

9. The biometric authentication device according to claim 1 , wherein the biometric information is a fingerprint or a vein.

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