Contactless authentication system and authentication method

Abstract

This contactless authentication system comprises: one or more illumination devices that irradiate a portion of a hand not contacting an object with illumination light including an optical component in the wavelength range of 1,380 nm or greater; and an imaging device that images the optical component in the aforementioned wavelength range within reflected light produced due to the illumination light being reflected on the aforementioned portion of the hand, thereby acquiring a fingerprint image and / or a palmprint image as authentication information.

Description

[Technical Field]

[0001] The present disclosure relates to a contactless authentication system and authentication method. [Background technology]

[0002] For personal authentication, it is common to capture images of hands and extract information characteristic of an individual from the captured images, such as the shape of the bumps that make up fingerprints and palm prints, and the distribution of sweat pores.

[0003] In general fingerprint authentication devices, as disclosed in Patent Document 1, for example, a method is used in which a finger is pressed against a glass surface such as a prism. With this method, light irradiated onto the finger is totally reflected at the concave parts of the finger that are not in contact with the glass surface, while light irradiated onto the finger is totally reflected at the convex parts of the finger that are in contact with the glass surface. As a result, a fingerprint image with high contrast can be obtained.

[0004] On the other hand, from the viewpoint of hygiene and the ability to authenticate a large number of people in a short time, there is an increasing demand for contactless authentication technology that does not require pressing a finger against a glass surface or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-334649 [Patent Document 2] Patent No. 6778876 [Patent Document 3] Japanese Patent Application Publication No. 2017-208812 [Patent Document 4] Patent No. 4235729 [Patent Document 5] US Patent Application Publication No. 2019 / 0252455 Summary of the Invention [Problem to be solved by the invention]

[0006] In authentication methods that do not require the hand to touch a glass surface, it is difficult to obtain a high-contrast image because the presence or absence of total reflection described above cannot be utilized. Using a low-contrast image as authentication information can lead to false authentications.

[0007] Therefore, the present disclosure provides a contactless authentication system and the like that can obtain authentication information that can suppress the occurrence of erroneous authentication from a hand that is not in contact with an object. [Means for solving the problem]

[0008] A contactless authentication system according to one embodiment of the present disclosure includes one or more illumination devices that irradiate illumination light containing light components in a wavelength range of 1380 nanometers or more onto a portion of a hand that is not in contact with an object, and an imaging device that captures an image of light components in the wavelength range in reflected light that is generated by reflecting the illumination light off the portion of the hand, thereby obtaining at least one of a fingerprint image and a palmprint image as authentication information.

[0009] An authentication method according to one embodiment of the present disclosure includes irradiating a portion of a hand that is not in contact with an object with illumination light containing light components in a wavelength range of 1380 nanometers or more, and capturing an image of light components in the wavelength range in reflected light that is generated by reflecting the illumination light off the portion of the hand, thereby obtaining at least one of a fingerprint image and a palmprint image as authentication information. [Effects of the Invention]

[0010] According to the present disclosure, authentication information that can reduce the occurrence of erroneous authentication can be obtained from a hand that is not in contact with an object. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 shows the results of imaging a finger illuminated with illumination light from LEDs with different center wavelengths. [Figure 2]FIG. 2 is a diagram showing the emission spectrum of the LED used to capture the fingerprint image shown in FIG. [Figure 3] FIG. 3 is a conceptual diagram showing the path of light irradiated onto the surface of a finger. [Figure 4] FIG. 4 is a diagram showing the wavelength dependency of the intensity of light within the skin when light with different wavelengths is incident on the skin. [Figure 5] FIG. 5 is a graph showing the wavelength dependence of the absorption coefficient of water. [Figure 6] FIG. 6 is a block diagram showing a schematic configuration of the contactless authentication system according to the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an example of a schematic configuration of a photoelectric conversion element included in the imaging element according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing the wavelength dependency of sunlight intensity on the earth's surface. [Figure 9] FIG. 9 is a flowchart showing an example of the operation of the contactless authentication system according to the first embodiment. [Figure 10] FIG. 10 is a block diagram showing a schematic configuration of a contactless authentication system according to the second embodiment. [Figure 11] FIG. 11 is a conceptual diagram showing a situation in which illumination light is irradiated onto the surface of a finger. [Figure 12] FIG. 12 is a flowchart showing an operation example of the contactless authentication system according to the second embodiment. [Figure 13] FIG. 13 is a block diagram showing a schematic configuration of a contactless authentication system according to a modification of the second embodiment. [Figure 14] FIG. 14 is a block diagram showing a schematic configuration of a contactless authentication system according to the third embodiment. [Figure 15] FIG. 15 is a diagram illustrating an example of changes in the emission intensity of illumination light and changes in the sensitivity of the imaging device according to the third embodiment. [Figure 16] FIG. 16 is a flowchart showing an operation example of the contactless authentication system according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Findings that led to one aspect of the present disclosure) As mentioned above, it is difficult to obtain a high-contrast fingerprint image when capturing an image of a hand without touching a glass surface or the like. Therefore, using such a fingerprint image as authentication information is likely to result in erroneous authentication. Therefore, the inventors conducted repeated fingerprint imaging experiments using illumination light of various wavelengths and obtained the following findings.

[0013] FIG. 1 shows the results of imaging a finger illuminated with illumination light using LEDs (light emitting diodes) manufactured by Thorlabs, each with a different central wavelength. FIG. 1 shows multiple fingerprint images captured using LEDs with emission central wavelengths of 970, 1050, 1200, 1300, 1450, 1550, and 1650 nanometers, respectively. The numbers attached to the fingerprint images in FIG. 1 indicate the central wavelengths of the LEDs. FIG. 2, provided for reference by Thorlabs, shows the emission spectrum of the LED used to capture the fingerprint image shown in FIG. 1. When capturing the fingerprint image shown in FIG. 1, illumination light was applied from diagonally forward on the side of the finger where the fingerprint was located, and the image was captured from the front of the finger.

[0014] As shown in Figure 1, when LEDs with central wavelengths of 970, 1050, 1200, and 1300 nanometers were used, the contrast of each fingerprint image was low. In contrast, when LEDs with central wavelengths of 1450, 1550, and 1650 nanometers were used, the contrast of each fingerprint image was high. In other words, the fingerprint images were clearly captured. Furthermore, when LEDs with central wavelengths of 1450, 1550, and 1650 nanometers were used, not only was the contrast of the fingerprint image high, but the images of sweat pores, which are the holes through which sweat escapes, were also clearly captured. Specifically, the white dots in the fingerprint image are sweat pores. Furthermore, when LEDs with central wavelengths of 1450, 1550, and 1650 nanometers were used, the images of skin wrinkles, as well as fingerprints, were clearly captured.

[0015] Similar imaging results were obtained in a test in which, instead of the LED mentioned above, a halogen lamp with a wide wavelength range was used as illumination light, a bandpass filter that transmits specific wavelengths was attached to the imaging device, the transmitted wavelength of the bandpass filter was changed, and an image was taken of the reflected light from the finger that passed through the bandpass filter.

[0016] Furthermore, the inventors have investigated the cause of this contrast difference and have discovered that the cause of the above phenomenon is scattered reflected light components called intracutaneous light, which penetrates into the skin and is then re-emitted.

[0017] FIG. 3 is a conceptual diagram showing the path of light irradiated onto the surface of a finger.

[0018] 3, a portion of light 1101 irradiated onto the surface of finger F is reflected by the surface and becomes surface reflected light 1102. The surface reflected light 1102 is greater at convex portions that are more likely to be hit by light 1101, and is less at concave portions that are in the shadows 1200 of the convex portions. Therefore, the component of surface reflected light 1102 contains a lot of information about the fingerprint, which is information about the unevenness of the finger.

[0019] Meanwhile, part of the light 1101 irradiated onto the surface of the finger F penetrates into the interior of the finger F. The light 1105 that penetrates into the interior of the finger F is scattered many times and spreads throughout the interior of the finger, becoming scattered light 1104 that travels in various directions. Part of the scattered light 1104 is re-emitted from the surface of the finger F. This light re-emitted from the surface of the finger F is also called intraskin light 1103. The intraskin light 1103 is the light 1101 scattered and reflected by the finger F. The intraskin light 1103 is light that has lost information about the surface of the finger F where it originally entered due to scattering within the finger F. Furthermore, the intraskin light 1103 is emitted almost equally from the convex and concave portions of the finger F. Therefore, the intraskin light 1103 contains almost no information about the fingerprint, which is information about the finger's concave and convex surfaces, like the surface reflected light 1102.

[0020] Due to the light path described above, the image of a fingerprint of a finger that is not in contact with a glass surface or the like is captured more clearly the more the surface reflected light 1102 component there is, and is captured less clearly the more the intraskin light 1103 component there is.

[0021] Next, the inventors conducted the following experiment to investigate the wavelength dependency of the light intensity within the skin.

[0022] Figure 4 shows the wavelength dependency of the intensity of intraskin light when light is incident on the skin at different wavelengths. Specifically, Figure 4 shows the wavelength dependency of the intensity when light is incident on the skin from an optical fiber core with a diameter of 400 micrometers pressed against the skin and received by optical fiber cores with a diameter of 400 micrometers pressed against the skin at center distances of 0.4 mm, 0.8 mm, and 1.2 mm from the center of the optical fiber core that the light entered.

[0023] As is clear from FIG. 4, intraskin light is significantly attenuated at wavelengths of 1380 nanometers or more compared to wavelengths of less than 1380 nanometers.

[0024] Furthermore, Figure 5 is a diagram showing the wavelength dependence of the absorption coefficient of water. Comparing the wavelength dependence of the absorption coefficient of water shown in Figure 5 with the wavelength dependence of intraskin light shown in Figure 4, it is clear that there is a high correlation. In other words, it is thought that the attenuation of intraskin light is mainly due to the influence of resonance absorption by the water contained in the skin.

[0025] The absorption coefficient of water shown in Figure 5 is greater at wavelengths of 1380 nanometers or longer than at wavelengths shorter than 1380 nanometers. In other words, the intensity of intraskin light is lower at wavelengths of 1380 nanometers or longer than at wavelengths shorter than 1380 nanometers. Note that the absorption coefficient of water shown in Figure 5 decreases at wavelengths longer than 1450 nanometers, but the absorption coefficient of water reaches a minimum at wavelengths around 1600 to 1700 nanometers, and is higher at wavelengths of 1600 nanometers or longer than the value at a wavelength of 1380 nanometers.

[0026] Furthermore, while the intraskin light component is strongly affected by absorption by water inside the finger as described above, the surface-reflected light component does not penetrate the skin and is therefore less affected by absorption by water. Therefore, at wavelengths of 1380 nanometers or longer, where the intraskin light component is significantly attenuated, the surface-reflected light component is the main component of the light reflected by the finger when irradiated onto the finger. Therefore, the fingerprint image obtained by such imaging contains more information about the surface irregularities that can be used for authentication. Thus, the inventors have discovered that imaging using light with wavelengths of 1380 nanometers or longer reduces the likelihood of erroneous authentication and enables more accurate and faster authentication. These findings are true not only when capturing a fingerprint image by capturing an image of a finger, but also when capturing a palm image by capturing an image of a palm.

[0027] Hereinafter, embodiments of the present disclosure conceived based on such findings will be described.

[0028] An outline of one aspect of the present disclosure is as follows.

[0029] A contactless authentication system according to one embodiment of the present disclosure includes one or more illumination devices that irradiate illumination light containing light components in a wavelength range of 1380 nanometers or more onto a portion of a hand that is not in contact with an object, and an imaging device that captures an image of light components in the wavelength range in reflected light that is generated by reflecting the illumination light off the portion of the hand, thereby obtaining at least one of a fingerprint image and a palmprint image as authentication information.

[0030] In this way, the imaging device captures light reflected from a hand that is not in contact with an object, the light having a wavelength range of 1380 nanometers or more, and acquires authentication information. Therefore, the influence of intraskin light is reduced, and authentication information that includes a lot of information about the unevenness of the hand's surface can be acquired. Authentication is performed using the authentication information acquired in this way, making it less likely that erroneous authentication will occur. Therefore, the contactless authentication system according to this embodiment can acquire authentication information from a hand that is not in contact with an object, which can reduce the occurrence of erroneous authentication.

[0031] Furthermore, for example, the authentication information may include information indicating the positions of sweat pores.

[0032] As a result, the authentication information includes information indicating the positions of sweat pores, which is expected to improve authentication accuracy, and by using such authentication information for authentication, the occurrence of erroneous authentication can be further reduced.

[0033] Also, for example, the imaging device may include a photoelectric conversion layer, and the sensitivity of the photoelectric conversion layer may have a peak in a wavelength range of 1380 nanometers or greater.

[0034] This allows for increased sensitivity of the imaging device in the wavelength range above 1380 nanometers.

[0035] Furthermore, for example, the photoelectric conversion layer may include quantum dots.

[0036] Quantum dots can have a steep absorption peak, making it possible to realize an imaging device that has high sensitivity to a specific wavelength above 1380 nanometers and low sensitivity to wavelengths other than the specific wavelength.

[0037] Furthermore, for example, the photoelectric conversion layer may contain semiconducting carbon nanotubes.

[0038] Semiconducting carbon nanotubes can have a steep absorption peak, making it possible to realize an imaging device that has high sensitivity to a specific wavelength of 1380 nanometers or more and low sensitivity to wavelengths other than the specific wavelength.

[0039] Furthermore, for example, the light components captured by the imaging device may include wavelengths at which sunlight on the Earth's surface is significantly attenuated. In other words, the imaging device may acquire the authentication information by capturing light components in a wavelength range of 1380 nanometers or more that includes wavelengths attenuated by sunlight on the Earth's surface. Note that the wavelengths attenuated by sunlight on the Earth's surface refer to wavelengths at which the rate attenuation of sunlight outside the atmosphere due to atmospheric absorption is significant when comparing the intensity of sunlight on the Earth's surface with the intensity of sunlight outside the atmosphere.

[0040] This reduces the influence of sunlight and makes it possible to obtain authentication information that is relatively more affected by reflected light. Therefore, by using such authentication information for authentication, it is possible to further reduce the occurrence of erroneous authentication.

[0041] Also, for example, the imaging device may include an optical filter, and the transmittance of the optical filter for light having a wavelength less than 1380 nanometers may be lower than the transmittance of the optical filter for light having a wavelength equal to or greater than 1380 nanometers.

[0042] This allows the sensitivity of the imaging device to be relatively increased in the wavelength range above 1380 nanometers.

[0043] Also, for example, the one or more lighting devices may periodically change the emission intensity of the illumination light, and the imaging device may periodically change the sensitivity of the imaging device in response to the change in the emission intensity of the illumination light.

[0044] This allows images captured by changing the relationship between the phase of the emission intensity of the illumination light and the phase of the sensitivity of the imaging device to be acquired as authentication information. In other words, since it is possible to acquire images in which the influence of the illumination light reflected by the hand is large and images in which the influence is small, it is possible to acquire authentication information in which the influence of ambient light is reduced by, for example, acquiring a differential image between these images.

[0045] Furthermore, for example, the one or more lighting devices may irradiate the illumination light onto the hand from a first direction and a second direction different from the first direction, and the imaging device may capture the reflected light resulting from the illumination light irradiated onto the hand from the first direction and the reflected light resulting from the illumination light irradiated onto the hand from the second direction.

[0046] In this way, by capturing images of the light reflected by the hand from different irradiation directions, the way the shadows of the hand's unevenness are formed changes, and images with different regions with high contrast resulting from the shadows of the hand's unevenness can be captured. This makes it possible to obtain authentication information that includes a larger amount of information about the unevenness of the hand's surface over a wider range.

[0047] Furthermore, for example, the one or more lighting devices may include a first lighting device that irradiates the illumination light onto the hand from the first direction and a second lighting device that irradiates the illumination light onto the hand from the second direction, and the timing at which the first lighting device irradiates the illumination light onto the hand may be different from the timing at which the second lighting device irradiates the illumination light onto the hand.

[0048] This allows illumination light to be irradiated onto the hand from a plurality of different irradiation directions with a simple configuration.

[0049] Also, for example, the one or more lighting devices may include an adjustment unit that changes the direction in which the illumination light is irradiated onto the hand, and the one or more lighting devices may use the adjustment unit to irradiate the illumination light onto the hand from the first direction and the second direction.

[0050] This allows illumination light to be irradiated onto the hand from a plurality of different irradiation directions without increasing the number of lighting devices.

[0051] Furthermore, for example, the light component captured by the imaging device may be a light component in the reflected light having a wavelength range of 1380 nanometers or more and less than 2500 nanometers. In other words, the imaging device may acquire at least one of the fingerprint image and the palm print image as the authentication information by capturing an image of a light component in the reflected light of the illumination light having a wavelength range of 1380 nanometers or more and less than 2500 nanometers.

[0052] As a result, in the wavelength range of less than 2500 nanometers, there is little thermal noise in the imaging device and little thermal radiation from the subject, making it possible to obtain clear authentication information.

[0053] An authentication method according to one embodiment of the present disclosure includes irradiating a portion of a hand that is not in contact with an object with illumination light containing light components in a wavelength range of 1380 nanometers or more, and capturing an image of light components in the wavelength range in reflected light that is generated by reflecting the illumination light off the portion of the hand, thereby obtaining at least one of a fingerprint image and a palmprint image as authentication information.

[0054] As a result, similar to the contactless authentication system described above, authentication information that includes a lot of information about the unevenness of the surface of the hand can be obtained from a hand that is not in contact with an object because the influence of intraskin light is small. Therefore, the authentication method according to this aspect can obtain authentication information from a hand that is not in contact with an object, which can reduce the occurrence of erroneous authentication.

[0055] Hereinafter, embodiments will be described with reference to the drawings.

[0056] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement and connection configurations, steps, and step sequences shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims are described as optional components. Furthermore, the drawings are not necessarily strict illustrations. Therefore, for example, the scales and the like do not necessarily match between the drawings. Furthermore, in the drawings, substantially identical components are designated by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0057] Furthermore, in this specification, terms indicating the relationship between elements, terms indicating the shape of elements, and numerical ranges are not expressions that express only the strict meaning, but are expressions that mean that they also include a substantially equivalent range, for example, a difference of about a few percent.

[0058] (Embodiment 1) [1. Contactless authentication system configuration] First, the configuration of the contactless authentication system according to this embodiment will be described. Fig. 6 is a block diagram showing a schematic configuration of the contactless authentication system 100 according to this embodiment.

[0059] As shown in FIG. 6, the contactless authentication system 100 includes an illumination device 110, an imaging device 120, and a management device 130. The contactless authentication system 100 acquires authentication information from a hand that is not in contact with an object. Specifically, the contactless authentication system 100 acquires authentication information from at least a part of a hand that is not in contact with an object. In the example shown in FIG. 6, the contactless authentication system 100 acquires authentication information from a finger F that is part of the hand of the person to be authenticated. The authentication information is a fingerprint image, a palm print image, or both a fingerprint image and a palm print image. In other words, the authentication information is an image that captures images of fingers, a palm, or both fingers and a palm. An example in which the contactless authentication system 100 acquires authentication information, i.e., a fingerprint image, from a finger F that is not in contact with an object will be described below.

[0060] In the contactless authentication system 100, the illumination device 110 irradiates illumination light 150 onto a finger F, which is a subject and is not in contact with a glass surface of a prism or the like. The imaging device 120 then captures light 160 of the illumination light 150 reflected by the finger F to acquire a fingerprint image as authentication information. As described above, the reflected light 160 includes surface reflected light from the finger F and intraskin light, which is scattered reflected light from the finger F. The following describes a case in which the illumination device 110 irradiates illumination light 150 onto a finger F that is not in contact with any object. Note that the finger F may have a portion in contact with an object. In this case, the illumination device 110 irradiates illumination light 150 onto at least the portion of the finger F that is not in contact with the object. The imaging device 120 captures light 160 of the illumination light 150 reflected by the portion of the finger F that is not in contact with the object.

[0061] The management device 130 controls the operations of the lighting device 110 and the image capturing device 120, and performs various information processing related to authentication information acquired by the image capturing device 120, for example.

[0062] Each component of the contactless authentication system 100 will be described in detail below.

[0063] [1.1. Lighting equipment] The illumination device 110 includes, for example, a light source 111 , an illumination optical system 112 , and an optical filter 113 .

[0064] The illumination device 110 irradiates the finger F, which is the subject, with illumination light 150 having a light component in a wavelength range of 1380 nanometers or more. The illumination light 150 has, for example, a light component having a wavelength of 1380 nanometers or more and less than 2500 nanometers. For convenience, in this specification, light that does not contain a visible light component is also referred to as "illumination light."

[0065] The illumination light 150 may include a light component with a wavelength less than 1380 nanometers. The illumination device 110, for example, irradiates illumination light 150 having a light component with a wavelength range of 1380 nanometers or more as a main light component. The illumination light 150 having a light component with a wavelength range of 1380 nanometers or more as a main light component means that, in the emission spectrum of the illumination light 150, the integral of the product of the emission intensity and the quantum efficiency of the image sensor 121 at wavelengths of 1380 nanometers or more is 50% or more of the integral of the product of the emission intensity and the quantum efficiency of the image sensor 121 over a wavelength range to which the image sensor 120 is sensitive, which will be described in detail later. Note that the wavelength range to which the image sensor 120 is sensitive refers to a wavelength range to which the image sensor 120 has a quantum efficiency that affects the imaging results, for example, a wavelength range to which the image sensor 120 has a quantum efficiency that is not zero.

[0066] The wavelength range to which the imaging device 120 is sensitive is determined mainly by the photoelectric conversion material used in the imaging element 121 and the optical filter 123. For example, in the case of an imaging element using a common indium gallium arsenide compound as the photoelectric conversion material, the wavelength range to which the imaging device 120 is sensitive is approximately 1700 nanometers or less. In the case of an imaging element using quantum dots containing lead sulfide as a core as the photoelectric conversion material, the wavelength range to which the imaging device 120 is sensitive is approximately 1600 nanometers or less, although this varies depending on the particle size of the quantum dots, etc.

[0067] Illumination light 150 may have a light component in a wavelength range to which image sensor 121 is not sensitive. Illumination light 150 may include three types of light components: (1) light components in a wavelength range to which image sensor 121 is sensitive, with wavelengths of 1380 nanometers or greater; (2) light components in a wavelength range to which image sensor 121 is sensitive, with wavelengths less than 1380 nanometers; and (3) light components in a wavelength range to which image sensor 121 is not sensitive. In the emission spectrum of illumination light 150, the value obtained by integrating the product of the emission intensity and the quantum efficiency of image sensor 121 in the wavelength range to which image sensor 121 is sensitive, that is, 1380 nanometers or greater, is equal to or greater than the value obtained by integrating the product of the emission intensity and the quantum efficiency of image sensor 121 in the wavelength range to which image sensor 121 is sensitive, that is, less than 1380 nanometers. The proportion of light component (3) in illumination light 150 is not particularly limited.

[0068] Therefore, if the image sensor 121 has significant sensitivity only to wavelengths of 1380 nanometers or longer, the illumination light 150 only needs to contain light components with sufficient intensity for imaging at wavelengths of 1380 nanometers or longer. For example, the illumination light 150 may contain light components in a wide wavelength range from ultraviolet to far infrared, as in the case of light emitted by a xenon lamp.

[0069] The illumination device 110 is disposed so as to illuminate an area where a fingerprint of a finger F is present when the finger F is not pressed against glass or the like, i.e., in a non-contact state. The finger F illuminated with illumination light 150 is not in contact with any object and is exposed to the air, for example. The illumination device 110 is disposed so that reflected light 160 from the surface of the finger F of the illumination light 150 illuminated onto the finger F enters the imaging device 120.

[0070] Furthermore, the illumination device 110 is disposed so as to irradiate the illumination light 150 at an angle such that the grooves between the fingerprint lines, which are the concave portions of the fingerprint area, are shaded by the fingerprint lines, which are the convex portions of the fingerprint area. In other words, the illumination device 110 is disposed so as to irradiate the illumination light 150 from an oblique direction, rather than perpendicularly, to the bottoms of the grooves between the fingerprint lines.

[0071] Furthermore, the irradiation direction of illumination light 150 from lighting device 110 and the imaging direction of imaging device 120 are, for example, different from each other. Note that the irradiation direction of illumination light 150 from lighting device 110 and the imaging direction of imaging device 120 may be the same direction.

[0072] The light source 111 emits light components with wavelengths of 1380 nanometers or more, in other words, light having luminous intensity. The light emitted by the light source 111 may also include light components with wavelengths of less than 1380 nanometers.

[0073] The light source 111 is a light source that emits light in a wide wavelength range that includes both light components with wavelengths equal to or greater than 1380 nanometers and light components with wavelengths less than 1380 nanometers. Examples of such light sources 111 include a halogen lamp, a xenon lamp, and a supercontinuum light source.

[0074] Alternatively, the light source 111 may be a light source that emits light having light components biased toward a specific wavelength range within a wavelength range of 1380 nanometers or more. The light source 111 emits light having a central wavelength of the light component within a wavelength range of 1380 nanometers or more, and having an emission spectrum in which the half-width of the light component is within a range of several hundred nanometers or less. Examples of such light sources 111 include LEDs, laser diodes, and superluminescent diodes. Specifically, the M1450L3 manufactured by Thorlabs, whose emission spectrum is shown in FIG. 2, has a central wavelength of approximately 1450 nanometers and a half-width of the light component of approximately 100 nanometers. The M1450L3 may be used as the light source 111. Alternatively, for example, the light source 111 may be a laser diode having a central wavelength of 1550 nanometers and a half-width of the light component of 1 nanometer or less.

[0075] The illumination optical system 112 has a function of irradiating the subject with light emitted by the light source 111. The illumination optical system 112 is disposed at a position where the light emitted by the light source 111 is incident. The illumination optical system 112 is composed of, for example, lenses and mirrors. Note that if a light source 111 with a limited direction of light emission, such as a bullet-type light-emitting diode, is used, the illumination optical system 112 does not need to be provided in the illumination device 110. Furthermore, the illumination optical system 112 may include a shutter, an aperture, and the like, as necessary.

[0076] The optical filter 113 has a function of reducing light components with wavelengths less than 1380 nanometers from the light emitted by the light source 111. The optical filter 113 is disposed on the optical path of the light emitted by the light source 111. The optical filter 113 is disposed, for example, between the light source 111 and the illumination optical system 112, but may also be disposed so as to be located between the illumination optical system 112 and the finger F.

[0077] Examples of the optical filter 113 include an interference filter made of a dielectric multilayer film and an absorption filter made of colored glass. The optical filter 113 may be a long-pass filter having a lower transmittance for light with wavelengths less than 1380 nanometers than for light with wavelengths equal to or greater than 1380 nanometers, or a band-pass filter having a wavelength range in which the transmittance for light is significantly higher around a specific central wavelength equal to or greater than 1380 nanometers. The wavelength range in which the band-pass filter has a significantly higher transmittance may coincide with the wavelengths to which the imaging device 120 has a particularly high sensitivity. For example, the imaging element 121 of the imaging device 120 has a sensitivity peak in the wavelength range in which the band-pass filter has a significantly higher transmittance. Note that if the light source 111 emits light having a wavelength component equal to or greater than 1380 nanometers as the main light component, the optical filter 113 may not be included in the illumination device 110.

[0078] [1.2. Imaging device] The imaging device 120 includes, for example, an imaging element 121, an imaging optical system 122, and an optical filter 123. The imaging device 120 is sensitive to wavelengths of 1380 nanometers or longer. For example, the imaging element 121 is sensitive to wavelengths of 1380 nanometers or longer, and thus the imaging device 120 captures light with wavelengths of 1380 nanometers or longer.

[0079] The image capturing device 120 is placed at a position where reflected light 160 from fingerprint lines, which are convex portions of a finger in a non-contact state, illuminated with illumination light 150, is incident.

[0080] The imaging device 120 captures an image of light components in a wavelength range of 1380 nanometers or more in the reflected light 160 from a fingerprint area of ​​the non-contact finger F illuminated with the illumination light 150. The imaging device 120 may also capture light components in a wavelength range of 1380 nanometers or more that includes the attenuation peak of sunlight on the Earth's surface, within the wavelength range of 1380 nanometers or more. Details of the wavelength range including the attenuation peak of sunlight will be described later. The imaging device 120 may also capture light components in the reflected light 160 in a wavelength range of 1380 nanometers or more but less than 2500 nanometers.

[0081] Alternatively, the imaging device 120 may capture reflected light 160 with a wavelength range of 1380 nanometers or greater as the main imaging component. For example, the imaging device 120 captures reflected light 160 with a wavelength range of 1380 nanometers or greater and less than 2500 nanometers as the main imaging component. Here, the main imaging component has the following meaning.

[0082] The image sensor 121 has a function of generating signal charges in response to incident photons. The imaging device 120 captures the reflected light 160 using the image sensor 121. The image sensor 121 generates signal charges, which are imaging components, in response to incident light with a wavelength of 1380 nanometers or longer. In other words, the image sensor 121 is sensitive to wavelengths of 1380 nanometers or longer. In this case, the ratio of signal charges generated per photon is called quantum efficiency. Quantum efficiency is wavelength dependent. Furthermore, the amount of photons incident on the image sensor 121 (i.e., the light components of the reflected light 160) is also wavelength dependent. Therefore, the amount of signal charge generated by light of a certain wavelength satisfies Equation 1: (Amount of signal charge generated by light of a certain wavelength) = (Amount of photons at a certain wavelength) × (Quantum efficiency at a certain wavelength) Equation 1

[0083] Here, the total amount of signal charge generated when reflected light 160 is incident on the image sensor 121 is a value obtained by integrating Equation 1 over the entire wavelength range for the reflected light 160. The entire wavelength range refers to the entire range of wavelengths of light to be imaged, and is, for example, the entire wavelength range in which the image sensor 121 has a non-zero quantum efficiency.

[0084] Light with a wavelength having a larger value for Equation 1 generates more signal charge than light with a wavelength having a smaller value for Equation 1, i.e., it has a greater impact on the imaging result. The wavelength range for the main imaging component refers to the wavelength range that mainly generates signal charge. Capturing reflected light 160 with a wavelength range of 1380 nanometers or more as the main imaging component means, for example, that the amount of signal charge generated by reflected light 160 in the wavelength range of 1380 nanometers or more is 50% or more of the total amount of signal charge generated by reflected light 160, and may also mean that it is 90% or more.

[0085] As described above, the imaging device 120 captures reflected light 160 with a wavelength range of 1380 nanometers or greater as the primary imaging component. As is clear from Equation 1, in order to capture a wavelength range of 1380 nanometers or greater as the primary imaging component, it is necessary that illumination light 150 has a light component with a wavelength of 1380 nanometers or greater and that the imaging element 121 has a non-zero quantum efficiency at wavelengths of 1380 nanometers or greater. For example, the quantum efficiency of the imaging element 121 for light with a wavelength of 1380 nanometers or greater is higher than the quantum efficiency of the imaging element 121 for light with a wavelength less than 1380 nanometers. This means that, in the wavelength dependence of the quantum efficiency of the imaging element 121, the value obtained by integrating the quantum efficiency at wavelengths of 1380 nanometers or greater is greater than the value obtained by integrating the quantum efficiency at wavelengths less than 1380 nanometers. Furthermore, in the wavelength dependency of the quantum efficiency of the image sensor 121, the value obtained by integrating the quantum efficiency over wavelengths of 1380 nanometers or more and less than 2500 nanometers may be greater than the value obtained by integrating the quantum efficiency over wavelengths of 380 nanometers or more and less than 1380 nanometers. Furthermore, the wavelength at which the image sensor 121 has high sensitivity, i.e., high quantum efficiency, may be matched with the wavelength at which the illumination light 150 has a large light component.

[0086] The wavelength range in which the image capture device 120 captures images as a main imaging component is, for example, the near-infrared region of less than 2500 nanometers. In the mid-infrared region of wavelengths equal to or greater than 2500 nanometers and the far-infrared region of wavelengths equal to or greater than 4000 nanometers, there is a lot of thermal noise in the image capture element 121, and the subject itself emits a lot of thermal radiation. Therefore, capturing an image in the mid-infrared region or the far-infrared region may make it difficult to obtain clear authentication information.

[0087] The image sensor 121 includes, for example, a photoelectric conversion material that converts photons into electric charges, and a peripheral circuit for reading out the electric charges generated by the photoelectric conversion material as signal charges. Examples of photoelectric conversion materials that enable the image sensor 121 to have sensitivity to wavelengths of 1380 nanometers or longer include indium gallium arsenide compounds, quantum dots containing lead sulfide or lead selenide as a core, and semiconducting carbon nanotubes.

[0088] The imaging element 121 is, for example, a stacked image sensor having a photoelectric conversion element including a photoelectric conversion layer containing a photoelectric conversion material. Fig. 7 is a cross-sectional view showing an example of a schematic configuration of a photoelectric conversion element 125 included in the imaging element 121. As shown in Fig. 7, the photoelectric conversion element 125 includes a pixel electrode 127, a counter electrode 128 arranged opposite to the pixel electrode 127, and a photoelectric conversion layer 126 located between the pixel electrode 127 and the counter electrode 128.

[0089] The photoelectric conversion layer 126 includes a photoelectric conversion material that absorbs incident light and generates hole-electron pairs as signal charges. The photoelectric conversion material is, for example, a semiconducting inorganic material or a semiconducting organic material that absorbs light with a wavelength of 1380 nanometers or longer. The photoelectric conversion layer 126 includes, for example, quantum dots, semiconducting carbon nanotubes, or both quantum dots and semiconducting carbon nanotubes as the photoelectric conversion material.

[0090] Semiconductor quantum dots and semiconducting carbon nanotubes have steep absorption peaks. The absorption peak wavelength of quantum dots can be controlled by the material and particle size of the semiconductor quantum dots. The absorption peak wavelength of semiconducting carbon nanotubes can be controlled by the chirality of the semiconducting carbon nanotubes. Therefore, by using at least one of semiconductor quantum dots and semiconducting carbon nanotubes as a photoelectric conversion material, the wavelength to which the sensor is sensitive can be easily adjusted, thereby realizing an image sensor 121 that has high sensitivity to a specific wavelength and low sensitivity to wavelengths other than the specific wavelength. For example, by including at least one of quantum dots and semiconducting carbon nanotubes that have an absorption peak at wavelengths equal to or greater than 1380 nanometers in the photoelectric conversion layer 126, an image sensor 121 that has high sensitivity to wavelengths equal to or greater than 1380 nanometers and low sensitivity to wavelengths shorter than 1380 nanometers can be realized.

[0091] The pixel electrodes 127 are electrodes for collecting signal charges generated in the photoelectric conversion layer 126. The peripheral circuits of the image sensor 121 read out the signal charges collected by the pixel electrodes 127. The pixel electrodes 127 are formed using a conductive material. Examples of the conductive material include metals such as aluminum and copper, metal nitrides, and polysilicon that has been doped with impurities to provide conductivity.

[0092] The counter electrode 128 is, for example, a transparent electrode made of a transparent conductive material. The counter electrode 128 is disposed on the side of the photoelectric conversion layer 126 on which light is incident. Therefore, light that has passed through the counter electrode 128 is incident on the photoelectric conversion layer 126. In this specification, "transparent" means that at least a portion of light in the wavelength range to be detected is transmitted through the counter electrode 128.

[0093] A voltage is applied to the counter electrode 128. By adjusting the voltage applied to the counter electrode 128, it is possible to set and maintain a desired potential difference between the counter electrode 128 and the pixel electrode 127. The counter electrode 128 is formed using a transparent conducting oxide (TCO) such as ITO, IZO, AZO, FTO, SnO2, TiO2, or ZnO.

[0094] In this way, in the stacked image sensor, the potential of the counter electrode 128 relative to the potential of the pixel electrode 127 is controlled, so that either the hole or the electron of the hole-electron pair generated in the photoelectric conversion layer 126 by photoelectric conversion can be collected by the pixel electrode 127 as a signal charge.

[0095] The imaging element 121 has, for example, a plurality of pixels that each read out a signal charge, and each of the plurality of pixels is provided with a photoelectric conversion element 125. In this case, a pixel electrode 127 is provided for each of the plurality of pixels, but the photoelectric conversion layer 126 and the counter electrode 128 may be provided across the plurality of pixels.

[0096] In addition, the photoelectric conversion element 125 may include other layers such as a charge transport layer, a charge blocking layer, and a buffer layer located between the photoelectric conversion layer 126 and the pixel electrode 127, between the photoelectric conversion layer and the counter electrode 128, or both between the photoelectric conversion layer 126 and the pixel electrode 127 and between the photoelectric conversion layer and the counter electrode 128.

[0097] 6 again, the imaging optical system 122 has a function of forming an image of a subject on the imaging element 121. The imaging optical system 122 is arranged on the incident side of the imaging element 121 on which reflected light 160 is incident. The imaging optical system 122 causes the reflected light 160 incident on the imaging optical system 122 to be incident on the imaging element 121. The imaging optical system 122 is composed of, for example, a lens and a curved mirror. For example, the imaging optical system 122 is selected to have good transmittance and imaging performance in the wavelength range in which imaging is performed as the main imaging component.

[0098] The optical filter 123 transmits, for example, light components with wavelengths of 1380 nanometers or more and blocks or attenuates light components with wavelengths less than 1380 nanometers. In other words, the optical filter 123 has a function of reducing light components with wavelengths less than 1380 nanometers from the reflected light 160. The optical filter 123 is disposed between the imaging optical system 122 and the imaging element 121, or on the incident side of the imaging optical system 122 on which the reflected light 160 is incident.

[0099] The optical filter 123 is, for example, a long-pass filter that has a lower transmittance for light with wavelengths less than 1380 nanometers than for light with wavelengths equal to or greater than 1380 nanometers. Examples of the optical filter 123 include an interference filter made of a dielectric multilayer film and an absorption filter made of colored glass.

[0100] Alternatively, the optical filter 123 may be a bandpass filter that has high light transmittance only in a range around a specific center wavelength of 1380 nanometers or more. The specific center wavelength of the bandpass filter may approximately match the wavelength at which the illumination light 150 has a large light component. For example, the peak wavelength of the light component of the illumination light 150 may be included in a range around the specific center wavelength of the bandpass filter. Furthermore, if the optical filter 113 of the illumination device 110 is a bandpass filter, the specific center wavelengths of the bandpass filters of the optical filters 113 and 123 may be the same. Note that, for example, if the image sensor 121 has high sensitivity only at 1380 nanometers or more, the optical filter 123 may not be included in the image capture device 120.

[0101] In this way, the imaging device 120 has the optical filter 123, which can reduce the light components with wavelengths less than 1380 nanometers that reach the imaging element 121. Therefore, in a situation such as outdoors where there is a lot of light other than the reflected light 160 of the illumination light 150 emitted by the lighting device 110 by the finger F, such as sunlight and ambient light, the proportion of light with wavelengths less than 1380 nanometers that enters the imaging element 121 can be reduced.

[0102] The imaging element 121 may have multiple pixels that each read signal charges, and only some of the pixels may capture images with wavelengths in the 1380 nanometer or greater range as the primary imaging component. For example, the imaging element 121 may have four types of pixels: R (red), G (green), B (blue), and IR (infrared) pixels. The imaging element 121 may capture images with wavelengths in the 1380 nanometer or greater range as the primary imaging component using information based on signal charges read only by the IR pixels. Information based on signal charges read by the R, G, and B pixels capturing visible light may be used to confirm the presence or absence of a subject to be authenticated. The imaging results of the IR pixels and other pixels may be compared to determine whether the subject is a real living finger or a fake finger. Details of the method for determining whether a finger is fake will be described in other embodiments.

[0103] [1.3. Wavelength range for imaging] In contactless authentication system 100 according to this embodiment, imaging device 120 captures an image with a wavelength range of 1380 nanometers or more as the main imaging component. In contactless authentication system 100, light source 111 of illumination device 110 and imaging element 121 of imaging device 120 are selected so that imaging is performed with this wavelength range as the main imaging component. In contactless authentication system 100, optical filter 113 that limits the wavelength range of illumination light 150 and optical filter 123 that limits the imaging wavelength range may be selected so that imaging is performed with this wavelength range as the main imaging component.

[0104] Furthermore, the imaging device 120 may capture an image of a specific wavelength range as the main imaging component within the wavelength range of 1380 nanometers or more as the main imaging component. The specific wavelength range is selected, for example, from the following viewpoints.

[0105] The first aspect is sunlight intensity. FIG. 8 is a diagram showing the wavelength dependence of sunlight intensity at the Earth's surface. As shown in FIG. 8, the sunlight intensity reaching the Earth's surface varies significantly depending on the wavelength. Specifically, the sunlight intensity reaching the Earth's surface exhibits strong attenuation in the wavelength range of 1380 nanometers or more, in the wavelength range of 1380 to 1500 nanometers, and in the wavelength range of 1780 to 1990 nanometers. This is due to sunlight absorption by the atmosphere. By utilizing such attenuated wavelengths of sunlight, the proportion of sunlight components incident on the imaging element 121 can be reduced. For example, the imaging device 120 captures images using a wavelength range including wavelengths of sunlight attenuated at the Earth's surface as the main imaging component. As a result, the proportion of images captured by the imaging device 120 using reflected light 160 is high. Furthermore, since the attenuation of sunlight is largely influenced by absorption by moisture in the atmosphere, at wavelengths where sunlight intensity is low, intraskin light is likely to be reduced due to absorption by moisture in the skin. This reduces the influence of ambient light and light within the skin, enabling more precise imaging and improving the contrast of the fingerprint image.

[0106] The influence of sunlight can be adjusted, for example, by the optical filter 123 included in the imaging device 120. For example, if the optical filter 123 is a bandpass filter, the influence of sunlight can be adjusted by the central wavelength and half width of the transmission band of the bandpass filter.

[0107] For example, when using a bandpass filter with a half-width of the transmission band of approximately 10 nanometers, by setting the center wavelength of the transmission band to a wavelength range of 1380 to 1420 nanometers or a wavelength range of 1820 to 1940 nanometers, the intensity of sunlight passing through the bandpass filter can be reduced to approximately 1 / 10 or less compared to when the center wavelength of the bandpass filter is in the visible range.

[0108] Similarly, when using a bandpass filter with a half-width of the transmission band of approximately 50 nanometers, by setting the central wavelength of the transmission band in the wavelength range of 1380 nanometers to 1430 nanometers, the intensity of sunlight passing through the bandpass filter can be reduced to approximately 1 / 10 or less compared to when the central wavelength of the bandpass filter is in the visible range.

[0109] Furthermore, in order to make the wavelength range including the above-mentioned solar attenuation peak wavelength the main imaging component in the imaging device 120, a light emitting diode, a laser diode, or a superluminescent diode having an emission peak in that wavelength range may be used for the light source 111 of the illumination device 110. Furthermore, when the optical filter 123 is the above-mentioned bandpass filter, the light source 111 of the illumination device 110 may have an emission peak in the transmission band of the bandpass filter.

[0110] The second consideration is eye safety. When the light source 111 is a laser diode, the intensity that can be emitted is limited from a safety standpoint. The intensity that is acceptable from a safety standpoint depends on the wavelength. For example, laser light in the wavelength range of 1400 nanometers to 2600 nanometers is highly absorbed by the eyeball and has little impact on the retina. Therefore, the acceptable intensity is higher than that of laser light of other wavelengths. The higher the output power of the light source 111, the faster the imaging device 120 can acquire images with less noise. Therefore, the imaging device 120 captures images using, for example, the wavelength range of the laser light emitted by the laser diode used as the light source 111 as the main imaging component. For example, a laser diode that emits laser light having a wavelength of 1550 nanometers is eye-safe, and high-output laser diodes are readily available.

[0111] The third aspect is the sensitivity of the image sensor 121. As described above, by using quantum dots or semiconducting carbon nanotubes as the photoelectric conversion material used in the image sensor 121, it is possible to realize an image sensor 121 that has high sensitivity to a specific wavelength and low sensitivity to wavelengths other than the specific wavelength. Therefore, the image sensor 120 captures images, for example, using the wavelength range of absorption resulting from the absorption peak of the photoelectric conversion material as the main imaging component. For example, semiconducting carbon nanotubes are characterized by having different resonance wavelengths, which are steep absorption peak wavelengths, depending on a physical quantity called chirality. The resonance of semiconducting carbon nanotubes with a single chirality has a narrow half-width of approximately tens of nanometers to hundreds of nanometers. Therefore, by using semiconducting carbon nanotubes as the photoelectric conversion material, it is possible to realize an image sensor 121 that has specifically high sensitivity in the wavelength range of absorption resulting from the resonance wavelength.

[0112] For example, a semiconducting carbon nanotube with chirality (9,8) has a resonance wavelength of approximately 1450 nanometers, and a semiconducting carbon nanotube with chirality (10,6) has a resonance wavelength of approximately 1400 nanometers. In this way, by using semiconducting carbon nanotubes with a resonance wavelength of 1380 nanometers or more as a photoelectric conversion material and matching the peak wavelength of light emitted from light source 111 to that resonance wavelength, it is possible to reduce the influence of ambient light with wavelengths other than those near the resonance wavelength.

[0113] The details of the imaging device using semiconducting carbon nanotubes as a photoelectric conversion material are described in detail in Patent Document 2 by the present inventors.

[0114] [1.4. Management device and other configurations] The management device 130 is, for example, a computer including a control unit 131, an extraction unit 132, an authentication unit 133, and a storage unit 135.

[0115] The control unit 131 is a processing unit for controlling the operations of the lighting device 110 and the imaging device 120. The control unit 131 outputs various control signals to the lighting device 110 and the imaging device 120.

[0116] The extraction unit 132 is a processing unit for extracting characteristic information from the authentication information that is the imaging result (that is, a fingerprint image, etc.).

[0117] The authentication unit 133 is a processing unit that performs judgment and personal authentication, etc., by comparing the information extracted by the extraction unit 132 with previously registered information, for example, information registered in the memory unit 135, and comparing the information with images captured by the imaging device 120.

[0118] The processing units such as the control unit 131, the extraction unit 132, and the authentication unit 133 are realized by, for example, one or more processors, and may be realized by a microcomputer or a dedicated circuit or the like.

[0119] The storage unit 135 is a storage device for storing imaging results and information used for processing in the processing unit. The storage unit 135 also stores programs executed by processing units such as the control unit 131, extraction unit 132, and authentication unit 133. The storage unit 135 is realized by, for example, a semiconductor memory or an HDD (Hard Disk Drive).

[0120] The components of management device 130 may be provided in multiple devices, and at least one of the components of management device 130 may be provided in lighting device 110 or imaging device 120.

[0121] The contactless authentication system 100 may further include a sensor for detecting a hand, such as a human sensor. The contactless authentication system 100 may also use the imaging device 120 as the sensor. For example, the control unit 131 may acquire a detection result of the sensor, and may use the detection of a finger F by the sensor as a trigger to start irradiating the illumination light 150 by the lighting device 110 and capturing an image by the imaging device 120.

[0122] [2. Example of contactless authentication system operation] Next, the operation of contactless authentication system 100 according to this embodiment will be described. Specifically, the authentication method implemented by contactless authentication system 100, which acquires authentication information from a hand that is not in contact with an object, will be described. Fig. 9 is a flowchart showing an example of the operation of contactless authentication system 100 according to this embodiment.

[0123] 9, first, the illumination device 110 irradiates the finger F with illumination light 150 having a light component at a wavelength of 1380 nanometers or more (step S11). The illumination device 110 irradiates the illumination light 150, for example, under the control of the control unit 131 or based on an operation by the user. Note that the illumination device 110 may irradiate the illumination light 150 at all times while the contactless authentication system 100 is operating.

[0124] Next, the imaging device 120 captures reflected light 160, which is generated by reflection of illumination light 150 irradiated onto the finger F from the finger F, using a wavelength range of 1380 nanometers or more as the main imaging component (step S12). The imaging device 120 captures the reflected light 160, for example, under the control of the control unit 131 or based on an operation from the user. As a result, the imaging device 120 acquires a fingerprint image, which is the imaging result, as authentication information. The fingerprint image may also include information indicating the positions of sweat pores on the finger F, as described using the image shown in FIG. 1. The imaging device 120 outputs the acquired fingerprint image to the management device 130, for example.

[0125] Next, the extraction unit 132 of the management device 130 acquires a fingerprint image from the imaging device 120 and extracts feature information that indicates the features of the finger F used for authentication (step S13). The extraction unit 132 extracts, as feature information, at least one piece of information from, for example, the fingerprint pattern, the distribution of the fingerprint bifurcation points, and the distribution of sweat pores.

[0126] Next, the authentication unit 133 performs authentication based on the feature information extracted by the extraction unit 132 (step S14). For example, information indicating the authentication candidate and the feature information are stored in association with each other in the storage unit 135, and the authentication unit 133 performs personal authentication by comparing the feature information extracted by the extraction unit 132 with the feature information stored in the storage unit 135. The authentication unit 133 outputs, for example, information for notifying the person to be authenticated of the authentication result. For the extraction of feature information and the comparison of feature information in steps S13 to S14, known fingerprint authentication technology may be used.

[0127] The processes from step S13 to step S14 may be performed by an external device.

[0128] As described above, in the contactless authentication system 100, the imaging device 120 captures reflected light 160 from a finger F that is not in contact with an object, using a wavelength range of 1380 nanometers or more as the main imaging component, and acquires a fingerprint image as authentication information. Therefore, the influence of intraskin light is reduced, and authentication information that includes a lot of information about the fingerprint irregularities of the finger F can be acquired. For example, a fingerprint image with high contrast is captured by the imaging device 120. The authentication unit 133 performs authentication using the fingerprint image acquired in this way, making it less likely that erroneous authentication will occur. In this way, the contactless authentication system 100 can acquire authentication information that can reduce the occurrence of erroneous authentication from a finger F that is not in contact with an object.

[0129] (Embodiment 2) Next, a contactless authentication system according to embodiment 2 will be described. In embodiment 2, an example of a contactless authentication system equipped with a plurality of lighting devices will be described. In the following description of embodiment 2, differences from embodiment 1 will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0130] [1. Contactless authentication system configuration] Fig. 10 is a block diagram showing a schematic configuration of contactless authentication system 200 according to the present embodiment. As shown in Fig. 10, contactless authentication system 200 differs from contactless authentication system 100 according to embodiment 1 in that contactless authentication system 200 includes, as a plurality of lighting devices, lighting device 110A and lighting device 110B instead of lighting device 110. That is, contactless authentication system 200 according to embodiment 2 includes lighting device 110A and lighting device 110B, which are a plurality of lighting devices, imaging device 120, and management device 130.

[0131] Like the illumination device 110, the illumination device 110A and the illumination device 110B each have a light source 111, an illumination optical system 112, and an optical filter 113. The illumination device 110A irradiates the finger F with illumination light 150A, and the illumination device 110B irradiates the finger F with illumination light 150B, which has an irradiation direction different from that of the illumination light 150A. The illumination devices 110A and 110B irradiate the finger F with illumination light 150A and illumination light 150B from different directions. Note that although the number of illumination devices included in the contactless authentication system 200 is two in the example shown in FIG. 10 , it may be three or more. Furthermore, the illumination device 110A and the illumination device 110B may be devices housed in a single common housing or the like.

[0132] In the contactless authentication system 200, the image capturing device 120 captures an image of reflected light 160A of illumination light 150A from a finger F and reflected light 160B of illumination light 150B from the finger F.

[0133] With this configuration, unlike in the first embodiment in which illumination light 150 is emitted from one irradiation direction, contactless authentication system 200 according to this embodiment emits illumination light 150A and illumination light 150B from a plurality of irradiation directions. Furthermore, in contactless authentication system 200, the lighting devices that emit illumination light can be switched sequentially, and lighting device 110A and lighting device 110B emit illumination light 150A and illumination light 150B onto finger F at different timings. In contactless authentication system 200, lighting device 110A and lighting device 110B emit illumination light 150A and illumination light 150B onto finger F at different timings, for example, based on the control of control unit 131 or a user operation.

[0134] The contactless authentication system 200 sequentially switches between irradiating the illumination light 150A and the illumination light 150B from a plurality of different irradiation directions, which provides the following advantages.

[0135] As explained above using Figure 3, a fingerprint image is captured clearly and the contrast is improved when the illumination light is irradiated onto the convex parts of the finger surface and the concave parts of the finger surface are in shadow.

[0136] FIG. 11 is a conceptual diagram showing a situation in which illumination light is irradiated onto the surface of a finger. In FIG. 11, arrows indicate illumination light irradiated from a direction oblique to the direction in which the finger F extends (the vertical direction in FIG. 11). As shown in FIG. 11, the finger F in a non-contact state, that is, not in contact with any object, forms a three-dimensional curved surface. Here, in the case of the illumination light irradiation direction shown in FIG. 11, the illumination light is well irradiated onto the first convex portion 411, the second convex portion 412, and the third convex portion 413 of the finger F. On the other hand, the illumination light is hardly irradiated onto the fourth convex portion 414 and the fifth convex portion 415 of the finger F.

[0137] Furthermore, in finger F, the illumination light is incident on first recess 421 because there is nothing blocking it. On the other hand, in finger F, the illumination light is blocked from second recess 422 by second convex portion 412, and from third recess 423 by third convex portion 413, so the illumination light does not strike second recess 422 or third recess 423. Furthermore, the illumination light does not strike fourth recess 424, including the surrounding convex portions.

[0138] To increase the contrast of the fingerprint image, the area of ​​the finger F where the image of the finger F is captured most clearly is the recessed area not illuminated by the illumination light, sandwiched between the protruding areas illuminated by the illumination light. In the situation shown in FIG. 11, the image near the second recessed area 422 is captured most clearly.

[0139] As described above, the contrast of a fingerprint image depends on the three-dimensional shape of the finger F and the direction of illumination light relative to the three-dimensional shape of the fingerprint. Therefore, by changing the direction of illumination light, the positions of the illuminated parts of the finger F and the parts of the finger F where shadows are cast by recesses can be changed, and the areas of the fingerprint image with high contrast can be changed. Therefore, by sequentially changing the direction of illumination light, it is possible to obtain a fingerprint image with high contrast over a wide range of the finger F. While FIG. 10 shows an example in which there are two illumination devices, it is clear that the more illumination devices are provided and the more the direction of illumination light can be changed, the wider the range of the finger F that can be imaged with high contrast.

[0140] Furthermore, the change in fingerprint contrast caused by a change in the direction of illumination light is due to the three-dimensional nature of the finger F and the fingerprint. Therefore, such a change in contrast does not occur in a fake fingerprint image printed on flat paper or displayed on an LCD display, etc. Therefore, information regarding the change in contrast of a fingerprint image caused by a change in the direction of illumination light can be used to determine whether or not the fingerprint is fake, in order to prevent fraudulent authentication using fake fingerprints.

[0141] [2. Example of contactless authentication system operation] Next, a description will be given of the operation of contactless authentication system 200 according to this embodiment. Fig. 12 is a flowchart showing an example of the operation of contactless authentication system 200 according to this embodiment.

[0142] 12, first, illumination device 110A, which is a first illumination device, irradiates finger F with illumination light 150A, which is a first illumination light (step S21). Then, imaging device 120 captures reflected light 160A generated by reflection of illumination light 150A irradiated onto finger F from finger F (step S22). As a result, imaging device 120 acquires a first fingerprint image, which is the imaging result, as authentication information. Imaging device 120 outputs the acquired first fingerprint image to management device 130, for example. Extraction unit 132 of management device 130 acquires the first fingerprint image from imaging device 120 and records it in storage unit 135.

[0143] Next, illumination device 110B, which is a second illumination device, irradiates finger F with illumination light 150B, which is a second illumination light having an irradiation direction different from that of the first illumination light (step S23). At this time, illumination device 110A is turned off and does not irradiate finger F with illumination light 150A. Then, image capture device 120 captures reflected light 160B generated by reflection of illumination light 150B irradiated onto finger F from finger F (step S24). As a result, image capture device 120 acquires a second fingerprint image, which is the image capture result, as authentication information. Image capture device 120 outputs the acquired second fingerprint image to management device 130, for example. Extraction unit 132 of management device 130 acquires the second fingerprint image from image capture device 120 and records it in storage unit 135.

[0144] Next, extraction unit 132 extracts feature information from the first fingerprint image and the second fingerprint image stored in storage unit 135 (step S25). Extraction unit 132 compares the first fingerprint image and the second fingerprint image and determines the area from which feature information is to be extracted based on the contrast information of each image. For example, extraction unit 132 compares the first fingerprint image and the second fingerprint image and determines, for each image, an area with higher contrast than the other image, i.e., an area where the fingerprint pattern or the like serving as feature information is clearly captured, and extracts feature information from the determined area. For example, extraction unit 132 divides each of the first fingerprint image and the second fingerprint image into multiple sections and compares the contrast values ​​of sections at the same position to extract, for each image, an area with a higher contrast value than the other image. Extraction unit 132 may also generate a composite image of the first fingerprint image and the second fingerprint image and extract feature information from the composite image. This allows feature information to be extracted for authentication from a wider range than when using a fingerprint image captured by capturing the light reflected by the finger F from illumination light irradiated onto the finger F from a single irradiation direction.

[0145] Next, the authentication unit 133 performs authentication based on the characteristic information extracted by the extraction unit 132 (step S26). In step S26, for example, the same process as in step S14 described above is performed.

[0146] In step S25, the extraction unit 132 may further compare the first fingerprint image with the second fingerprint image to determine whether the captured finger is an actual living finger or a fake finger printed or displayed on a flat surface. For example, the extraction unit 132 compares the first fingerprint image with the second fingerprint image, and determines that the finger is a fake finger if the similarity between the first fingerprint image and the second fingerprint image is equal to or greater than a predetermined level, and determines that the finger is a living finger if the similarity is less than the predetermined level. The extraction unit 132, for example, outputs information for notifying the person to be authenticated of the determination result.

[0147] [3. Modifications] Next, a description will be given of a contactless authentication system according to a modification of embodiment 2. In embodiment 2, illumination light is emitted from a plurality of illumination devices, and the illumination light is irradiated onto a finger from a plurality of different irradiation directions, but in the modification of embodiment 2, the irradiation direction of the illumination light from the illumination devices is changed, and the illumination light is irradiated onto a finger from a plurality of different irradiation directions.

[0148] Fig. 13 is a block diagram showing a schematic configuration of a contactless authentication system 200A according to this modification. As shown in Fig. 13, contactless authentication system 200A differs from contactless authentication system 100 according to embodiment 1 in that contactless authentication system 200A includes lighting device 210 instead of lighting device 110. That is, contactless authentication system 200A according to the modification of embodiment 2 includes lighting device 210, imaging device 120, and management device 130.

[0149] The illumination device 210 is a device that can change the irradiation direction of the illumination light 250 that it emits. In addition to the light source 111, the illumination optical system 112, and the optical filter 113 that are the same as those of the illumination device 110, the illumination device 210 further includes an adjustment unit 211 that adjusts the irradiation direction of the illumination light 250 toward the finger F.

[0150] The adjustment unit 211 changes the irradiation direction of the illumination light 250 with respect to the finger F. The adjustment unit 211 has, for example, a mechanism for moving the illumination device 210. As a result, the illumination device 210 moves so as to change the irradiation direction of the illumination light 250 with respect to the finger F. The adjustment unit 211 may also have, for example, a mechanism for moving the illumination optical system 112. As a result, the illumination optical system 112 changes the optical path of the light emitted from the light source 111, thereby changing the irradiation direction of the illumination light 250. The adjustment unit 211 is configured, for example, by a driving device such as an actuator or a motor connected to the housing of the illumination device 210 or the illumination optical system 112. The adjustment unit 211 may also be configured by a movable shaft and support member, a slider, or the like for manually changing the irradiation direction of the illumination light 250.

[0151] In the operation of contactless authentication system 200A, in step S21 of the flowchart shown in FIG. 12, illumination device 210 irradiates finger F with illumination light 250 as first illumination light. In addition, in step S23, illumination device 210 irradiates illumination light 250 so that adjustment unit 211 changes the irradiation direction of illumination light 250 to become second illumination light having an irradiation direction different from that of the first illumination light. Adjustment unit 211 changes the irradiation direction of illumination light 250 based on, for example, control by control unit 131 of management device 130 or an operation by a user. As a result, imaging device 120 captures reflected light 260 and acquires a first fingerprint image and a second fingerprint image. For the other steps, the same operations as those of contactless authentication system 200 are performed.

[0152] (Embodiment 3) Next, a contactless authentication system according to embodiment 3 will be described. In embodiment 3, an example of a contactless authentication system including an illumination device with a modulation illumination function and an imaging device with a sensitivity modulation function will be described. In the following description of embodiment 3, differences from embodiments 1 and 2 will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0153] [1. Contactless authentication system configuration] Fig. 14 is a block diagram showing a schematic configuration of contactless authentication system 300 according to the present embodiment. As shown in Fig. 14, contactless authentication system 300 differs from contactless authentication system 100 according to the first embodiment in that contactless authentication system 300 includes, instead of illumination device 110 and imaging device 120, illumination device 310 that periodically changes the emission intensity of illumination light 350 and imaging device 320 that periodically changes the sensitivity. That is, contactless authentication system 300 includes illumination device 310, imaging device 320, and management device 130. Note that, in this specification, periodically changing the emission intensity or sensitivity may be referred to as modulation.

[0154] The illumination device 310 has a light source 311, an illumination optical system 312, and an optical filter 113. The imaging device 320 has an image sensor 321, an imaging optical system 322, and an optical filter 123. The requirements for the wavelength of illumination light 350 emitted by the illumination device 310 and the wavelength range captured as the main imaging component by the imaging device 320 are basically the same as those for the contactless authentication system 100 according to the first embodiment.

[0155] The illumination device 310 has a function of periodically changing the emission intensity of the illumination light 350 it irradiates. This function may be realized, for example, by using a light-emitting element, such as a laser diode or a light-emitting diode, that has a function of adjusting the light intensity by current control or voltage control, and a power supply that periodically and repeatedly changes the current or voltage, as the light source 311. Alternatively, the light source 311 may be a light source that emits light whose intensity periodically changes over time, such as a pulsed laser. Alternatively, the illumination optical system 312 of the illumination device 310 may include a shutter or a chopping blade that can periodically open and close, thereby periodically changing the emission intensity of the illumination light 350 irradiated toward the finger F, which is the subject. Alternatively, the illumination device 310 may have an acousto-optical element or an electro-optical modulator, and may use these to modulate the intensity of the illumination light 350.

[0156] The illumination device 310 may change the intensity of the illumination light 350 continuously, such as with an offset sine wave, or may change the intensity of the illumination light 350 discretely, such as with a pulse train.

[0157] Since the emission intensity of the illumination light 350 changes periodically, the emission intensity of the reflected light 360 of the illumination light 350 by the finger F also changes periodically.

[0158] The image capture device 320 has a function of periodically changing its sensitivity in response to periodic changes in the illumination light 350 during an exposure period. Here, the exposure period refers to the period from when the image capture element 321 resets the accumulated signal charge and starts accumulating the signal charge until when it starts reading out the signal charge. The period of change in the sensitivity of the image capture device 320 is, for example, the same as the period of change in the emission intensity of the illumination light 350. Note that if the change in the intensity of the illumination light 350 and the change in the sensitivity of the image capture device are both discrete pulses, the period of one may be an integer multiple of the period of the other.

[0159] An example of an imaging device 320 with the function of high-speed sensitivity modulation is an ICCD camera (image intensifier camera). In an ICCD camera, electrons generated when light is incident on the light-receiving surface are multiplied by a multichannel plate, and then collide with a fluorescent screen, and the fluorescence generated there is imaged by the camera. At this time, the sensitivity can be changed periodically by periodically changing the voltage applied to the multichannel plate.

[0160] Examples of the imaging element 321 for realizing the imaging device 320 having the function of modulating sensitivity at high speed include a stacked image sensor and a charge distribution element.

[0161] A stacked image sensor is an imaging element having a structure in which a photoelectric conversion layer is sandwiched between a counter electrode and a pixel electrode, as shown in FIG. 7. In a stacked image sensor, sensitivity depends on the potential difference between the transparent electrode and the pixel electrode, i.e., the bias voltage. By setting the bias voltage below a predetermined threshold, it is possible to make the sensitivity substantially zero. Even if the bias voltage is above the predetermined threshold, the sensitivity varies depending on the bias voltage, for example. Sensitivity modulation in such a stacked image sensor is described in detail, for example, in Patent Document 3 by the present inventor.

[0162] A charge distribution element is an imaging element that has two or more charge collection sections, or one or more charge collection sections and a charge discard section, for the photoelectric conversion area of ​​each pixel. Examples of charge distribution elements include multi-tap CCDs and transfer modulation stacked image sensors.

[0163] Multi-tap CCDs are described in detail in Patent Document 4. Transfer modulation stacked image sensors are described in detail in International Publication No. 2021 / 176876 and Patent Document 5 by the present inventors.

[0164] In the case of a charge distribution element, if a configuration is provided in which two or more charge collection units are provided for one photoelectric conversion region, two fingerprint images can be simultaneously obtained as the result of imaging by modulating two sensitivities with different phases. As will be described later, in this embodiment, ambient light can be effectively eliminated by obtaining both an imaging result obtained by changing the sensitivity so that it is high in a phase in which the intensity of illumination light 350 is high, and an imaging result obtained by changing the sensitivity so that it is high in a phase in which the intensity of illumination light 350 is low. In this way, by using a charge distribution element as image sensor 321, the above two imaging results can be simultaneously obtained, and ambient light can be effectively eliminated.

[0165] Furthermore, the imaging device 320 may periodically change the sensitivity by, for example, including a shutter or chopper in the imaging optical system 322 that physically blocks light incident on the imaging element 321 periodically.

[0166] For example, under the control of the control unit 131, the contactless authentication system 300 switches the relative relationship between the phase of the change in intensity of the illumination light 350 and the phase of the change in sensitivity of the image capture device 320 between two states. More specifically, the contactless authentication system 300 switches between a case where the sensitivity of the image capture device 320 is high in a phase where the emission intensity of the illumination light 350 is high, and a case where the sensitivity of the image capture device 320 is high in a phase where the emission intensity of the illumination light 350 is low.

[0167] FIG. 15 is a diagram illustrating an example of changes in the emission intensity of illumination light 350 and changes in the sensitivity of the imaging device 320. Part (a) of FIG. 15 illustrates an example of changes in the emission intensity of illumination light 350, and parts (b) and (c) of FIG. 15 illustrate Sensitivity Example 1 and Sensitivity Example 2, which are examples of changes in the sensitivity of the imaging device 320, respectively. For example, when the contactless authentication system 300 is irradiated with illumination light 350 shown in part (a) of FIG. 15, the imaging device 320 switches between capturing images with the sensitivity of Sensitivity Example 1 and capturing images with the sensitivity of Sensitivity Example 2. The period during which the sensitivity of the imaging device 320 is high in Sensitivity Example 1 and the period during which the sensitivity of the imaging device 320 is high in Sensitivity Example 2 are the same length. Furthermore, the sensitivity of the imaging device 320 in a phase during which the sensitivity of the imaging device 320 is high in Sensitivity Example 1 is the same as the sensitivity of the imaging device 320 in a phase during which the sensitivity of the imaging device 320 is high in Sensitivity Example 2. In FIG. 15, the period during which the emission intensity of the illumination light 350 is high is shorter than the period during which the sensitivity of the imaging device 320 is high, but the period during which the emission intensity of the illumination light 350 is high may be the same as the period during which the sensitivity of the imaging device 320 is high.

[0168] Such control of the light emission intensity and sensitivity may be realized, for example, by a configuration in which, in addition to the lighting device 310 and the imaging device 320, a periodic signal generator such as a function generator (not shown in Fig. 14) is provided in the contactless authentication system 300, and both the lighting device 310 and the imaging device 320 receive the output from the periodic signal generator. Alternatively, such control of the light emission intensity and sensitivity may be realized by the control unit 131 outputting a periodic signal to the lighting device 310 and the imaging device 320. Alternatively, a circuit or the like having a function of outputting such a periodic signal may be included in the lighting device 310 or the imaging device 320.

[0169] [2. Example of contactless authentication system operation] Next, a description will be given of the operation of contactless authentication system 300 according to this embodiment. Fig. 16 is a flowchart showing an example of the operation of contactless authentication system 300 according to this embodiment.

[0170] 16, first, the illumination device 310 irradiates the finger F with illumination light 350 whose intensity changes periodically (step S31). For example, the illumination device 310 irradiates the finger F with illumination light 350 having the emission intensity shown in part (a) of FIG.

[0171] Next, the imaging device 320 captures reflected light 360 generated by the reflection of illumination light 350 irradiated onto the finger F from the finger F, in a state in which the phase of the change in the emission intensity of the illumination light 350 and the phase of the change in the sensitivity of the imaging device 320 have a first phase relationship (step S32). For example, as shown in parts (a) and (b) of FIG. 15 , the imaging device 320 changes the sensitivity at the same cycle as the change in the emission intensity of the illumination light 350, so that the phase of the change in the emission intensity of the illumination light 350 and the phase of the change in the sensitivity of the imaging device 320 have a phase relationship in which the sensitivity of the imaging device 320 is high when the emission intensity of the illumination light 350 is high. As a result, the imaging device 320 acquires a third fingerprint image, which is the image capture result, as authentication information. The imaging device 320 outputs the acquired third fingerprint image to the management device 130, for example. The extraction unit 132 of the management device 130 acquires the third fingerprint image from the imaging device 320 and records it in the storage unit 135.

[0172] Next, the imaging device 320 captures reflected light 360 generated by the reflection of illumination light 350 irradiated onto the finger F from the finger F, in a state in which the phase of the change in the emission intensity of the illumination light 350 and the phase of the change in the sensitivity of the imaging device 320 have a second phase relationship (step S33). For example, as shown in parts (a) and (c) of FIG. 15 , the imaging device 320 changes the sensitivity at the same cycle as the change in the emission intensity of the illumination light 350, so that the phase of the change in the emission intensity of the illumination light 350 and the phase of the change in the sensitivity of the imaging device 320 have a phase relationship in which the sensitivity of the imaging device 320 is high when the emission intensity of the illumination light 350 is low. As a result, the imaging device 320 acquires a fourth fingerprint image, which is the image capture result, as authentication information. The imaging device 320 outputs the acquired fourth fingerprint image to the management device 130, for example. The extraction unit 132 of the management device 130 acquires the fourth fingerprint image from the imaging device 320 and records it in the storage unit 135.

[0173] Next, extraction unit 132 generates a difference image between the third and fourth fingerprint images stored in storage unit 135 (step S34). Extraction unit 132 generates a difference image, for example, by subtracting the fourth fingerprint image from the third fingerprint image. Specifically, extraction unit 132 generates the difference image by calculating the difference in pixel value of each pixel between the third and fourth fingerprint images, for example.

[0174] Next, the extraction unit 132 extracts feature information to be used for authentication from the generated differential image (step S35). In step S35, the same process as in step S13 above is performed, except that the differential image is used instead of the fingerprint image.

[0175] Next, the authentication unit 133 performs authentication based on the characteristic information extracted by the extraction unit 132 (step S36). In step S36, for example, the same process as in step S14 described above is performed.

[0176] As a result, the third fingerprint image and the fourth fingerprint image contain the effects of not only illumination light 350 but also light other than illumination light 350, such as sunlight and room illumination light, i.e., so-called ambient light. If the period during which image capture device 320 is highly sensitive is the same in step S32 and step S33, the ambient light is contained approximately equally in each of the third fingerprint image and the fourth fingerprint image. Therefore, the ambient light component is subtracted from the differential image between the third fingerprint image and the fourth fingerprint image. Note that even if the periods during which image capture device 320 is highly sensitive are different, the ambient light component can be subtracted by applying a correction coefficient corresponding to the difference in the length of the periods when generating the differential image.

[0177] On the other hand, the third fingerprint image is an imaging result obtained when the sensitivity of the imaging device 320 is high in a phase where the emission intensity of the illumination light 350 is high, and therefore includes more of the reflected light 360 component of the illumination light 350 from the finger F than the fourth fingerprint image. This is because the third fingerprint image is an imaging result obtained when the sensitivity of the imaging device 320 is high in a phase where the emission intensity of the illumination light 350 is high, and the fourth fingerprint image is an imaging result obtained when the sensitivity of the imaging device 320 is high in a phase where the emission intensity of the illumination light 350 is low. As a result, the reflected light 360 component remains in the differential image because the ambient light component is subtracted from the third fingerprint image. Therefore, the differential image includes information derived from the reflected light 360 with the influence of ambient light reduced. As a result, the contrast derived from the fingerprint shape in the differential image is increased, making it easier to extract extracted information and improving authentication accuracy.

[0178] Note that the above operation example is merely an example, and a similar effect can be obtained by capturing a fingerprint image with two phase relationships between illumination light intensity change and sensitivity change that have different amounts of reflected light 360 component included in the fingerprint image. For example, instead of changing the phase of the sensitivity of the image capture device 320, a fingerprint image captured with a different phase relationship may be obtained by changing the phase of the emission intensity of the illumination light 350. Furthermore, the cycle of change in the emission intensity of the illumination light 350 and the cycle of change in the sensitivity of the image capture device 320 do not need to be constant.

[0179] Furthermore, if the image capturing element 321 is a charge distribution element, steps S32 and S33 can be performed simultaneously, which shortens the image capturing time and reduces changes in the ambient light and subject between capturing the two fingerprint images, thereby effectively eliminating the ambient light.

[0180] (Other embodiments) The contactless authentication system according to the present disclosure has been described above based on the embodiments and modifications, but the present disclosure is not limited to these embodiments and modifications.

[0181] For example, the imaging device may capture reflected light with a wavelength range of 1380 nanometers or more as the primary imaging component, and may also capture reflected light with a wavelength range of less than 1380 nanometers as the primary imaging component. In this case, for example, the imaging device may have multiple optical filters with different transmission wavelength ranges, and switch between the multiple optical filters to capture reflected light with different wavelength ranges as the primary imaging component. The imaging device's imaging element may have pixels for capturing light with a wavelength of 1380 nanometers or more and pixels for capturing light with a wavelength of less than 1380 nanometers. The contactless authentication system may also include, as multiple imaging devices, an imaging device that captures reflected light with a wavelength range of 1380 nanometers or more as the primary imaging component, and an imaging device that captures reflected light with a wavelength range of less than 1380 nanometers as the primary imaging component.

[0182] When the subject is an actual finger, the contrast of a fingerprint image obtained by imaging with the wavelength range of 1380 nanometers or more as the main imaging component is higher than the contrast of a fingerprint image obtained by imaging with the wavelength range of less than 1380 nanometers as the main imaging component. This is because, as mentioned above, the ratio of surface reflected light to scattered reflected light originating from intraskin light changes depending on the wavelength due to the spectral absorption characteristics of the tissue that makes up the finger.

[0183] On the other hand, in the case of a fake finger made of resin, a finger image printed on paper, or a finger image displayed on a display, the relationship between the contrast of a fingerprint image captured using wavelengths above 1380 nanometers as the primary imaging component and the contrast of a fingerprint image captured using wavelengths below 1380 nanometers as the primary imaging component may differ from that of a real finger. This is because the spectral absorption characteristics of a fake finger may differ from those of a real finger. For example, because a fake finger has less water absorption than a real finger, the contrast difference between the two fingerprint images of the fake finger is smaller than the contrast difference between the two fingerprint images of a real finger. Therefore, it may be possible to detect a fake finger based on the contrast relationship between fingerprint images captured using two different wavelength ranges as the primary imaging components. For example, in addition to personal authentication, the authentication unit of the management device may acquire the two fingerprint images and compare them to determine whether the subject is a fake finger.

[0184] Furthermore, for example, the lighting device may have a function of irradiating a finger with linear illumination light and sequentially changing the illumination position. Since the density of the illumination light can be increased compared to when the illumination light is irradiated in a planar manner, the imaging device can obtain an image with a high signal-to-noise ratio. Furthermore, when linear light is irradiated onto a three-dimensional finger, the shape of the irradiated area becomes curved. This can be utilized to identify fake fingers displayed on flat printed materials or flat displays. The illumination position can be changed, for example, by a galvanometer mirror.

[0185] Furthermore, for example, in the above-described embodiment and modified examples, the subject is a finger, but the subject may be a palm, or both the finger and the palm may be the subject.

[0186] Furthermore, for example, although the contactless authentication system is realized by a plurality of devices in the above-described embodiment and modified examples, it may be realized by a single device. Furthermore, when the contactless authentication system is realized by a plurality of devices, the components of the contactless authentication system described in the above-described embodiment and modified examples may be distributed among the plurality of devices in any manner.

[0187] Furthermore, the contactless authentication system does not need to include all of the components described in the above embodiments and modifications, and may be configured with only the components required to perform the intended operation.

[0188] Also, for example, the contactless authentication system may be equipped with a communication unit, and the management device may be an external device such as a user's smartphone, a dedicated device brought in by the user, or a cloud server, and authentication may be performed by the contactless authentication system communicating with the external device using the communication unit.

[0189] In the above-described embodiment, the processing performed by a specific processing unit may be performed by another processing unit. The order of multiple processing operations may be changed, or multiple processing operations may be performed in parallel.

[0190] In the above-described embodiments, each component may be realized by executing a software program suitable for that component, or by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0191] Furthermore, each component may be realized by hardware. Each component may be a circuit (or integrated circuit). These circuits may form a single circuit as a whole, or each may be a separate circuit. Furthermore, each of these circuits may be a general-purpose circuit or a dedicated circuit.

[0192] Furthermore, the general or specific aspects of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0193] For example, the present disclosure may be realized as the contactless authentication system of the above-described embodiment, or as a program for causing a computer to execute the authentication method performed by the processing unit, or as a computer-readable non-transitory recording medium on which such a program is recorded.

[0194] In addition, as long as they do not deviate from the gist of this disclosure, various modifications that would occur to those skilled in the art to the embodiments and examples, as well as other forms constructed by combining some of the components in the embodiments and examples, are also included in the scope of this disclosure. [Industrial Applicability]

[0195] The contactless authentication system and authentication method according to the present disclosure can be used for, for example, building entrance control and authentication at airport gates. [Explanation of symbols]

[0196] 100, 200, 200A, 300 Contactless Authentication System 110, 110A, 110B, 210, 310 lighting equipment 111, 311 light source 112, 312 Illumination optical system 113, 123 Optical filters 120, 320 imaging device 121, 321 image sensor 122, 322 Imaging optical system 125 Photoelectric conversion element 126 Photoelectric conversion layer 127 pixel electrode 128 Counter Electrode 130 Management device 131 Control Unit 132 Extraction part 133 Authentication Department 135 Storage section 150, 150A, 150B, 250, 350 illumination light 160, 160A, 160B, 260, 360 reflected light 211 Adjustment section 411 First protrusion 412 Second convex part 413 Third convex part 414 Fourth Convexity 415 Fifth Bump 421 First recess 422 Second recess 423 Third Recess 424 Fourth Recess 1101, 1105 light 1102 Surface reflected light 1103 Inner skin light 1104 Scattered light 1200 Yin F finger

Claims

1. one or more lighting devices that irradiate illumination light containing a light component in a wavelength range of 1380 nanometers or more onto a portion of the hand that is not in contact with an object; an imaging device that captures an image of a light component in the wavelength range in light reflected by the part of the hand when the illumination light is reflected, thereby acquiring at least one of a fingerprint image and a palm print image as authentication information; Contactless authentication system.

2. The authentication information includes information indicating the position of sweat pores. The contactless authentication system according to claim 1 .

3. the imaging device includes a photoelectric conversion layer; The sensitivity of the photoelectric conversion layer has a peak in the wavelength range. The contactless authentication system according to claim 1 or 2.

4. The photoelectric conversion layer contains quantum dots. The contactless authentication system according to claim 3 .

5. The photoelectric conversion layer contains semiconducting carbon nanotubes.

5. The contactless authentication system according to claim 3 or 4.

6. The light component imaged by the imaging device includes wavelengths at which sunlight on the Earth's surface is significantly attenuated. The contactless authentication system according to any one of claims 1 to 5.

7. the imaging device includes an optical filter; The transmittance of the optical filter for light having a wavelength of less than 1380 nanometers is lower than the transmittance of the optical filter for light having a wavelength of 1380 nanometers or more. The contactless authentication system according to any one of claims 1 to 6.

8. the one or more lighting devices periodically change the emission intensity of the illumination light; the imaging device periodically changes the sensitivity of the imaging device in response to a change in the emission intensity of the illumination light; The contactless authentication system according to any one of claims 1 to 7.

9. the one or more lighting devices irradiate the illumination light onto the hand from a first direction and a second direction different from the first direction; the imaging device captures an image of the reflected light caused by the illumination light irradiated onto the hand from the first direction and the reflected light caused by the illumination light irradiated onto the hand from the second direction. The contactless authentication system according to any one of claims 1 to 8.

10. the one or more lighting devices include a first lighting device that irradiates the illumination light onto the hand from the first direction and a second lighting device that irradiates the illumination light onto the hand from the second direction, a timing at which the first lighting device irradiates the hand with the illumination light is different from a timing at which the second lighting device irradiates the hand with the illumination light; The contactless authentication system according to claim 9.

11. the one or more lighting devices include an adjustment unit that changes the direction in which the illumination light is irradiated onto the hand, the one or more lighting devices irradiate the illumination light onto the hand from the first direction and the second direction using the adjustment unit; The contactless authentication system according to claim 9.

12. The light component captured by the imaging device is a light component in the reflected light having a wavelength range of 1380 nanometers or more and less than 2500 nanometers. The contactless authentication system according to any one of claims 1 to 11.

13. irradiating a part of the hand that is not in contact with an object with illumination light that includes a light component in a wavelength range of 1380 nanometers or more; capturing an image of a light component in the wavelength range in reflected light generated by reflecting the illumination light on the part of the hand, thereby obtaining at least one of a fingerprint image and a palm print image as authentication information. Authentication method.

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