Information processing device, information processing method, and recording medium

Abstract

This information processing device 3 comprises: an application means 311 for applying a stimulation including light, image, and / or sound that induces a change in a subject's biological response; and a determining means 312 for determining, on the basis of a correlation between the stimulation and the biological reaction occurring in the patient to whom the stimulation was applied, whether the subject is a living body.

Description

Technical Field

[0007] ,

[0001] This disclosure relates to the technical field of an information processing apparatus, an information processing method, and a recording medium that can determine whether a target is a living body, for example.

Background Art

[0002] An example of an information processing apparatus that can determine whether a target is a living body is described in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] This disclosure aims to provide an information processing apparatus, an information processing method, and a recording medium for improving the technologies described in prior art documents.

Means for Solving the Problems

[0005] One aspect of the information processing apparatus includes an applying means for applying a stimulus including at least one of light, video, and sound that induces a change in the biological reaction of a target, and a determining means for determining whether the target is a living body based on the correlation between the stimulus and the biological reaction that occurs in the target to which the stimulus is applied.

[0006] One aspect of the information processing method includes applying a stimulus including at least one of light, video, and sound that induces a change in the biological reaction of a target, and determining whether the target is a living body based on the correlation between the stimulus and the biological reaction that occurs in the target to which the stimulus is applied.

[0007] One embodiment of a recording medium is a recording medium on which a computer program is recorded that causes a computer to execute an information processing method which includes applying a stimulus including at least one of light, images, and sounds that induces a change in the biological response of a subject, and determining whether or not the subject is a living organism based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram showing the configuration of the information processing device in the first embodiment. [Figure 2] Figure 2 is a block diagram showing the overall configuration of the authentication system in the second embodiment. [Figure 3] Figure 3 is a block diagram showing the configuration of the impersonation detection device in the second embodiment. [Figure 4] Figure 4 is a flowchart showing the flow of the impersonation detection operation performed by the impersonation detection device in the second embodiment. [Figure 5] Figure 5 is a timing chart showing the pupil diameter calculated based on a person image in which a living person (the person being identified) is captured, and the pupil diameter calculated based on a person image in which a non-living simulated object is captured, when a stimulus including light directed towards the eyes of a living person is applied to the living person. [Figure 6] Figure 6 is a plan view showing the characteristic points (in other words, landmarks) of the person being imaged. [Figure 7] Figure 7 is a timing chart showing an example of the correlation between eye size and stimulus. [Figure 8] Figure 8 is a plan view showing an example of an image that indirectly induces the adjustment of the human lens's focus. [Figure 9] Figure 9 is a plan view showing an example of an image that indirectly induces the adjustment of the human lens's focus. [Figure 10]Figure 10(a) is a cross-sectional view showing reflected light emitted from a relatively thin lens, and Figure 10(b) is a cross-sectional view showing reflected light emitted from a relatively thick lens. [Figure 11] Figure 11 is a timing chart showing an example of the correlation between the direction the face is facing, the direction the gaze is directed, and the stimulus. [Modes for carrying out the invention]

[0009] The following describes embodiments of the information processing device, information processing method, and recording medium with reference to the drawings.

[0010] (1) First Embodiment First, a first embodiment of the information processing device, information processing method, and recording medium will be described. Hereinafter, with reference to Figure 1, the information processing device, information processing method, and recording medium of the first embodiment will be described using the information processing device 1000 to which the information processing device, information processing method, and recording medium of the first embodiment are applied. Figure 1 is a block diagram showing the configuration of the information processing device 1000 in the first embodiment.

[0011] The information processing device 1000 is capable of determining whether or not a subject is a living organism. To determine whether or not a subject is a living organism, the information processing device 1000 comprises a stimulus application unit 1001 and a determination unit 1002, as shown in Figure 1. The stimulus application unit 1001 applies a stimulus that induces a biological response in the subject. The stimulus that induces a biological response in the subject may include at least one of light, images, and sound. The determination unit 1002 determines whether or not a subject is a living organism based on the correlation between the stimulus and the biological response that occurs in the subject to which the stimulus was applied.

[0012] The information processing device 1000 of this first embodiment can appropriately determine whether a subject is a living organism, compared to the information processing device of the first comparative example, which determines whether a subject is a living organism without using a correlation between a stimulus and the biological response that occurs in the subject to the stimulus. The details of the reason for this will be explained in the second embodiment.

[0013] (2) Second Embodiment Next, a second embodiment of the information processing apparatus, the information processing method, and the recording medium will be described. Below, the information processing apparatus, the information processing method, and the recording medium in the second embodiment will be described using an authentication system SYS to which the information processing apparatus, the information processing method, and the recording medium in the second embodiment are applied.

[0014] The authentication system SYS authenticates an authenticated person using a person image IMG generated by the camera 1 (see FIG. 2 described later) capturing a person existing in front of the camera 1 (hereinafter referred to as "authenticated person"). Specifically, the authentication system SYS may authenticate the authenticated person by performing a matching process of determining whether the person captured in the person image IMG matches a person (hereinafter referred to as "registered person") previously registered in the authentication system SYS.

[0015] The authentication system SYS may perform biometric authentication of acquiring biometric information of the authenticated person from the person image IMG and authenticating the authenticated person based on the acquired biometric information. For example, when the face of the authenticated person is captured in the person image IMG, the authentication system SYS may perform face authentication of authenticating the authenticated person based on the face of the authenticated person. When the iris of the authenticated person is captured in the person image IMG, the authentication system SYS may perform iris authentication of authenticating the authenticated person based on the iris pattern of the authenticated person. When the fingerprint of the authenticated person is captured in the person image IMG, the authentication system SYS may perform vein authentication of authenticating the authenticated person based on the fingerprint pattern of the authenticated person. When the vein of the authenticated person is captured in the person image IMG, the authentication system SYS may perform vein authentication of authenticating the authenticated person based on the vein pattern of the authenticated person.

[0016] Here, typically, camera 1 captures an image of a person actually present in front of camera 1. In this case, the person captured in the person image IMG (hereinafter referred to as the "person being captured") matches the person to be authenticated who is actually present in front of camera 1. Therefore, the matching process that determines whether the person captured in the person image IMG matches the registered person is equivalent to the matching process that determines whether the person to be authenticated who is present in front of camera 1 matches the registered person. For this reason, if it is determined that the person captured matches the registered person, the authentication system SYS determines that the authentication of the person to be authenticated (i.e., the authentication of the person captured in the person image IMG, hereafter the same) has been successful because the person to be authenticated matches the registered person. On the other hand, if it is determined that the person captured does not match the registered person, the authentication system SYS determines that the authentication of the person to be authenticated has failed because the person to be authenticated does not match the registered person.

[0017] On the one hand, a malicious authenticated person may cause a camera 1 to image a simulated object imitating a registered person different from the authenticated person in order to impersonate a registered person different from the authenticated person. As an example of the simulated object, there is a photograph in which a registered person is captured. As an example of the simulated object, there is a display that displays an image of a registered person. As an example of the simulated object, there is a mask imitating the face of a registered person. As an example of the simulated object, there is a shaped object imitating the vein pattern or fingerprint pattern of a registered person. As an example of the simulated object, there is a robot imitating a registered person. In this case, camera 1 will image the simulated object instead of the authenticated person actually present in front of camera 1. In this case, although there is actually no registered person in front of camera 1, a registered person will be captured as the imaged person in the person image IMG generated by camera 1 (actually, a simulated object imitating the registered person will be captured as the imaged person). As a result, the authentication system SYS may determine, through the collation process, that the imaged person captured in the person image IMG (in this case, the person imitated by the simulated object) matches the registered person. Therefore, the authentication system SYS may erroneously determine that the authentication of the authenticated person has succeeded. Specifically, the authentication system SYS may erroneously determine that the authenticated person actually present in front of camera 1 matches the registered person although there is actually no registered person in front of the camera. In other words, although the authentication system SYS should determine that the authentication of the authenticated person has failed because there is an authenticated person different from the registered person in front of camera 1, the authentication system SYS may erroneously determine that the authentication of the authenticated person has succeeded.

[0018] Therefore, the authentication system SYS, which authenticates the person to be authenticated, is required to prevent a malicious person to be authenticated from impersonating a different registered person. Accordingly, in addition to the authentication operation to authenticate the person to be authenticated, the authentication system SYS performs an impersonation detection operation to determine whether the person to be authenticated is impersonating another person. Specifically, the authentication system SYS performs an impersonation detection operation to determine whether the person to be authenticated in front of camera 1 is impersonating another person by determining whether the person to be captured in the person image IMG is a living being or not (specifically, whether it is a simulated object or not).

[0019] The following describes in detail the configuration and operation of the authentication system SYSa, which performs this impersonation detection operation.

[0020] (2-1) Overall configuration of the authentication system SYS in the second embodiment First, the overall configuration of the authentication system SYS in the second embodiment will be described with reference to Figure 2. Figure 2 is a block diagram showing the overall configuration of the authentication system SYS in the second embodiment.

[0021] As shown in Figure 2, the authentication system SYS comprises a camera 1, an authentication device 2, a spoofing detection device 3 (which may also be called an information processing device), and a stimulus application device 4.

[0022] Camera 1 is capable of capturing an area to be captured. Normally, the area to be captured contains a person to be authenticated who is actually present in front of Camera 1. In this case, Camera 1 captures the person to be authenticated, thereby generating a person image (IMG) in which the person to be authenticated is captured. Alternatively, as described above, if the person to be authenticated is impersonating a registered person using a simulated object that mimics the registered person, the area to be captured contains the simulated object. In this case, Camera 1 captures the simulated object, thereby generating a person image (IMG) in which a registered person different from the person to be authenticated is captured. Camera 1 outputs the generated person image (IMG) to the authentication device 2 and the impersonation detection device 3, respectively.

[0023] Authentication device 2 acquires a person image (IMG) from camera 1. Authentication device 2 uses the acquired person image (IMG) to perform an authentication operation to authenticate the person to be authenticated. In other words, authentication device 2 uses the acquired person image (IMG) to determine whether the person captured in the person image (IMG) is the same as a registered person. If it is determined that the person captured is the same as a registered person, the authentication of the person to be authenticated is determined to have been successful. On the other hand, if it is determined that the person captured is not the same as a registered person, the authentication of the person to be authenticated is determined to have failed.

[0024] Authentication device 2 may acquire biometric information of the person being captured in the person image IMG from the person image IMG and perform biometric authentication to authenticate the person to be authenticated based on the acquired biometric information. In this case, the simulated object described above may be considered to be an object that replicates the biometric information of the registered person. As an example of biometric information, as already mentioned above, at least one of the following can be cited: information about the face, information about the iris pattern, information about the fingerprint pattern, and information about the vein pattern.

[0025] The impersonation detection device 3 acquires a person image (IMG) from camera 1. Using the acquired person image (IMG), the impersonation detection device 3 performs an impersonation detection operation to determine whether the person being authenticated is impersonating another person. Specifically, based on the acquired person image (IMG), the impersonation detection device 3 detects the biological responses of the person being captured in the person image (IMG). In particular, the impersonation detection device 3 detects the biological responses of the person being captured in the person image (IMG) while applying stimuli to the person being captured that induce changes in their biological responses. Subsequently, based on the detected biological responses, the impersonation detection device 3 determines whether the person being authenticated is impersonating another person.

[0026] When camera 1 captures an image of a person to be authenticated who is actually present in front of camera 1, the stimulus applied to the person to induce a change in the biological response of the person captured in the person image (IMG) is applied to the same person to be authenticated. In this case, the biological response of the person to be authenticated should change in a manner that correlates with the applied stimulus, due to the stimulus applied to the person to be authenticated. Therefore, camera 1 will capture an image of the person to be authenticated whose biological response changes in a manner that correlates with the applied stimulus. As a result, the biological response of the person captured in the person image (IMG) also changes in a manner that correlates with the applied stimulus. Therefore, if the biological response of the person captured in the person image (IMG) changes in a manner that correlates with the stimulus, it is assumed that the person captured in the person image (IMG) is the same person to whom the stimulus was applied. In other words, it is assumed that the person captured in the person image (IMG) is a living being and not a simulated object. As a result, it is assumed that the person to be authenticated is not impersonating another person.

[0027] On the other hand, when camera 1 captures an image of a simulated object that mimics a registered person, the stimulus applied to the person captured in the person image (IMG) to induce a change in the subject's biological response is actually applied to a different person being authenticated. Even in this case, the biological response of the authenticated person changes in a manner correlated with the applied stimulus, due to the stimulus applied to the authenticated person. However, camera 1 captures an image of a simulated object whose biological response does not change, rather than an authenticated person whose biological response changes in a manner correlated with the applied stimulus. As a result, it is unlikely that the biological response of the person captured in the person image (IMG) will change in a manner correlated with the applied stimulus. Therefore, if the biological response of the person captured in the person image (IMG) does not change in a manner correlated with the stimulus, it is assumed that the person captured in the person image (IMG) is not the same as the authenticated person to whom the stimulus was applied. In other words, it is assumed that the person captured in the person image (IMG) is a simulated object that is not a living organism. As a result, it is assumed that the person being authenticated is impersonating another person.

[0028] Thus, in the second embodiment, the impersonation detection device 3 applies a stimulus to the person being photographed (actually, the person being authenticated, hereinafter the same) that induces a biological response in the person being photographed in the person image IMG, and determines whether or not the person being photographed in the person image IMG is a living being based on the correlation between the biological response of the person being photographed in the person image IMG and the applied stimulus. If it is determined that the person being photographed in the person image IMG is a living being, the impersonation detection device 3 determines that the person being authenticated is not impersonating another person. If it is determined that the person being photographed in the person image IMG is not a living being, the impersonation detection device 3 determines that the person being authenticated is impersonating another person.

[0029] The impersonation detection device 3 applies a stimulus to the person being imaged using the stimulus application device 4. Therefore, the stimulus application device 4 includes a device capable of generating a stimulus to be applied to the person being imaged.

[0030] For example, the biological responses of living organisms can be altered by light irradiated onto them. Therefore, the stimulation device 4 may irradiate the person being imaged with light to provide a stimulus that induces a biological response in the person being imaged. In this case, the stimulation device 4 may include a light irradiation device capable of irradiating light onto the person being imaged.

[0031] For example, the biological response of a living organism may change as a result of an image displayed to the organism. Therefore, the stimulation device 4 may apply a stimulus to the person being imaged that induces a biological response in the person being imaged by displaying (i.e., outputting) an image to the person being imaged. In this case, the stimulation device 4 may include a display device (i.e., a display) capable of displaying an image to the person being imaged. In the second embodiment, "image" may mean at least one of a moving image and a still image.

[0032] For example, the biological response of a living organism may be altered by sound emitted towards the organism. Therefore, the stimulation device 4 may emit sound towards the person being imaged to provide a stimulus that induces a biological response in the person being imaged. In this case, the stimulation device 4 may include a sound output device (i.e., a speaker) capable of emitting sound towards the person being imaged.

[0033] The authentication system SYS may be used, for example, to manage the entry and exit of authenticated persons to and from a restricted area. Specifically, a restricted area is an area where authenticated persons who meet predetermined entry conditions are permitted to enter, while authenticated persons who do not meet the predetermined entry conditions are not permitted to enter (i.e., are prohibited from entering). In this case, the authentication device 2 may authenticate the authenticated person by determining whether the authenticated person is the same as a registered person who is permitted to enter the restricted area.

[0034] The authentication system SYS may be used, for example, to verify the identity of a person to be authenticated who is conducting a commercial transaction. In this case, the authentication device 2 may authenticate the person to be authenticated by determining whether the person to be authenticated who is about to conduct a commercial transaction with the other party is the same as a registered person who corresponds to the person the other party recognizes as their trading partner.

[0035] The authentication system SYS may be implemented as a single device equipped with a camera 1 and a stimulus device 4, and capable of functioning as both an authentication device 2 and a spoofing detection device 3. For example, the authentication system SYS may be implemented as a smartphone equipped with a camera 1 and a stimulus device 4, and capable of functioning as both an authentication device 2 and a spoofing detection device 3. For example, the authentication system SYS may be implemented as a tablet PC equipped with a camera 1 and a stimulus device 4, and capable of functioning as both an authentication device 2 and a spoofing detection device 3. In this case, the authentication system SYS can be constructed using relatively inexpensive and general-purpose equipment without requiring special equipment for authentication and spoofing detection operations.

[0036] (2-2) Configuration of the impersonation detection device 3 in the second embodiment Next, the configuration of the impersonation detection device 3 of the second embodiment will be described with reference to Figure 3. Figure 3 is a block diagram showing the configuration of the impersonation detection device 3 of the second embodiment.

[0037] As shown in Figure 3, the impersonation detection device 3 comprises an arithmetic unit 31, a storage device 32, and a communication device 33. Furthermore, the impersonation detection device 3 may also include an input device 34 and an output device 35. However, the impersonation detection device 3 does not need to include at least one of the input device 34 and the output device 35. The arithmetic unit 31, the storage device 32, the communication device 33, the input device 34, and the output device 35 may be connected via a data bus 36.

[0038] The arithmetic unit 31 includes, for example, at least one of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and an FPGA (Field Programmable Gate Array). The arithmetic unit 31 reads a computer program. For example, the arithmetic unit 31 may read a computer program stored in the storage device 32. For example, the arithmetic unit 31 may read a computer program stored in a computer-readable and non-temporary recording medium using a recording medium reading device (not shown) provided by the impersonation detection device 3. The arithmetic unit 31 may obtain a computer program from a device (not shown) located outside the impersonation detection device 3 via a communication device 33 (or other communication device) (i.e., it may download or read the program). The arithmetic unit 31 executes the read computer program. As a result, logical functional blocks for performing the operations that the impersonation detection device 3 should perform (for example, the impersonation detection operations described above) are realized within the arithmetic unit 31. In other words, the arithmetic unit 31 can function as a controller for realizing the logical functional blocks necessary to perform the actions (in other words, processes) that the impersonation detection device 3 should perform.

[0039] Figure 3 shows an example of a logical functional block implemented within the computing unit 31 to perform authentication operations. As shown in Figure 3, the computing unit 31 implements a stimulus application control unit 311, which is a specific example of a "application means," and a spoofing determination unit 312, which is a specific example of a "determination means." The stimulus application control unit 311 controls the stimulus application device 4 to apply a stimulus to the person being photographed in the person image IMG that induces a biological response in the person being photographed. The spoofing determination unit 312 determines whether the person being photographed in the person image IMG is a living being or not, based on the correlation between the biological response of the person being photographed in the person image IMG and the applied stimulus.

[0040] The storage device 32 is capable of storing desired data. For example, the storage device 32 may temporarily store a computer program executed by the arithmetic unit 31. The storage device 32 may temporarily store data that the arithmetic unit 31 uses temporarily when it is executing a computer program. The storage device 32 may store data that the impersonation detection device 3 stores long-term. The storage device 32 may include at least one of the following: RAM (Random Access Memory), ROM (Read Only Memory), hard disk drive, magneto-optical disk drive, SSD (Solid State Drive), and disk array device. In other words, the storage device 32 may include a non-temporary recording medium.

[0041] The communication device 33 can communicate with devices outside the impersonation detection device 3. For example, the communication device 33 may be able to communicate with the camera 1 and the stimulation device 4, respectively. In this case, the stimulation control unit 311 may transmit control signals to the stimulation device 4 via the communication device 33 to control the stimulation device 4. The impersonation detection unit 312 may acquire a person image IMG from the camera 1 via the communication device 32.

[0042] The input device 34 is a device that receives information input to the impersonation detection device 3 from outside the impersonation detection device 3. For example, the input device 34 may include an operating device (e.g., at least one of a keyboard, mouse, and touch panel) that can be operated by the operator of the impersonation detection device 3. For example, the input device 34 may include a reading device that can read information recorded as data on a recording medium that can be attached externally to the impersonation detection device 3.

[0043] The output device 35 is a device that outputs information to the outside of the impersonation detection device 3. For example, the output device 35 may output the information as an image. That is, the output device 35 may include a display device (so-called display) capable of displaying an image that shows the information to be output. For example, the output device 35 may output the information as sound. That is, the output device 35 may include an audio device (so-called speaker) capable of outputting sound. For example, the output device 35 may output the information onto paper. That is, the output device 35 may include a printing device (so-called printer) capable of printing the desired information onto paper.

[0044] (2-3) Impersonation detection operation of the second embodiment Next, with reference to Figure 4, the impersonation detection operation performed by the impersonation detection device 3 of the second embodiment will be described. Figure 4 is a flowchart showing the flow of the impersonation detection operation performed by the impersonation detection device 3 in the second embodiment.

[0045] As shown in Figure 4, the stimulus application control unit 311 controls the stimulus application device 4 to apply a stimulus to the person being imaged that induces a biological response of the person captured in the person image IMG (step S11). As a result, the stimulus application device 4 applies a stimulus to the person being imaged that induces a biological response of the person captured in the person image IMG (step S11).

[0046] During the period when stimulation is applied, camera 1 images the target area. Specifically, camera 1 images the target area at a predetermined imaging rate. For example, camera 1 images the target area at an imaging rate that captures the target area a desired number of times per second. As a result, camera 1 generates multiple person images (IMG) corresponding to time-series data. Camera 1 outputs the generated multiple person images (IMG) to the impersonation detection device 3.

[0047] The impersonation detection unit 312 acquires multiple person images (IMG) from camera 1 (step S12). Subsequently, the impersonation detection unit 312 detects the biological response of the person captured in each person image (IMG) based on each person image (IMG) acquired in step S12 (step S13).

[0048] A biological response may be of any kind, as long as it is a response specific to living organisms. A biological response may be of any kind, as long as it is a response that rarely or never occurs in non-living simulated objects. For example, a biological response may include a response that occurs in the eyes of a living organism. An example of a response that occurs in the eyes is at least one of pupil dilation and pupil constriction. Another example of a response that occurs in the eyes is a change in the thickness of the lens (i.e., a change in the focal point of the lens). Another example of a response that occurs in the eyes is a movement of the gaze. Another example of a response that occurs in the eyes is a movement of the eyelids (typically blinking). For example, a biological response may include a response that occurs in the body of a living organism. An example of a response that occurs in the body is a movement of the face of a living organism (e.g., a change in the orientation of the face).

[0049] In step S13, the impersonation detection unit 312 detects a biological response by calculating an index value of the biological response based on the person image IMG. The index value of the biological response typically quantitatively indicates the degree of the biological response. For example, to detect a biological response that includes at least one of pupil dilation and pupil constriction, the impersonation detection unit 312 may calculate an index value indicating the diameter of the pupil. For example, to detect a biological response that includes a change in the thickness of the lens, the impersonation detection unit 312 may calculate an index value indicating the direction of the reflected light emitted from the eye. For example, to detect a biological response that includes movement of the gaze, the impersonation detection unit 312 may calculate an index value indicating the direction of the gaze. For example, to detect a biological response that includes movement of the eyelids, the impersonation detection unit 312 may calculate an index value indicating the distance between the upper and lower eyelids. For example, to detect a biological response that includes movement of the face, the impersonation detection unit 312 may calculate an index value indicating the direction of the face.

[0050] In step S13, the impersonation detection unit 312 may detect a biological response occurring in the part of the person being imaged that was stimulated in step S11. For example, if the eyes of the person being imaged are stimulated, the impersonation detection unit 312 may detect a biological response occurring in the eyes of the person being imaged. Specifically, if the eyes of the person being imaged are stimulated with at least one of light and an image, the impersonation detection unit 312 may detect a biological response occurring in the eyes of the person being imaged. For example, if the ears of the person being imaged are stimulated, the impersonation detection unit 312 may detect a biological response occurring in the ears of the person being imaged. Specifically, for example, if the ears of the person being imaged are stimulated with sound, the impersonation detection unit 312 may detect a biological response occurring in the ears of the person being imaged. In this case, the impersonation detection unit 312 may be considered to be detecting a direct biological response that reflexively causes a reaction in the stimulated area as the stimulus propagates from the receptor to the central nervous system.

[0051] In step S13, the impersonation detection unit 312 may detect a biological response occurring in a different part of the person being imaged than the part of the person being stimulated in step S11. For example, if the person being imaged has an eye stimulus, the impersonation detection unit 312 may detect a biological response occurring in a different part of the person being imaged than the eye. Specifically, if the person being imaged has an eye stimulus that includes at least one of light and an image, the impersonation detection unit 312 may detect a biological response (e.g., facial movement) occurring in a different part of the person being imaged than the eye. For example, if the person being imaged has an ear stimulus, the impersonation detection unit 312 may detect a biological response occurring in a different part of the person being imaged than the ear. Specifically, for example, if the person being imaged has an ear stimulus that includes sound, the impersonation detection unit 312 may detect a biological response (e.g., at least one of eyelid movement, gaze movement, and facial movement) occurring in a different part of the person being imaged than the ear. In this case, the impersonation detection unit 312 may be considered to be detecting an indirect biological response that, after the stimulus has propagated from the receptor to the central nervous system, triggers a reaction in a different site from the site that received the stimulus through a complex process (for example, a process that triggers the recall of some memory due to the stimulus).

[0052] Subsequently, the impersonation detection unit 312 calculates the correlation between the biological response (in particular, the index value of the biological response) detected in step S13 and the stimulus applied in step S11 (step S14). Then, it determines whether the correlation between the biological response (in particular, the index value of the biological response) and the stimulus calculated in step S14 is a correlation specific to the organism (step S15).

[0053] When a biological stimulus is applied to a living organism and a biological response is detected in that organism, the correlation between the stimulus applied to the organism and the biological response is often a biologically specific correlation determined by the type of biological response and the type of stimulus. For example, the time from when a stimulus is applied to a living organism until a biological response occurs as a result of that stimulus is often a biologically specific time determined by the type of biological response and the type of stimulus. For example, the duration during which a biological response occurs in a living organism as a result of a stimulus applied to it is often a biologically specific period determined by the type of biological response and the type of stimulus. For example, the time from when a biological response occurs due to a stimulus applied to a living organism until that biological response begins to decrease is often a biologically specific time determined by the type of biological response and the type of stimulus. For example, the degree (in other words, magnitude) of a biological response that occurs in a living organism as a result of a stimulus applied to it is often a biologically specific degree determined by the type of biological response and the type of stimulus. For example, biological responses that occur in a living organism in response to a stimulus applied to it often change in a manner specific to that organism, depending on the type of biological response and the type of stimulus (for example, becoming larger or smaller).

[0054] For example, when a living organism is subjected to a stimulus including light directed towards its eyes, the organism experiences a biological response in which the pupil constricts so that the amount of light incident on the retinal photoreceptors falls below a tolerable level. Subsequently, when the stimulation including light directed towards the organism's eyes ends, the organism experiences a biological response in which the pupil dilates. Therefore, as shown in Figure 5, the pupil diameter calculated as an indicator value of the biological response from a person image IMG in which the authenticated person is captured as the subject begins to decrease within a certain time (e.g., a few milliseconds to a few seconds or a few minutes) after the stimulus is applied, and converges toward a diameter corresponding to the intensity of the light by decreasing with a time constant corresponding to the intensity of the light directed towards the eyes. Furthermore, the pupil diameter begins to increase within a certain time (e.g., a few milliseconds to a few seconds or a few minutes) after the stimulation ends, and converges toward a diameter corresponding to the intensity of the ambient light by increasing with a time constant corresponding to the intensity of the light directed towards the eyes. Furthermore, the size of the pupil diameter corresponds to the size corresponding to the intensity of the light directed towards the eyes. In other words, there is a biologically specific correlation between biological response and stimulation, as shown in Figure 5. On the other hand, the pupil diameter, calculated as an indicator of biological response based on a person image IMG in which a non-living simulated object is included as the person being imaged, does not change even when stimulation is applied, as shown in Figure 5. In other words, there is no biologically specific correlation between biological response and stimulation, as shown in Figure 5.

[0055] Therefore, if the correlation between the biological response and the stimulus calculated in step S14 is a correlation specific to a living organism, it is highly likely that the person being imaged is a living organism. In other words, it is highly likely that the person being authenticated is a living organism and is appearing in the person image IMG as the person being imaged, and that the person being authenticated is not impersonating another person. On the other hand, if the correlation between the biological response and the stimulus calculated in step S14 is not a correlation specific to a living organism, it is highly likely that the person being imaged is not a living organism. In other words, it is highly likely that a non-living dummy object (i.e., an object that mimics a registered person other than the person being authenticated) is appearing in the person image IMG as the person being imaged, and that the person being authenticated is impersonating another person. Therefore, if it is determined that the correlation between the biological response and the stimulus calculated in step S14 is a correlation specific to a living organism (step S15: Yes), the impersonation detection unit 312 determines that the person being authenticated is a living organism (i.e., the person being authenticated is not impersonating another person). On the other hand, if the correlation between the biological response and the stimulus calculated in step S14 is determined not to be a correlation specific to a living organism (step S15: No), the impersonation detection unit 312 determines that the person being authenticated is not a living organism (i.e., the person being authenticated is impersonating another person).

[0056] Information regarding biological correlations specific to a living organism, determined according to the type of biological response and the type of stimulus (hereinafter referred to as "biological correlation information"), may be pre-calculated using the results of experiments in which stimuli are actually applied to each of a large number of sample individuals and the biological responses that occur in the stimulated sample individuals are actually detected. In this case, the impersonation detection device 3 may pre-store the biological correlation information determined according to the type of biological response and the type of stimulus in the storage device 32. Specifically, the impersonation detection device 3 may pre-store the biological correlation information determined according to the type of stimulus applied in step S11 and the type of biological response detected in step S13 in the storage device 32. For example, if a stimulus including light irradiated towards the eyes of the person being imaged is applied in step S11 and a biological response including dilation and constriction of the pupil of the person being imaged is detected in step S13, the impersonation detection device 3 may pre-store the biological correlation information calculated in advance using the results of experiments in which stimuli including light are actually applied to each of the eyes of a large number of sample individuals and the diameter of the pupils of the stimulated sample individuals is actually detected in the storage device 32. As a result, the impersonation detection unit 312 can appropriately determine whether the correlation between the biological response and the stimulus calculated in step S14 is a correlation unique to the organism, based on the detection result of the biological response in step S13 and the biological correlation information pre-stored in the storage device 32.

[0057] The impersonation detection unit 312 may determine whether the correlation between the biological response and the stimulus calculated in step S14 is a correlation unique to the organism, based on the similarity between the biological correlation information pre-stored in the storage device 32 and the correlation calculated in step S14. For example, if the similarity between the biological correlation information pre-stored in the storage device 32 and the correlation calculated in step S14 is similar enough that the similarity exceeds a predetermined determination threshold, the impersonation detection unit 312 may determine that the correlation calculated in step S14 is a correlation unique to the organism. For example, if the similarity between the biological correlation information pre-stored in the storage device 32 and the correlation calculated in step S14 is not similar enough that the similarity exceeds a predetermined determination threshold, the impersonation detection unit 312 may determine that the correlation calculated in step S14 is not a correlation unique to the organism.

[0058] The impersonation detection unit 312 may estimate a biological response that is presumed to be detected in step S13 when a stimulus is applied in step S11, based on the manner in which the stimulus is applied in step S11 (for example, at least one of the time the stimulus is applied and the degree of the applied stimulus) and biological correlation information pre-stored in the storage device 32. In other words, the impersonation detection unit 312 may estimate a correlation between a biological response and a stimulus that is presumed to be calculated in step S14 when a stimulus is applied in step S11. In this case, the impersonation detection unit 312 may determine whether the correlation between the biological response and the stimulus calculated in step S14 is a correlation unique to the organism, based on the similarity between the correlation between the biological response and the stimulus calculated in step S14 and the estimated correlation between the biological response and the stimulus. For example, if the similarity between the calculated correlation and the estimated correlation is so similar that the similarity exceeds a predetermined determination threshold, the impersonation detection unit 312 may determine that the correlation calculated in step S14 is a correlation unique to the organism. For example, if the spoofing detection unit 312 finds that the calculated correlation and the estimated correlation are not similar enough that the similarity exceeds a predetermined threshold, it may determine that the correlation calculated in step S14 is not a correlation specific to the living organism.

[0059] (2-4) Technical effects of the SYS authentication system As explained above, the authentication system SYS of the second embodiment (in particular, the impersonation detection device 3) actively applies stimuli to the person being photographed (actually, the person being authenticated) that induce a biological response of the person being photographed as captured in the person image IMG, and determines whether the person being authenticated is impersonating another person based on the correlation between the biological response of the person being photographed as captured in the person image IMG and the applied stimuli. Therefore, as described above, in a situation where the person being authenticated is impersonating another person using a simulated object (i.e., a copy of another person's biological information), the authentication system SYS can appropriately determine that the person being authenticated is impersonating another person. In other words, the authentication system SYS can appropriately prevent the person being authenticated from impersonating another person using a simulated object (i.e., a copy of another person's biological information). This is because a simulated object does not respond to actively applied stimuli. In other words, the authentication system SYS can solve the first technical problem: the possibility of misidentifying a person being authenticated who is impersonating another person using a simulated object (i.e., a copy of another person's biometric information).

[0060] Furthermore, there is a second comparative example of an impersonation detection device that instructs the person being imaged to move in a predetermined movement pattern, and if the person being imaged does not perform the specific movement instructed, it determines that the person captured in the person image IMG is not a living being (i.e., the person being authenticated is impersonating someone else). In general, such an impersonation detection device of the second comparative example instructs the person being imaged to move in a movement pattern unrelated to the authentication operation, so a person being authenticated who is trying to impersonate someone else can easily identify the predetermined movement pattern used in the impersonation detection operation. As a result, if the person being authenticated moves a robot, which is an example of a simulated object, in a specific movement pattern, the impersonation detection device of the second comparative example has a second technical problem: it will incorrectly determine that the person being imaged is a living being. On the other hand, the authentication system SYS of the second embodiment (particularly the impersonation detection device 3) determines whether the person being imaged is a living being based on the biological response of the person being imaged to a stimulus. In other words, the authentication system SYS determines whether a person being scanned is a living being based on the unconscious biological responses of the person being scanned, rather than on the person's conscious (in other words, spontaneous) movements. Therefore, the authentication system SYS does not need to instruct the person being scanned to move in a predetermined movement pattern in order to determine whether or not the person being scanned is impersonating another person. That is, the authentication system SYS can perform impersonation detection without the person being scanned being aware that the authentication system SYS is performing impersonation detection. In this case, it is difficult for the person being scanned to move a robot, which is an example of a simulated object, in such a way that its biological responses change in a manner correlated with the applied stimulus. Therefore, in a situation where the person being scanned is impersonating another person using a robot, which is an example of a simulated object, the authentication system SYS can appropriately determine that the person is impersonating another person. In other words, the authentication system SYS can appropriately prevent the person being scanned from impersonating another person using a robot, which is an example of a simulated object.In other words, the SYS authentication system can solve the second technical challenge: the possibility that an authenticated person could impersonate another person by moving a robot in a specific movement pattern.

[0061] Furthermore, the authentication system SYS of the second embodiment (in particular, the impersonation detection device 3) provides the person being imaged with a stimulus including at least one of light, video, and sound. In this case, the authentication system SYS may provide at least one of light, video, and sound to the person being imaged as a performance of the authentication operation (or as a performance of some service). For example, the authentication system SYS may provide at least one of video and sound as a stimulus to explain the authentication operation. As a result, the authentication system SYS can provide a stimulus to the person being imaged in order to perform the impersonation detection operation without the person being authenticated who is trying to impersonate another person knowing about the existence of the stimulus provided to the person being imaged. In other words, the authentication system SYS can perform the impersonation detection operation without making the person being authenticated aware that the authentication system SYS is performing the impersonation detection operation. As a result, it becomes even more difficult for the person being authenticated to move a robot, which is an example of a simulated object, in such a way that its biological response changes in a manner correlated with the stimulus provided. Therefore, in situations where the person being authenticated is impersonating another person using a robot or other simulant object, the authentication system SYS can more appropriately determine that the person being authenticated is impersonating another person. In other words, the authentication system SYS can more appropriately prevent the person being authenticated from impersonating another person using a robot or other simulant object.

[0062] Furthermore, the authentication system SYS can perform impersonation detection without using special equipment for the impersonation detection operation. For example, as mentioned above, one way to reliably prevent a person to be authenticated from impersonating another person using a simulated object (i.e., a copy of another person's biometric information) is to use biometric information that requires special equipment to acquire in order to authenticate the person to be authenticated. An example of such special equipment is a device using magnetic resonance imaging (MRI) that can generate bio-tomographic images, which are an example of biometric information. However, such special equipment would lead to a significant increase in the cost of the authentication system SYS. However, the authentication system SYS can perform impersonation detection by using a generally inexpensive and general-purpose device called camera 1. The authentication system SYS can perform impersonation detection by using a generally inexpensive and general-purpose device, at least one of a light irradiation device, a display, and a speaker, as a stimulation device 4. Therefore, the authentication system SYS can solve the third technical problem of requiring special equipment to prevent a person to be authenticated from impersonating another person.

[0063] Furthermore, the authentication system SYS of the second embodiment (in particular, the impersonation detection device 3) determines whether the person to be authenticated is impersonating another person not only based on the presence or absence of a biological response when a stimulus is applied, but also based on the correlation between the stimulus and the biological response. In other words, the authentication system SYS determines whether the person to be authenticated is impersonating another person by determining whether the biological response changes in a manner that correlates with the applied stimulus. For example, as described above, if a stimulus including light irradiated towards the eyes of the person to be imaged is applied in step S11 and a biological response including dilation and constriction of the pupil of the person to be imaged is detected in step S13, the authentication system SYS determines whether the person to be authenticated is impersonating another person by determining whether the pupil dilated or constricted in a manner that correlates with the applied stimulus, rather than simply determining whether the pupil dilated or constricted. For this reason, the authentication system SYS can determine whether the person to be authenticated is impersonating another person with higher accuracy than the impersonation detection device of the third comparative example, which determines whether the person to be authenticated is impersonating another person without using the correlation between the stimulus and the biological response.

[0064] Furthermore, as described above, the authentication system SYS of the second embodiment (in particular, the impersonation detection device 3) may determine whether the person being authenticated is impersonating another person based on a biological response occurring in a different area of ​​the person being imaged than the area of ​​the person to which the stimulus was applied in step S11. In this case, the authentication system SYS will determine whether the person being authenticated is impersonating another person based on an indirect biological response that, after the stimulus has propagated from the receptor to the central nervous system, causes a response in a different area of ​​the body than the area that received the stimulus through a complex process (for example, a process that triggers the recall of some memory due to the stimulus). In other words, the authentication system SYS can determine whether the person being authenticated is impersonating another person based on a biological response that is difficult to explain in terms of a direct causal relationship with the applied stimulus. Such a biological response that is difficult to explain in terms of a direct causal relationship with the applied stimulus is difficult for a person being authenticated to fake if they are trying to impersonate another person. Therefore, the authentication system SYS can appropriately determine whether the person being authenticated is impersonating another person. In other words, the authentication system SYS can effectively prevent an authenticated person from impersonating another person.

[0065] (2-5) Specific examples of impersonation detection operations Next, we will explain a specific example of the impersonation detection process.

[0066] (2-5-1) First specific example of impersonation detection operation First, let's describe the first specific example of the impersonation detection operation. The first specific example of the impersonation detection operation is an impersonation detection operation in which, in step S11 in Figure 4, a stimulus is applied to the person being imaged that induces eyelid movement, and in step S13 in Figure 4, a biological response including eyelid movement (i.e., blinking) of the person being imaged is detected.

[0067] Stimuli that induce eyelid movement may include stimuli applied directly to the eyeball. Stimuli applied directly to the eyeball may include at least one of stimuli that come into contact with the eyeball and stimuli that blow air onto the eyeball. When such stimuli applied directly to the eyeball are applied to a living organism, humans (i.e., living organisms, hereafter the same) are likely to blink in order to protect their eyes. Therefore, stimuli applied directly to the eyeball can be used as stimuli that induce eyelid movement.

[0068] The stimulus that induces eyelid movement may include light shone into the eye. When light shines into the eye, humans are likely to feel glare and blink. Therefore, light shone into the eye can be used as a stimulus to induce eyelid movement. For similar reasons, the stimulus that induces eyelid movement may include images that humans perceive as glare.

[0069] When a person recognizes an action performed by another living organism (e.g., another human or an animal), that person tends to empathize with that action and synchronize with it. Therefore, stimuli that induce eyelid movement may include images of other living organisms blinking. As a result, a person who recognizes an image of another living organism blinking is likely to blink in empathy with that organism's blinking. For this reason, images of other living organisms blinking can be used as stimuli to induce eyelid movement.

[0070] Individuals experiencing tension may blink as an indirect response to that tension. They may blink more frequently than those who are not experiencing tension. The number of consecutive blinks in a tense individual may be greater than in a non-tension individual. The speed of eyelid movement in a tense individual may be faster than in a non-tension individual. Therefore, stimuli that induce eyelid movement may include stimuli that increase a person's level of tension compared to before the stimulus was applied.

[0071] Stimuli that increase human tension may include images that increase human tension. Examples of images that increase human tension include images of rapidly approaching objects, images of a view seen by a person looking down from a high place, images of sharp objects, images of cars (or motorcycles, etc.) participating in a race, and images of living beings in danger, at least one of these.

[0072] Stimuli that increase human tension may include sounds that increase human tension. Examples of sounds that increase human tension include wind noise (i.e., noise caused by airflow), sounds that change from high to low pitch while decreasing in volume, impact sounds (or sounds with high sharpness values), and at least one of the following: animal screams.

[0073] Stimuli that increase human tension may include tasks that increase human tension. Examples of tasks that increase human tension include tasks that require memory recall (e.g., tasks that require answering a question that requires memory recall within a time limit), tasks that require calculation (e.g., tasks that require completing calculations within a time limit), games (e.g., games in which one competes with others for points), and quizzes (e.g., quizzes in which one competes with others for the number of correct answers). Such tasks can increase human tension more efficiently because they require the person assigned the task to perform an active task. Furthermore, games or quizzes can solve the second technical problem mentioned above because they can be assigned as a performance for authentication actions (or as a performance for some kind of service), as described above. Such tasks may also be assigned as video or audio that explains the content of the task and requests its execution.

[0074] Tasks requiring memory recall may include tasks requiring the recall of confidential information known only to the person performing the task. In this case, the confidential information may be pre-registered with the impersonation detection device 3, and the impersonation detection device 3 may, based on the pre-registered confidential information, assign tasks requiring the recall of confidential information known only to the person performing the task as a stimulus to increase the person's sense of tension. Similarly, tasks requiring calculation may include tasks requiring calculations using confidential information known only to the person performing the task. In this case, the confidential information may be pre-registered with the impersonation detection device 3, and the impersonation detection device 3 may, based on the numbers in the pre-registered confidential information, assign tasks requiring calculations using confidential information known only to the person performing the task (for example, addition using the numbers indicated by the confidential information) as a stimulus to increase the person's sense of tension.

[0075] Furthermore, when such confidential information is used, the authentication device 1 may authenticate the person to be authenticated based on biometric information, and may also require the person to be authenticated to input confidential information and authenticate the person to be authenticated based on the input confidential information. In other words, the authentication device 1 may perform multi-factor authentication.

[0076] A person in a state of tension may blink out of relief when that tension is relieved. Therefore, stimuli that induce eyelid movement may include stimuli that reduce the person's tension compared to before the stimulus was applied. In particular, stimuli that induce eyelid movement may include a first stimulus that increases the person's tension and a second stimulus that is added after the first stimulus is applied and reduces the person's tension. In this case, the impersonation detection device 3 may apply a first stimulus that increases the person's tension (e.g., an image, sound, or task), and then apply a second stimulus that reduces the person's tension.

[0077] Stimuli that relieve human tension may include images that relieve human tension. Examples of images that relieve human tension include images that encourage the viewer to rest, images that include luxury items (e.g., at least one of tea, coffee, and cigarettes), images that include items used for rest (e.g., at least one of a bed and a sofa), and images that include natural scenery (e.g., at least one of the convex parts of the sea, mountains, and grasslands).

[0078] Stimuli that relieve human tension may include sounds that relieve human tension. Examples of sounds that relieve human tension include natural sounds (for example, at least one of the sounds of waves and forests), classical music, and at least one of the sounds of a baby breathing while sleeping.

[0079] When the stimulus application control unit 311 applies a stimulus that induces eyelid movement, the impersonation detection unit 312 detects the subject's biological response, including blinking, as captured in the person image IMG (step S13 in Figure 4). For example, when the subject blinks, the distance between the subject's upper and lower eyelids changes. Therefore, the impersonation detection unit 312 may calculate the distance between the subject's upper and lower eyelids (hereinafter referred to as "eye size") as an index value of the biological response, including blinking. Specifically, the impersonation detection unit 312 may extract feature points (in other words, landmarks) of the subject's upper and lower eyelids based on the person image IMG. An example of the feature points of the subject's upper and lower eyelids is conceptually shown in Figure 6. Figure 6 shows the facial feature points of the person being photographed, including the feature points of the upper and lower eyelids, respectively. Subsequently, the impersonation detection unit 312 may calculate the eye size based on the positions of the feature points of the upper and lower eyelids of the person being photographed. In this way, the impersonation detection unit 312 can detect biological responses, including blinking, relatively easily without using any special equipment.

[0080] Subsequently, the impersonation detection unit 312 calculates the correlation between biological responses, including blinking, and the stimulus (step S14 in Figure 4). For example, the impersonation detection unit 312 calculates the correlation between eye size and the stimulus. Figure 7 shows an example of the correlation between eye size and stimulus calculated by the impersonation detection unit 312 when a stimulus that induces blinking is actually applied to the authenticated person, who is a living organism. As shown in Figure 7, when the person being imaged (i.e., a human) blinks, the eye size of the authenticated person changes, decreasing and then increasing. Therefore, the impersonation detection unit 312 can detect biological responses, including blinking, by calculating the eye size. Figure 7 shows an example where the authenticated person blinks twice within a certain period. The impersonation detection unit 312 determines whether the authenticated person is impersonating another person by determining whether the correlation between blinking and stimulus shown in Figure 7 is a correlation unique to living organisms. For example, the person being authenticated is likely to blink at a biologically specific time determined by the time the stimulus was applied to the authenticated person. For example, the person being authenticated is likely to blink at a biologically specific speed determined by the stimulus applied to the authenticated person. As an example, humans are likely to blink in such a way that the speed at which they close their eyelids is faster than the speed at which they open them, due to biologically specific characteristics. For example, the person being authenticated is likely to blink at a biologically specific frequency determined by the stimulus applied to the authenticated person. For this reason, the impersonation detection unit 312 may use at least one of the following as information indicating the correlation between blinking and the stimulus: information regarding the time the blink occurred, information regarding the speed at which the eyelids move due to blinking, and information regarding the frequency at which blinking occurs, to determine whether the calculated correlation between blinking and the stimulus is a biologically specific correlation. As a result, the impersonation detection unit 312 can appropriately determine whether the authenticated person is impersonating another person.

[0081] (2-5-2) Second specific example of impersonation detection operation First, a second specific example of the impersonation detection operation will be described. The second specific example of the impersonation detection operation is an impersonation detection operation in which, in step S11 in Figure 4, a stimulus is applied to the person being imaged that induces adjustment of the focus of the lens of the person's eye, and in step S13 in Figure 4, a biological response including the adjustment of the focus of the lens of the person being imaged is detected.

[0082] The lens adjusts focus by changing its thickness. Therefore, stimuli that induce lens adjustment may be considered substantially equivalent to stimuli that change the thickness of the lens. Similarly, biological responses that involve lens adjustment may be considered substantially equivalent to biological responses that involve changing the thickness of the lens.

[0083] The focus of the human lens adjusts according to the distance from the person (especially the human eye) to the object the person is looking at. Therefore, stimuli that induce adjustment of the focus of the human lens may include stimuli that cause the person to perceive an object moving back and forth relative to them.

[0084] However, in order to provide a human with a stimulus that causes them to perceive an object moving back and forth, the authentication system SYS would require a special device for moving the object. Furthermore, if the movement of the object is unrelated to the authentication process, a person attempting to impersonate another person could easily identify that the object is moving for the purpose of detecting impersonation. On the other hand, humans perceive the position of an object in three-dimensional space using information about the enlargement or reduction of the object's size caused by its movement in the forward and backward direction relative to the human. Furthermore, humans perceive the position of an object in three-dimensional space using information about the sound emitted by the object. For this reason, a stimulus that induces the adjustment of the human lens's focus may include at least one of the images and sounds that indirectly induce the adjustment of the human lens's focus.

[0085] Images that indirectly induce the adjustment of the lens of the human eye may include images that indirectly induce the adjustment of the lens of the eye by inducing an illusion of stereoscopic vision. As an example of an image that indirectly induces the adjustment of the lens of the eye by inducing an illusion of stereoscopic vision, as shown in Figure 8, an image showing an object that gradually enlarges (or gradually shrinks) so that a person can perceive it as an object moving back and forth. In this case, the person experiences the illusion that the object is gradually approaching or gradually moving away from the person, and thus the focus of the human lens of the eye is adjusted. Another example of an image that indirectly induces the adjustment of the lens of the eye by inducing an illusion of stereoscopic vision may include images showing an object that becomes out of focus after being enlarged (or reduced), as shown in Figure 9. In other words, another example of an image that indirectly induces the adjustment of the lens of the eye by inducing an illusion of stereoscopic vision may include images showing an object that becomes out of focus while being enlarged (or reduced). An example of an out-of-focus object is a blurred or smudged object. In this case, the human eye experiences the illusion that its focus is not properly adjusted, which in turn causes the lens of the human eye to adjust its focus.

[0086] Sounds that indirectly induce the adjustment of the human lens's focus may include sounds that induce an illusion of stereoscopic vision, thereby indirectly inducing the adjustment of the lens's focus. An example of a sound that induces an illusion of stereoscopic vision, thereby indirectly inducing the adjustment of the lens's focus, is the sound of an object gradually approaching or gradually moving away from a person. In this case, the person experiences the illusion that the object is gradually approaching or gradually moving away from them, which causes the focus of their lens to adjust.

[0087] Sounds that indirectly induce the adjustment of the human lens's focus may be added along with images that indirectly induce the adjustment of the human lens's focus. In this case, the human lens's focus will be adjusted more easily because the person is more likely to experience the illusion that the object is gradually approaching or gradually moving away from them. In this case, at least one of the following may be used as the sound that indirectly induces the adjustment of the human lens's focus: a sound with increased volume, a sound with increased pitch, a sound with increased sharpness, and a sound with increased roughness.

[0088] When the stimulus application control unit 311 applies a stimulus that induces adjustment of the lens focus, the impersonation detection unit 312 detects a biological response, including the response of adjusting the lens focus of the person captured in the person image IMG (step S13 in Figure 4). However, directly detecting the response of adjusting the lens focus based on the person image IMG is not always easy. Specifically, as mentioned above, the response of adjusting the lens focus is equivalent to the response of changing the thickness of the lens, so directly detecting the thickness of the lens itself based on the person image IMG is not always easy. Therefore, the impersonation detection unit 312 may calculate an index value that indirectly indicates the response of adjusting the lens focus based on the person image IMG.

[0089] For example, when the focus of the lens is adjusted (i.e., the thickness of the lens changes), the direction of emission of reflected light (i.e., reflected light of the incident light) emitted from the lens into which the incident light was incident changes. For example, Figure 10(a) is a cross-sectional view showing reflected light 606 and 607 emitted from a relatively thin lens 604, and Figure 10(b) is a cross-sectional view showing reflected light 606 and 607 emitted from a relatively thick lens 604. As shown in Figures 10(a) and 10(b), incident light 605 incident on the lens 606 is reflected from the front and back surfaces of the lens 604, respectively. As a result, reflected light 606 reflected from the front surface of the lens 604 and reflected light 607 reflected from the back surface of the lens 604 are emitted. When a person looks at a nearby object, the lens 604 is thicker compared to when a person looks at a distant object. Therefore, Figure 10(a), in which the lens 604 is relatively thin, shows the lens 604 of a human looking at a distant object, and Figure 10(b), in which the lens 604 is relatively thick, shows the lens 604 of a human looking at a nearby object. As shown in Figures 10(a) and 10(b), when the thickness of the lens 604 changes, the direction of emission of reflected light 606 and 607 changes. This is because when the thickness of the lens 604 changes, the radius of curvature of the front and back surfaces of the lens 604 changes. For this reason, the direction of emission of reflected light 606 and 607 from the lens 604 can be used as an indicator value that indirectly shows the lens's response to adjust its focus. Therefore, the impersonation detection unit 312 may calculate the direction of emission of at least one of the reflected light 606 and 607 from the lens 604 based on the person image IMG.

[0090] To calculate the direction of emission of reflected light from the crystalline lens, the authentication system SYS may introduce incident light from a point light source (or an image simulating a point light source) onto the crystalline lens. In this case, the image formed by the reflected light from the crystalline lens is called a Purkinje-Sanson mirror image. In particular, the image formed by the reflected light from the surface of the crystalline lens is called the Purkinje-Sanson mirror image P3, and the image formed by the reflected light from the back surface of the crystalline lens is called the Purkinje-Sanson mirror image P4. Therefore, the impersonation detection unit 312 may detect the Purkinje-Sanson mirror images P3 and P4 based on the person image IMG, and calculate the direction of emission of reflected light from the crystalline lens based on the positions of the detected Purkinje-Sanson mirror images P3 and P4.

[0091] The impersonation detection unit 312 may calculate the angle between an axis extending along the propagation direction of reflected light from the crystalline lens and a predetermined reference axis as the direction of emission of reflected light from the crystalline lens. In other words, the impersonation detection unit 312 may calculate the rotation angle of an axis extending along the propagation direction of reflected light from the crystalline lens, with a predetermined reference axis as the reference, as the direction of emission of reflected light from the crystalline lens. This angle may be called the emission angle.

[0092] Furthermore, the reflected light from the crystalline lens is extremely low in intensity. For this reason, in order to facilitate the detection of the reflected light from the crystalline lens (for example, the detection of Purkinje-Sanson mirror images P3 and P4), flashing or changing brightness incident light (i.e., modulated incident light) may be incident on the crystalline lens. In this case, the spoofing detection unit 312 may detect the reflected light from the crystalline lens by extracting an image component synchronized with the modulation, similar to a lock-in amplifier or heterodyne detection.

[0093] Furthermore, incident light entering the lens is also reflected by both the front and back surfaces of the cornea. In this case, the image formed by the reflected light from the front surface of the cornea is called the Purkinje-Sanson mirror image P1, and the image formed by the reflected light from the back surface of the cornea is called the Purkinje-Sanson mirror image P2. In this case, the impersonation detection unit 312 may calculate the Purkinje-Sanson mirror images P1 and P2 based on the person image IMG, and calculate the direction of emission of reflected light from the lens based on the calculated positions of the Purkinje-Sanson mirror images P1 and P2. However, unlike the lens, the cornea hardly reacts to stimuli (for example, it does not deform). Moreover, because the cornea can be easily replicated by artificial eyes, a malicious person being identified can easily impersonate another person by using a simulated object (for example, an artificial eye) that mimics the cornea of ​​another person. Therefore, the impersonation detection unit 312 does not need to use the direction of emission of reflected light from the cornea to determine whether the person being authenticated is impersonating another person. In other words, the impersonation detection unit 312 does not need to calculate the direction of emission of reflected light from the cornea to determine whether the person being authenticated is impersonating another person.

[0094] Subsequently, the impersonation detection unit 312 calculates the correlation between the direction of emission of reflected light from the lens (i.e., an index value of the response that adjusts the focus of the lens) and the stimulus (step S14 in Figure 4). The impersonation detection unit 312 determines whether the person being authenticated is impersonating another person by determining whether the calculated correlation between the direction of emission of reflected light and the stimulus is a correlation unique to the living organism. As a result, the impersonation detection unit 312 can appropriately determine whether the person being authenticated is impersonating another person.

[0095] (2-5-3) Third specific example of impersonation detection operation Next, a third specific example of the impersonation detection operation will be described. The third specific example of the impersonation detection operation is an impersonation detection operation in which, in step S11 in Figure 4, stimuli are applied to the person being imaged that induce movement of the person's face and gaze, and in step S13 in Figure 4, biological responses including movement of the person's face and gaze are detected.

[0096] Humans typically move their faces and eyes with conscious intent. However, a person's face and eyes can also be moved unconsciously by external stimuli. For example, a person's face and eyes can be moved unconsciously in response to light. For example, a person's face and eyes can be moved unconsciously in response to an explosion or a scream. Therefore, stimuli that induce facial and eye movements may include stimuli that induce facial and eye movements without the person being aware of it. However, stimuli that induce facial and eye movements may also include stimuli that consciously induce facial and eye movements in the person.

[0097] The stimuli that induce facial and gaze movements may include light shone upon a person from a predetermined direction. In this case, the person is likely to move their face and gaze to face the predetermined direction as a result of the light shone upon them from that predetermined direction. In other words, the person is likely to estimate the direction from which the light shone through stereoscopic vision and move their face and gaze to face the estimated direction. For this reason, light shone upon a person from a predetermined direction can be used as a stimulus to induce facial and gaze movements.

[0098] The stimuli that induce facial and gaze movements may include images displayed to a person from a predetermined direction. In this case, the person is likely to move their face and gaze to face the predetermined direction as a result of the images displayed to them from that predetermined direction. In other words, the person is likely to estimate the direction from which the image was displayed using stereoscopic vision and move their face and gaze to face the estimated direction. For this reason, images displayed to a person from a predetermined direction can be used as stimuli that induce facial and gaze movements.

[0099] An image displayed to a person from a predetermined direction may include images that cause the person who notices the image to face a specific direction without explicitly indicating which direction they should face. For example, an image displayed to a person from a predetermined direction may include an image containing the message, "Please look this way." In this case, it becomes even more difficult for a robot, which is an example of a simulated object, to move its face and gaze in a manner that correlates with the displayed image. Therefore, the impersonation detection device 3 can more effectively prevent the authenticated person from impersonating another person using a robot, which is an example of a simulated object.

[0100] The stimuli that induce facial and gaze movements may include sounds emitted from a predetermined direction towards a person. In this case, a person is likely to move their face and gaze to face a predetermined direction as a result of the sound directed at them from that direction. In other words, a person is likely to estimate the direction from which the sound was emitted using spatial sound and move their face and gaze to face that estimated direction. For this reason, sounds emitted from a predetermined direction towards a person can be used as stimuli that induce facial and gaze movements.

[0101] Sounds emitted from a predetermined direction toward a person may include sounds that cause the person to face a specific direction without explicitly indicating which direction they should face. For example, sounds emitted from a predetermined direction toward a person may include sounds equivalent to the instruction, "Please look this way." In this case, it becomes even more difficult for a robot, which is an example of a simulated object, to move its face and gaze in a manner that correlates with the emitted sound. Therefore, the impersonation detection device 3 can more effectively prevent the authenticated person from impersonating another person using a robot, which is an example of a simulated object.

[0102] The predetermined direction from which light, which is a stimulus that induces facial and gaze movements, is emitted may be the direction in which camera 1 is located from the perspective of the person being captured by camera 1. In this case, the light may be emitted from the direction in which camera 1 is located as a stimulus that induces facial and gaze movements. Similarly, the predetermined direction in which an image, which is a stimulus that induces facial and gaze movements, is displayed may be the direction in which camera 1 is located from the perspective of the person being captured by camera 1. In this case, the image may be displayed from the direction in which camera 1 is located as a stimulus that induces facial and gaze movements. Similarly, the predetermined direction in which sound, which is a stimulus that induces facial and gaze movements, is output may be the direction in which camera 1 is located from the perspective of the person being captured by camera 1. In this case, the sound may be output from the direction in which camera 1 is located as a stimulus that induces facial and gaze movements. In this case, the person being captured is typically likely to move their face and gaze to face the direction in which camera 1 is located. Here, since camera 1 captures an image of the person to be authenticated in order to perform the authentication operation, it is natural for the person to move their face and gaze so that they face the direction of camera 1 during the authentication operation. Therefore, the impersonation detection device 3 can perform the impersonation detection operation without the person to be authenticated being aware that the impersonation detection device 3 is performing the impersonation detection operation. Furthermore, because the impersonation detection device 3 can enable the person to move their face and gaze so that they face the direction of camera 1, camera 1 can properly capture an image of the person to be authenticated during the authentication operation.

[0103] When the stimulus application control unit 311 applies a stimulus that induces facial and gaze movements, the impersonation detection unit 312 detects the biological response, including the facial and gaze movements of the person being photographed in the person image IMG (step S13 in Figure 4). For example, when the face of the person being photographed moves, the direction the face of the person being photographed is facing changes. Similarly, for example, when the gaze of the person being photographed moves, the direction the gaze of the person being photographed is facing changes. Therefore, the impersonation detection unit 312 may calculate (i.e., detect) the direction the face of the person being photographed is facing and the direction the gaze of the person being photographed is facing. In this case, for example, the impersonation detection unit 312 may calculate the direction the face of the person being photographed is facing using an existing method for calculating the direction a human face is facing. As an example, the impersonation detection unit 312 may extract feature points (in other words, landmarks) of the face of the person being photographed based on the person image IMG, and calculate the orientation of the face based on the extracted feature points. Similarly, for example, the impersonation detection unit 312 may calculate the direction in which the subject's gaze is directed using an existing method for calculating the direction in which a person's gaze is directed. As an example, the impersonation detection unit 312 may extract feature points (in other words, landmarks) of the subject's eyes based on the person image IMG, and calculate the direction of the gaze based on the extracted feature points. In this way, the impersonation detection unit 312 can relatively easily detect biological responses, including facial and gaze movements, without using any special equipment.

[0104] The impersonation detection unit 312 may calculate the angle (view angle) between the line of sight axis extending along the direction in which the human's gaze is directed and a predetermined reference axis, as the direction in which the human's gaze is directed. In other words, the impersonation detection unit 312 may calculate the rotation angle (view angle) of the line of sight axis with respect to a predetermined reference axis, as the direction in which the human's gaze is directed. For example, the impersonation detection unit 312 may calculate the rotation angle of the line of sight axis in the pan direction, which is the direction of rotation around the vertical axis. For example, the impersonation detection unit 312 may calculate the rotation angle of the line of sight axis in the roll direction, which is the direction of rotation around an axis extending along the front-to-back direction of the human. For example, the impersonation detection unit 312 may calculate the rotation angle of the line of sight axis in the tilt direction, which is the direction of rotation around an axis extending along the left-to-right direction of the human.

[0105] The impersonation detection unit 312 may calculate the angle (face angle) between the face axis extending along the direction the human face is facing and a predetermined reference axis, as the direction the human face is facing. In other words, the impersonation detection unit 312 may calculate the rotation angle of the face axis with respect to a predetermined reference axis, as the direction the human face is facing. For example, the impersonation detection unit 312 may calculate the rotation angle of the face axis in the pan direction, which is the direction of rotation around the vertical axis. For example, the impersonation detection unit 312 may calculate the rotation angle of the face axis in the roll direction, which is the direction of rotation around an axis extending along the front-to-back direction of the human. For example, the impersonation detection unit 312 may calculate the rotation angle of the face axis in the tilt direction, which is the direction of rotation around an axis extending along the left-to-right direction of the human.

[0106] Subsequently, the impersonation detection unit 312 calculates the correlation between the biological response, including facial and eye movements, and the stimulus (step S14 in Figure 4). For example, the impersonation detection unit 312 calculates the correlation between the direction the face is facing and the direction the gaze is directed and the stimulus. Figure 11 shows an example of the correlation between the direction the face is facing (face angle) and the direction the gaze is directed (gaze angle) and the stimulus calculated by the impersonation detection unit 312 when a stimulus that induces facial and eye movements is actually applied to the person being authenticated, who is a living organism. As shown in Figure 11, when the person being imaged who has been stimulated moves their face, the face angle of the person being authenticated changes. Similarly, when the person being imaged who has been stimulated moves their gaze, the gaze angle of the person being authenticated changes. The impersonation detection unit 312 determines whether the person being authenticated is impersonating another person by determining whether the correlation between the direction the face is facing and the direction the gaze is directed and the stimulus, as shown in Figure 11, is a correlation unique to a living organism. As a result, the impersonation detection unit 312 can appropriately determine whether or not the authenticated person is impersonating another person.

[0107] As can be seen from Figure 11, when a person under authentication attempts to impersonate another person using a robot, which is an example of a simulated object, the person under authentication needs to change the robot's face angle and its gaze angle in the pan, tilt, and roll directions, respectively, in sync with each other in response to the applied stimulus. However, it is extremely difficult for the person under authentication to control the robot to mimic all three gaze angles and three face angles. For this reason, the impersonation detection device 3 can more effectively prevent the person under authentication from impersonating another person using a robot, which is an example of a simulated object.

[0108] (2-6) Variations In the above description, the authentication system SYS comprises the authentication device 1 and the impersonation detection device 3 as separate devices. However, the authentication system SYS may also comprise a single device that functions as both the authentication device 1 and the impersonation detection device 3. In other words, the authentication device 1 and the impersonation detection device 3 may be integrated into a single unit.

[0109] (3) Note The following additional information is disclosed regarding the embodiments described above. [Note 1] A means for providing a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, A determination means for determining whether or not the subject is a living organism, based on the correlation between the stimulus and the biological response that occurs in the subject to which the stimulus is applied. An information processing device equipped with the following features. [Note 2] The aforementioned means applies the stimulus to the first part of the subject, The correlation includes the correlation between the stimulus and the biological response occurring in a second site of the subject that is different from the first site to which the stimulus was applied. The information processing device described in Appendix 1. [Note 3] The aforementioned biological response includes blinking. The information processing device described in Appendix 1 or 2. [Note 4] The aforementioned stimulus application means applies the stimulus by outputting an image of a living organism blinking toward the subject, The correlation includes a correlation between the stimulus and at least one of the time at which the blink occurred and the frequency at which the blink occurred. The information processing device described in Appendix 3. [Note 5] The aforementioned means provides the stimulus by outputting at least one of the video and sound that increases the subject's sense of tension toward the subject. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. The information processing device described in Appendix 3 or 4. [Note 6] The aforementioned means provides the stimulus by outputting to the subject at least one of an image and sound that increases the subject's tension and at least one of an image and sound that reduces the subject's tension. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. An information processing device as described in any one of the items 3 to 5 of the appendix. [Note 7] The aforementioned means provides the stimulus by outputting a task that increases the subject's tension and by encouraging the subject to rest to alleviate their tension. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. An information processing device as described in any one of the items 3 to 6 of the appendix. [Note 8] The aforementioned biological response includes a response that adjusts the focus of the subject's lens, The correlation includes the correlation between the stimulus and the direction of emission of reflected light from at least one of the front and back surfaces of the lens, to which light from a point light source or an image simulating a point light source is incident. Information processing devices as described in Appendix 1 to 7. [Note 9] The providing means provides the stimulus by outputting an image to the subject showing at least one object that is gradually enlarged or gradually reduced. The information processing device described in Appendix 8. [Note 10] The aforementioned stimulus is provided by outputting an image to the subject showing an object that becomes out of focus after being enlarged or reduced. The information processing device described in Appendix 8 or 9. [Note 11] The aforementioned biological response includes the movement of the subject's face and the movement of the subject's gaze. Information processing devices as described in Appendix 1 to 10. [Note 12] The providing means provides the stimulus by irradiating the target with light from a predetermined direction, outputting an image to the target from a predetermined direction, and / or outputting sound to the target from a predetermined direction. The information processing device described in Appendix 11. [Note 13] The system further includes an authentication means for authenticating a subject using an image generated by the imaging device capturing the subject, The predetermined direction is the direction in which the imaging device is located, as viewed from the perspective of the subject. The information processing device described in Appendix 11 or 12. [Note 14] The subject is given a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, Based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus, it is determined whether or not the subject is a living organism. Information processing methods including [Note 15] On the computer, The subject is given a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, Based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus, it is determined whether or not the subject is a living organism. A recording medium on which a computer program is stored that causes an information processing method including [specific information processing method] to be executed.

[0110] At least some of the constituent elements of each embodiment described above can be appropriately combined with at least some other constituent elements of each embodiment described above. Some of the constituent elements of each embodiment described above may not be used. Furthermore, to the extent permitted by law, all of the disclosures of the documents cited above in this disclosure (e.g., published gazettes) shall be incorporated as part of the description of this disclosure.

[0111] This disclosure may be modified as appropriate, insofar as it does not contradict the technical idea that can be inferred from the claims and the entire specification. Information processing devices, information processing methods and recording media that include such modifications are also included in the technical idea of ​​this disclosure. [Explanation of symbols]

[0112] 1 Camera 2 Authentication device 3. Impersonation detection device 31 Arithmetic unit 311 Stimulation Control Unit 312 Impersonation detection unit 1000 Information Processing Devices 1001 Assignment section 1002 Judgment section SYS Authentication Device IMG People Images

Claims

1. A means for providing a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, Based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus , a determination means for determining whether the subject is a living organism Equipped with, The aforementioned biological response includes a response that adjusts the focus of the subject's lens, The correlation includes the correlation between the stimulus and the direction of emission of reflected light from at least one of the front and back surfaces of the crystalline lens into which light from a point light source or an image simulating a point light source is incident. The light incident on the crystalline lens is modulated, and the reflected light from at least one of the front and back surfaces of the crystalline lens is detected by extracting an image component synchronized with the modulation. Information processing device.

2. The aforementioned means applies the stimulus to the first part of the subject, The correlation includes the correlation between the stimulus and the biological response occurring in a second body part of the subject that is different from the first body part to which the stimulus was applied. The information processing apparatus according to claim 1.

3. The aforementioned biological response includes blinking. The information processing apparatus according to claim 1 or 2.

4. The aforementioned means outputs an image of a living being blinking toward the subject. , apply the aforementioned stimulus, The correlation includes a correlation between the stimulus and at least one of the time at which the blink occurred and the frequency at which the blink occurred. The information processing apparatus according to claim 3.

5. The aforementioned means provides the stimulus by outputting at least one of the video and sound that increases the subject's sense of tension toward the subject. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. The information processing apparatus according to claim 3 or 4.

6. The aforementioned means provides the stimulus by outputting to the subject at least one of an image and sound that increases the subject's tension and at least one of an image and sound that reduces the subject's tension. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. The information processing apparatus according to any one of claims 3 to 5.

7. The aforementioned means provides the stimulus by outputting a task that increases the subject's tension and by encouraging the subject to rest to alleviate their tension. The correlation includes the correlation between the stimulus and at least one of the time at which the blink occurred, the speed at which the eyelid moved due to the blink, and the frequency at which the blink occurred. The information processing apparatus according to any one of claims 3 to 6.

8. The subject is given a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, Based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus , determining whether the subject is a living organism Includes, The aforementioned biological response includes a response that adjusts the focus of the subject's lens, The correlation includes the correlation between the stimulus and the direction of emission of reflected light from at least one of the front and back surfaces of the crystalline lens into which light from a point light source or an image simulating a point light source is incident. The light incident on the crystalline lens is modulated, and the reflected light from at least one of the front and back surfaces of the crystalline lens is detected by extracting an image component synchronized with the modulation. The information processing method performed by computers.

9. On the computer, The subject is given a stimulus that includes at least one of light, images, and sounds that induces a change in the subject's biological response, Based on the correlation between the stimulus and the biological response that occurs in the subject to the stimulus , determining whether the subject is a living organism Includes, The aforementioned biological response includes a response that adjusts the focus of the subject's lens, The correlation includes the correlation between the stimulus and the direction of emission of reflected light from at least one of the front and back surfaces of the crystalline lens into which light from a point light source or an image simulating a point light source is incident. The light incident on the crystalline lens is modulated, and the reflected light from at least one of the front and back surfaces of the crystalline lens is detected by extracting an image component synchronized with the modulation. A computer program that executes information processing methods.

Images