Biological detection device, control method, and program

Abstract

To provide a living-body detection device, a control method, and a program for preventing impersonation using a 3D mask, or the like.SOLUTION: A living-body detection apparatus 2000 controls a display screen 30 to be displayed on a display device 20 of a terminal 60, acquires captured images 40-1, 40-2 generated by imaging a target while the display screen is displayed, and determines whether the target is a living body or not, using the captured images. The display screen 30 includes a plurality of regions 32 having different displays. The control is performed to change the contrast for display in the regions in accordance with the intensity of ambient light of the display device 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to biological detection using images.

Background Art

[0002] Techniques for performing biological detection using a camera have been developed. Biological detection as used herein means determining whether an object imaged by a camera is a living body. For example, biological detection is used for preventing forgery using a photograph.

[0003] As a prior art document related to biological detection using a camera, for example, there is Patent Document 1. The system of Patent Document 1 discloses a technique of controlling an illumination lamp to change the illumination environment, acquiring images of a person taken in different illumination environments respectively, and using these images to determine whether the imaged object is a person.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This disclosure aims to improve the technique disclosed in Patent Document 1.

Means for Solving the Problems

[0006] The biological detection device disclosed herein includes a display control unit that controls a display screen to be displayed on a display device, an acquisition unit that acquires a captured image generated by capturing an object while the display screen is being displayed, and a biological detection unit that determines whether the object is a living body using the captured image. The display screen has a plurality of regions with different displays. The display control unit changes the contrast of the displays in the plurality of regions according to the intensity of ambient light around the display device.

[0007] The program disclosed herein causes a computer to execute a display control step of causing a display device to display a display screen including a plurality of regions with different displays, an acquisition step of acquiring a captured image generated by capturing an object while the display screen is being displayed, a biological detection step of determining whether the object is a living body using the captured image, and a step of changing the contrast of the displays in the plurality of regions according to the intensity of ambient light around the display device.

[0008] The control method disclosed herein is executed by a computer. The control method includes a display control step of causing a display device to display a display screen including a plurality of regions with different displays, an acquisition step of acquiring a captured image generated by capturing an object while the display screen is being displayed, a biological detection step of determining whether the object is a living body using the captured image, and a step of changing the contrast of the displays in the plurality of regions according to the intensity of ambient light around the display device.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted as necessary for clarity of explanation. In the drawings, fillings with colors other than white are represented using patterns such as dot patterns unless otherwise specified. Also, various predetermined values (such as threshold values) are assumed to be stored in a storage device in advance unless otherwise specified.

[0011] [Embodiment 1] [Overview] FIG. 1 is a diagram illustrating an overview of the operation of the biological detection device 2000 according to Embodiment 1. Here, FIG. 1 is a diagram for facilitating understanding of the overview of the biological detection device 2000, and the operation of the biological detection device 2000 is not limited to that shown in FIG. 1.

[0012] The living body detection device 2000 determines whether the target object 50 imaged by the camera 10 is a living body (i.e., living body detection). For example, the living body detection device 2000 discriminates between a case where the target object 50 is a real person and a case where the target object 50 is other than a living body such as a photograph of a person (i.e., a case where a photograph of a person or the like is imaged instead of a real person). However, the target of living body detection is not limited to humans, and may be other animals such as dogs and snakes, or inanimate objects such as robots. In the following disclosure, a case where a person is the target of living body detection is exemplified, but the same method can also be applied to cases where other animals or inanimate objects such as robots are the targets of living body detection.

[0013] For this purpose, the living body detection device 2000 controls the output of the screen by the display device 20. For example, the display device 20 is provided in a terminal 60 (such as a smartphone) used by the user. Specifically, the living body detection device 2000 causes the display device 20 to display a plurality of screens 30 at different timings. For example, in the example of FIG. 1, after the living body detection device 2000 causes the screen 30-1 to be displayed on the display device 20, the screen displayed on the display device 20 is changed from the screen 30-1 to the screen 30-2.

[0014] Here, at least one screen 30 has a plurality of regions 32. Among the plurality of regions 32, there are at least two regions 32 with different displays. For example, the screen 30-1 in FIG. 1 has a region 32-1 filled with white and a region 32-2 filled with black. For the sake of illustration, black is represented by a dot pattern.

[0015] For each of at least two screens 30, the camera 10 captures the target object 50 while the screen 30 is being displayed on the display device 20, and generates a captured image 40 representing the result. For example, in FIG. 1, the captured image 40-1 is generated by the imaging performed while the screen 30-1 is being displayed, and the captured image 40-2 is generated by the imaging performed while the screen 30-2 is being displayed.

[0016] The biological detection device 2000 acquires the plurality of captured images 40 generated in this way, and determines whether the target object 50 is a living body by using the plurality of acquired captured images 40.

[0017] <An example of the effect> According to the biological detection device 2000 of the present embodiment, imaging by the camera 10 is performed while the screen 30 is being displayed on the display device 20. Here, when the target object 50 is a photograph of a paper with a face shown thereon, a display device on which an image of a face is displayed, etc., the light irradiated from the display device 20 is irradiated onto the photograph, etc., and the reflected light thereof is imaged by the camera 10. On the other hand, when the target object 50 is a real person, the light irradiated from the display device 20 is irradiated onto the real face, and the reflected light thereof is imaged by the camera 10.

[0018] The shapes of the paper, the display device, etc. are substantially flat and are significantly different from the shape of a real face. Therefore, it can be said that the characteristics of the reflected light are significantly different from each other between the case where the light irradiated from the display device 20 is irradiated onto a photograph of a paper, etc. and the case where it is irradiated onto a real face. And such a difference in the characteristics of the reflected light appears in the captured image 40 obtained by imaging the reflected light with the camera 10.

[0019] According to the biological detection device 2000, by analyzing the captured image 40 obtained by imaging the above-described reflected light, it is possible to determine whether the target object 50 is a living body based on such a difference in characteristics.

[0020] In the system of Patent Document 1, light is irradiated from one illumination lamp onto the object to be biometrically detected. Therefore, only limited changes in the illumination environment, such as "making the entire screen bright" or "making the entire screen dark", can be realized. In this regard, in the biometric detection device 2000 of the present embodiment, the screen 30 includes a plurality of regions 32 with different displays. Therefore, the pattern of light irradiated from the display device 20 onto the target object 50 can be flexibly set. For example, as shown in FIG. 1, various patterns of light, such as "the left half is bright and the right half is dark" or "the right half is bright and the left half is dark", can be irradiated onto the target object 50.

[0021] According to the biometric detection device 2000 of the present embodiment, the target object 50 is irradiated with various patterns of light as described above, and using the captured image 40 in which the reflected light is captured, it is determined whether the target object 50 is a living body. Therefore, compared with a case where only relatively simple patterns of light, such as "making the entire screen bright" or "making the entire screen dark", can be irradiated onto the target object 50, the determination of whether the target object 50 is a living body can be performed with higher accuracy.

[0022] Hereinafter, the biometric detection device 2000 of the present embodiment will be described in more detail.

[0023] <Example of Functional Configuration> FIG. 2 is a block diagram illustrating the functional configuration of the biometric detection device 2000 according to Embodiment 1. The biometric detection device 2000 includes a display control unit 2020, an acquisition unit 2040, and a biometric detection unit 2060. The display control unit 2020 causes the display device 20 to display a plurality of screens 30 at different timings. Here, at least one screen 30 has a plurality of regions 32. Also, at least two regions 32 include different displays. The acquisition unit 2040 acquires a plurality of captured images 40 generated by the camera 10 while each of the plurality of screens 30 is being displayed. The biometric detection unit 2060 determines whether the target object 50 is a living body using the plurality of captured images 40.

[0024] <Example of Hardware Configuration> Each functional component of the biological detection device 2000 may be implemented by hardware (e.g., hard-wired electronic circuits, etc.) that implements each functional component, or may be implemented by a combination of hardware and software (e.g., a combination of an electronic circuit and a program that controls it). Hereinafter, the case where each functional component of the biological detection device 2000 is implemented by a combination of hardware and software will be further described.

[0025] FIG. 3 is a block diagram illustrating the hardware configuration of a computer 500 that realizes the biological detection device 2000. The computer 500 is an arbitrary computer. For example, the computer 500 is a stationary computer such as a PC (Personal Computer) or a server machine. In addition, for example, the computer 500 is a portable computer such as a smartphone, a tablet terminal, or a notebook PC. When the terminal 60 is used, the biological detection device 2000 may be provided integrally with the terminal 60 or separately.

[0026] The computer 500 may be a dedicated computer designed to realize the biological detection device 2000, or may be a general-purpose computer. For example, by installing a predetermined application on the computer 500, each function of the biological detection device 2000 is realized on the computer 500. The above application is composed of programs for realizing the functional components of the biological detection device 2000.

[0027] Computer 500 has a bus 502, a processor 504, a memory 506, a storage device 508, an input / output interface 510, and a network interface 512. The bus 502 is a data transmission path for the processor 504, the memory 506, the storage device 508, the input / output interface 510, and the network interface 512 to transmit and receive data from each other. However, the method of connecting the processor 504 and the like to each other is not limited to bus connection.

[0028] The processor 504 is various processors such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), or an ASIC (Application Specific Integrated Circuit). The memory 506 is a main storage device realized using, for example, RAM (Random Access Memory). The storage device 508 is an auxiliary storage device realized using a hard disk, an SSD (Solid State Drive), a memory card, or a ROM (Read Only Memory).

[0029] The input / output interface 510 is an interface for connecting the computer 500 and an input / output device. For example, a camera 10 and a display device 20 are connected to the input / output interface 510.

[0030] The network interface 512 is an interface for connecting the computer 500 to a network. This network may be a LAN (Local Area Network) or a WAN (Wide Area Network).

[0031] The storage device 508 stores a program (the program that realizes the aforementioned application) for realizing each functional component of the biological detection device 2000. The processor 504 reads out and executes this program in the memory 506, thereby realizing each functional component of the biological detection device 2000.

[0032] The biological detection device 2000 may be realized by one computer 500 or may be realized by a plurality of computers 500. In the latter case, the configurations of the respective computers 500 do not have to be the same and can be different from each other.

[0033] <Regarding the display device 20> The display device 20 is any display device capable of displaying the screen 30. For example, the display device 20 is communicably connected to a terminal 60 operated by a user and is configured to display a screen output from the terminal 60. The terminal 60 is any computer used by the user. When the target object 50 is a real person and the terminal 60 is used by the target object 50, the user of the terminal 60 is the target object 50. On the other hand, when forgery is attempted using a photograph or the like as the target object 50, the user of the terminal 60 is the person who caused the camera 10 to image such a photograph or the like. The terminal 60 may be realized by a portable computer such as a smartphone, a tablet terminal, or a notebook PC, or may be realized by a stationary computer such as a desktop PC.

[0034] When the terminal 60 is realized by a portable computer, the display device 20 is a display device provided in the terminal 60. On the other hand, when the terminal 60 is realized by a stationary computer, the display device 20 is a display device communicably connected to the terminal 60 and configured to display a screen output from the terminal 60.

[0035] The biological detection device 2000 may be provided integrally with the terminal 60 or separately. When the terminal 60 is provided separately from the biological detection device 2000, the hardware configuration of the computer that realizes the terminal 60 is represented by, for example, FIG. 3 in the same manner as the computer 500.

[0036] Also, a part of the functions of the biological detection device 2000 may be provided in the terminal 60, and other functions may be provided in a computer other than the terminal 60. For example, the display control unit 2020 and the acquisition unit 2040 are provided in the terminal 60, and the biological detection unit 2060 is provided in the server device. In this case, for example, a plurality of captured images 40 generated by the camera 10 are transmitted from the terminal 60 to the server device. Then, the server device performs biological detection by analyzing the received captured images 40 and transmits information indicating the result to the terminal 60.

[0037] The display device 20 is not limited to being communicably connected to the terminal 60 operated by the user. For example, the display device 20 can be realized as a display device viewable by a person passing through the gate at the entrance of a facility whose gate opening and closing are controlled by a computer. In this case, for example, face authentication and biological detection using the camera 10 are performed on a person trying to pass through the gate. Specifically, using the captured image of the target object 50 obtained from the camera 10, it is determined whether the target object 50 is registered as a person who can pass through the gate. Further, the biological detection device 2000 controls the display device 20 to perform biological detection on the target object 50. And when the target object 50 is registered as a person who can pass through the gate and, moreover, the target object 50 is determined to be a living body, the gate is opened by the gate control device that controls the opening and closing of the gate. On the other hand, when the target object 50 is not registered as a person who can pass through the gate or the target object 50 is determined not to be a living body, the gate is not opened (when the gate is open, the gate is closed by the gate control device). By performing biological detection, it is possible to prevent forgery using a registered person's face photo or the like.

[0038] In a case where the opening and closing of the gate are controlled based on the results of face authentication and biometric detection, face authentication and biometric detection may be performed using a terminal 60 such as a smartphone used by the user. Specifically, first, when the user operates the terminal 60, biometric detection by the face authentication and biometric detection device 2000 is performed. The gate control device controls the opening and closing of the gate by obtaining information representing the results of face authentication and biometric detection from the terminal 60. The information representing the results of face authentication and biometric detection is transmitted, for example, wirelessly from the terminal 60 to the gate control device. In addition, for example, the terminal 60 causes a display device 20 to display information (such as a two-dimensional code) representing the results of face authentication and biometric detection, and causes a reader communicably connected to the gate control device to read the information. The gate control device controls the opening and closing of the gate based on the information read by the reader.

[0039] <Regarding the camera 10> The camera 10 is used at a position and posture where it can capture the face of the target object 50 while the light output from the display area of the display device 20 irradiates the face of the target object 50. For example, the camera 10 is a camera built in the vicinity of the display area of the display device 20. Such a camera is called an in-camera. However, the camera 10 is not limited to a camera built in the terminal 60 like an in-camera. For example, a portable camera (such as a web camera) attached to the edge of the display device 20 can be used as the camera 10. In addition, for example, the camera 10 may be installed at a position separated from the display device 20. For example, in the example of controlling the opening and closing of the gate according to the result of biometric detection by the biometric detection device 2000 described above, a surveillance camera installed so that a person trying to pass through the gate enters the imaging range can be used as the camera 10.

[0040] The camera 10 may be a still camera that generates still images, or a video camera that generates videos. When the camera 10 is a still camera, the camera 10 generates a captured image 40 in a state where each of a plurality of screens 30 is being displayed on the display device 20. On the other hand, when the camera 10 is a video camera, for example, the camera 10 generates video data by performing imaging during a period including the time from when the first screen 30 is displayed until the last screen 30 is displayed. In this case, the captured image 40 is a video frame that constitutes the video data.

[0041] <Flow of processing> FIG. 4 is a flowchart illustrating the flow of processing executed by the biological detection device 2000 according to Embodiment 1. S102 to S106 constitute a loop process A. The loop process A is executed for each of the screens 30 to be displayed on the display device 20.

[0042] In S102, the display control unit 2020 determines whether or not the loop process A has been executed for all the screens 30. If the loop process A has been executed for all the screens 30, the process in FIG. 4 proceeds to S108. On the other hand, if there is still a screen 30 that has not been the target of the loop process A, the display control unit 2020 selects one of them. The screen 30 selected here is denoted as screen i. After the screen 30 is selected, the process in FIG. 4 proceeds to S104.

[0043] Note that the selection order of the screens 30 is arbitrary. For example, the display control unit 2020 selects the screens 30 in a predetermined order. Alternatively, for example, the display control unit 2020 may select the screens 30 in a random order.

[0044] The display control unit 2020 causes the screen i to be displayed on the display device 20 (S104). Since S106 is the end of the loop process A, the process in FIG. 4 proceeds to S102. Note that after the screen i is displayed on the display device 20 by the execution of S104, imaging is performed by the camera 10, and a captured image 40 is generated.

[0045] After the end of the loop process A, the acquisition unit 2040 acquires a plurality of captured images 40 (S108). The living body detection unit 2060 performs living body detection on the target object 50 using the plurality of acquired captured images 40 (S110).

[0046] <Regarding screen 30> The screen 30 has a plurality of regions 32. Among the screens 30 displayed on the display device 20, at least one screen 30 has a plurality of regions 32. Among the plurality of regions 32, at least two regions 32 include different displays. The regions 32 including different displays are, for example, regions 32 with different colors or brightness from each other, or regions 32 including different characters, symbols, or figures. By including such two regions 32 in the screen 30, the display device 20 on which the screen 30 is displayed can irradiate the target object 50 with light having non-uniform brightness.

[0047] FIG. 5 is a diagram illustrating a screen 30 composed of two regions 32. The screen 30-1 is divided into two regions 32-1 and 32-2 by a vertical boundary line. The region 32-1 is the left half region of the screen 30-1, and the region 32-2 is the right half region of the screen 30-1. The regions 32-1 and 32-2 are filled with different colors (all pixels are the same color). Note that instead of setting colors for all pixels of the region 32 (completely filling the region 32), colors may be set only for some pixels of the region 32. For example, in the region 32, pixels with colors set (pixels to be lit) and pixels without colors set (pixels not to be lit) may be arranged alternately.

[0048] On the other hand, the screen 30-2 is divided into two regions 32-3 and 32-4 by a horizontal boundary line. The region 32-3 is the upper half region of the screen 30-2, and the region 32-4 is the lower half region of the screen 30-2. The regions 32-3 and 32-4 are filled with different colors.

[0049] Note that any color such as white, black, red, or blue can be used for the color of the region 32. Also, when the display device 20 can output invisible light such as infrared light, the invisible light may be utilized. For example, after the process of "irradiating visible light from the left half of the display device 20 and irradiating infrared light from the right half of the display device 20", the process of "irradiating infrared light from the left half of the display device 20 and irradiating visible light from the right half of the display device 20" can be considered. Note that when using invisible light, it is necessary to use a sensor capable of detecting the invisible light. For example, when using visible light and infrared light, a camera capable of imaging visible light and a camera capable of imaging infrared light are used.

[0050] In both the screen 30-1 and the screen 30-2 in FIG. 5, the sizes of the two regions 32 are the same as each other. However, the sizes of the regions 32 may be different from each other.

[0051] In FIG. 5, the boundary line of the region 32 is a straight line in the vertical or horizontal direction. However, the boundary line of the region 32 is not limited to a straight line in the vertical or horizontal direction and may be a slanted line. Also, the boundary line is not limited to a straight line and may be a curve, a zigzag line, or the like.

[0052] The number of regions 32 included in the screen 30 may be three or more. For example, the screen 30 is divided into n (n>=2) parts in the horizontal or vertical direction. FIG. 6 is a diagram illustrating a screen 30 having three regions 32. In FIG. 6, the screen 30-1 is divided into three parts in the horizontal direction (there are three regions 32 arranged in the horizontal direction). On the other hand, the screen 30-2 is divided into three parts in the vertical direction (there are three regions 32 arranged in the vertical direction).

[0053] Here, when the screen 30 has three or more regions 32, the displays of a plurality of non-adjacent regions 32 may be the same as each other. For example, in the screen 30-1 of FIG. 6, the regions 32-1 and 32-3 are filled with the same color, while the region 32-2 is filled with a different color. On the other hand, in the screen 30-2 of FIG. 6, the three regions 32 are each filled with a different color.

[0054] Also, the screen 30 may be divided in both the horizontal and vertical directions. FIG. 7 is a diagram illustrating a case where the screen 30 is divided in both the horizontal and vertical directions. In FIG. 7, the screen 30-1 is divided into four by a horizontal boundary line and a vertical boundary line. On the other hand, the screen 30-2 is divided into four by two diagonal lines.

[0055] Here, there are various ways to make the displays in the plurality of regions 32 different from each other. For example, as described above, the plurality of regions 32 are filled with different colors. When filling the regions 32 with different colors, it is preferable to use colors with different brightness levels in order to make the brightness of the light emitted from the display device 20 different when these regions 32 are being displayed.

[0056] In addition, for example, the regions 32 may be filled with patterns such as a grid pattern or a dot pattern. In this case, it is preferable to change the characteristics of the pattern used to make the brightness of the light emitted from the display device 20 different. For example, in the case of a grid pattern, the brightness of the light emitted from the display device 20 can be changed by changing the size of the grid or the thickness of the lines. Also, in the case of a dot pattern, the brightness of the light emitted from the display device 20 can be changed by changing the size of the dots or the spacing between the dots.

[0057] In addition, for example, the regions 32 may include characters, symbols, or figures. Also in this case, the brightness of the light emitted from the display device 20 can be changed by changing the size or spacing of the characters, symbols, or figures included in the regions 32.

[0058] Also, when the brightness of the display area of the display device 20 can be changed for each part, the plurality of areas 32 may display the same color with different brightnesses. For example, in the screen 30-1 of FIG. 5, the area 32-1 is set as a relatively bright white area, and the area 32-2 is set as a relatively dark white area. By doing so, even when the plurality of areas 32 are filled with the same color, the brightness of the light irradiated from the display device 20 can be made different for each area 32. Also, a relatively dark area 32 can be realized by making it an area where no light is irradiated.

[0059] <<Relationship between the position of the camera 10 and the splitting method>> The position of the boundary line that divides the screen 30 into a plurality of areas 32 may be determined based on the relative position of the camera 10 with respect to the display device 20. When a person takes a picture of themselves with the camera 10, there is a high possibility that the terminal 60 is held so that the position of the camera 10 becomes the center of the face. Therefore, by determining the position of the boundary line of the screen 30 based on the position of the camera 10, the boundary line of the screen 30 can be positioned at the center of the target object 50. Thus, it becomes possible to change the characteristics of the light irradiated onto the target object 50 with the center of the target object 50 as the boundary, such as "shining bright light on the left half of the face and dark light on the right half of the face". Since the shape of the face is generally bilaterally symmetric, comparison can be made easily by shining lights with different characteristics on the left and right sides of the face.

[0060] FIG. 8 is a diagram illustrating a case where the boundary line in the screen 30 is determined based on the position of the camera 10. The camera 10 in FIG. 8 is provided on the left side rather than at the center of the display area of the display device 20 in the horizontal direction.

[0061] In the case of screen 30-1, the straight line drawn vertically downward from camera 10 serves as boundary line 34-1. That is, the screen 30 is divided into left and right parts with reference to the straight line drawn vertically downward from camera 10. Here, since camera 10 is provided on the left side, region 32-1 is smaller than region 32-2.

[0062] On the other hand, in the case of screen 30-2, while determining boundary line 34 with reference to the position of camera 10, the screen 30 is bisected. Specifically, the upper end of boundary line 34-2 is determined by the intersection of the straight line drawn vertically downward from camera 10 and the upper side of the display area of display device 20. And region 32-4 is a straight line drawn diagonally downward to the right from the above upper end so that screen 30-2 is bisected by boundary line 34-2.

[0063] Note that when the screen 30 is divided either horizontally or vertically, which way it is divided may be determined by the position of camera 10. Specifically, when camera 10 is provided above or below the display area of display device 20, the display control unit 2020 divides the screen 30 horizontally. On the other hand, when camera 10 is provided on the left or right side of the display area of display device 20, the display control unit 2020 divides the screen 30 vertically.

[0064] In order to determine boundary line 34 based on the position of camera 10, the biometric detection device 2000 needs to be able to grasp the positional relationship between camera 10 and the display area of display device 20. For example, set the position of one end of boundary line 34 determined as described above in the biometric detection device 2000 in advance. As another example, for instance, the position of one end of boundary line 34 may be set by the user of terminal 60. For example, the biometric detection device 2000 allows the user of terminal 60 to specify a position on the display area of display device 20. Then, the biometric detection device 2000 uses the x coordinate of the specified position as the x coordinate of the upper end of boundary line 34.

[0065] Note that not only one end of the boundary line 34 but also the boundary line 34 itself may be set for the user of the terminal 60. For example, the user is made to draw a line on the display device 20 and the line is used as the boundary line 34. When it is desired to determine the boundary line 34 based on the user's face, for example, an image of the user's face (captured image 40) captured by the camera 10 is displayed on the display device 20. Then, for example, by displaying a guidance message such as "Please draw a line passing through the center of your face" on the display device 20, the boundary line 34 based on the user's face is set.

[0066] Further, the biometric detection device 2000 may automatically determine the boundary line 34 by detecting the face from the captured image 40 and based on the position of the face on the captured image 40 (for example, a vertical line passing through the center of the face).

[0067] <Control of Display of Screen 30: S102 - S106> The display control unit 2020 causes the display device 20 to display a plurality of screens 30 at different timings (S102 - S106). As the plurality of screens 30, the various screens 30 described above can be used. Note that two or more types of screens 30 are displayed on the display device 20, and at least one of them has a plurality of different regions 32. Among the screens 30 displayed on the display device 20, there may be included a screen 30 that is not divided into a plurality of regions 32.

[0068] FIG. 9 is a first diagram illustrating a plurality of screens 30 displayed on the display device 20 by the display control unit 2020. In the example of FIG. 9, the screens 30 are displayed in the order of screen 30 - 1, screen 30 - 2, screen 30 - 3, and screen 30 - 4.

[0069] Screen 30-1 has its left half painted white and its right half painted black. Screen 30-2 has its left half painted black and its right half painted white. Screen 30-3 is entirely painted white. Screen 30-4 is entirely painted black.

[0070] FIG. 10 is a second diagram illustrating a plurality of screens 30 displayed on the display device 20 by the display control unit 2020. In FIG. 10, m screens 30 are displayed in order. These m screens 30 are generated by gradually moving the boundary line between the left region 32 painted white and the right region 32 painted black to the right.

[0071] Note that when moving the boundary line as shown in FIG. 10, a plurality of patterns of screens 30 may be displayed for one position of the boundary line. For example, in the example of FIG. 10, assume that the display of the region 32 is changed every 1 second while moving the boundary line every 3 seconds. In this case, with the position of the boundary line fixed, three patterns of screens 30 are displayed. For example, by displaying three types of screens 30: a screen 30 where the left region 32 is white, a screen 30 where the left region 32 is a relatively bright gray, and a screen 30 where the left region 32 is a relatively dark gray, a plurality of patterns of screens 30 can be displayed with the boundary line fixed. However, the region 32 whose display is changed with the boundary line fixed is not limited to only one region 32, and the display of each of a plurality of regions 32 may be changed.

[0072] Note that the time for which each screen 30 is displayed on the display device 20 may be of the same length or of different lengths.

[0073] The camera 10 needs to be able to capture images of two or more screens 30 at the timing when the screen 30 is being displayed on the display device 20. For this purpose, for example, the display control unit 2020 controls the imaging by the camera 10. Specifically, the biometric detection device 2000 repeats the process of "displaying the screen 30 on the display device 20 and then causing the camera 10 to perform imaging" while changing the screen 30. By doing so, for each screen 30, an imaging image 40 can be obtained for the state in which the screen 30 is being displayed on the display device 20.

[0074] However, the imaging timing by the camera 10 does not necessarily have to be controlled by the display control unit 2020. For example, the camera 10 is configured to perform repeated imaging. By switching the screen 30 displayed on the display device 20 while the camera 10 is performing repeated imaging, an imaging image 40 for the state in which each screen 30 is being displayed can be obtained. In this case, for example, it is preferable that the length of time during which one screen 30 is displayed on the display device 20 is set to be longer than the imaging cycle of the camera 10. By doing so, for each of all the screens 30, one or more imaging images 40 generated while the screen 30 is being displayed on the display device 20 can be obtained. However, the length of time during which the screen 30 is being displayed on the display device 20 does not necessarily have to be set to be longer than the imaging cycle of the camera 10.

[0075] In addition, when three or more screens 30 are being displayed on the display device 20, it is not necessarily required to generate imaging images 40 for all the screens 30. For example, in the example of FIG. 10, assume that the camera 10 is a video camera and the imaging cycle of the camera 10 is longer than the movement cycle of the boundary line. In this case, among the m screens 30, for any one or more of the screens 30, there is a possibility that imaging by the camera 10 is not performed while the screen 30 is being displayed. However, if two or more imaging images 40 can be acquired, biometric detection by the biometric detection unit 2060 can be realized.

[0076] <Acquisition of imaging image 40: S108> The acquisition unit 2040 acquires a plurality of captured images 40 generated by the camera 10 (S108). Here, various methods can be used to acquire the image generated by the camera. For example, the acquisition unit 2040 accesses the storage device in which the captured image 40 is stored to acquire the captured image 40. Here, the storage device may be provided either inside or outside the camera 10. In addition, for example, the acquisition unit 2040 may acquire the captured image 40 by receiving the captured image 40 transmitted from the camera 10 to the biometric detection device 2000.

[0077] <Execution of biometric detection: S110> The biometric detection unit 2060 performs biometric detection using the acquired plurality of captured images 40. Specifically, the biometric detection unit 2060 determines whether the target object 50 imaged by the camera 10 is a living body.

[0078] As described above, in the case where the target object 50 is a photograph of paper or the like and the case where the target object 50 is a real person or the like, the shape of the target object 50 is significantly different, and such a shape difference appears in the captured image 40 as a difference in the characteristics of the reflected light. Therefore, for example, the biometric detection unit 2060 determines whether the target object 50 is a living body based on the characteristics of the color and brightness distribution of the target object 50 on the captured image 40.

[0079] There are various specific methods for realizing biometric detection by the biometric detection unit 2060. For example, biometric detection is realized using a learned discrimination model. This discrimination model outputs data indicating a determination result as to whether an object captured by the camera 10 is a living body in response to the input of a plurality of captured images 40. The data indicating the determination result is, for example, a label that indicates 1 when the object captured by the camera 10 is a living body and indicates 0 when the object captured by the camera 10 is not a living body. Such a discrimination model can be realized by a neural network such as a CNN (Convolutional Neural Network). However, the type of the discrimination model is not limited to neural networks. According to the method of performing biometric detection using such a learned discrimination model, an algorithm for determining whether the target object 50 is a living body can be easily constructed in a data-driven manner.

[0080] The learning of the discrimination model can be realized using training data composed of a combination of "a plurality of captured images 40, correct labels". For example, it is assumed that the display control unit 2020 causes the display device 20 to display three types of screens 30, namely, the screen 30 of the first pattern to the screen 30 of the third pattern. In this case, corresponding to each of the screen 30 of the first pattern to the screen 30 of the third pattern, the captured image 40 of the first pattern to the captured image 40 of the third pattern are obtained. Here, the captured image 40 of the nth pattern (n is an integer from 1 to 3) is the captured image 40 generated by the camera 10 while the screen 30 of the nth pattern is being displayed on the display device 20. When three patterns of captured images 40 are obtained in this way, for the learning of the discrimination model, training data composed of a combination of "the captured image 40 of the first pattern, the captured image 40 of the second pattern, the captured image 40 of the third pattern, correct labels" is used.

[0081] It is preferable to perform the learning of the identification model using both the training data of positive examples and the training data of negative examples. The training data of positive examples includes a plurality of captured images 40 obtained when the living body is imaged by the camera 10 and a correct label (for example, 1) indicating that the living body has been imaged by the camera 10. On the other hand, the training data of negative examples includes a plurality of captured images 40 obtained when the camera 10 images something other than the living body and a correct label (for example, 0) indicating that something other than the living body has been imaged by the camera 10. By using both the training data of positive examples and the training data of negative examples, it is possible to learn the difference between the captured images 40 obtained when the living body is imaged and the captured images 40 obtained when something other than the living body is imaged.

[0082] <Output of Results> The living body detection device 2000 outputs information indicating the result of living body detection (hereinafter referred to as detection result information). The detection result information indicates the determination result as to whether the target object 50 is a living body or not. It is preferable that the detection result information is displayed on a display device (for example, the display device 20) that can be viewed by the user of the terminal 60. However, the detection result information may be output to other devices than the display device of the terminal 60.

[0083] <Other Processes> In addition to the light irradiated from the display device 20, the target object 50 is irradiated with ambient light (such as sunlight or illumination light) around the display device 20. When the ambient light is extremely stronger than the light irradiated from the display device 20, the ambient light becomes dominant, and even if the intensity of the light irradiated from the display device 20 is changed, the change is less likely to appear in the captured image 40. Therefore, it is preferable that the living body detection using the living body detection device 2000 is performed in a place where the ambient light is not too strong.

[0084] Therefore, for example, the biological detection device 2000 may identify the intensity of ambient light before controlling the display device 20 by the display control unit 2020, and start a series of processes for biological detection (S102 to S110 in FIG. 4) only when it is determined that the ambient light is below a threshold value. By doing so, it is possible to perform the biological detection process when the intensity of the ambient light is appropriate.

[0085] The identification of the intensity of ambient light is performed, for example, using an illuminance sensor. The illuminance sensor may be pre-built into the display device 20 or the terminal 60 in advance, or may be prepared separately. When the ambient light is greater than the threshold value, for example, the biological detection device 2000 causes the display device 20 to display a message prompting it to move to a darker place (a place where the ambient light is weaker than the current situation). By doing so, when the terminal 60 is not being used in an appropriate environment, the user can be informed of this, and the terminal 60 can be used in an appropriate environment.

[0086] Note that the method for determining whether the intensity of the ambient light is appropriate is not limited to the method of measuring the intensity of the ambient light with a sensor. For example, the biological detection device 2000 determines whether the intensity of the ambient light is appropriate based on the brightness of the captured image 40. The captured image 40 may be generated while the screen 30 is being displayed on the display device 20, or may be generated while the screen 30 is not being displayed on the display device 20. For example, the biological detection device 2000 determines that the intensity of the ambient light is appropriate when the statistical value (for example, the average value) of the brightness of all or some of the pixels included in the captured image 40 is below a threshold value. On the other hand, when the statistical value is greater than the threshold value, the biological detection device 2000 determines that the intensity of the ambient light is not appropriate.

[0087] For example, in addition, while a relatively bright screen 30 (e.g., a screen 30 that is entirely white) is being displayed on the display device 20, the biometric detection device 2000 compares the captured image 40 generated by the camera 10 with the captured image 40 generated by the camera 10 while a relatively dark screen 30 (e.g., a screen 30 that is entirely black) is being displayed on the display device 20, and determines whether there is a sufficient difference in luminance (e.g., the difference in luminance is equal to or greater than a threshold value). The difference in luminance can be represented, for example, by the difference between the statistical value (e.g., the average value) of the luminance of all the pixels included in the former captured image 40 and the statistical value of the luminance of all the pixels included in the latter captured image 40.

[0088] However, in calculating the statistical value of the luminance, the luminance of the region including the target object 50 may be given priority over the luminance of other regions. For example, the biometric detection device 2000 detects the region including the target object 50 from the captured image 40, and calculates the statistical value of the luminance using only the luminance of the region. For example, in addition, the biometric detection device 2000 may calculate a weighted average of the luminance of the entire image after assigning a greater weight to the luminance of the region including the target object 50 than to other regions.

[0089] If it is determined that there is not a sufficient difference in luminance, it is considered that the ambient light is too strong. Therefore, if it is determined that there is not a sufficient difference in luminance, for example, the biometric detection device 2000 does not determine whether the target object 50 is a living body, and causes the display device 20 to display a message prompting the user to move to a slightly darker place and then retry the biometric detection. The method of determining whether the ambient light is too strong by comparing the captured images 40 in this way has the advantage that hardware (such as an illuminance sensor) for specifying the intensity of the ambient light is not required.

[0090] The display control unit 2020 may change the screen 30 to be displayed on the display device 20 according to the intensity of the ambient light. For example, it is preferable to increase the contrast of the screen 30 as the ambient light is stronger. By doing so, the probability that the ambient light becomes dominant can be reduced. Also, by doing so, since the contrast of the screen 30 becomes lower as the ambient light is weaker, the power consumption of the display device 20 can be reduced. The contrast of the screen 30 can be realized by either one or both of two measures: "making the relatively bright area 32 brighter" and "making the relatively dark area 32 darker".

[0091] For example, a plurality of screens 30 to be displayed on the display device 20 are determined in advance for each level of the intensity of the ambient light (hereinafter referred to as the ambient light level). A screen 30 with a higher contrast is associated with a higher ambient light level. The display control unit 2020 identifies which ambient light level the current intensity of the ambient light corresponds to, and uses the screen 30 associated with the identified ambient light level.

[0092] In addition, for example, the display control unit 2020 may generate a screen 30 adapted to the intensity of the ambient light by changing (correcting) the colors of the pixels included in one or more areas 32 included in the screen 30 according to the intensity of the ambient light. For example, a correction coefficient α that increases in value as the ambient light is stronger is prepared. The value range of the correction coefficient α is, for example, 0 < α ≤ 1. By multiplying this correction coefficient by the brightness of the color included in the area 32, the area 32 can be made brighter as the ambient light is stronger.

[0093] Before the biological detection device 2000 causes the display device 20 to display the screen 30, it may acquire the captured image 40 and perform face detection processing, and start a series of processes for biological detection in response to the detection of a face from the captured image 40. This is because when a face is not detected from the captured image 40, biological detection cannot be performed. For example, after the biological detection device 2000 causes the display device 20 to display a message to capture a face, it repeatedly acquires the captured image 40 and performs face detection processing. Then, when a face is detected from the captured image 40, it starts a series of processes for biological detection. On the other hand, when a face is not detected from the captured image 40 for a certain period of time, the biological detection device 2000 causes the display device 20 to display a message prompting to capture a face.

[0094] Furthermore, when a face is detected from the captured image 40, the biological detection device 2000 may determine whether the size of the face is sufficiently large. For example, the biological detection device 2000 starts a series of processes for biological detection only when the size of the face is sufficiently large. On the other hand, when the size of the face is not sufficiently large, the biological detection device 2000 causes the display device 20 to display a message prompting to capture the face larger.

[0095] Whether the size of the face is sufficiently large is determined, for example, by comparing the area of the face region of the target object 50 in the captured image 40 with a threshold value. In addition, for example, whether the size of the face is sufficiently large may be determined by comparing the distance between the left eye and the right eye, rather than the size of the face itself, with a threshold value. In this case, the biological detection device 2000 detects the left eye and the right eye of the target object 50 from the captured image 40 and calculates the distance between them. Then, the biological detection device 2000 determines whether the calculated distance is less than or equal to the threshold value. When the distance between the eyes is less than or equal to the threshold value, the biological detection device 2000 determines that the size of the face is sufficiently large. On the other hand, when the distance between the eyes is greater than the threshold value, the biological detection device 2000 determines that the size of the face is not sufficiently large.

[0096] In addition, for example, the biometric detection device 2000 may determine whether the size of the face is sufficient based on the distance between the display device 20 and the target object 50. For example, when the distance between the display device 20 and the target object 50 is equal to or less than a threshold value, the biometric detection device 2000 determines that the size of the face is sufficient. On the other hand, when the distance between the display device 20 and the target object 50 is greater than the threshold value, the biometric detection device 2000 determines that the size of the face is insufficient. Note that various methods can be used to calculate the distance between the display device 20 and the target object 50, such as a method using a depth sensor. Further, instead of the distance between the display device 20 and the target object 50, the distance between the camera 10 and the target object 50 may be used. In this case, by using a stereo camera or a camera with a depth sensor as the camera 10, the distance between the camera 10 and the target object 50 can be grasped.

[0097] In addition, in order to make it easier for the user to capture an image of an appropriate face size, the biometric detection device 2000 may cause the display device 20 to display a guide indicating an appropriate face size. FIG. 11 is a diagram illustrating a guide indicating an appropriate face size. The elliptical frame represents the position where the face should be placed. The dotted line represents the position where the center line (a line passing through the center) of the face should be placed. By displaying such a guide, the user can perform imaging more easily.

[0098] The biometric detection device 2000 may detect that the center line of the user's face in the captured image 40 overlaps with the center line of the face indicated by the above-described guide (the dotted line in FIG. 11), and start a series of biometric detection processes in response to the detection. Thereby, since biometric detection is performed at the timing when the face is in an appropriate posture, the accuracy of biometric detection is improved. Note that existing techniques can be used for the technique of specifying the center line of the face by image analysis.

[0099] In addition, for example, the biological detection device 2000 may detect that the target object 50 has blinked using the captured image 40, and start a series of biological detection processes in response to the detection. Note that existing technologies can be used for the technology of detecting blinks from time-series images.

[0100] [Embodiment 2] Similar to the biological detection device 2000 of Embodiment 1, the biological detection device 2000 of Embodiment 2 performs biological detection on the target object 50. However, the biological detection device 2000 of Embodiment 2 realizes biological detection by a method different from that of the biological detection device 2000 of Embodiment 1.

[0101] As a premise, in this embodiment, the camera 10 captures a state in which the face orientation of the person (target object 50) to be biologically detected is moved left and right while the line-of-sight direction is fixed. FIG. 12 is a diagram illustrating a state in which the face orientation is moved left and right while the line-of-sight direction is fixed (while continuously looking at the same place). The line of sight is fixed at a point on the terminal 60.

[0102] Here, when the face captured by the camera 10 is a real face, the target person can move their eyes independently of the face movement, so the face direction can be changed while keeping the line-of-sight direction fixed. And when an operation of changing the face direction over time while keeping the line-of-sight direction fixed is performed, the difference between the face direction and the line-of-sight direction changes over time. For example, when both the face and the line of sight are facing forward, the difference between the face direction and the line-of-sight direction is small, while when the face is facing either left or right while keeping the line of sight facing forward, the difference between the face direction and the line-of-sight direction is large.

[0103] On the other hand, for the purpose of impersonation, assume that the target person is wearing a wearable item (such as a so-called 3D mask) with someone else's face depicted on it. In this case, since the eyes are depicted on the mask or the like, the eyes cannot be moved independently of the facial movement. That is, the direction of the line of sight also changes together with the direction of the face. Therefore, even if an attempt is made to perform an operation of changing the direction of the face over time while fixing the line of sight direction, in reality, whether the difference between the face direction and the line of sight direction changes over time or the amount of change becomes small.

[0104] FIG. 13 is a diagram illustrating the temporal changes in the face direction and the line of sight direction when the face is shaken left and right while fixing the line of sight direction. In both graphs, the solid line represents the face direction, and the dotted line represents the line of sight direction. The left graph represents the case where the face imaged by the camera 10 is a real face. On the other hand, the right graph represents the case where the face imaged by the camera 10 is a 3D mask. As can be seen by comparing these graphs, when wearing a 3D mask, the difference between the face direction and the line of sight direction becomes relatively small.

[0105] Therefore, the biological detection device 2000 determines whether the target object 50 is a living body based on the difference between the face direction and the line of sight direction. Specifically, the biological detection device 2000 acquires a plurality of captured images 40 generated at different times by the camera 10, specifies the face direction and the line of sight direction for the face of the target person shown in each captured image 40, and calculates the difference therebetween. Here, for the face included in the image, existing techniques can be used for the technique of specifying the face direction and the line of sight direction. Then, the biological detection device 2000 determines whether the target object 50 shown in the captured image 40 is a living body based on the difference between the face direction and the line of sight direction. When it is necessary to distinguish the captured image 40 of the second embodiment from the captured image 40 of the first embodiment, the captured image 40 of the second embodiment may also be referred to as the "second captured image".

[0106] In addition, in order to realize the above-described biological detection, the biological detection device 2000 causes the display device 20 of the terminal 60 to display information indicating a guide for causing the target object 50 to perform a desired operation (hereinafter referred to as guide information). The biological detection device 2000 outputs at least both guide information indicating a guide regarding the line-of-sight direction and guide information indicating a guide regarding the face orientation. Note that these pieces of guide information may be output simultaneously or may be output at different timings from each other.

[0107] FIG. 14 is a first diagram illustrating guide information. In FIG. 14, a screen 80 including the guide information is displayed on the display device 20. The screen 80 includes a mark indicating a position at which the line of sight should be directed and a message saying "Please direct your line of sight here" as a guide regarding the line-of-sight direction. Further, the screen 80 includes a message saying "Please move your face left and right" as a guide regarding the face orientation.

[0108] Note that in the following description, unless otherwise specified, the directions of the face and the line of sight of the target object 50 are represented with the front direction (the direction in which the display device 20 is viewed from the front) as a reference angle of 0°, the right direction as a positive angle, and the left direction as a negative angle.

[0109] <An example of the operation and effect> As one method of impersonating another person, as described above, a method of using a 3D mask or the like on which another person's face is drawn can be considered. Here, as described above, in a state where a 3D mask or the like is worn, the line of sight moves together with the face, while in a state where the 3D mask is not worn, the line of sight can be moved independently of the face. Therefore, there is a difference in the difference between the face direction and the line-of-sight direction between the case where a 3D mask or the like is worn and the case where it is not.

[0110] In this regard, according to the biological detection device 2000, the situation where the face is shaken left and right while the line-of-sight direction is fixed is imaged by the camera 10. Then, the biological detection device 2000 analyzes the captured image 40 obtained from the camera 10 to calculate the difference between the face direction and the line-of-sight direction, and performs biological detection based on the difference. Therefore, according to the biological detection device 2000, it is possible to prevent fraud using a 3D mask or the like.

[0111] <Example of functional configuration> FIG. 15 is a block diagram illustrating the functional configuration of the biological detection device 2000 according to Embodiment 2. The biological detection device 2000 according to Embodiment 2 includes a second display control unit 2080, a second acquisition unit 2100, and a second biological detection unit 2120. The second display control unit 2080 causes the display device 20 of the terminal 60 to display guide information. The second display control unit 2080 acquires a plurality of captured images 40 generated by the camera 10 after the display of the guide information. The second biological detection unit 2120 specifies the face direction and the line-of-sight direction of the face of the target object 50 for each of the plurality of captured images 40. Then, the second biological detection unit 2120 determines whether the target object 50 is a living body based on the difference between the face direction and the line-of-sight direction specified for each captured image 40.

[0112] <Example of hardware configuration> The hardware configuration of the biological detection device 2000 according to Embodiment 2 is represented, for example, by FIG. 3, similar to the hardware configuration of the biological detection device 2000 according to Embodiment 1. However, the storage device 508 according to Embodiment 2 stores a program for realizing each function of the biological detection device 2000 according to Embodiment 2.

[0113] <Flow of processing> FIG. 16 is a flowchart illustrating the flow of processing executed by the biological detection device 2000 according to Embodiment 2. The second display control unit 2080 causes the guide information to be displayed on the display device 20 (S202). The second acquisition unit 2100 acquires a plurality of captured images 40 (S204). The second biological detection unit 2120 calculates the difference between the line-of-sight direction and the face direction of the target object 50 for each of the plurality of captured images 40 (S206). Note that the line-of-sight direction and the face direction do not necessarily need to be calculated for all of the captured images 40. The second biological detection unit 2120 determines whether the target object 50 is a living body based on the difference between the face direction and the line-of-sight direction calculated for each of the plurality of captured images 40 (S208).

[0114] Note that the flow of processing executed by the biological detection device 2000 according to Embodiment 2 is not limited to the flow shown in FIG. 16. For example, the captured images 40 used by the second biological detection unit 2120 do not necessarily need to be acquired all at once. For example, the biological detection device 2000 repeats the processes of "1) acquiring one new captured image 40 and 2) calculating the difference between the face direction and the line-of-sight direction for the acquired captured image 40" to calculate the difference between the face direction and the line-of-sight direction for each of the plurality of captured images 40.

[0115] In addition, for example, the timing at which the guide information is displayed is not limited to before the acquisition of the captured images 40. For example, as will be described later, the biological detection device 2000 determines whether the operation being performed by the target object 50 is an appropriate operation, and when an appropriate operation is not being performed, may display guide information for causing an appropriate operation to be performed.

[0116] <Regarding the guide information> The guide information displayed on the display device 20 by the second display control unit 2080 is various. For example, as in the example shown in FIG. 14, the guide for the line-of-sight direction indicates the position where the line of sight should be fixed, and the guide for the face direction indicates the direction in which the face should be moved. By looking at this guide, the target object 50 can understand that it should shake its face from side to side while fixing the line-of-sight direction.

[0117] In addition, for example, the second display control unit 2080 displays guide information indicating the next action to be performed by the target object 50 according to the movement of the face of the target object 50. FIG. 17 is a diagram illustrating guide information indicating the next action to be performed by the target object 50. On each of the screens 90-1 to 90-3 displayed on the display device 20 in FIG. 17, guide information including a message for the target object 50, a guide indicating the position to direct the line of sight, and a guide indicating the direction to face the face is displayed. By displaying such guides on the display device 20, the target object 50 can easily grasp which direction to face.

[0118] First, the second display control unit 2080 causes the display device 20 to display the screen 90-1. In the guide information displayed on the screen 90-1, as a guide regarding the face direction, a message prompting to face the front and an image of a face facing the front are displayed. Also, as a guide regarding the line-of-sight direction, a cross mark and an image of eyes are displayed.

[0119] The second display control unit 2080 determines whether or not the face of the target object 50 is facing the front. The direction of the face of the target object 50 is calculated by the second biometric detection unit 2120 using the captured image 40.

[0120] Here, it is preferable to keep the screen 90-1 displayed until the face of the target object 50 faces the front. By doing so, biometric detection can be prevented from starting until the face of the target object 50 faces the reference front direction. However, if the face of the target object 50 does not face the front even after a predetermined time has elapsed, it may be determined that the target object 50 is not a living body due to a timeout.

[0121] Once it is determined that the face of the target object 50 is facing forward, the second display control unit 2080 causes the display device 20 to display the screen 90-2. On the screen 90-2, as a guide regarding the face direction, a message prompting to face left, an arrow pointing left, and an image of a face facing left are displayed. Also, as a guide regarding the line-of-sight direction, a cross mark and an image of eyes are displayed.

[0122] The second display control unit 2080 determines whether the face of the target object 50 is facing left. For example, when the direction of the face of the target object 50 is equal to or less than a threshold value, it is determined that the face of the target object 50 is facing left.

[0123] On the display device 20, the screen 90-2 continues to be displayed until the face of the target object 50 faces left. However, if the face of the target object 50 does not face forward even after a predetermined time has elapsed, it may be determined that the target object 50 is not a living body due to a timeout.

[0124] Once it is determined that the face of the target object 50 is facing left, the second display control unit 2080 causes the display device 20 to display the screen 90-3. On the screen 90-3, as a guide regarding the face direction, a message prompting to face right, an arrow pointing right, and an image of a face facing right are displayed. Also, as a guide regarding the line-of-sight direction, a cross mark and an image of eyes are displayed.

[0125] In this way, by sequentially displaying the screens 90-1, 90-2, and 90-3, it is possible to prompt the target object 50 to change the face direction in the order of front, left, and right while fixing the line of sight. Also, thereafter, if the screens 90-2 and 90-3 are further alternately displayed, it is possible to prompt the target object 50 to repeatedly move the face direction left and right.

[0126] Note that, so that the target object 50 can more easily understand how to move the face, the guide representing the face direction may be displayed as an animation. FIG. 18 is a diagram illustrating an animation of the guide representing the face direction.

[0127] Here, it is preferable that the guidance information is displayed on the display device 20 together with the captured image 40 generated by the camera 10. For example, in a mobile terminal such as a smartphone, when using the camera, the result of imaging by the camera can be displayed on the display device in real time. Therefore, also in the terminal 60, in this way, the captured image 40 generated by the camera 10 is displayed on the display device 20 in real time, and the guidance information is displayed on the display device 20 together with (for example, superimposed on) the captured image 40. By doing so, the target object 50 can perform the operation of shaking the face left and right while fixing the line of sight while checking the state of its own face and line of sight.

[0128] For example, in the case of the animation guidance information shown in FIG. 18, it is preferable to display the captured image 40 generated by the camera 10 on the display device 20 in real time together with the animation. Thereby, the target object 50 can appropriately shake the face left and right by moving its own face so that the animation and its own face overlap. Therefore, the target object 50 can perform the operation necessary for biometric detection more intuitively. However, the animation representing the movement of the face may be displayed at a position that does not overlap with the face of the target object 50 (for example, a corner of the screen).

[0129] In addition, for example, when the operation performed by the target object 50 is not an appropriate operation, the second display control unit 2080 may display guidance information for enabling the target object 50 to perform an appropriate operation. For example, the second display control unit 2080 determines whether the amplitude of the swing of the face of the target object 50 is sufficiently large (whether it is equal to or greater than a threshold value). The amplitude of the swing of the face of the target object 50 can be calculated as the difference between the maximum value and the minimum value of the direction of the face of the target object 50.

[0130] When the magnitude of the face swing width of the target object 50 is smaller than the threshold value, the second display control unit 2080 causes the display device 20 to display guide information requesting to increase the face swing width. For example, guide information including a message such as "Please move your face more widely" is displayed. By displaying such guide information, the target object 50 can be made to understand that it should swing its face more widely. And when the face swing width is increased according to such a guide, when the target object 50 is a real face, the difference between the face direction and the line-of-sight direction becomes larger. Therefore, biometric detection can be performed with higher accuracy.

[0131] As another case where the operation performed by the target object 50 is not appropriate, a case where the line of sight of the target object 50 is not fixed can be considered. Therefore, for example, the second display control unit 2080 determines whether or not the line of sight of the target object 50 is fixed, and when the line of sight of the target object 50 is not fixed, causes the display device 20 to display guide information including a message prompting the fixation of the line of sight. For example, guide information including a message such as "Please do not move your line of sight" is displayed. By displaying such guide information, the target object 50 can be made to understand that it cannot fix the line-of-sight direction.

[0132] Note that whether or not the line of sight is fixed can be calculated based on, for example, a change in the line-of-sight direction. For example, when the absolute value of the difference between the line-of-sight direction calculated when the target object 50 is facing forward and the current line-of-sight direction is equal to or greater than the threshold value, it is determined that the line of sight is not fixed.

[0133] The second display control unit 2080 may cause the display device 20 to display guide information indicating the gaze position and facial direction of the target object 50 so that the target object 50 can understand the gaze position and facial direction of the target object 50. Fig. 19 is a diagram illustrating an example of guide information including the gaze position and facial direction of the target object 50. In Fig. 19, the current gaze position is represented by a white circle. The target object 50 can intuitively fix the gaze by adjusting the gaze position so that the white circle overlaps with the cross.

[0134] In addition, in Fig. 19, the current face direction is represented by a black circle. By looking at the black circle, the target object 50 can intuitively know in which direction its face is facing. Note that Fig. 19 shows a case in which the target object 50 is required to face forward. Therefore, the target object 50 can intuitively face the face forward by adjusting the face direction so that the black circle overlaps with the cross.

[0135] In addition, when a series of processes for live body detection are started when the target object 50 faces forward, the live body detection device 2000 may determine whether or not both the white circle and the black circle overlap with the cross in the example of Figure 19, and if it is determined that both overlap with the cross, start the series of processes for live body detection.

[0136] The guide indicating the face direction is not limited to that shown in Fig. 19. Fig. 20 is a second diagram illustrating an example of guide information including the gaze position and face direction of the target object 50. In Fig. 20, the marks indicating the current gaze position and the current face direction are the same as those in Fig. 19.

[0137] In Fig. 20, a black circle representing the face direction is displayed in a horizontally long rectangular frame. A black star is also displayed as a mark representing the target face direction. Furthermore, a message is also displayed encouraging the user to move the face direction to the direction of the star. The target object 50 can intuitively change the face direction to an appropriate direction by changing the face direction so that the black circle overlaps with the black star.

[0138] In addition, when the face direction of the biological detection device 2000 moves to the maximum direction (the black star mark in FIG. 20), the display device 20 may display guide information for prompting the face direction to stay in that direction for a certain period of time (for example, 2 seconds).

[0139] As another case where the operation performed by the target object 50 is not appropriate, a case where the face movement is too fast can be considered. Therefore, the second display control unit 2080 may display a guide on the display device 20 to prompt the face movement to slow down when the face movement is too fast. The speed of the face movement can be represented, for example, by the difference in the position of the face in the imaging images 40 adjacent in time series. In addition, for example, the difference in the face movement may be represented by the amount of change in the face direction over time.

[0140] For example, the second display control unit 2080 determines whether the speed of the face movement is equal to or greater than a threshold value. When the speed of the face movement is equal to or greater than the threshold value, the second display control unit 2080 causes the display device 20 to display guide information for prompting the face movement to slow down. This guide information includes, for example, a message such as "Please move your face more slowly." In addition, for example, the animation of the face movement shown in FIG. 17 may be included in the guide information. In this case, in the animation included in the guide information, the face may move slower than normal.

[0141] In addition, the second display control unit 2080 may display a guide regarding the posture of the body part (e.g., shoulders, etc.) in addition to the face. For example, the second display control unit 2080 calculates the direction of the body of the target object 50 using the captured image 40, and based on the calculated body direction, determines whether the body is facing forward (e.g., whether the absolute value of the difference between the body direction and the front direction is less than or equal to a threshold). When it is determined that the body is not facing forward, the second display control unit 2080 causes the display device 20 to display guide information for prompting the body to face forward. For example, this guide information includes a message such as "Please face your body forward." In addition, for example, the guide information may include an image of a body facing the front direction.

[0142] In the above example, the guide information is displayed on the display device 20. However, in addition to or instead of the display on the display device 20, the guide information may be output as sound. For example, various messages such as "Please face forward" and "Please face left while keeping your line of sight fixed" are output as voice messages. Also, as described above, when it is detected that the operation of the target object 50 is inappropriate, a voice message corresponding to the detected state may be output. For example, voice messages such as "Please turn your line of sight a little more to the upper right" and "Please move your face a little more slowly" are output. Also, when the direction can be represented by sound such as stereo sound, the direction in which the line of sight or face should be directed may be represented by the direction of the sound. For example, a message "Please face your face in the direction where the sound is coming from" is output as a sound heard from the right direction.

[0143] <Biological detection: S206, S208> The second biological detection unit 2120 calculates the face direction and the line-of-sight direction of the target object 50 included in each captured image 40 using the face image of the target object 50, and calculates the difference between them (S206). Then, based on the difference between the face direction and the line-of-sight direction calculated for each captured image 40, it is determined whether the target object 50 is a living body (S208). For example, when there is a sufficient difference between the face direction and the line-of-sight direction of the target object 50, the second biological detection unit 2120 determines that the target object 50 is a living body. On the other hand, when there is no sufficient difference between the face direction and the line-of-sight direction of the target object 50, the second biological detection unit 2120 determines that the target object 50 is not a living body.

[0144] Whether there is a sufficient difference between the face direction and the line-of-sight direction of the target object 50 is determined, for example, by comparing the difference between the face direction and the line-of-sight direction with a threshold value. As a specific example, the second biological detection unit 2120 calculates the difference between the face direction and the line-of-sight direction for each captured image 40, and determines whether the maximum value of the difference between the face direction and the line-of-sight direction is equal to or greater than a first threshold value. When the maximum value of the difference between the face direction and the line-of-sight direction is equal to or greater than the first threshold value, it is determined that there is a sufficient difference between the face direction and the line-of-sight direction. On the other hand, when the maximum value of the difference between the face direction and the line-of-sight direction is less than the first threshold value, it is determined that there is no sufficient difference between the face direction and the line-of-sight direction. Here, since the right direction is defined as the positive direction, the fact that the maximum value of the difference between the face direction and the line-of-sight direction is equal to or greater than the first threshold value means that when the face is turned to the right, there is a sufficient difference between the face direction and the line-of-sight direction (in other words, the face is turned sufficiently to the right while the line of sight is fixed).

[0145] For example, whether there is a sufficient difference between the face direction and the line-of-sight direction of the target object 50 may be determined by comparing the minimum value of the difference between the face direction and the line-of-sight direction with a second threshold value. When the minimum value of the difference between the face direction and the line-of-sight direction is less than or equal to the second threshold value, it is determined that there is a sufficient difference between the face direction and the line-of-sight direction. On the other hand, when the minimum value of the difference between the face direction and the line-of-sight direction is greater than the second threshold value, it is determined that there is no sufficient difference between the face direction and the line-of-sight direction. Here, since the left direction is set as the negative direction, the fact that the minimum value of the difference between the face direction and the line-of-sight direction is less than or equal to the second threshold value means that when the face is turned to the left, there is a sufficient difference between the face direction and the line-of-sight direction (in other words, with the line of sight fixed, the face is turned sufficiently large to the left).

[0146] When the face is sufficiently swung to both the left and right while the line of sight is fixed, the second biometric detection unit 2120 may determine that there is a sufficient difference between the face direction and the line-of-sight direction. In this case, for example, the second biometric detection unit 2120 determines whether "the maximum value of the difference between the face direction and the line-of-sight direction is greater than or equal to the first threshold value and the minimum value of the difference between the face direction and the line-of-sight direction is less than or equal to the second threshold value". When the maximum value of the difference between the face direction and the line-of-sight direction is greater than or equal to the first threshold value and the minimum value of the difference between the face direction and the line-of-sight direction is less than or equal to the second threshold value, the second biometric detection unit 2120 determines that there is a sufficient difference between the face direction and the line-of-sight direction. On the other hand, when the maximum value of the difference between the face direction and the line-of-sight direction is not greater than or equal to the first threshold value, or the minimum value of the difference between the face direction and the line-of-sight direction is not less than or equal to the second threshold value, the second biometric detection unit 2120 determines that there is no sufficient difference between the face direction and the line-of-sight direction.

[0147] By performing the determination for both the left and right directions in this way, it is possible to prevent impersonation using a 3D mask or the like with higher accuracy. For example, in a certain 3D mask, assume that the direction of the drawn line of sight is greatly biased to the right. And assume that the target object 50 tries to perform impersonation by wearing this 3D mask. In this case, when the target object 50 turns its face to the left, since the face is facing left while the line of sight is facing right, the difference between the face direction and the line of sight direction becomes large. Therefore, when the user turns to the left, it may be difficult to detect impersonation based on the difference between the face direction and the line of sight direction. On the other hand, in this case, when the user turns to the right, since both the face and the line of sight are facing right, the difference between the face direction and the line of sight direction becomes small. Therefore, when the user turns to the right, it is possible to detect impersonation based on the difference between the face direction and the line of sight direction. From the above, it is preferable to make the target object 50 face both the left and the right.

[0148] The biometric detection device 2000 may cause the target object 50 to perform a series of operations of shaking the face left and right a plurality of times, and for each of these plurality of operations, determine whether there is a sufficient difference between the face direction and the line of sight direction. A series of operations of shaking the face left and right refers to a series of operations of "turning the face to the left and then turning the face to the right", or a series of operations of "turning the face to the right and then turning the face to the left". For example, the second biometric detection unit 2120 treats a series of operations of shaking the face left and right as one set, and analyzes a plurality of captured images 40 to detect a plurality of sets of operations. The second biometric detection unit 2120 calculates either one or both of the maximum value and the minimum value of the difference between the face direction and the line of sight direction for each set, and determines whether the target object 50 is a living body according to the calculation result.

[0149] For example, the second biometric detection unit 2120 determines whether there is a sufficient difference between the face direction and the line-of-sight direction for each of a predetermined number n (n is an integer) of sets. Then, the second biometric detection unit 2120 determines whether the number of sets for which it is determined that there is a sufficient difference between the face direction and the line-of-sight direction is equal to or greater than a predetermined number m (m is an integer greater than or equal to 1 and less than or equal to n). When the number of sets for which it is determined that there is a sufficient difference between the face direction and the line-of-sight direction is equal to or greater than m, the second biometric detection unit 2120 determines that the target object 50 is a living body. On the other hand, when the number of sets for which it is determined that there is a sufficient difference between the face direction and the line-of-sight direction is less than the predetermined number m, the second biometric detection unit 2120 determines that the target object 50 is not a living body.

[0150] In addition, for example, the second biometric detection unit 2120 determines whether there is a sufficient difference between the face direction and the line-of-sight direction for each set detected within a predetermined time, and may determine that the target object 50 is a living body when the number of sets for which it is determined that there is a sufficient difference between the face direction and the line-of-sight direction is equal to or greater than m.

[0151] In addition, for example, the second biometric detection unit 2120 may repeatedly cause the target object 50 to swing its face from side to side until the number of sets for which it is determined that there is a sufficient difference between the face direction and the line-of-sight direction becomes m or more. In this case, for each series of operations in which the target object 50 swings its face from side to side, the second biometric detection unit 2120 determines whether there is a sufficient difference between the face direction and the line-of-sight direction for the series of operations. When it is determined that there is a sufficient difference between the face direction and the line-of-sight direction, 1 is added to a counter. The second biometric detection unit 2120 determines that the target object 50 is a living body when the counter becomes m or more. On the other hand, when the counter does not become m or more (for example, when a predetermined time elapses before the counter becomes m or more), the second biometric detection unit 2120 determines that the target object 50 is not a living body.

[0152] In addition, when the operation of shaking the face left and right is not performed correctly, the counter may be cleared to 0. Cases where the operation of shaking the face left and right is not performed correctly include: 1) cases where the face cannot be sufficiently turned to the left or right (for example, in the example of FIG. 25, before the black circle overlaps the black star, the case where the face is turned to the right), and 2) cases where it is determined that there is not enough difference between the face direction and the line-of-sight direction. When the counter is cleared in this way, it is determined that the target object 50 is a living body only when the correct operation of shaking the face left and right is continuously performed m times. On the other hand, until the correct operation of shaking the face left and right is continuously performed m times, it is not determined that the target object 50 is a living body. Note that an upper limit may be set for the number of times the counter is cleared, and when the number of times the counter is cleared reaches the upper limit, it may be determined that the target object 50 is not a living body. Also, a time limit may be set for the operation time, and when the operation of shaking the face left and right is not continuously performed correctly m times within the time limit, it may be determined that the target object 50 is not a living body.

[0153] Instead of handling the operations of turning the face to the right and turning the face to the left as a set, these operations may be counted individually. In this case, the number of times the operation of turning the face to the right and the operation of turning the face to the left should be performed (the predetermined number m described above) may be the same as each other or different from each other. In the latter case, for example, it is possible to "make the operation of turning the face to the left three times and make the operation of turning the face to the right two times".

[0154] In addition, when the operation of shaking the face left and right is performed multiple times in this way, the display control unit 2020 may display the number of times the operation has been correctly performed on the display device 20. Also, each time the operation is performed, a display (such as a circle mark or an OK display) indicating whether the operation has been correctly performed may be displayed on the display device 20.

[0155] <Modification Example 1 of Embodiment 2> In the biological detection device 2000 of Embodiment 2, the display device 20 may be moved left and right while keeping the line of sight fixed at a specific position (for example, the cross mark in FIG. 14 etc.) on the display device 20 without moving the face. FIG. 21 is a diagram illustrating the operation of the target object 50 in the biological detection device according to Modification 1 of Embodiment 2. Also in this case, when the front direction of the display device 20 is taken as the reference direction (0°), the direction of the face and the line of sight direction change in the same manner as the graph shown in FIG. 13. Therefore, also in the biological detection device 2000 of this modification, for each of the plurality of captured images 40, the difference between the face direction and the line of sight direction of the target object 50 is calculated, and based on the difference, it can be determined whether the target object 50 is a living body or not.

[0156] The specific method for determining whether the target object 50 is a living body is as described above. However, the biological detection device 2000 detects the operation of shaking the display device 20 left and right instead of detecting the operation of shaking the face left and right. Note that the operation of shaking the display device 20 left and right can be detected based on the change in the direction of the face with respect to the display device 20. For example, whether the display device 20 has been sufficiently moved to the right can be determined by determining whether the direction of the face with respect to the display device 20 has been sufficiently moved to the left. Similarly, whether the display device 20 has been sufficiently moved to the left can be determined by determining whether the direction of the face with respect to the display device 20 has been sufficiently moved to the right.

[0157] Here, in the biological detection device 2000 of this modification, the guidance information may include something different from the case of Embodiment 2. Specifically, the biological detection device 2000 causes the display device 20 to display guidance information that prompts shaking the terminal 60 left and right instead of prompting shaking the face left and right. Also, it is preferable to display guidance information that prompts not to move the face.

[0158] FIG. 22 is a diagram illustrating guide information in the biological detection device 2000 according to Modification 1 of Embodiment 2. In this example, first, the screen 100-1 is displayed. On the screen 100-1, a message is displayed prompting the user to face the terminal 60 (display device 20) forward while keeping the face still and fixing the line of sight on the cross mark on the display device 20.

[0159] Thereafter, the screen 100-2 is displayed. On the screen 100-2, a message is displayed prompting the user to move the terminal 60 to the left while keeping the face still and fixing the line of sight on the cross mark on the display device 20. The screen 100-2 is displayed, for example, in response to detecting that both the direction of the line of sight of the target object 50 and the direction of the face are facing the front of the display device 20.

[0160] Thereafter, the screen 100-3 is displayed. On the screen 100-3, a message is displayed prompting the user to move the terminal 60 to the right while keeping the face still and fixing the line of sight on the cross mark on the display device 20. The screen 100-3 is displayed, for example, in response to detecting that the terminal 60 has been sufficiently moved to the left while keeping the face still and fixing the line of sight on the cross mark on the display device 20. The determination of whether the terminal 60 has been sufficiently moved to the left can be realized, for example, by determining whether the direction of the face has turned sufficiently to the right (whether the direction of the face has reached or exceeded the positive threshold).

[0161] When the terminal 60 is repeatedly moved left and right, the screen 100-2 is displayed again. The screen 100-2 is displayed, for example, in response to detecting that the terminal 60 has been sufficiently moved to the right while keeping the face still and fixing the line of sight on the cross mark on the display device 20. The determination of whether the terminal 60 has been sufficiently moved to the right can be realized, for example, by determining whether the direction of the face has turned sufficiently to the left (whether the direction of the face has reached or fallen below the negative threshold).

[0162] <Modification 2 of Embodiment 2> In the biological detection device 2000 of Embodiment 2, while fixing the orientation of the display device 20 (without moving the display device 20 and keeping the face orientation facing the front of the display device 20), the line of sight may be swung left and right. FIG. 23 is a diagram illustrating the operation of the target object 50 in the biological detection device 2000 of Modification 2 of Embodiment 2.

[0163] This case corresponds to reversing the handling of the line-of-sight direction and the face direction in the biological detection device 2000 of Embodiment 2. That is, instead of fixing the line-of-sight direction, the face direction is fixed, and instead of swinging the face left and right, the line of sight is swung left and right. Also, in the guidance information, in the biological detection device 2000 of Modification 2 of Embodiment 2, the same guidance as that performed for the line-of-sight direction in the biological detection device 2000 of Embodiment 2 is performed for the face direction. That is, instead of the guidance for fixing the line-of-sight direction, the guidance for fixing the face direction is displayed. Further, in the biological detection device 2000 of Embodiment 2, the same guidance as that performed for the face direction is performed for the line-of-sight direction in the biological detection device 2000 of Modification 2 of Embodiment 2. That is, instead of the guidance for turning the face forward or left and right, the guidance for turning the line of sight forward or left and right is displayed.

[0164] FIG. 24 is a diagram illustrating the guidance information in the biological detection device 2000 of Modification 2 of Embodiment 2. In this example, first, the screen 110-1 is displayed. On the screen 110-1, a message is displayed prompting to direct the line of sight to the front of the display device 20 without moving the face.

[0165] After that, the screen 110-2 is displayed. On the screen 110-2, a message is displayed prompting to move the line of sight to the left without moving the face. The screen 110-2 is displayed, for example, in response to detecting that both the line-of-sight direction and the face direction of the target object 50 are facing the front of the display device 20.

[0166] Thereafter, screen 110-3 is displayed. A message prompting the user to move their gaze to the right without moving their face is displayed on screen 110-3. Screen 110-3 is displayed, for example, in response to detecting that with the face direction fixed forward, the gaze has been sufficiently moved to the left (the gaze direction has become equal to or less than the negative threshold). Note that on screen 110-3, since it is viewed with the gaze directed to the left, a rightward arrow is displayed at a position closer to the left.

[0167] When repeatedly moving the gaze left and right, screen 110-2 is displayed again. Screen 110-2 is displayed, for example, in response to detecting that with the face direction fixed forward, the gaze has been sufficiently moved to the right (the gaze direction has become equal to or greater than the positive threshold). However, since it is viewed with the gaze directed to the right, it is preferable that the leftward arrow is displayed at a position closer to the right.

[0168] <Regarding the combination with Embodiment 1> The biometric detection device 2000 of Embodiment 1 and the biometric detection device 2000 of Embodiment 2 perform biometric detection in different ways. Therefore, for the same target object 50, it is preferable that both biometric detection by the biometric detection device 2000 of Embodiment 1 and biometric detection by the biometric detection device 2000 of Embodiment 2 (which may be Modification 1 or Modification 2) are performed. FIG. 25 is a flowchart illustrating the processing flow when biometric detection by the biometric detection device 2000 of Embodiment 1 and biometric detection by the biometric detection device 2000 of Embodiment 2 are performed in sequence. In the example of FIG. 25, after biometric detection by the biometric detection device 2000 of Embodiment 1 (a series of processes shown in the flowchart of FIG. 4) is performed, biometric detection by the biometric detection device 2000 of Embodiment 2 (a series of processes shown in the flowchart of FIG. 16) is performed. However, after biometric detection by the biometric detection device 2000 of Embodiment 2 is performed, biometric detection by the biometric detection device 2000 of Embodiment 1 may also be performed.

[0169] For example, these biometric detections can be performed as part of user authentication. For example, as one of the user authentication methods, there is a method of capturing an image of the user's face with a camera and comparing the face with a pre-registered face to determine whether the user is a registered user. At this time, in order to prevent others from impersonating a registered user by using a photo or the like of a registered user, it is preferable to confirm that the object captured by the camera is a living body rather than a photo or the like. Therefore, in addition to confirming that the target object 50 is a registered user by comparing the image of the target object 50 with the image of the registered user, it is preferable to use the biometric detection device 2000 to confirm that the target object 50 is a living body (that is, impersonation using a photo or the like or a 3D mask, etc. is not being performed). Note that the process of confirming that the target object 50 is a registered user and the process of confirming that the target object 50 is a living body may be performed either first or in parallel.

[0170] <Method for preventing replacement of the target object 50> When biometric detection is performed using multiple methods, it is preferable to ensure that the processing is performed on the same target object 50 from the beginning to the end. For example, when biometric detection by the biometric detection device 2000 of Embodiment 1 is performed and then biometric detection by the biometric detection device 2000 of Embodiment 2 is performed, the same target object 50 should be the target of biometric detection from the start of biometric detection by the biometric detection device 2000 of Embodiment 1 until the completion of biometric detection by the biometric detection device 2000 of Embodiment 2. By doing so, it is possible to prevent the use of means of impersonation that are difficult to prevent with that method by changing the target of biometric detection for each type of method for realizing biometric detection.

[0171] For example, the biological detection device 2000 performs the following processes. First, as a premise, the biological detection device 2000 executes two or more types of biological detection processes. For example, it is assumed that the biological detection process performed by the biological detection device 2000 in Embodiment 1 (hereinafter, the first biological detection process) and the biological detection process performed by the biological detection device 2000 in Embodiment 2 (hereinafter, the second biological detection process) are carried out. In this case, between when the first biological detection process starts (after S102 in FIG. 25 starts first) and when the second biological detection process is completed (until S208 in FIG. 25 is completed), while the process for biological detection is in progress, the biological detection device 2000 repeatedly determines whether the same target object 50 continues to be imaged by the camera 10. And when it is determined that there is a possibility that the same target object 50 is not continuously imaged by the camera 10, the biological detection device 2000 ends the biological detection process.

[0172] The determination of whether the same target object 50 continues to be imaged by the camera 10 can be realized, for example, by tracking the target object 50. Specifically, the biological detection device 2000 tracks the target object 50 by analyzing the captured images 40 generated by the camera 10 in time series. The biological detection device 2000 repeatedly determines whether the target object 50 is included in the captured image 40 based on the tracking. And if the target object 50 is no longer included in the captured image 40 before a series of biological detection processes are completed, the biological detection device 2000 determines that the same target object 50 is not continuously imaged by the camera 10. On the other hand, while the target object 50 continues to be included in the captured image 40, it is determined that the same target object 50 continues to be imaged by the camera 10. In tracking, the area in the captured image 40 searched to detect the target object 50 is limited to near the area detected last time. Therefore, there is an advantage that the processing load required for detecting the target object 50 is reduced.

[0173] For example, in addition, the biological detection device 2000 may register the image feature amount of the target object 50 at the start of the biological detection process, and determine whether the target object 50 continues to be imaged by the camera 10 by confirming that the image feature amount continues to be included in the captured image 40. In this case, before a series of biological detection processes are started (for example, before S102 in FIG. 25 is first started), the biological detection device 2000 detects the target object 50 from the captured image 40 and registers the image feature amount of the target object 50 (stores it in the storage device). The biological detection device 2000 then detects the registered image feature amount of the target object 50 from the subsequently obtained captured image 40.

[0174] The process of detecting the image feature amount of the target object 50 from the captured image 40 may be performed for all the captured images 40, or may be performed for some of the captured images 40. In the latter case, for example, the biological detection device 2000 detects the image feature amount of the target object 50 for the captured images 40 at predetermined time intervals (for every predetermined number). For example, in addition, the biological detection device 2000 detects the image feature amount of the target object 50 for the captured image 40 obtained at that time in response to a specific condition being satisfied. In the case of the biological detection device 2000 of Embodiment 1, the specific condition is, for example, that the screen 30 displayed on the display device 20 has been changed. Also, in the case of the biological detection device 2000 of Embodiment 2, the specific condition is, for example, any one or more of the conditions such as the face facing forward (the face direction becomes 0°), the face facing left (the face direction becomes less than or equal to the negative threshold), the face facing right (the face direction becomes greater than or equal to the positive threshold), and the face moving.

[0175] Before a series of biometric detection processes are completed, if the image feature amount of the target object 50 stops being detected from the captured image 40, the biometric detection device 2000 determines that the same target object 50 is not continuously captured by the camera 10. On the other hand, if the image feature amount of the target object 50 continues to be detected from the captured image 40 until a series of biometric detection processes are completed, it is determined that the same target object 50 is continuously captured by the camera 10. According to the method of detecting the image feature amount of the target object 50 from the captured image 40, even when an object other than the target object 50 can be captured by the camera 10, it is possible to accurately determine whether the target object 50 is continuously captured by the camera 10.

[0176] When it is determined that the same target object 50 is not continuously captured by the camera 10, it is preferable for the biometric detection device 2000 to take some measures. For example, the biometric detection device 2000 can be set to restart the biometric detection of the target object 50 from the beginning (for example, from S102 in FIG. 25). At this time, it is preferable to display a message such as "Please continue to photograph yourself with the camera 10" on the display device 20 to make the user recognize that they must continue to photograph themselves with the camera 10. Among other things, for example, the biometric detection device 2000 may display information indicating which of the multiple types of biometric detections the biometric detection being performed was when it was determined that the same target object 50 was not continuously captured by the camera 10 on the display device 20.

[0177] Also, when the retry of the biometric detection process occurs a predetermined number of times or more (it may be once), the biometric detection process may be prohibited from being performed any further. Also, a process for protecting the account of the user targeted for impersonation may be performed. For example, as described above, assume that biometric detection is performed as part of user authentication. In this case, for example, assume that Person A attempts to impersonate registered user B. Specifically, assume that Person A causes the camera 10 to capture a photo of user B, and after it is determined that the person to be authenticated is user B, biometric detection is performed by the biometric detection device 2000. Then, assume that due to tracking of the target object 50 described above, the retry of the biometric detection occurs a predetermined number of times or more. In this case, for example, the biometric detection device 2000 protects the account of user B by locking the account of user B or sending a warning notification to the mobile terminal of user B. By doing so, the damage caused by impersonation can be more appropriately prevented.

[0178] Note that the biometric detection device 2000 may perform the same process as the process performed when the same target object 50 is not continuously imaged when a plurality of human faces are detected from the captured image 40.

[0179] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0180] In the above example, the program can be stored using various types of non-transitory computer readable media and provided to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROM, CD-R, CD-R / W, semiconductor memories (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM). Also, the program may be provided to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer readable media can supply the program to the computer via wired communication paths such as electric wires and optical fibers, or wireless communication paths.

[0181] Some or all of the above embodiments may also be described as follows, but are not limited thereto. (Appendix 1) A computer readable medium storing a program executed by a computer, wherein the program causes the computer to perform a display control step of causing a display device to display a first screen including displays in a plurality of regions and a second screen including a display different from the first screen, an acquisition step of acquiring a plurality of captured images generated by capturing an object with a camera while the first screen and the second screen are respectively being displayed, and a biometric detection step of determining whether the object is a living body using the plurality of captured images. A computer-readable medium in which the first screen includes at least two regions with different displays. (Appendix 2) Among the plurality of regions included in the first screen, at least two of the regions include displays of different colors, displays of different brightnesses, or different characters, symbols, or figures, the computer-readable medium according to Appendix 1. (Appendix 3) In the display control step, the boundaries of the plurality of regions included in the first screen are determined based on the positional relationship between the camera that generates the captured image and the display device, the computer-readable medium according to Appendix 1 or 2. (Appendix 4) The boundaries of the plurality of regions included in the first screen are determined by a user input, the computer-readable medium according to Appendix 1 or 2. (Appendix 5) The program has an identification model learned to output a label indicating whether the object shown in the captured image is a living body in response to the input of a plurality of the captured images. In the display control step, by inputting the plurality of captured images acquired in the acquisition step into the identification model and obtaining the label from the identification model, a determination is made as to whether the object is a living body, the computer-readable medium according to any one of Appendices 1 to 4. (Appendix 6) The identification model is learned using both positive training data and negative training data. The positive training data includes a plurality of captured images obtained by capturing the face of a real person while the first screen and the second screen are respectively being displayed, and data indicating that the captured object is a living body. The negative training data includes a plurality of captured images obtained by capturing an image of a human face while the first screen and the second screen are respectively being displayed, and data indicating that the captured object is not a living body, the computer-readable medium according to Appendix 5. (Appendix 7) In the display control step, identify the intensity of the ambient light around the display device, and when the intensity of the ambient light is equal to or less than a threshold value, cause the display device to display the first screen and the second screen. The computer-readable medium according to any one of Appendices 1 to 6. (Appendix 8) In the display control step, when the intensity of the ambient light is greater than a threshold value, output a message that prompts the user to move to a place where the ambient light is weaker than the current intensity. The computer-readable medium according to Appendix 7. (Appendix 9) In the display control step, identify the intensity of the ambient light around the display device, and determine the display to be included in at least one of the first screen and the second screen according to the intensity of the ambient light. The computer-readable medium according to any one of Appendices 1 to 8. (Appendix 10) A second display control step of causing the display device to display a guide regarding the direction of the line of sight and a guide regarding the direction of the face, A second acquisition step of acquiring a captured image generated by capturing the target a plurality of times with the camera, Using the face image of the target shown in each of the captured images, calculate the difference between the direction of the face and the direction of the line of sight for each of the captured images, and based on the calculated difference, determine whether the target is a living body. Execute the second biometric detection step. In the second display control step, cause the display device to display a guide that prompts the user to shake the face left and right while continuing to look at the same place. The computer-readable medium according to any one of Appendices 1 to 9. (Appendix 11) In the second display control step, Cause the display device to display a guide that prompts the user to turn the face in the first direction without moving the line of sight, Determine whether the direction of the face of the target is the first direction, When the direction of the face of the target is the first direction, cause the display device to display a guide that prompts the user to turn the face in the second direction without moving the line of sight. The computer-readable medium according to Appendix 10. (Appendix 12) In the second display control step, it is determined whether or not the magnitude of the swing width of the face of the subject is equal to or greater than a threshold value. When the magnitude of the swing width of the face is less than the threshold value, a guide for prompting the subject to swing the face more widely is caused to be displayed on the display device. The computer-readable medium according to Appendix 10 or 11. (Appendix 13) In the second display control step, it is determined whether or not the speed at which the face of the subject moves is equal to or greater than a threshold value. When the speed at which the face moves is less than the threshold value, a guide for prompting the subject to move the face more slowly is caused to be displayed on the display device. The computer-readable medium according to any one of Appendices 10 to 12. (Appendix 14) In the second display control step, it is determined whether or not the line-of-sight direction of the subject is fixed. When the line-of-sight direction is not fixed, a guide for prompting the subject not to move the line-of-sight direction is caused to be displayed on the display device. The computer-readable medium according to any one of Appendices 10 to 13. (Appendix 15) In the second display control step, any one or more of a display representing the direction of the face of the subject, a display representing the direction in which the subject should face the face, a display representing the line-of-sight direction of the subject, and a display representing the direction in which the subject should direct the line of sight are caused to be displayed on the display device. The computer-readable medium according to any one of Appendices 10 to 14. (Appendix 16) Using the captured image generated by the camera between when the display of the screen by the display control step starts and when the biometric detection is performed by the second biometric detection step, it is determined whether or not the same subject is continuously imaged by the camera. When the same subject is not continuously imaged, the process is restarted from the display control step. The computer-readable medium according to any one of Appendices 10 to 15. (Appendix 17) By tracking the subject, it is determined whether or not the subject appears in each of the captured images. The computer-readable medium according to Supplementary Note 16, which determines that the same object has not been continuously imaged when an imaging image in which the object is not shown is detected. (Supplementary Note 18) detecting image feature amounts of the object from each of the imaging images, The computer-readable medium according to Supplementary Note 16, which determines that the same object has not been continuously imaged when an imaging image that does not include the image feature amount of the object is detected. (Supplementary Note 19) a display control unit that causes a display device to display a first screen including displays in a plurality of regions respectively and a second screen including a display different from the first screen; an acquisition unit that acquires a plurality of imaging images generated by imaging an object with a camera while the first screen and the second screen are respectively being displayed; a living body detection unit that determines whether or not the object is a living body using the plurality of imaging images, a living body detection device, wherein the first screen includes at least two regions with different displays. (Supplementary Note 20) The living body detection device according to Supplementary Note 19, wherein at least two of the plurality of regions included in the first screen include displays of different colors, displays of different brightnesses, or different characters, symbols, or figures. (Supplementary Note 21) The display control unit determines a boundary of the plurality of regions included in the first screen based on a positional relationship between the camera that generates the imaging image and the display device, according to the living body detection device of Supplementary Note 19 or 20. (Supplementary Note 22) The boundary of the plurality of regions included in the first screen is determined by a user input, according to the living body detection device of Supplementary Note 19 or 20. (Supplementary Note 23) having an identification model learned to output a label indicating whether or not the object shown in the imaging image is a living body in response to input of the plurality of imaging images, The display control unit, the acquisition unit inputs the acquired plurality of captured images into the identification model, and obtains the label from the identification model to determine whether the target is a living body, the biological detection device according to any one of appendices 19 to 22. (Appendix 24) The identification model is trained using both positive example training data and negative example training data, The positive example training data includes a plurality of captured images obtained by capturing the face of a real person while the first screen and the second screen are respectively displayed, and data indicating that the captured target is a living body, The negative example training data includes a plurality of captured images obtained by capturing an image of a human face while the first screen and the second screen are respectively displayed, and data indicating that the captured target is not a living body, the biological detection device according to appendix 23. (Appendix 25) The display control unit identifies the intensity of the ambient light around the display device, and when the intensity of the ambient light is equal to or less than a threshold value, causes the first screen and the second screen to be displayed on the display device, the biological detection device according to any one of appendices 19 to 24. (Appendix 26) When the intensity of the ambient light is greater than the threshold value, the display control unit outputs a message prompting the user to move to a place where the ambient light is weaker than the current intensity, the biological detection device according to appendix 25. (Appendix 27) The display control unit identifies the intensity of the ambient light around the display device, and determines the display to be included in at least one of the first screen and the second screen according to the intensity of the ambient light, the biological detection device according to any one of appendices 19 to 26. (Appendix 28) A second display control unit that causes the display device to display a guide regarding the direction of the line of sight and a guide regarding the direction of the face, A second acquisition unit that acquires captured images generated by capturing the target a plurality of times with the camera, Using the image of the face of the subject shown in each of the captured images, a second biological detection unit calculates the difference between the face direction and the line-of-sight direction for each of the captured images, and determines whether the subject is a living body based on the calculated difference. The second display control unit causes the display device to display a guide for prompting the subject to swing the face left and right while continuously looking at the same place. The biological detection device according to any one of Appendices 19 to 27. (Appendix 29) The second display control unit displays a guide on the display device for prompting the subject to turn the face in a first direction without moving the line of sight. determines whether the face direction of the subject is the first direction. When the face direction of the subject is the first direction, the second display control unit causes the display device to display a guide for prompting the subject to turn the face in a second direction without moving the line of sight. The biological detection device according to Appendix 28. (Appendix 30) The second display control unit determines whether the amplitude of the swing of the face of the subject is equal to or greater than a threshold value. When the amplitude of the swing of the face is less than the threshold value, the second display control unit causes the display device to display a guide for prompting the subject to swing the face more greatly. The biological detection device according to Appendix 28 or 29. (Appendix 31) The second display control unit determines whether the speed at which the face of the subject moves is equal to or greater than a threshold value. When the speed at which the face moves is less than the threshold value, the second display control unit causes the display device to display a guide for prompting the subject to move the face more slowly. The biological detection device according to any one of Appendices 28 to 30. (Appendix 32) The second display control unit determines whether the line-of-sight direction of the subject is fixed. When the line-of-sight direction is not fixed, the second display control unit causes the display device to display a guide for prompting the subject not to move the line-of-sight direction. The biological detection device according to any one of Appendices 28 to 31. (Appendix 33) The second display control unit causes the display device to display any one or more of a display representing the direction of the face of the object, a display representing the direction in which the object should face, a display representing the line-of-sight direction of the object, and a display representing the direction in which the object should direct its line of sight. The biological detection device according to any one of Appendices 28 to 32. (Appendix 34) Using the captured image generated by the camera between the start of the display of the screen by the display control unit and the performance of biological detection by the second biological detection unit, it is determined whether the same object is continuously captured by the camera. If the same object is not continuously captured, the display control unit starts over. The biological detection device according to any one of Appendices 28 to 33. (Appendix 35) By tracking the object, it is determined whether the object appears in each of the captured images. When a captured image in which the object does not appear is detected, it is determined that the same object is not continuously captured. The biological detection device according to Appendix 34. (Appendix 36) The image feature amount of the object is detected from each of the captured images. When a captured image that does not include the image feature amount of the object is detected, it is determined that the same object is not continuously captured. The biological detection device according to Appendix 34. (Appendix 37) A control method executed by a computer, comprising: a display control step of causing a display device to display a first screen including displays in a plurality of regions respectively and a second screen including a display different from the first screen; an acquisition step of acquiring a plurality of captured images generated by capturing an object with a camera while the first screen and the second screen are respectively being displayed; a biological detection step of determining whether the object is a living body using the plurality of captured images, The control method, wherein the first screen includes at least two regions with different displays. (Appendix 38) Among the plurality of regions included in the first screen, at least two of the regions have different color displays, different brightness displays, or different characters, symbols, or figures, and the control method according to Supplementary Note 37. (Supplementary Note 39) In the display control step, the boundary of the plurality of regions included in the first screen is determined based on the positional relationship between the camera that generates the captured image and the display device, and the control method according to Supplementary Note 37 or 38. (Supplementary Note 40) The boundary of the plurality of regions included in the first screen is determined by user input, and the control method according to Supplementary Note 37 or 38. (Supplementary Note 41) The computer has an identification model learned to output a label indicating whether the object shown in the captured image is a living body in response to the input of a plurality of the captured images, In the display control step, a plurality of the captured images obtained in the acquisition step are input into the identification model, and the label is obtained from the identification model to determine whether the object is a living body, and the control method according to any one of Supplementary Notes 37 to 40. (Supplementary Note 42) The identification model is learned using both positive example training data and negative example training data, The positive example training data includes a plurality of captured images obtained by capturing the face of a real person while the first screen and the second screen are respectively displayed, and data indicating that the captured object is a living body, The negative example training data includes a plurality of captured images obtained by capturing an image of a human face while the first screen and the second screen are respectively displayed, and data indicating that the captured object is not a living body, and the control method according to Supplementary Note 41. (Supplementary Note 43) In the display control step, the intensity of ambient light around the display device is specified, and when the intensity of the ambient light is equal to or less than a threshold value, the first screen and the second screen are caused to be displayed on the display device. The control method according to any one of Appendices 37 to 42. (Appendix 44) In the display control step, when the intensity of the ambient light is greater than the threshold value, a message is output to prompt the movement of the ambient light to a place where the ambient light is weaker than the current intensity. The control method according to Appendix 43. (Appendix 45) In the display control step, the intensity of ambient light around the display device is specified, and according to the intensity of the ambient light, the display included in at least one of the first screen and the second screen is determined. The control method according to any one of Appendices 37 to 44. (Appendix 46) A second display control step of causing the display device to display a guide regarding the direction of the line of sight and a guide regarding the direction of the face, A second acquisition step of acquiring a captured image generated by capturing the target a plurality of times with the camera, Using the face image of the target shown in each of the captured images, the difference between the direction of the face and the direction of the line of sight is calculated for each of the captured images, and based on the calculated difference, a second biometric detection step of determining whether the target is a living body is performed. In the second display control step, a guide prompting the user to shake the face left and right while continuously looking at the same place is caused to be displayed on the display device. The control method according to any one of Appendices 37 to 45. (Appendix 47) In the second display control step, A guide prompting the user to turn the face in the first direction without moving the line of sight is displayed on the display device, It is determined whether the direction of the face of the target is the first direction, When the direction of the face of the target is the first direction, a guide prompting the user to turn the face in the second direction without moving the line of sight is caused to be displayed on the display device. The control method according to Appendix 46. (Appendix 48) In the second display control step, it is determined whether or not the magnitude of the swing range of the face of the target is equal to or greater than a threshold value. When the magnitude of the swing range of the face is less than the threshold value, a guide prompting the face to swing more greatly is caused to be displayed on the display device, the control method according to appended note 46 or 47. (Appended Note 49) In the second display control step, it is determined whether or not the speed at which the face of the target moves is equal to or greater than a threshold value. When the speed at which the face moves is less than the threshold value, a guide prompting the face to move more slowly is caused to be displayed on the display device, the control method according to any one of appended notes 46 to 48. (Appended Note 50) In the second display control step, it is determined whether or not the line-of-sight direction of the target is fixed. When the line-of-sight direction is not fixed, a guide prompting the line-of-sight direction not to move is caused to be displayed on the display device, the control method according to any one of appended notes 46 to 49. (Appended Note 51) In the second display control step, any one or more of a display representing the direction of the face of the target, a display representing the direction in which the target should face the face, a display representing the line-of-sight direction of the target, and a display representing the direction in which the target should direct the line of sight are caused to be displayed on the display device, the control method according to any one of appended notes 46 to 50. (Appended Note 52) Using the captured image generated by the camera between when the display of the screen by the display control step is started and when the biological detection is performed by the second biological detection step, it is determined whether or not the same target is continuously captured by the camera. When the same target is not continuously captured, the process is restarted from the display control step, the control method according to any one of appended notes 46 to 51. (Appended Note 53) By tracking the target, it is determined whether or not the target appears in each of the captured images. When a captured image in which the target does not appear is detected, it is determined that the same target is not continuously captured, the control method according to appended note 52. (Appended Note 54) Detect the image feature amount of the object from each of the captured images, The control method according to supplementary note 52, which determines that the same object has not been continuously imaged when an image in which the image feature amount of the object is not included is detected.

Explanation of Signs

[0182] 10 Camera 20 Display device 30 Screen 32 Region 34 Boundary line 40 Captured image 50 Target object 60 Terminal 80, 90, 100, 110 Screens 500 Computer 502 Bus 504 Processor 506 Memory 508 Storage device 510 Input / output interface 512 Network interface 2000 Biometric detection device 2020 Display control unit 2040 Acquisition unit 2060 Biometric detection unit 2080 Second display control unit 2100 Second acquisition unit 2120 Second biometric detection unit

Claims

1. A display control unit that controls a display screen to be displayed on a display device; an acquisition unit that acquires a captured image generated by capturing an image of an object while the display screen is being displayed; a living body detection unit that determines whether the target is a living body using the captured image, the display screen has a plurality of areas each having a different display; the display control unit changes a contrast of the display in the plurality of regions in accordance with an intensity of ambient light around the display device; the display control unit changes the display so that the contrast is increased as the intensity of the ambient light increases, The display control unit increases the contrast by making one of the plurality of regions darker than the other region darker.

2. The biological detection device according to claim 1 , wherein the display control unit changes the display so that the contrast is lowered as the intensity of the ambient light becomes weaker.

3. the display screen includes at least a first display screen and a second display screen different from the first display screen; The biological detection device according to claim 1 , wherein the captured image is an image generated by capturing an image of the target while the first display screen and the second display screen are being displayed, respectively.

4. The biological detection device according to claim 3 , wherein the display control unit determines the position of a straight line representing a boundary between the plurality of regions so that the camera is positioned on an extension of the straight line.

5. The display control unit controls the display so that at least two of the multiple regions are displayed in different colors, different brightnesses, or include different letters, symbols, or figures.

6. a display control step of causing a display device to display a display screen including a plurality of areas with different displays; an acquisition step of acquiring a captured image generated by capturing an image of an object while the display screen is being displayed; a live body detection step of determining whether or not the target is a live body using the captured image; varying the contrast of the display in the plurality of regions in response to an intensity of ambient light around the display device; In the step of changing the contrast, the display is changed so that the contrast becomes higher as the intensity of the ambient light increases; A program for increasing the contrast by making one area darker than the other area darker in the plurality of areas in the step of changing the contrast.

7. 1. A computer-implemented control method comprising: a display control step of causing a display device to display a display screen including a plurality of areas with different displays; an acquisition step of acquiring a captured image generated by capturing an image of an object while the display screen is being displayed; a live body detection step of determining whether or not the target is a live body using the captured image; and varying the contrast of the display in the plurality of regions in response to an intensity of ambient light around the display device; In the step of changing the contrast, the display is changed so that the contrast becomes higher as the intensity of the ambient light increases; A control method in which, in the step of changing the contrast, one of the plurality of regions is displayed darker than the other region, thereby increasing the contrast.

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