Imaging equipment

Abstract

A photography device (10) that comprises a reflecting plate (20) that covers a photography space (102) of a passage (101) for a person (100) from one or both sides of the passage (101) and diffusely reflects sub-terahertz waves, a first light source (41) that emits sub-terahertz waves at the reflecting plate (20), and a first detector (51) that receives sub-terahertz waves that have been emitted by the first light source (41), diffusely reflected by the reflecting plate (20), and then reflected by the person (100) and generates an image on the basis of the reflected waves received. The first light source (41) and the first detector (51) are arranged so as to be further to a first direction side than the center of the photography space (102) in the direction in which the passage (101) extends.

Description

[Technical field]

[0001] The present disclosure relates to an imaging device. [Background technology]

[0002] Conventionally, imaging devices that capture images of an object using terahertz waves and sub-terahertz waves are known. For example, Patent Document 1 discloses an image acquisition device that captures an image of a subject using terahertz waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-87725 A Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art In an imaging device that captures an image of an object using sub-terahertz waves, it is required to effectively irradiate the object with sub-terahertz waves in order to improve image quality, etc.

[0005] The present disclosure provides an imaging device capable of effectively irradiating an object to be imaged with sub-terahertz waves. [Means for solving the problem]

[0006] An imaging device according to one aspect of the present disclosure includes a reflector that covers a shooting space on a passageway through which an object to be photographed passes from at least one of both sides of the passageway and diffusely reflects sub-terahertz waves, a first light source that emits sub-terahertz waves toward the reflector, and a first detector that receives the sub-terahertz waves that are emitted from the first light source and then diffusely reflected by the reflector and are reflected by the object to be photographed and generates an image based on the received reflected waves, wherein the first light source and the first detector are positioned on the first direction side of the center of the shooting space in the direction in which the passageway extends. Effect of the Invention

[0007] According to an image capturing device according to an aspect of the present disclosure, an object to be captured can be effectively irradiated with sub-terahertz waves. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the appearance of an imaging device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a configuration of the imaging device according to the embodiment. [Diagram 3] FIG. 3 is a schematic diagram of the imaging device according to the embodiment when viewed from above. [Figure 4] FIG. 4 is a schematic diagram showing a cross-sectional structure of a reflector according to the embodiment. [Figure 5A] FIG. 5A is a schematic diagram showing an example of a first light source according to an embodiment when viewed from the front. [Figure 5B] FIG. 5B is a schematic diagram showing another example of the first light source according to the embodiment when viewed from the front. [Figure 6A] FIG. 6A is a diagram for explaining an example of the operation of the imaging device according to the embodiment. [Figure 6B] FIG. 6B is a diagram for explaining an example of the operation of the imaging device according to the embodiment. [Figure 6C] FIG. 6C is a diagram for explaining an example of the operation of the imaging device according to the embodiment. [Figure 6D] FIG. 6D is a diagram for explaining an example of the operation of the imaging device according to the embodiment. [Figure 7] FIG. 7 is a schematic diagram of an image capturing device according to the first modification of the embodiment, as viewed from above. [Figure 8A] FIG. 8A is a diagram for explaining an example of the operation of the imaging device according to the first modification of the embodiment. [Figure 8B] FIG. 8B is a diagram for explaining an example of the operation of the imaging device according to the first modification of the embodiment. [Figure 8C]FIG. 8C is a diagram for explaining an example of the operation of the imaging device according to the first modification of the embodiment. [Figure 8D] FIG. 8D is a diagram for explaining an example of the operation of the imaging device according to the first modification of the embodiment. [Figure 9] FIG. 9 is a schematic diagram of an image capturing device according to the second modification of the embodiment, as viewed from above. [Figure 10A] FIG. 10A is a diagram for explaining an example of the operation of the imaging device according to the second modification of the embodiment. [Figure 10B] FIG. 10B is a diagram for explaining an example of the operation of the imaging device according to the second modification of the embodiment. [Figure 11] FIG. 11 is a schematic diagram of an image capturing device according to the third modification of the embodiment, as viewed from above. [Figure 12A] FIG. 12A is a diagram for explaining an example of the operation of the imaging device according to the third modification of the embodiment. [Figure 12B] FIG. 12B is a diagram for explaining an example of the operation of the imaging device according to the third modification of the embodiment. [Figure 12C] FIG. 12C is a diagram for explaining an example of the operation of the imaging device according to the third modification of the embodiment. [Figure 12D] FIG. 12D is a diagram for explaining an example of the operation of the imaging device according to the third modification of the embodiment. [Figure 13] FIG. 13 is a schematic diagram of a reflector according to a modified example, as viewed from the front. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Summary of the Disclosure) An outline of one aspect of the present disclosure is as follows.

[0010] An imaging device according to one aspect of the present disclosure includes a reflector that covers a shooting space on a passageway through which an object to be photographed passes from at least one of both sides of the passageway and diffusely reflects sub-terahertz waves, a first light source that emits sub-terahertz waves toward the reflector, and a first detector that receives the sub-terahertz waves that are emitted from the first light source and then diffusely reflected by the reflector and are reflected by the object to be photographed and generates an image based on the received reflected waves, wherein the first light source and the first detector are positioned on the first direction side of the center of the shooting space in the direction in which the passageway extends.

[0011] In this specification, "sub-terahertz waves" refers to electromagnetic waves with a frequency of 0.05 THz or more and 2 THz or less. In this specification, sub-terahertz waves may be electromagnetic waves with a frequency of 0.08 THz or more and 1 THz or less. In addition, in this specification, "diffuse reflection" refers to sub-terahertz waves that are incident on a reflector at one macroscopic incident angle and are reflected at multiple reflection angles by the uneven surface structure having multiple microscopic unevenness.

[0012] According to this aspect, since the imaging space is covered with a reflector from at least one side of the imaging space, the sub-terahertz waves emitted from the first light source are diffusely reflected by the reflector and enter the imaging object. As a result, the inner surface of the reflector functions as a surface light source, and the sub-terahertz waves are irradiated from various angles over a relatively wide range toward the imaging object. In addition, while visible light is likely to be diffusely reflected by the surface of the imaging object, the sub-terahertz waves have a longer wavelength than visible light, so that the size of the surface unevenness of the imaging object is likely to be equal to or smaller than the wavelength of the sub-terahertz waves, and are likely to be specularly reflected by the surface of the imaging object. Therefore, when the direction of the sub-terahertz waves incident on the imaging object is limited to one direction, the direction of the reflected waves by the imaging object is also limited, and therefore the reflected waves by the imaging object are unlikely to head toward the detector. On the other hand, in this aspect, the object to be photographed is irradiated with sub-terahertz waves from various angles, and the waves reflected by the specular reflection from the object to be photographed are also emitted at various angles, so that even if the sub-terahertz waves are specularly reflected from the surface of the object to be photographed, they tend to head toward the detector. Therefore, the photographing device according to this aspect can effectively irradiate the object to be photographed with sub-terahertz waves. Furthermore, by effectively irradiating the object to be photographed with sub-terahertz waves, the amount of reflected waves entering the first detector increases. Therefore, the image quality of the image generated by the first detector is improved.

[0013] Also, for example, the reflecting plates may sandwich the photographing space from both sides of the passage.

[0014] As a result, since the imaging space is sandwiched between the reflectors, the sub-terahertz waves emitted from the light source are diffusely reflected at least once by the reflectors before entering the imaging target. Also, the sub-terahertz waves emitted from the light source to the reflectors are repeatedly diffusely reflected by the reflectors and tend to remain within the imaging space. Therefore, the imaging device can more effectively irradiate the imaging target with sub-terahertz waves.

[0015] Also, for example, the imaging device may further include a second light source that emits sub-terahertz waves toward the reflector, and a second detector that receives the sub-terahertz waves that are emitted from the second light source and then diffusely reflected by the reflector, reflected by the object to be imaged, and generates an image based on the received reflected waves, and the second light source and the second detector may be located in a second direction that is opposite to the first direction and is closer to the center of the imaging space in the direction in which the passage extends.

[0016] In this way, the first detector generates an image of the object in a first direction, and the second detector generates an image of the object in a second direction, so that images of both sides of the object in the direction in which the passage extends can be generated.

[0017] Also, for example, the imaging device may further include a light source control unit that controls the emission of sub-terahertz waves from each of the first light source and the second light source, wherein the light source control unit causes the first light source to emit sub-terahertz waves during a first period and does not cause the second light source to emit sub-terahertz waves, and causes the second light source to emit sub-terahertz waves during a second period different from the first period and does not cause the first light source to emit sub-terahertz waves, the first detector generates an image based on reflected waves from the object to be photographed received during the first period, and the second detector generates an image based on reflected waves from the object to be photographed received during the second period.

[0018] As a result, the first light source and the second light source do not emit sub-terahertz waves at the same time when the first detector and the second detector generate images. Therefore, when the first detector generates an image, the sub-terahertz waves originating from the second light source do not enter simultaneously with the waves reflected by the object to be photographed, and when the second detector generates an image, the sub-terahertz waves originating from the first light source do not enter simultaneously with the waves reflected by the object to be photographed. Therefore, the imaging device can generate an image in which the image of the waves reflected by the object to be photographed is clear.

[0019] Also, for example, one of the first detector and the second detector may start exposure for generating an image based on the received reflected waves from the object to be photographed immediately after the other of the first detector and the second detector completes exposure for generating an image based on the received reflected waves from the object to be photographed.

[0020] This allows the generation of an image by the first detector and the generation of an image by the second detector to be performed without any time interval, so that the object can be photographed from both the front and back without any time interval, thereby reducing the area of ​​the object that is not photographed.

[0021] Also, for example, when the object to be photographed passes through the photographing space, the first detector may generate an image based on a wave reflected by the object to be photographed passing through the end of the photographing space on the second direction side in the direction in which the passage extends, and the second detector may generate an image based on a wave reflected by the object to be photographed passing through the end of the photographing space on the first direction side in the direction in which the passage extends.

[0022] As a result, images of the object are captured at both ends of the shooting space in the direction in which the passage extends. Therefore, even when capturing both an image of the surface of the object in the first direction and an image of the surface of the object in the second direction, the length of the reflector in the direction in which the passage extends can be shortened.

[0023] Also, for example, the first detector may receive reflected waves from the object to be photographed at multiple times while the object passes through the photographing space, and generate multiple images based on each of the received reflected waves.

[0024] This allows images of a plurality of aspects of the object to be captured to be generated while the object passes through the capture space.

[0025] Also, for example, the first detector may generate multiple images based on a reflected wave from the object to be photographed that is located in a second direction, which is opposite to the first direction, relative to the reflector in the direction in which the passage extends, and a reflected wave from the object to be photographed passing through the photographing space.

[0026] As a result, the photographing device generates an image of the object to be photographed before the object enters the photographing space, so that the length of the reflector path in the extending direction can be shortened.

[0027] Also, for example, the imaging device may include a plurality of the first detectors, and the plurality of first detectors may be arranged along the extending direction of the passage.

[0028] This makes it possible to change the first detector that generates an image in accordance with the movement of the object to be photographed in the direction in which the passage extends.

[0029] Also, for example, the imaging device may further include a third detector that receives the sub-terahertz waves that are emitted from the first light source and then diffusely reflected by the reflector, reflected by the object to be imaged, and generates an image based on the received reflected waves, and the third detector may be located on the first direction side of the center of the imaging space in the direction in which the passage extends, and the first detector and the third detector may have different incident directions of the reflected waves from the object to be imaged.

[0030] As a result, images are generated by the first detector and the third detector based on reflected waves from surfaces of the object to be photographed that face in different directions.

[0031] Also, for example, the first detector may be located closer to the first direction than the reflector in the direction in which the passage extends, and the first light source may be located between the reflector and the first detector.

[0032] As a result, the first light source and the first detector are positioned on the same side of the reflector. Also, the first light source emits sub-terahertz waves toward the reflector from a position closer to the reflector than the first detector. Furthermore, after being emitted from the first light source, the sub-terahertz waves are diffusely reflected by the reflector and irradiated onto the object to be photographed without traveling toward the first detector. Therefore, the sub-terahertz waves emitted from the first light source can be used efficiently.

[0033] Furthermore, for example, the first light source may include at least one of a plurality of point light sources arranged along the reflector when viewed from the direction in which the passage extends, each of which radiates sub-terahertz waves, and a line light source extending along the reflector and radiating sub-terahertz waves.

[0034] This allows the first light source to emit sub-terahertz waves widely along the reflector when viewed from the direction in which the passage extends.

[0035] Hereinafter, the embodiment will be specifically described with reference to the drawings.

[0036] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0037] Furthermore, in this specification, terms indicating the relationship between elements, such as "parallel," terms indicating the shape of an element, such as "flat plate," terms indicating time, such as "immediately after," and numerical ranges are not expressions that only express a strict meaning, but are expressions that include a substantially equivalent range, for example, a difference of about a few percent.

[0038] In addition, the drawings are not necessarily strict illustrations. In the drawings, the same reference numerals are used for substantially the same configurations, and duplicated explanations are omitted or simplified.

[0039] (Embodiment) [composition] First, the configuration of the imaging device according to the embodiment will be described.

[0040] Fig. 1 is a schematic diagram showing the appearance of an image capturing device 10 according to the present embodiment. In Fig. 1, components other than a reflector 20 are omitted.

[0041] 1, the image capturing device 10 is an image capturing device that, for example, irradiates sub-terahertz waves onto a person 100 when the person 100 passes through an image capturing space 102 on a passage 101 sandwiched between reflectors 20, and captures an image based on the reflected waves of the irradiated sub-terahertz waves by the person 100. The image capturing space 102 is a space on the passage 101 that is covered by the reflector 20. The image capturing device 10 also captures an image of a dangerous object, such as a knife, that the person 100 conceals under clothing, for example. The person 100 and the dangerous object, such as a knife, that the person 100 conceals under clothing, are each an example of an object to be captured.

[0042] Each component of the imaging device 10 will be described in detail below. Fig. 2 is a block diagram showing the configuration of the imaging device 10 according to the present embodiment. Fig. 3 is a schematic diagram of the imaging device 10 according to the present embodiment as viewed from above. Fig. 3 shows a person 100 passing through an imaging space 102. Fig. 3 also shows an example of the path of the sub-terahertz waves emitted from the first light source 41 and the second light source 42 with arrows.

[0043] The photographing device 10 includes a reflector 20, a first light source 41, a second light source 42, a first detector 51, a second detector 52, a third detector 53, a fourth detector 54, a light source control unit 60, a photographing control unit 70, a sensor 80, and an image processing unit 90. Hereinafter, the first light source 41 and the second light source 42 may be collectively referred to simply as "light source". Also, the first detector 51, the second detector 52, the third detector 53, and the fourth detector 54 may be collectively referred to simply as "detector".

[0044] The reflecting plate 20 covers the space above the passage 101 through which the person 100 passes, specifically the photographing space 102, from at least one of both sides of the passage 101. Specifically, covering at least one of both sides of the passage 101 means covering at least one of both sides, that is, two directions perpendicular to the direction in which the passage 101 extends, when the passage 101 is viewed from above. In this embodiment, the reflecting plate 20 sandwiches the photographing space 102 above the passage 101 through which the person 100 passes, from both sides of the passage 101. In other words, the reflecting plate 20 covers the photographing space 102 from both sides of the passage 101. The photographing space 102 is, for example, a space sandwiched between the inner surfaces (inner surfaces 25 described later) of the reflecting plate 20 in the space above the passage 101. In this embodiment, a pair of reflecting plates 20 are erected from the floor surface on both sides of the passage 101 and face each other. That is, the pair of reflectors 20 consisting of two pieces are arranged so as to sandwich the passage 101 in a top view. In addition, in the illustrated example, the pair of reflectors 20 are arranged so as to be parallel to each other. In addition, in the illustrated example, the pair of reflectors 20 are each vertically erected with respect to the floor surface on which the passage 101 is provided. The height of the upper end of the reflector 20 from the passage 101 is not particularly limited, but is, for example, 1.5 m or more and 5.0 m or less. The shape of the reflector 20 when viewed from the direction in which the passage 101 extends is two I-shaped in the case of a pair of reflectors 20, but the shape is not particularly limited. The reflector 20 may be arranged so that there is a reflector 20 on at least one of the two sides of the shooting space 102, and the shape of the reflector 20 when viewed from the direction in which the passage 101 extends may be I-shaped, J-shaped, L-shaped, U-shaped, C-shaped, frame-shaped, annular, or the like. For example, the photographing device 10 may further include a reflector other than the pair of reflectors 20, or may include one reflector formed by extending and connecting the ends of the pair of reflectors 20. Note that the photographing device 10 is required to include at least one reflector 20, and may include, for example, only one of the pair of reflectors 20.

[0045] Each of the pair of reflectors 20 is plate-shaped. Each of the pair of reflectors 20 has an inner surface 25 and an outer surface 28 as two surfaces that are the front surface when viewed from the thickness direction of the reflector 20. The pair of reflectors 20 are arranged so that the inner surface 25 of one of the pair of reflectors 20 faces the inner surface 25 of the other of the pair of reflectors 20. In other words, the inner surface 25 is the surface of the reflector 20 on the shooting space 102 side. For example, each of the pair of reflectors 20 is flat and has the inner surface 25 and the outer surface 28 parallel to the inner surface 25. In other words, the thickness of the reflector 20 is uniform. The planar shape of the pair of reflectors 20 is not particularly limited, but is, for example, rectangular.

[0046] The reflector 20 diffusely reflects the sub-terahertz waves. Specifically, the reflector 20 diffusely reflects the sub-terahertz waves incident at least from the imaging space 102 side (i.e., the inside of the pair of reflectors 20). The reflector 20 is located between the first light source 41 and the second light source 42. The sub-terahertz waves emitted from the first light source 41 and the second light source 42 are diffusely reflected at least once by at least one of the pair of reflectors 20 and irradiated to the person 100, as shown in FIG. 3. In this way, by sandwiching the imaging space 102 between the reflectors 20 that diffusely reflect the sub-terahertz waves, the sub-terahertz waves incident on the imaging space 102 tend to remain, and the sub-terahertz waves are irradiated to the person 100 from various angles.

[0047] Furthermore, because the reflector 20 is flat, the imaging device 10 can be made thinner and smaller than when a component such as a spherical mirror that focuses the sub-terahertz waves on the person 100 is used to reflect the sub-terahertz waves.

[0048] Next, the detailed configuration of the reflector 20 will be described.

[0049] Fig. 4 is a schematic diagram showing the cross-sectional structure of the reflector 20. Fig. 4 is an enlarged view of a portion of the cross section of the reflector 20. Note that in Fig. 4, the diagonal hatching indicating the cross section has been omitted for ease of viewing.

[0050] The reflector 20 has a reflecting member 21, and two covering members 24 and a covering member 27. The reflector 20 has a structure in which the covering member 24, the reflecting member 21, and the covering member 27 are layered in this order from the shooting space 102 side.

[0051] The reflecting member 21 is a sheet-like member that diffusely reflects sub-terahertz waves. The reflecting member 21 is located between the covering member 24 and the covering member 27. The reflecting member 21 has two main surfaces 22 and 23 that are the two front surfaces when viewed from the thickness direction of the reflecting member 21. The main surfaces 22 and 23 are uneven surfaces that diffusely reflect sub-terahertz waves. The main surface 22 is located on the shooting space 102 side of the reflecting member 21, and the main surface 23 is located on the opposite side of the shooting space 102 side of the reflecting member 21. Both of the two main surfaces 22 and 23 of the reflecting member 21 are covered by the covering member 24 and the covering member 27, respectively. Specifically, the main surface 22 of the reflecting member 21 on the shooting space 102 side is covered by the covering member 24, and the main surface 23 of the reflecting member 21 on the opposite side of the shooting space 102 side is covered by the covering member 27. Therefore, the main surfaces 22 and 23 do not constitute the surface of the reflector 20 and are not exposed. As a result, if the main surfaces 22 and 23, which are uneven surfaces, were exposed, there is a possibility that the uneven surfaces would come into contact with the person 100; however, the main surfaces 22 and 23 are covered by the covering members 24 and 27, respectively, so that the reflector 21 is protected.

[0052] In the principal surface 22 and the principal surface 23, which are respectively uneven surfaces, for example, the average length RSm of the roughness curve element is equal to or greater than the wavelength of the sub-terahertz wave emitted from the first light source 41 and the second light source 42. Specifically, in the principal surface 22 and the principal surface 23, for example, the average length RSm of the roughness curve element is equal to or greater than 0.15 mm, and may be equal to or greater than 0.3 mm. This allows the sub-terahertz wave to be efficiently diffusely reflected by the principal surface 22 and the principal surface 23. In the example shown in FIG. 4, the uneven shapes of the principal surface 22 and the principal surface 23 are the same. Note that the uneven shapes of the principal surface 22 and the principal surface 23 may be different. In addition, it is sufficient that the principal surface 22 on the side of the shooting space 102 of the reflecting member 21 is an uneven surface, and the principal surface 23 may be a flat surface.

[0053] The reflective member 21 is made of a conductive material such as a metal or a conductive oxide. Examples of metals include pure metals (single metals) and alloys containing at least one metal such as copper, aluminum, nickel, iron, stainless steel, silver, gold, or platinum. Examples of conductive oxides include transparent conductive oxides such as ITO (Indium Tin Oxide), IZO (InZnO; Indium Zinc Oxide), AZO (AlZnO: Aluminum Zinc Oxide), FTO (Florine-doped Tin Oxide), SnO2, TiO2, and ZnO2.

[0054] The covering members 24 and 27 each transmit sub-terahertz waves. For example, the covering members 24 and 27 each transmit 50% or more of the sub-terahertz waves incident from the thickness direction of the reflector 20. The covering members 24 and 27 each may transmit 80% or more, or 90% or more of the sub-terahertz waves incident from the thickness direction of the reflector 20.

[0055] The covering member 24 is located on the photographing space 102 side of the reflecting member 21, and covers the main surface 22. The surface of the covering member 24 located on the opposite side of the reflecting member 21 side of the covering member 24 constitutes the inner surface 25 of the reflecting plate 20. The inner surface 25 is a flat surface that does not have an uneven shape like the main surface 22. As a result, even if a person 100 passing through the passage 101 hits the inner surface 25 of the reflecting plate 20, the person 100 is prevented from hitting the uneven surface of the reflecting member 21 (i.e., the main surface 22), and the person 100 and the main surface 22 are protected. In addition, since the inner surface 25 of the reflecting plate 20 is a flat surface, the reflecting plate 20 can be easily cleaned.

[0056] The covering member 27 is located on the opposite side of the reflecting member 21 from the photographing space 102 side, and covers the main surface 23. The surface of the covering member 27 located on the opposite side of the reflecting member 21 side constitutes the outer surface 28 of the reflecting plate 20. The outer surface 28 is a flat surface that does not have an uneven shape like the main surface 23. This makes it easier to clean the reflecting plate 20.

[0057] The material of the covering member 24 and the covering member 27 may be any material that can be processed into the shape of the covering member 24 and the covering member 27 and can maintain the shape. For example, a resin material is used as the material of the covering member 24 and the covering member 27. The resin material may be, for example, a transparent amorphous resin material that transmits visible light, or a crystalline resin material that diffusely reflects visible light.

[0058] The reflector 20 is formed, for example, by the following method. First, the covering member 24 is formed by molding a resin material with a mold having an uneven surface, or by machining a plate-shaped resin material to have unevenness, and the reflector 21 is formed on the formed covering member 24 by deposition, spraying, or the like. Then, the formed reflector 21 is covered with the resin material of the covering member 27 by coating or hot melt attachment, or the like, to obtain the reflector 20. Alternatively, a metal plate is machined to have unevenness as the material of the reflector 21, and the unevenly processed metal plate is coated with the resin material of the covering member 24 and the covering member 27, or the resin material is hot melt attached or inserted into the metal plate to obtain the reflector 20. Alternatively, the covering member 24 and the covering member 27 may be formed using a 3D printer.

[0059] With the above-described configuration, as shown in FIG. 4, sub-terahertz waves incident on reflector 20 from the inside of the pair of reflectors 20 (i.e., the side of shooting space 102) penetrate into covering member 24, are diffusely reflected by main surface 22 of reflecting member 21, and are emitted from inner surface 25 toward shooting space 102 at various angles.

[0060] The pair of reflectors 20 may have the same configuration and material, for example. Note that the pair of reflectors 20 may differ from each other in at least one of the configuration and material.

[0061] 2 and 3, the components of the imaging device 10 will be described further.

[0062] The first light source 41 and the second light source 42 are light sources that emit sub-terahertz waves to the reflector 20. Specifically, the first light source 41 and the second light source 42 each emit sub-terahertz waves to at least one inner surface 25 of the pair of reflectors 20. As shown in Fig. 3, the first light source 41 and the second light source 42 emit sub-terahertz waves to the reflector 20 such that a portion of the sub-terahertz waves emitted by the first light source 41 and the second light source 42 is diffusely reflected by the reflector 20 multiple times. A portion of the sub-terahertz waves emitted by the first light source 41 and the second light source 42 may be directly incident on the person 100.

[0063] The first light source 41 and the second light source 42 emit sub-terahertz waves, for example, based on the control of the light source control unit 60. Furthermore, the first light source 41 and the second light source 42 may emit sub-terahertz waves all the time during use, or may emit sub-terahertz waves at regular time intervals.

[0064] The first light source 41 and the second light source 42 are supported by, for example, a support member (not shown) or the like. The first light source 41 and the second light source 42 are realized by, for example, a known sub-terahertz wave generating element and a circuit that supplies a current to the sub-terahertz wave generating element.

[0065] The first light source 41 is located forward of the center of the shooting space 102 in the direction in which the passage 101 extends. The center of the shooting space 102 is the center of the space formed by being sandwiched between the reflectors 20. In the example shown in FIG. 3, the first light source 41 is located forward of the reflector 20 in the direction in which the passage 101 extends. Hereinafter, the front in the direction in which the passage 101 extends may be simply referred to as "front", and the rear in the direction in which the passage 101 extends may be simply referred to as "rear". In addition, in this specification, "front" and "rear" do not refer to the front and rear of the progress of the person 100 in the passage 101, but are terms that refer to relative directions. Specifically, one direction in the direction in which the passage 101 extends is referred to as "front", and the other direction that is the opposite direction to the one direction is referred to as "rear". In this specification, the front is an example of a first direction, and the rear is an example of a second direction. The first light source 41 emits sub-terahertz waves from the front side of the reflector 20 toward the inner surface 25 of the reflector 20 .

[0066] The first light source 41 is located near the front end of each of the pair of reflectors 20 and is spaced apart from the reflector 20. The first light source 41 is located between the first detector 51 and the third detector 53 and the reflector 20. As a result, the first light source 41, the first detector 51 and the third detector 53 are located on the same side of the reflector 20, specifically, on the front side. The first light source 41 emits sub-terahertz waves to the reflector 20 from a position closer to the reflector 20 than the first detector 51 and the third detector 53. After being emitted from the first light source 41, the sub-terahertz waves are diffusely reflected by the reflector 20 and irradiated to the person 100 without proceeding to the first detector 51 side and the third detector 53 side. Therefore, the sub-terahertz waves emitted from the first light source 41 can be efficiently used.

[0067] The first light source 41 may be located, for example, in the imaging space 102 or in front of the first detector 51 and the third detector 53.

[0068] The first light source 41 includes, for example, a point light source that emits sub-terahertz waves. FIG. 5A is a schematic diagram showing an example of the first light source 41 as viewed from the front. In FIG. 5A, components other than the first light source 41 and the reflector 20 are omitted. As shown in FIG. 5A, the first light source 41 includes a plurality of point light sources 41a that are arranged along the reflector 20 and emit sub-terahertz waves when viewed from the direction in which the passage 101 extends. In this embodiment, the plurality of point light sources 41a are arranged along the direction in which the pair of reflectors 20 are erected. In FIG. 5A, three point light sources 41a are arranged along one front end of the pair of reflectors 20, and three point light sources 41a are arranged along the other front end of the pair of reflectors 20. That is, the first light source 41 includes a pair of a plurality of point light sources 41a arranged along the direction in which the pair of reflectors 20 are erected. The number of the plurality of point light sources 41a arranged is not particularly limited, and may be two or four or more. 5A, the pair of point light sources 41a are arranged symmetrically with respect to a virtual plane P1. The virtual plane P1 is a vertical plane that passes through the center of the shooting space 102 and is aligned with the direction in which the passage 101 extends. The point light sources 41a may be arranged on only one side of the pair of reflectors 20.

[0069] Also, the first light source 41 may include another light source instead of the multiple point light sources 41a. FIG. 5B is a schematic diagram showing another example of the first light source 41 seen from the front. In FIG. 5B, components other than the first light source 41 and the reflector 20 are omitted. As shown in FIG. 5B, the first light source 41 includes a line light source 41b that extends along the reflector 20 and emits sub-terahertz waves when seen from the direction in which the passage 101 extends. In this embodiment, the line light source 41b extends along the direction in which the pair of reflectors 20 are erected. In FIG. 5B, one line light source 41b is arranged so as to extend along one front end of the pair of reflectors 20, and one line light source 41b is arranged so as to extend along the other front end of the pair of reflectors 20. That is, the first light source 41 includes a pair of line light sources 41b. The number of line light sources 41b arranged so as to extend along each front end of the pair of reflectors 20 may be two or more. 5B, the pair of line light sources 41b are disposed symmetrically with respect to the imaginary plane P1. Note that the line light source 41b may be disposed on only one side of the pair of reflectors 20.

[0070] Thus, when viewed from the direction in which passage 101 extends, first light source 41 includes at least one of a plurality of point light sources 41a that are lined up along reflector 20 and each radiate sub-terahertz waves, and line light source 41b that extends along reflector 20 and radiates sub-terahertz waves. This allows first light source 41 to emit sub-terahertz waves widely along reflector 20 when viewed from the direction in which the passage extends. As a result, person 100 is effectively irradiated with sub-terahertz waves.

[0071] The second light source 42 is located behind the center of the imaging space 102 in the direction in which the passage 101 extends. In the example shown in Fig. 3, the second light source 42 is located behind the reflector 20. The second light source 42 emits sub-terahertz waves from behind the reflector 20 toward the inner surface 25 of the reflector 20.

[0072] The second light source 42 is located near the rear end of each of the pair of reflectors 20 and is spaced apart from the reflectors 20. The second light source 42 is located between the reflectors 20 and the second and fourth detectors 52 and 54.

[0073] The second light source 42 may be located, for example, in the shooting space 102, or may be located behind the second detector 52 and the fourth detector 54. In addition, when the image capturing device 10 does not capture an image of the rear surface of the person 100, the second light source 42 does not need to be provided in the image capturing device 10.

[0074] The second light source 42 includes, for example, at least one of a point light source and a line light source that radiates sub-terahertz waves. The point light source and the line light source included in the second light source 42 are similar to the first light source 41. For this reason, the point light source and the line light source included in the second light source 42 can be explained by replacing the first light source 41 with the second light source 42 and replacing the front with the rear in the explanation of Figs. 5A and 5B above.

[0075] 2 and 3, the components of the imaging device 10 will be described further.

[0076] The first detector 51 receives the sub-terahertz waves that are emitted from the first light source 41 and then diffusely reflected by the reflector 20 and reflected by the person 100. The first detector 51 generates an image based on the received reflected waves. The first detector 51 outputs the generated image to the image processing unit 90. The generation of an image by a detector such as the first detector 51 is also referred to as "taking an image". The first detector 51 performs exposure and generates an image at the timing when the first light source 41 emits the sub-terahertz waves.

[0077] The first detector 51 is located forward of the center of the imaging space in the extending direction of the passage 101. In the example shown in Fig. 3, the first detector 51 is located forward of the reflector 20 in the extending direction of the passage 101. The first detector 51 captures an image of the front surface of the person 100. The first detector 51 is supported by, for example, a support member or the like (not shown).

[0078] The first detector 51 includes an image sensor 55 and an optical system 56 .

[0079] The image sensor 55 receives the sub-terahertz waves emitted from a light source such as the first light source 41 and then diffusely reflected by the reflector 20, and reflected by the person 100. The image sensor 55 detects the intensity of the received reflected waves, and generates an image based on the detected intensity. Specifically, the image sensor 55 converts an image of the sub-terahertz waves emitted from the object to be photographed during exposure into an electrical signal according to the intensity. Then, the image sensor 55 generates an image based on the converted electrical signal. The image generated by the image sensor 55 is output to the image processing unit 90.

[0080] Sub-terahertz waves are specularly reflected by the human body, metal, etc., and pass through clothes, bags, etc. Therefore, the image sensor 55 receives waves reflected specularly by the body of the person 100 from an area of ​​the body of the person 100 that is included in the angle range in which the image sensor 55 can receive waves. For example, a wave reflected by the person 100 passing through the area indicated by the dashed line extending from the first detector 51 in Fig. 3 is incident on the image sensor 55. Furthermore, if the person 100 is concealing a knife or the like, the image sensor 55 receives a wave reflected specularly by the concealed knife from an area included in the angle range in which the image sensor 55 can receive waves.

[0081] The image sensor 55 is composed of, for example, a plurality of pixels each including a detection element for detecting sub-terahertz waves, and peripheral circuits.

[0082] The optical system 56 forms an image of the sub-terahertz waves, which are emitted from a light source such as the first light source 41 and then diffusely reflected by the reflector 20 and reflected by the person 100, on the image sensor 55. The optical system 56 includes, for example, at least one lens. Note that the first detector 51 does not need to include the optical system 56, and the reflected waves may be directly incident on the image sensor 55.

[0083] The second detector 52 receives the sub-terahertz waves that are emitted from the second light source 42 and then diffusely reflected by the reflector 20 and reflected by the person 100. The second detector 52 generates an image based on the received reflected waves. The second detector 52 outputs the generated image to the image processing unit 90. The second detector 52 performs exposure and generates an image at the timing when the second light source 42 emits the sub-terahertz waves.

[0084] The second detector 52 is located behind the center of the shooting space 102 in the direction in which the passage 101 extends. In the example shown in FIG. 3, the second detector 52 is located behind the reflector 20. The second detector 52 captures an image of the rear surface of the person 100. The second detector 52 is supported by, for example, a support member or the like (not shown). In this way, the imaging device 10 is provided with the first detector 51 and the second detector 52, so that images of both the front and rear sides of the person 100 can be generated.

[0085] The second detector 52 includes an image sensor 55a and an optical system 56a. The image sensor 55a and the optical system 56a are the same as the image sensor 55 and the optical system 56 described above, and therefore a detailed description thereof will be omitted.

[0086] In addition, when the image capturing device 10 does not capture an image of the rear surface of the person 100, the second detector 52 does not have to be provided in the image capturing device 10.

[0087] The third detector 53 receives the sub-terahertz waves that are emitted from the first light source 41 and then diffusely reflected by the reflector 20 and reflected by the person 100. The third detector 53 generates an image based on the received reflected waves. The third detector 53 outputs the generated image to the image processing unit 90. The third detector 53 performs exposure and generates an image at the timing when the first light source 41 emits the sub-terahertz waves.

[0088] The third detector 53 is located forward of the center of the photographing space 102 in the direction in which the passage 101 extends. In the example shown in FIG. 3, the third detector 53 is located forward of the reflector 20. The third detector 53 is supported by, for example, a support member not shown. The first detector 51 and the third detector 53 are disposed at different positions in a top view of the passage 101. The first detector 51 and the third detector 53 have different incident directions of reflected waves from the person 100. As a result, the first detector 51 and the third detector 53 generate images based on reflected waves from faces of the person 100 facing different directions. Therefore, for example, it is possible to reduce blind spots when the photographing device 10 detects a dangerous object such as a knife concealed by the person 100.

[0089] For example, the first detector 51 and the third detector 53 are symmetrically positioned with respect to the imaginary plane P1. Therefore, the direction of incidence of the reflected wave of the first detector 51 and the direction of incidence of the reflected wave of the third detector 53 are symmetrical with respect to the imaginary plane P1. Moreover, the first detector 51 and the third detector 53 are aligned along a direction perpendicular to the extension direction of the passage 101 when viewed from above the passage 101.

[0090] The third detector 53 includes an image sensor 55b and an optical system 56b. The image sensor 55b and the optical system 56b are the same as the image sensor 55 and the optical system 56 described above, and therefore a detailed description thereof will be omitted.

[0091] The fourth detector 54 receives the sub-terahertz waves that are emitted from the second light source 42 and then diffusely reflected by the reflector 20 and reflected by the person 100. The fourth detector 54 generates an image based on the received reflected waves. The fourth detector 54 outputs the generated image to the image processing unit 90. The fourth detector 54 performs exposure and generates an image at the timing when the second light source 42 emits the sub-terahertz waves.

[0092] The fourth detector 54 is located rearward of the center of the photographing space 102 in the extending direction of the passage 101. In the example shown in FIG. 3, the fourth detector 54 is located rearward of the reflector 20. The fourth detector 54 is supported by, for example, a support member not shown. The positional relationship between the second detector 52 and the fourth detector 54 is similar to the positional relationship between the first detector 51 and the third detector 53. The positional relationship between the second detector 52 and the fourth detector 54 can be explained by replacing the first detector 51 in the explanation of the positional relationship between the first detector 51 and the third detector 53 with the second detector and the third detector 53 with the fourth detector 54.

[0093] The fourth detector 54 includes an image sensor 55c and an optical system 56c. The image sensor 55c and the optical system 56c are the same as the image sensor 55 and the optical system 56 described above, and therefore a detailed description thereof will be omitted.

[0094] At least one of the third detector 53 and the fourth detector 54 does not have to be provided in the imaging device 10.

[0095] The light source control unit 60 controls the emission of sub-terahertz waves from each of the first light source 41 and the second light source 42. The light source control unit 60 controls, for example, the timing at which each of the first light source 41 and the second light source 42 emits sub-terahertz waves. For example, the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves and the second light source 42 not to emit sub-terahertz waves in a first period, and causes the second light source 42 to emit sub-terahertz waves and does not cause the first light source 41 to emit sub-terahertz waves in a second period different from the first period.

[0096] The light source control unit 60 controls the emission of sub-terahertz waves from each of the first light source 41 and the second light source 42, based on, for example, signals acquired from the imaging control unit 70 and the sensor 80. The light source control unit 60 includes, for example, a processor and a memory, and is realized by the processor executing a program stored in the memory.

[0097] The imaging control unit 70 controls the timing at which each detector generates an image. For example, the imaging control unit 70 causes the first detector 51 and the third detector 53 to generate images in synchronization, and causes the second detector 52 and the fourth detector 54 to generate images in synchronization. The imaging control unit 70 also causes each detector to generate an image based on, for example, the timing of emission of sub-terahertz waves from the first light source 41 and the second light source 42. The imaging control unit 70 may cause each detector to generate an image based on a signal from the sensor 80 or the like. The imaging control unit 70 includes, for example, a processor and a memory, and is realized by the processor executing a program stored in the memory.

[0098] The sensor 80 is a sensor for detecting the presence of the person 100. The sensor 80 outputs, for example, a signal indicating the presence of the person 100 to the light source control unit 60 and the photography control unit 70. The sensor 80 is, for example, a camera that captures moving images. The sensor 80 may be another sensor such as a human presence sensor. Furthermore, although the number of sensors 80 included in the photographing device 10 is one in the example shown in FIG. 3, the photographing device 10 may be provided with multiple sensors 80.

[0099] Upon receiving an image from each detector, the image processing unit 90 outputs the received image to the outside, and also performs image processing on the received image and outputs the result of the image processing to the outside.

[0100] The image processing performed by the image processing unit 90 may be, for example, a process of determining whether or not an object having a predetermined characteristic (e.g., an object having the characteristics of a blade) is included in the image output from the detector, and outputting a predetermined detection signal (e.g., an alarm indicating that an object having the characteristics of a blade has been photographed) if it is determined that an object having the predetermined characteristic is included. The image processing unit 90 may also perform a synthesis process on the images received from each detector. The image processing unit 90 includes, for example, a processor and a memory, and is realized by the processor executing a program stored in the memory.

[0101] The photographing device 10 does not necessarily have to include the image processing unit 90, and the detector may output the image to an external image processing device. Also, the function of the image processing unit 90 may be provided in each detector.

[0102] Here, the irradiation mode of the sub-terahertz waves in the imaging device 10 according to the present embodiment will be described with reference to FIG. 3. The sub-terahertz waves (arrows in FIG. 3) emitted from the light source to the reflector 20 are diffusely reflected by the reflector 20 and enter the person 100 because the imaging space 102 is covered by the reflector 20 from the side of the imaging space 102. As a result, the inner surface 25 of the reflector 20 functions as a surface light source, and the sub-terahertz waves are irradiated from various angles over a relatively wide range toward the person 100. Therefore, the imaging device 10 can effectively irradiate the person 100 with the sub-terahertz waves. In addition, in the present embodiment, the reflectors 20 are plate-shaped and face each other across the imaging space 102, so the sub-terahertz waves emitted from the light source are diffusely reflected at least once by the reflector 20 and enter the person 100. Furthermore, most of the sub-terahertz waves emitted from the light source to the reflector 20 are repeatedly diffusely reflected in the photographing space 102, and therefore tend to remain in the space of the photographing space 102 located above the passage 101 through which the person 100 passes. Therefore, the photographing device 10 can irradiate the person 100 with the sub-terahertz waves more effectively.

[0103] Furthermore, since the sub-terahertz waves are irradiated from various angles over a relatively wide area on person 100, the reflected waves of the sub-terahertz waves reflected over a relatively wide area on person 100 enter the detector. Also, since the sub-terahertz waves emitted from the light source to reflector 20 tend to remain in the space of imaging space 102, the amount of reflected waves entering the detector increases. This improves the quality of the image generated by the detector. As a result, for example, the detection accuracy improves when imaging device 10 is used to detect dangerous objects such as knives concealed by person 100.

[0104] [Example] Next, an example of the operation of the photographing device 10 according to the present embodiment will be described.

[0105] In the following operation example, the operation of the image capturing device 10 capturing an image of a person 100 passing through the capture space 102 from the rear to the front will be described. FIGS. 6A, 6B, 6C, and 6D are diagrams for explaining an operation example of the image capturing device 10 according to the present embodiment. FIGS. 6A, 6B, 6C, and 6D show the image capturing device 10 viewed from above. For ease of viewing, the sensor 80 is omitted in FIGS. 6A, 6B, 6C, and 6D. In FIGS. 6A, 6B, 6C, and 6D, the first light source 41 and the second light source 42 are hatched with dots when they emit sub-terahertz waves, and are not hatched with dots when they do not emit sub-terahertz waves. In FIGS. 6A, 6B, 6C, and 6D, an example of the path of the sub-terahertz waves emitted from the reflector 20 is shown by a solid arrow. The same applies to the diagrams for explaining operation examples in the following modifications.

[0106] First, as shown in Fig. 6A, in step S1, person 100 enters photographing space 102 and passes through the rear end of photographing space 102. When light source control unit 60 detects that person 100 is present at the rear end of photographing space 102, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. For example, light source control unit 60 detects the presence of person 100 by receiving a signal indicating that person 100 is present at the rear end of photographing space 102 from sensor 80. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0107] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20, and are irradiated from the inner surface 25 to the person 100. Specifically, the sub-terahertz waves emitted from the inner surface 25 located in front of the person 100 are irradiated to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the first detector 51. The first detector 51 receives the reflected waves from the person 100. The imaging control unit 70 causes the first detector 51 to generate an image based on the reflected waves received by the first detector 51 at the timing when the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves. That is, the first detector 51 generates an image based on the reflected waves from the person 100 passing through the rear end of the imaging space 102. As a result, the first detector 51 generates an image of the front surface of the person 100. The first detector 51 outputs the generated image to the image processing unit 90. The light source control unit 60 detects that the generation of the image by the first detector 51 is completed, and turns off the first light source 41, for example.

[0108] In step S1, the first detector 51 generates an image based on the received reflected waves from the person 100 during a first period during which the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves and does not cause the second light source 42 to emit sub-terahertz waves. If the second light source 42 emits sub-terahertz waves when the first detector 51 generates an image, the sub-terahertz waves emitted from the second light source 42 located behind the person 100 may enter the first detector 51 simultaneously with the reflected waves from the person 100. Therefore, the image generated by the first detector 51 based on the reflected waves from the person 100 may become unclear. On the other hand, in step S1, the first detector 51 generates an image based on the reflected waves from the person 100 received during the first period during which the second light source 42 does not emit sub-terahertz waves, so the image based on the reflected waves from the person 100 is clear.

[0109] Next, as shown in FIG. 6B, in step S2, the person 100 moves forward from the position in step S1 and is located in the center of the photographing space 102 in the direction in which the passage 101 extends. When the light source control unit 60 detects that the person 100 exists in the center of the photographing space 102, the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves. For example, the light source control unit 60 detects the presence of the person 100 by receiving a signal from the sensor 80 indicating that the person 100 exists in the center of the photographing space 102 in the direction in which the passage 101 extends. In addition, at this time, the light source control unit 60 does not cause the second light source 42 to emit sub-terahertz waves. Instead of detecting the presence of the person 100, the light source control unit 60 may cause the first light source 41 to emit sub-terahertz waves after a predetermined time has elapsed since the generation of the image of the first detector 51 in step S1. The predetermined time is set to, for example, the time it takes the person 100 to take about one to two steps.

[0110] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20, and are irradiated from the inner surface 25 to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the first detector 51. The first detector 51 receives the reflected waves from the person 100. The imaging control unit 70 causes the first detector 51 to generate an image based on the reflected waves received by the first detector 51 at the timing when the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves. As a result, the first detector 51 generates an image of the front surface of the person 100. The first detector 51 outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of the image by the first detector 51 has been completed, and turns off the first light source 41.

[0111] In this manner, in steps S1 and S2, the first detector 51 receives reflected waves from the person 100 at multiple timings while the person 100 passes through the imaging space 102. Then, the first detector 51 generates multiple images based on the respective reflected waves received. In this way, multiple images of the person 100 are generated while the person 100 passes through the imaging space 102. Therefore, for example, an image including a portion not captured in one image is generated, and it is possible to improve detection accuracy and the like when the imaging device 10 is used to detect a dangerous object or the like concealed by the person 100.

[0112] Also, in step S2, similarly to step S1, the first detector 51 generates an image based on the reflected wave from the person 100 received in the first period. Also, in step S2, the range in which the reflected wave from the person 100 enters the first detector 51 is the range indicated by the dashed line extending from the first detector 51 in FIG. 6B, and the second light source 42 and a part of the reflector 20 are located in this range. Therefore, when the second light source 42 emits sub-terahertz waves, the sub-terahertz waves originating from the second light source 42 are particularly likely to enter the first detector 51. Therefore, during the first period in which the second light source 42 does not emit sub-terahertz waves, the first detector 51 generates an image, and the effect of making the image of the reflected wave from the person 100 clear is remarkable.

[0113] In step S1, the light source control unit 60 may not turn off the first light source 41, but may keep the first light source 41 emitting sub-terahertz waves until generation of an image by the first detector 51 in step 2 is completed. In this case, for example, when the imaging control unit 70 detects that the person 100 is present in the center of the imaging space 102, it causes the first detector 51 to generate an image.

[0114] Next, in step S3 immediately after step S2, as shown in Fig. 6C, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. Specifically, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves immediately after the completion of exposure in the generation of an image by the first detector 51 in step S2. The light source control unit 60 acquires a signal indicating the timing at which the generation of an image by the first detector 51 ends, for example, via the imaging control unit 70. The signal is, for example, a signal indicating the end of exposure of the image sensor 55. At this time, the light source control unit 60 does not cause the first light source 41 to emit sub-terahertz waves.

[0115] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20 and irradiated from the inner surface 25 to the person 100. Specifically, the sub-terahertz waves emitted from the inner surface 25 located behind the person 100 are irradiated to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the second detector 52. The second detector 52 receives the reflected waves from the person 100. The imaging control unit 70 causes the second detector 52 to start generating an image at the timing when the light source control unit 60 causes the second light source 42 to emit the sub-terahertz waves, that is, immediately after the completion of the exposure in the generation of the image by the first detector 51 in step S2. In other words, the second detector 52 starts the exposure in the generation of the image based on the reflected wave by the person 100 received by the first detector 51 immediately after the completion of the exposure in the generation of the image based on the reflected wave by the person 100 received by the first detector 51 in step S2. In this way, the second detector 52 captures an image of the rear surface of the person 100 immediately after the first detector 51 captures an image in step S2. The second detector 52 outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of the image by the second detector 52 is completed, and turns off the second light source 42.

[0116] In this way, in steps S2 and S3, imaging by the first detector 51 and imaging by the second detector 52 are performed without any time interval. This allows imaging of the person 100 from both the front and back without any time interval, reducing the area of ​​the person 100's body that is not imaged during imaging, thereby improving the detection accuracy when the imaging device 10 is used to detect dangerous objects, etc., concealed by the person 100.

[0117] In step S3, the second detector 52 generates an image based on the reflected waves from the person 100 received during a second period during which the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves and does not cause the first light source 41 to emit sub-terahertz waves. If the first light source 41 emits sub-terahertz waves when the second detector 52 generates an image, the sub-terahertz waves emitted from the first light source 41 located in front of the person 100 may enter the second detector 52 simultaneously with the reflected waves from the person 100. This may cause the image generated by the second detector 52 due to the reflected waves from the person 100 to become unclear. On the other hand, in step S3, the second detector 52 generates an image based on the reflected waves from the person 100 received during the second period during which the first light source 41 does not emit sub-terahertz waves, so that the image due to the reflected waves from the person 100 becomes clear. In step S3, the range in which the reflected waves from person 100 enter second detector 52 is the range indicated by the dashed line extending from second detector 52 in Fig. 6C, and the first light source 41 and a part of reflector 20 are located in this range. Therefore, when second light source 42 is emitting sub-terahertz waves, sub-terahertz waves originating from first light source 41 are particularly likely to enter second detector 52. Therefore, during the second period in which first light source 41 is not emitting sub-terahertz waves, the second detector 52 generates an image, which significantly improves the clarity of the image of the reflected waves from person 100.

[0118] In steps S2 and S3, the detector that first generates an image may be the second detector 52, not the first detector 51. That is, in the description of steps S2 and S3, the first light source 41 and the second light source 42 may be interchanged, and the first detector 51 and the second detector 52 may be interchanged.

[0119] Next, as shown in FIG. 6D, in step S4, the person 100 moves forward from the position in step S3 and is located at the front end of the imaging space 102. That is, the person 100 passes through the front end of the imaging space 102. When the light source control unit 60 detects that the person 100 is present at the front end of the imaging space 102, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. For example, the light source control unit 60 detects the presence of the person 100 by receiving a signal indicating the presence at the front end of the imaging space 102 from the sensor 80. At this time, the light source control unit 60 does not cause the first light source 41 to emit sub-terahertz waves.

[0120] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20 and are irradiated from the inner surface 25 to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the second detector 52. The second detector 52 receives the reflected waves from the person 100. The imaging control unit 70 causes the second detector 52 to generate an image based on the reflected waves received by the second detector 52 at the timing when the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. That is, the second detector 52 generates an image based on the reflected waves from the person 100 passing through the front end of the imaging space 102. As a result, the second detector 52 captures an image of the rear surface of the person 100. The second detector 52 outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of an image by the second detector 52 is completed, and turns off the second light source 42.

[0121] In this way, in steps S3 and S4, the second detector 52 receives the reflected waves from the person 100 at multiple timings while the person 100 passes through the shooting space 102. Then, the second detector 52 generates multiple images based on each of the received reflected waves. This provides the same effect as the generation of images by the first detector 51 in steps S1 and S2.

[0122] Also in step S4, similar to step S3, the second detector 52 generates an image based on the waves reflected by the person 100 received in the second period. Therefore, similar to step S3, an effect of making the image based on the waves reflected by the person 100 clear can be obtained.

[0123] In the above-described operation example of the imaging device 10, the imaging control unit 70, for example, causes the first detector 51 and the third detector 53 to operate synchronously, and causes the second detector 52 and the fourth detector 54 to operate synchronously. That is, the third detector 53 operates similarly to the first detector 51, and the fourth detector 54 operates similarly to the second detector 52. Therefore, the operations of the third detector 53 and the fourth detector 54 will be described by replacing the first detector 51 with the third detector 53 and the second detector 52. These are also the same in the operation examples in each modified example described below.

[0124] Furthermore, the image processing unit 90 may perform image processing to combine the image generated by the first detector 51 and the image generated by the third detector 53. Furthermore, the image processing unit 90 may perform image processing to combine the image generated by the second detector 52 and the image generated by the fourth detector 54.

[0125] In the above-described operation example of the imaging device 10, the detectors generate images of the person 100 at the positions shown in Fig. 6A, Fig. 6B, Fig. 6C, and Fig. 6D, but the position of the person 100 is not limited to these positions. The position of the person 100 when the detector generates the image of the person 100 may be, for example, a position where the inner surface 25 can emit sub-terahertz waves to the person 100 from the detector side. The position where the person 100 is imaged in steps S2 and S3 is a position where the inner surface 25 located either in front of or behind the person 100 can emit sub-terahertz waves to the person 100. The position where the person 100 is imaged in steps S2 and S3 is, for example, the center of the imaging space 102 in the direction in which the passage 101 extends, as described above.

[0126] Furthermore, during steps S1 to S4, each detector may continuously generate images and selectively output, from among the plurality of continuously generated images, an image generated at the timings of steps S1 to S4 to the image processing unit 90. Furthermore, each detector may continuously generate images and output all of the plurality of continuously generated images to the image processing unit 90. In this case, the image processing unit 90, for example, selects an image generated at the timings of steps S1 to S4 from among the plurality of received images and performs image processing on the selected image.

[0127] [Variation 1] Next, an imaging device according to a first modified example of the embodiment will be described.

[0128] The imaging device according to the first modification of the embodiment is mainly different from the imaging device according to the embodiment in that imaging by the first detector and imaging by the second detector are performed multiple times without any time interval. Also, the imaging device according to the first modification of the embodiment has a longer reflector length in the direction in which the passage extends and a longer distance between the first detector and the second detector than the imaging device according to the embodiment. The following description will focus on the differences from the embodiment, and the description of the commonalities will be omitted or simplified.

[0129] Fig. 7 is a schematic diagram of the photographing device 10a according to this modification when viewed from above. As shown in Fig. 7, the photographing device 10a is configured to include a reflector 20a instead of the reflector 20 of the photographing device 10. The photographing device 10a has the same configuration as the photographing device 10 except for the reflector 20a.

[0130] The reflecting plate 20a covers the photographing space 102 on the passage 101 through which the person 100 passes from at least one of both sides of the passage 101. In this modification, the reflecting plate 20a sandwiches the photographing space 102 on the passage 101 through which the person 100 passes from both sides of the passage 101. In this modification, a pair of reflecting plates 20a are erected from the floor surface on both sides of the passage 101 through which the person 100 passes and face each other. Each of the pair of reflecting plates 20a has an inner surface 25a and an outer surface 28a as two surfaces that are the front surface when viewed from the thickness direction of the reflecting plate 20a. The reflecting plate 20a has the same configuration as the reflecting plate 20 except that the reflecting plate 20a is longer in the extension direction of the passage 101 than the reflecting plate 20, and detailed description thereof will be omitted.

[0131] Next, an example of the operation of the imaging device 10a according to this modified example will be described.

[0132] In the following operation example, the image capturing device 10a captures an image of a person 100 passing through an image capturing space 102 from the rear to the front. Figures 8A, 8B, 8C, and 8D are diagrams for explaining an operation example of the image capturing device 10a according to this modification.

[0133] 8A, in step S11, person 100 enters photographing space 102 and passes through the rear side of photographing space 102. When light source control unit 60 detects that person 100 is present on the rear side of photographing space 102, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0134] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20a, and are irradiated onto the person 100 from the inner surface 25a. The subsequent operation of the imaging device 10a is the same as that of step S2 above, and therefore a detailed description thereof will be omitted. As a result, the first detector 51 generates an image based on the reflected waves from the person 100 passing behind in the imaging space 102.

[0135] Next, in step S12 immediately after step S11, as shown in Fig. 8B, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. Specifically, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves immediately after the completion of exposure in generating an image by the first detector 51 in step S11. At this time, the light source control unit 60 does not cause the first light source 41 to emit sub-terahertz waves.

[0136] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20a and irradiated onto the person 100 from the inner surface 25a. The subsequent operation of the image capturing device 10a is similar to that of step S3 above, and therefore detailed description will be omitted. As a result, the image capturing control unit 70 causes the second detector 52 to start exposure for generating an image immediately after the first detector 51 completes exposure for generating an image in step S11. In other words, the second detector 52 captures an image of the rear surface of the person 100 immediately after the first detector 51 captures an image in step S11.

[0137] 8C, in step S13, person 100 moves forward from the position in step S12 and is located on the forward side in image capture space 102. In other words, person 100 passes through the forward side in image capture space 102. When light source control unit 60 detects that person 100 is present on the forward side in image capture space 102, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0138] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20a, and are irradiated onto the person 100 from the inner surface 25a. The subsequent operation of the imaging device 10a is the same as that of step S2 above, and therefore a detailed description thereof will be omitted. As a result, the first detector 51 generates an image based on the reflected waves from the person 100 passing in front of the imaging space 102.

[0139] Next, in step S14 immediately after step S13, as shown in Fig. 8D, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. Specifically, the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves immediately after the completion of exposure in generating an image by the first detector 51 in step S13.

[0140] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20a and irradiated onto the person 100 from the inner surface 25a. The subsequent operation of the image capturing device 10a is similar to that of step S3 above, and therefore detailed description will be omitted. As a result, the image capturing control unit 70 causes the second detector 52 to start exposure for generating an image immediately after the first detector 51 completes exposure for generating an image in step S13. In other words, the second detector 52 captures an image of the rear surface of the person 100 immediately after the first detector 51 captures an image in step S13.

[0141] As described above, in steps S11 and S12, the first detector 51 and the second detector 52 capture images without any time interval. Also, in steps S13 and S14, the first detector 51 and the second detector 52 capture images without any time interval. This allows the person 100 to be captured from both the front and back of the person 100 multiple times without any time interval while the person 100 passes through the capture space 102, and generates images of multiple aspects of the person 100 while the person 100 passes through the capture space 102. This further improves the detection accuracy when the capture device 10a is used to detect dangerous objects or the like concealed by the person 100.

[0142] Furthermore, in steps S11 and S12, in order to capture images of both the front and back surfaces of person 100 at the same position of person 100, and to irradiate person 100 with sub-terahertz waves equivalent to those in the operational example of the embodiment, reflectors 20a must be located on both the front and back of person 100. The same is true for steps S13 and S14. Therefore, in order to capture images of person 100 from both the front and back, multiple times without any time intervals, without degrading the image quality of the captured image, the length of reflector 20a is longer than that of reflector 20 by the length of the surface for emitting sub-terahertz waves to person 100.

[0143] [Variation 2] Next, an imaging device according to a second modification of the embodiment will be described.

[0144] The imaging device according to the second modification of the embodiment is different from the imaging device according to the embodiment mainly in that the first detector and the second detector each capture an image when a person is located at a predetermined location. Also, the imaging device according to the second modification of the embodiment has a shorter length of the reflector in the direction in which the passage extends and a shorter distance between the first detector and the second detector compared to the imaging device according to the embodiment. The following description will focus on the differences from the embodiment, and will omit or simplify the description of the commonalities.

[0145] Fig. 9 is a schematic diagram of an image capturing device 10b according to this modified example when viewed from above. As shown in Fig. 9, the image capturing device 10b is configured to include a reflector 20b instead of the reflector 20 of the image capturing device 10. The image capturing device 10b has the same configuration as the image capturing device 10 except for the reflector 20b.

[0146] The reflecting plate 20b covers the photographing space 102 on the passage 101 through which the person 100 passes from at least one of both sides of the passage 101. In this modification, the reflecting plate 20b sandwiches the photographing space 102 on the passage 101 through which the person 100 passes from both sides of the passage 101. In this modification, a pair of reflecting plates 20b are erected from the floor surface on both sides of the passage 101 through which the person 100 passes and face each other. Each of the pair of reflecting plates 20b has an inner surface 25b and an outer surface 28b as two surfaces that are the front surface when viewed from the thickness direction of the reflecting plate 20b. The reflecting plate 20b has the same configuration as the reflecting plate 20 except that the length of the reflecting plate 20b in the extension direction of the passage 101 is shorter than that of the reflecting plate 20, and detailed description thereof will be omitted.

[0147] Next, an example of the operation of the image capturing device 10b according to this modified example will be described.

[0148] In the following operation example, the image capturing device 10b captures an image of a person 100 passing through an image capturing space 102 from the rear to the front. Figures 10A and 10B are diagrams for explaining an operation example of the image capturing device 10b according to this modification.

[0149] 10A, in step S21, person 100 enters photographing space 102 and passes through the rear end of photographing space 102. When light source control unit 60 detects that person 100 is present at the rear end of photographing space 102, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0150] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20b, and are irradiated onto the person 100 from the inner surface 25b. The subsequent operation of the imaging device 10b is the same as that of step S1 above, and therefore a detailed description thereof will be omitted. As a result, the first detector 51 generates an image based on the waves reflected by the person 100 passing through the rear end of the imaging space 102.

[0151] 10B, in step S22, person 100 moves forward from the position in step S21 and is located at the front end of imaging space 102. In other words, person 100 passes through the front end of imaging space 102. When light source control unit 60 detects that person 100 is present at the front end of imaging space 102, light source control unit 60 causes second light source 42 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause first light source 41 to emit sub-terahertz waves.

[0152] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20b, and are irradiated onto the person 100 from the inner surface 25b. The subsequent operations are similar to those in step S4 above, and therefore detailed explanations will be omitted. As a result, the second detector 52 generates an image based on the waves reflected by the person 100 passing through the front end of the imaging space 102.

[0153] As described above, in the imaging device 10b, the first detector 51 generates an image based on the reflected wave by the person 100 passing through the rear end of the imaging space 102 in the direction in which the passage 101 extends. The second detector 52 generates an image based on the reflected wave by the person 100 passing through the front end of the imaging space 102 in the direction in which the passage 101 extends. In this manner, images of the person 100 are captured at both ends of the imaging space 102. Therefore, even when both an image of the front surface of the person 100 and an image of the rear surface of the person 100 are captured, the length of the reflector 20b for diffusively reflecting the sub-terahertz wave on both the front and rear sides of the person 100 in the direction in which the passage 101 extends is not required. Therefore, even when both an image of the front surface of the person 100 and an image of the rear surface of the person 100 are captured, the length of the reflector 20b in the direction in which the passage 101 extends can be shortened. As a result, the imaging device 10b can be made smaller. In addition, when person 100 passes through shooting space 102, he or she may feel a sense of claustrophobia because he or she is sandwiched between reflectors 20b. However, by shortening the length of reflector 20b, the sense of claustrophobia felt by person 100 is reduced.

[0154] For example, in step S21, the first detector 51 does not capture images before and after the person 100 moves from the rear end to the center of the shooting space 102 as in steps S1 to S2 described above, but captures the person 100 when he is located at the rear end of the shooting space 102. Therefore, in the direction in which the passage 101 extends, the length of the reflector 20b can be made shorter than the length of the reflector 20 by the length of the movement of the person 100 from steps S1 to S2.

[0155] The operation of emitting sub-terahertz waves by the light source in the image capturing device 10b is not limited to the above-mentioned operation example. For example, the image capturing device 10b may not include the light source control unit 60, and the first light source 41 and the second light source 42 may be light sources that emit sub-terahertz waves constantly or at regular intervals during use. In step S21, the range in which the reflected wave from the person 100 enters the first detector 51 is the range indicated by the dashed line extending from the first detector 51 in FIG. 10A, and the second light source 42 and the reflector 20b are not located in the range. In other words, the first detector 51 is disposed in a positional relationship such that the second light source 42 and the reflector 20b are not included in the angle range in which the first detector 51 can receive the reflected wave from the person 100 when the person 100 is located at the rear end of the image capturing space 102. Similarly, in step S22, the range in which the reflected waves from the person 100 enter the second detector 52 is the range indicated by the dashed line extending from the second detector 52 in Fig. 10B, and the first light source 41 and the reflector 20b are not located in this range. In other words, the second detector 52 is disposed in a positional relationship such that the first light source 41 and the reflector 20b are not within the angle range in which the second detector 52 can receive the reflected waves from the person 100 when the person 100 is located at the front end of the shooting space. Therefore, even if the first light source 41 and the second light source 42 simultaneously emit sub-terahertz waves in steps S21 and S22, the image generated by the first detector 51 and the second detector 52 due to the reflected waves from the person 100 is unlikely to become unclear.

[0156] [Variation 3] Next, an imaging device according to a third modification of the embodiment will be described.

[0157] The imaging device according to the third modification of the embodiment is mainly different from the imaging device according to the embodiment in that the detector generates images of people who are located in front of and behind the reflector and people who are passing through the imaging space. In addition, the imaging device according to the third modification of the embodiment is also different from the imaging device according to the embodiment in that a plurality of detectors are provided. In addition, the imaging device according to the third modification of the embodiment has a shorter length of the reflector in the direction in which the passage extends and a shorter distance between the first detector and the second detector than the imaging device according to the embodiment. The following description will focus on the differences from the embodiment, and the description of the commonalities will be omitted or simplified.

[0158] Fig. 11 is a schematic diagram of the photographing device 10c according to this modification when viewed from above. As shown in Fig. 11, the photographing device 10c is configured to include a reflector 20c instead of the reflector 20 of the photographing device 10, and includes a plurality of first detectors 51a, 51b, a plurality of second detectors 52a, 52b, a plurality of third detectors 53a, 53b, and a plurality of fourth detectors 54a, 54b instead of the first detector 51, the second detector 52, the third detector 53, and the fourth detector 54 of the photographing device 10. In the photographing device 10c, the configuration other than the reflector 20c, the plurality of first detectors 51a, 51b, the plurality of second detectors 52a, 52b, the plurality of third detectors 53a, 53b, and the plurality of fourth detectors 54a, 54b is the same as that of the photographing device 10.

[0159] The reflecting plate 20c covers the photographing space 102 on the passage 101 through which the person 100 passes from at least one of both sides of the passage 101. In this modification, the reflecting plate 20c sandwiches the photographing space 102 on the passage 101 through which the person 100 passes from both sides of the passage 101. In this modification, a pair of reflecting plates 20c is erected from the floor surface on both sides of the passage 101 through which the person 100 passes and faces each other. Each of the pair of reflecting plates 20c has an inner surface 25c and an outer surface 28c as two surfaces that are the front surface when viewed from the thickness direction of the reflecting plate 20c. The reflecting plate 20c has the same configuration as the reflecting plate 20 except that the length in the extension direction of the passage 101 is shorter than that of the reflecting plate 20, and detailed description thereof will be omitted.

[0160] The first detectors 51a and 51b are each located forward of the reflector 20c in the direction in which the passage 101 extends. The first detectors 51a and 51b are lined up along the direction in which the passage 101 extends. Specifically, the first detectors 51a and 51b are lined up in this order from the side farther from the reflector 20c, i.e., the front side, along the direction in which the passage 101 extends. Each of the first detectors 51a and 51b includes an image sensor 55 and an optical system 56, similar to the first detector 51.

[0161] The second detectors 52a, 52b are each located rearward of the reflector 20c in the direction in which the passage 101 extends. The second detectors 52a and 52b are lined up in this order from the side farther from the reflector 20c, i.e., from the rearward side, along the direction in which the passage 101 extends. Each of the second detectors 52a, 52b includes an image sensor 55a and an optical system 56a, similar to the second detector 52.

[0162] The multiple third detectors 53a, 53b are each located forward of the reflector 20c in the direction in which the passage 101 extends. The third detectors 53a and 53b are lined up in this order from the side farther from the reflector 20c, i.e., from the forward side, along the direction in which the passage 101 extends. Each of the multiple third detectors 53a, 53b includes an image sensor 55b and an optical system 56b, similar to the third detector 53.

[0163] The multiple fourth detectors 54a, 54b are each located rearward of the reflector 20c in the direction in which the passage 101 extends. The fourth detectors 54a and 54b are lined up in this order from the side farther from the reflector 20c, i.e., from the rearward side, along the direction in which the passage 101 extends. Each of the multiple fourth detectors 54a, 54b includes an image sensor 55c and an optical system 56c, similar to the fourth detector 54.

[0164] Next, an example of the operation of the imaging device 10c according to this modified example will be described.

[0165] In the following operation example, the image capturing device 10c captures an image of a person 100 passing through the image capturing space 102 from the rear to the front. Figures 12A, 12B, 12C, and 12D are diagrams for explaining an operation example of the image capturing device 10c according to this modification.

[0166] First, as shown in Fig. 12A, in step S31, person 100 moves toward shooting space 102 and is positioned behind reflector 20c. When light source control unit 60 detects that person 100 is behind reflector 20c, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. For example, light source control unit 60 detects the presence of person 100 by receiving a signal indicating that person 100 is behind reflector 20c from sensor 80. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0167] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20c, and are irradiated onto the person 100 from the inner surface 25c. The reflected waves from the person 100 of the sub-terahertz waves irradiated onto the person 100 are incident on the first detector 51b. The first detector 51b receives the reflected waves from the person 100. The imaging control unit 70 causes the first detector 51b to generate an image based on the reflected waves received by the first detector 51b at the timing when the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves. As a result, the first detector 51b generates an image of the front surface of the person 100. The first detector 51b outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of the image by the first detector 51b has been completed, and turns off the first light source 41.

[0168] 12B, in step S32, person 100 moves forward from the position in step S31, enters photographing space 102, and is located at the rear end of photographing space 102. In other words, person 100 passes through the rear end of photographing space 102. When light source control unit 60 detects that person 100 is present at the rear end of photographing space 102, light source control unit 60 causes first light source 41 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause second light source 42 to emit sub-terahertz waves.

[0169] The sub-terahertz waves emitted from the first light source 41 are diffusely reflected at least once by the reflector 20c, and are irradiated from the inner surface 25c to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the first detector 51a. The first detector 51a receives the reflected waves from the person 100. The imaging control unit 70 causes the first detector 51a to generate an image based on the reflected waves received by the first detector 51a at the timing when the light source control unit 60 causes the first light source 41 to emit sub-terahertz waves. That is, the first detector 51a generates an image based on the reflected waves from the person 100 passing through the rear end of the imaging space 102. As a result, the first detector 51a generates an image of the front surface of the person 100. The first detector 51a outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of an image by the first detector 51a is completed, and turns off the first light source 41.

[0170] In this way, in steps S31 and S32, the first detectors 51a and 51b generate a plurality of images based on the reflected waves from the person 100 located behind the reflector 20c in the direction in which the passage 101 extends, and the reflected waves from the person 100 passing through the photographing space 102. As a result, the photographing device 10c generates an image of the person 100 before the person 100 enters the photographing space 102, so the length of the reflector 20c in the direction in which the passage 101 extends can be shortened. As a result, the photographing device 10c can be made smaller. In addition, the person 100 may feel a sense of claustrophobia when passing through the photographing space 102 because he or she is sandwiched between the reflectors 20c, but the shortening of the length of the reflector 20c reduces the claustrophobia of the person 100. For example, in the direction in which the passage 101 extends, the length of the reflector 20c can be made shorter than the length of the reflector 20b by the length of the movement of the person 100 from step S31 to step S32.

[0171] In addition, in steps S31 and S32, the detector that generates the image is changed to the first detector 51a and the first detector 51b that are aligned in the direction in which the passage 101 extends, so that an image is captured based on the reflected wave at a similar angle of incidence to the detector.

[0172] In addition, in steps S31 and S32, the angle range of the sub-terahertz waves incident on person 100 is narrower than that in the operation example (for example, step S1) of the above-mentioned embodiment. However, in steps S31 and S32, the angle range of the sub-terahertz waves incident on person 100 is different, and therefore images are captured based on the reflected waves of the sub-terahertz waves incident at different angles by person 100. Specifically, in step S31, sub-terahertz waves with a relatively small inclination with respect to inner surface 25c are incident on person 100, and in step S32, sub-terahertz waves with a relatively large inclination with respect to inner surface 25c are incident on person 100. As a result, the faces of person 100 captured in the multiple captured images are different, and it is possible to suppress a decrease in detection accuracy when imaging device 10c is used to detect a dangerous object or the like concealed by a person.

[0173] Also, for example, by arranging the first detector 51a and the first detector 51b apart by the length of movement of the person 100 from step S31 to step S32, the angles of incidence of the reflected waves from the person 100 to the first detector 51a and the first detector 51b become the same. In this case, the angle range of the sub-terahertz waves incident on the person 100 is different in step S31 and step S32, so that the reflected waves originating from the different inclinations of the sub-terahertz waves incident on the person 100 are reflected toward the detectors. That is, in step S31 and step S32, the sub-terahertz waves incident on the person 100 with different inclinations with respect to the inner surface 25c are reflected toward the detectors. Therefore, the angles of incidence of the reflected waves from the person 100 incident on the first detector 51a and the first detector 51b during shooting become the same, so that the overlapping range of the faces of the person 100 shot in the images shot by the first detector 51a and the first detector 51b is reduced.

[0174] Furthermore, the image processing unit 90 may perform image processing to synthesize the image generated by the first detector 51b in step S31 and the image generated by the first detector 51a in step S32.

[0175] 12C, in step S33, person 100 moves forward from the position in step S32 and is located at the front end of imaging space 102. In other words, person 100 passes through the front end of imaging space 102. When light source control unit 60 detects that person 100 is present at the front end of imaging space 102, light source control unit 60 causes second light source 42 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause first light source 41 to emit sub-terahertz waves.

[0176] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20c, and are irradiated from the inner surface 25c to the person 100. The reflected waves from the person 100 of the sub-terahertz waves irradiated to the person 100 are incident on the second detector 52a. The second detector 52a receives the reflected waves from the person 100. The imaging control unit 70 causes the second detector 52a to generate an image based on the reflected waves received by the second detector 52a at the timing when the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. That is, the second detector 52a generates an image based on the reflected waves from the person 100 passing through the front end of the imaging space 102. As a result, the second detector 52a captures an image of the rear surface of the person 100. The second detector 52a outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of an image by the second detector 52a is completed, and turns off the second light source .

[0177] 12D, in step S34, person 100 moves forward from the position in step S33 and is positioned in front of reflector 20c. When light source control unit 60 detects that person 100 is in front of reflector 20c, light source control unit 60 causes second light source 42 to emit sub-terahertz waves. At this time, light source control unit 60 does not cause first light source 41 to emit sub-terahertz waves.

[0178] The sub-terahertz waves emitted from the second light source 42 are diffusely reflected at least once by the reflector 20c, and are irradiated onto the person 100 from the inner surface 25c. The reflected waves from the person 100 of the sub-terahertz waves irradiated onto the person 100 are incident on the second detector 52b. The second detector 52b receives the reflected waves from the person 100. The imaging control unit 70 causes the second detector 52b to generate an image based on the reflected waves received by the second detector 52b at the timing when the light source control unit 60 causes the second light source 42 to emit sub-terahertz waves. As a result, the second detector 52b generates an image of the rear surface of the person 100. The second detector 52b outputs the generated image to the image processing unit 90. The light source control unit 60 detects, for example, that the generation of the image by the second detector 52b has been completed, and turns off the second light source 42.

[0179] In this way, in generating images from the plurality of second detectors 52a, 52b in steps S33 and S34, the same effect as in generating images from the plurality of first detectors 51a, 51b in steps S31 and S32 can be obtained.

[0180] In this modification, the imaging device 10c may include one first detector 51 instead of the multiple first detectors 51a and 51b. In this case, the first detector 51 may be disposed at any position between the positions where the first detectors 51a and 51b are disposed. The imaging device 10c may also include a drive mechanism for moving the first detector 51 between the positions where the first detectors 51a and 51b are disposed, and the first detector 51 may move to the position of the first detector 51b in step S31 and move to the position of the first detector 51a in step S32. These are the same for the multiple second detectors 52a and 52b, the multiple third detectors 53a and 53b, and the multiple fourth detectors 54a and 54b as for the multiple first detectors 51a and 51b.

[0181] (Other embodiments) Although the imaging device according to the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the spirit of the present disclosure, various modifications conceived by a person skilled in the art to these embodiments and forms constructed by combining components in different embodiments are also included within the scope of one or more aspects of the present disclosure.

[0182] For example, in the above embodiment and each modified example, the reflectors 20, 20a, 20b, and 20c are each flat, but this is not limited thereto. At least a part of the reflectors 20, 20a, 20b, and 20c may be curved. The reflectors 20, 20a, 20b, and 20c may be curved such that at least one of the upper side, the front side, and the rear side of the pair of reflectors 20 approaches each other. Also, the reflectors 20, 20a, 20b, and 20c may be provided in a plurality of divided pieces.

[0183] In the above-described embodiment and each modification, the imaging device 10, 10a, 10b, 10c may include a reflector located at least one above and below the imaging space 102, in addition to the pair of reflectors 20, 20a, 20b, 20c, which diffusely reflects the sub-terahertz waves. FIG. 13 is a schematic diagram of a reflector according to the modification seen from the front. In FIG. 13, components of the imaging device other than the reflector 20d are omitted. As shown in FIG. 13, the three reflectors 20d sandwich the imaging space 102 from both sides of the passage 101, and further cover the upper side of the imaging space 102. This suppresses the sub-terahertz waves incident on the imaging space 102 from exiting from the upper side of the imaging space 102, so that the sub-terahertz waves tend to remain in the imaging space 102. For example, three reflectors 20d may be provided in the image capture devices 10, 10a, 10b, and 10c instead of the pairs of reflectors 20, 20a, 20b, and 20c.

[0184] In the above embodiment and each modified example, the reflectors 20, 20a, 20b, and 20c have the reflecting member 21, the covering member 24, and the covering member 27, but this is not limited thereto. The reflector 20 may have only one of the covering member 24 and the covering member 27. Furthermore, the reflectors 20, 20a, 20b, and 20c may be composed of the reflecting member 21 without having the covering member 24 and the covering member 27. In this case, the main surface 22 constitutes the inner surface 25, and the main surface 23 constitutes the outer surface 28.

[0185] Furthermore, in the above-described embodiment and each modified example, the photographing devices 10, 10a, 10b, and 10c may not include the light source control unit 60, the photographing control unit 70, and the sensor 80. For example, the photographing devices 10, 10a, 10b, and 10c may include an operation receiving unit that receives an operation from a user, and may photograph the person 100 and perform the operation of the operation examples of the above-described embodiment and each modified example based on the operation from the user.

[0186] In addition, in the above-described embodiment and each of the modified examples, the object to be photographed is person 100, but this is not limiting. The object to be photographed may be luggage or the like.

[0187] Furthermore, in the above embodiment and each modification, the photographing devices 10, 10a, 10b, and 10c may not include the photographing control unit 70, and for example, in the photographing devices 10, 10a, 10b, and 10c, each detector may have the function of the photographing control unit 70. Furthermore, each detector may output a plurality of continuously generated images to the image processing unit 90 without controlling the timing of image generation.

[0188] Furthermore, in the above-described embodiments and variations, the photographing devices 10, 10a, 10b, and 10c may not be equipped with the sensor 80, and for example, the light source control unit 60 and the photographing control unit 70 may acquire signals from an external sensor such as a camera provided around the photographing devices 10, 10a, 10b, and 10c.

[0189] Also, for example, the imaging device 10 does not need to include all of the components described in the above embodiment and each modified example, and may be composed of only the components required to perform the desired operation.

[0190] In the above embodiment, each component such as the light source control unit 60, the photography control unit 70, and the image processing unit 90 may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

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

[0192] In addition, the comprehensive or specific aspects of the present invention may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM. Also, the present invention may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a non-transitory recording medium. For example, the present invention may be realized as a program for causing a computer to execute control performed by a control unit or the like provided in each component of the imaging device.

[0193] Furthermore, the order of the processes in the operation of the imaging device described in the above embodiment is merely an example. The order of the processes may be changed, or the processes may be performed in parallel.

[0194] Furthermore, the above-described embodiment can be modified, replaced, added, omitted, and the like in various ways within the scope of the claims or their equivalents. [Industrial Applicability]

[0195] The present disclosure is widely applicable to imaging devices that capture images of objects. [Explanation of symbols]

[0196] 10, 10a, 10b, 10c Imaging device 20, 20a, 20b, 20c reflector 21 Reflective material 22, 23 Main surface 24, 27 Covering material 25, 25a, 25b, 25c inner surface 28, 28a, 28b, 28c external surface 41 1st light source 41a Point light source 41b Line light source 42 Second light source 51, 51a, 51b First detector 52, 52a, 52b Second detector 53, 53a, 53b Third detector 54, 54a, 54b Fourth detector 60 Light source control unit 70 Shooting control section 80 Sensors 90 Image Processing Section 100 people Aisle 101 102 Shooting Space

Claims

1. a reflector that covers at least one of both sides of a photographing space on a passage through which a photographing object passes and diffusely reflects the sub-terahertz wave; a first light source that emits sub-terahertz waves toward the reflector; a second light source that emits sub-terahertz waves toward the reflector; a first detector that receives a sub-terahertz wave that is emitted from the first light source and then diffusely reflected by the reflector, and that receives the reflected wave from the object to be photographed, and generates an image based on the received reflected wave; a second detector that receives the sub-terahertz waves emitted from the second light source and then diffusely reflected by the reflector, and that receives the reflected waves from the object to be photographed, and generates an image based on the received reflected waves; a light source control unit that controls emission of the sub-terahertz waves from the first light source and the second light source, The first light source and the first detector are located on a first direction side relative to a center of the shooting space in an extension direction of the passage, The second light source and the second detector are located on a second direction side, which is the opposite direction to the first direction, from the center of the shooting space in the extending direction of the passage, The light source control unit is by causing the first light source to emit sub-terahertz waves and causing the second light source not to emit sub-terahertz waves during a first period, sub-terahertz waves are emitted from the first direction side toward the reflector by the first light source and sub-terahertz waves are not emitted from the second direction side of the object to be photographed by the second light source; by causing the second light source to emit sub-terahertz waves and causing the first light source to not emit sub-terahertz waves during a second period different from the first period, the second light source emits sub-terahertz waves toward the reflector from the second direction side, and the first light source does not emit sub-terahertz waves from the first direction side of the object to be photographed, The first detector generates an image based on a reflected wave from the object to be photographed received during the first period, The second detector generates an image based on a reflected wave from the object to be photographed received during the second period. Filming equipment.

2. The reflectors sandwich the photographing space from both sides of the passage. The imaging device according to claim 1 .

3. Further comprising a sensor for detecting the object to be photographed, When the light source control unit receives a signal from the sensor indicating that the object to be photographed is present at an end of the photographing space on the second direction side, the light source control unit causes the first light source to emit sub-terahertz waves to start the first period.

3. The imaging device according to claim 1.

4. Further comprising a sensor for detecting the object to be photographed, when the light source control unit receives from the sensor a signal indicating that the object to be photographed is present in a center of the photographing space, the light source control unit causes the first light source to emit sub-terahertz waves to start the first period, and immediately after the first period, causes the second light source to emit sub-terahertz waves to start the second period.

3. The imaging device according to claim 1.

5. one of the first detector and the second detector starts exposure for generating an image based on the received reflected wave from the object immediately after completion of exposure for generating an image based on the received reflected wave from the object by the other of the first detector and the second detector. The imaging device according to claim 1 .

6. When the object passes through the shooting space, The first detector generates an image based on a reflected wave by the object passing through an end portion of the imaging space on the second direction side in the extending direction of the passage, The second detector generates an image based on a reflected wave from the object passing through the end of the imaging space on the first direction side in the extending direction of the passage. The imaging device according to claim 1 .

7. The first detector receives reflected waves from the object at a plurality of timings while the object passes through the imaging space, and generates a plurality of images based on the received reflected waves. The imaging device according to claim 1 .

8. The first detector generates a plurality of images based on a reflected wave from the object to be photographed that is located on the second direction side of the reflector in the direction in which the passage extends, and a reflected wave from the object to be photographed that is passing through the photographing space. The imaging device according to claim 1 .

9. A plurality of the first detectors are provided, The first detectors are arranged in a line along an extension direction of the passage. The imaging device according to claim 8.

10. a third detector that receives a reflected wave of the sub-terahertz wave emitted from the first light source and then diffusely reflected by the reflector, the reflected wave being reflected by the object to be photographed, and generates an image based on the received reflected wave; The third detector is located on the first direction side relative to the center of the imaging space in the extending direction of the passage, The first detector and the third detector have different incident directions of reflected waves from the object to be photographed. The imaging device according to claim 1 .

11. The first detector is located on the first direction side of the reflector in the direction in which the passage extends, The first light source is located between the reflector and the first detector. The imaging device according to claim 1 .

12. the first light source includes at least one of a plurality of point light sources arranged along the reflector and each emitting a sub-terahertz wave, and a line light source extending along the reflector and emitting a sub-terahertz wave, when viewed from the extending direction of the passage; The imaging device according to any one of claims 1 to 11.

13. Further comprising a sensor for detecting the object to be photographed, when receiving from the sensor a signal indicating that the object to be photographed is present in the second direction from the photographing space, the light source control unit causes the first light source to emit sub-terahertz waves to start the first period.

3. The imaging device according to claim 1.

14. A light-emitting diode having two reflectors, The pair of reflectors sandwich the photographing space from both sides of the passage, the first light source includes at least one of a plurality of point light sources arranged along the first direction side end of each of the pair of reflectors, each emitting a sub-terahertz wave, and a line light source extending along the first direction side end of each of the pair of reflectors, when viewed from the extending direction of the passage, and emitting a sub-terahertz wave. The imaging device according to any one of claims 1 to 13.

Images