Imaging equipment

Abstract

This photography device (10) comprises: a scattering reflective part (20) having a reflective plate (30) that reflects sub-terahertz waves in a scattered manner, the scattering reflective part (20) covering a photography space (102) in a passage (101) through which a person (100) passes from at least one of two sides of the passage (101); a light source (50) that emits sub-terahertz waves toward the reflective plate (30); and a detector (60) that receives reflected waves reflected by the person (100), the reflected waves being sub-terahertz waves reflected in a scattered manner by the reflective plate (30) after having been emitted from the light source (50), and that detects the strength of the received reflected waves. The scattering reflective part (20) has a visible-light-transmitting region that transmits visible light.

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 that can effectively irradiate 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 comprises a diffuse reflection unit that covers an imaging space on a passageway through which an object to be imaged passes from at least one of both sides and has a reflector that diffusely reflects sub-terahertz waves, a light source that emits sub-terahertz waves toward the reflector, and a detector that receives the sub-terahertz waves that are emitted from the light source and then diffusely reflected by the reflector and are reflected by the object to be imaged and detects the intensity of the received reflected waves, wherein the diffuse reflection unit has a visible light transmitting region that transmits visible light.

[0007] In addition, an imaging device according to one aspect of the present disclosure includes a diffuse reflection unit 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 has a reflector that diffusely reflects sub-terahertz waves, a light source that emits sub-terahertz waves toward the reflector, and a detector that receives the sub-terahertz waves that are emitted from the light source and then diffusely reflected by the reflector and reflected by the object to be photographed and detects the intensity of the received reflected waves, wherein the reflector reflects visible light from the side of the shooting space. Effect of the Invention

[0008] 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]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the appearance of an imaging device according to the first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a configuration of the imaging device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram of the imaging device according to the first embodiment as viewed from above. [Figure 4] FIG. 4 is a schematic diagram showing a cross-sectional structure of the diffuse reflector according to the first embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing a cross-sectional structure of the reflector according to the first embodiment. [Figure 6] FIG. 6 is a block diagram showing a configuration of an imaging device according to the second embodiment. [Figure 7] FIG. 7 is a schematic diagram showing a cross-sectional structure of a diffuse reflector according to the second embodiment. [Figure 8] FIG. 8 is a schematic diagram showing a cross-sectional structure of a reflector according to the second embodiment. [Figure 9] FIG. 9 is a block diagram showing a configuration of an imaging device according to the first modification of the second embodiment. In FIG. [Figure 10] FIG. 10 is a schematic diagram showing a cross-sectional structure of a diffuse reflector according to a first modification of the second embodiment. [Figure 11] FIG. 11 is a schematic diagram showing a cross-sectional structure of a reflector according to Modification 1 of Embodiment 2. In FIG. [Figure 12] FIG. 12 is a block diagram showing a configuration of an imaging device according to the third embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a cross-sectional structure of a diffuse reflector according to the third embodiment. [Figure 14] FIG. 14 is a schematic diagram showing a cross-sectional structure of another example of the diffuse reflector according to the third embodiment. In FIG. [Figure 15] FIG. 15 is a schematic diagram showing a cross-sectional structure of still another example of the diffuse reflector according to the third embodiment. In FIG. [Figure 16] FIG. 16 is a block diagram showing a configuration of an imaging device according to the fourth embodiment. [Figure 17] FIG. 17 is a schematic diagram showing a cross-sectional structure of a diffuse reflector above which a lighting fixture is provided, according to the fourth embodiment. [Figure 18] FIG. 18 is a schematic diagram showing a cross-sectional structure of another example of the diffuse reflector having a lighting fixture provided above, according to the fourth embodiment. [Figure 19] FIG. 19 is a schematic diagram of an imaging device according to a modified example, as viewed from above. [Figure 20] FIG. 20 is a schematic diagram of an imaging device according to another modified example, as viewed from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Summary of the Disclosure) An outline of one aspect of the present disclosure is as follows.

[0011] An imaging device according to one aspect of the present disclosure includes a diffuse reflection unit that covers an imaging space on a passageway through which an object to be imaged passes from at least one of both sides of the passageway and has a reflector that diffusely reflects sub-terahertz waves, a light source that emits sub-terahertz waves toward the reflector, and a detector that receives the sub-terahertz waves that are emitted from the light source and then diffusely reflected by the reflector and reflected by the object to be imaged and detects the intensity of the received reflected waves, wherein the diffuse reflection unit has a visible light transmitting region that transmits visible light.

[0012] 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 also refer to 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.

[0013] 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 light source are diffusely reflected by the reflector and enter the imaging object. As a result, the entire surface of the reflector on the imaging space side functions as a surface light source, and the imaging object is irradiated with the sub-terahertz waves from various angles over a relatively wide range. 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 embodiment, 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. Thus, the photographing device according to this embodiment can effectively irradiate the object to be photographed with sub-terahertz waves.

[0014] In addition, since the photographing space is covered by the reflector of the diffuse reflecting unit from at least one of the two sides of the passage, if the diffuse reflecting unit does not have a visible light transmission area, visible light from outside the diffuse reflecting unit is unlikely to enter the photographing space. Therefore, if the photographing subject is a person, the person passing through the photographing space to photograph is likely to feel a sense of claustrophobia. In contrast, if the diffuse reflecting unit has a visible light transmission area, visible light from outside the diffuse reflecting unit is incident on the photographing space. As a result, the photographing device according to this aspect can suppress the claustrophobia felt by the person passing through the photographing space to photograph.

[0015] Also, for example, the visible light transmitting region may be in the region where the reflector is located, and the reflector may have a sheet-shaped sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves and transmits visible light, and may transmit visible light.

[0016] This makes it possible to realize an imaging device equipped with a diffuse reflection unit having a reflector that diffusely reflects sub-terahertz waves while transmitting visible light. Therefore, since the region that diffusely reflects sub-terahertz waves and the region that transmits visible light are located on the same reflector, it is possible to suppress a sense of occlusion for a person when the object to be imaged is a person, without reducing the efficiency of irradiating the object with sub-terahertz waves.

[0017] Furthermore, for example, the sub-terahertz wave reflecting member may be a conductive thin film.

[0018] This makes it possible to easily manufacture a sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves and transmits visible light.

[0019] Furthermore, for example, the sub-terahertz wave reflecting member may be a conductive mesh.

[0020] This makes it possible to easily manufacture a sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves and transmits visible light.

[0021] Furthermore, for example, the sub-terahertz wave reflecting member may be a punching metal.

[0022] This makes it possible to easily manufacture a sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves and transmits visible light.

[0023] Also, for example, the reflector may further have at least one visible light transmitting member that transmits sub-terahertz waves and visible light, at least one of two main surfaces of the sub-terahertz wave reflecting member being covered by the visible light transmitting member, the visible light transmitting member having a flat surface on the side of the visible light transmitting member opposite to the sub-terahertz wave reflecting member side, and the flat surface may constitute a surface of the reflector.

[0024] This allows the main surface of the sub-terahertz wave reflecting member to be protected by the visible light transmitting member. Furthermore, since the surface of the reflecting plate is configured as a flat surface, the reflecting plate can be easily cleaned.

[0025] Also, for example, both of the two main surfaces may be covered by the visible light transmitting member having the flat surface.

[0026] As a result, both sides of the sub-terahertz wave reflecting member are covered with the visible light transmitting member, improving the visibility of the object when viewed through the reflecting plate.

[0027] Also, for example, the reflector may further cover at least a portion of the upper side of the imaging space.

[0028] As a result, the reflector is also positioned above the imaging space, so that the sub-terahertz waves emitted from the light source toward the reflector are more likely to remain within the imaging space.

[0029] Also, for example, the visible light transmitting area may be an area in which a gap provided in the diffuse reflection section is located, the gap is located above the shooting space, and the width of the gap may be smaller than the height of the diffuse reflection section from the passage.

[0030] As a result, a visible light transmission region is formed simply by providing a gap in the diffuse reflection section, so that a diffuse reflection section having a visible light transmission region can be easily manufactured. Also, although a gap is provided in the diffuse reflection section, the width of the gap is smaller than the height of the diffuse reflection section from the passage, so that the sub-terahertz waves incident on the imaging space are less likely to leak through the gap.

[0031] Also, for example, the gap may extend in the direction in which the passage extends, and the width of the gap may be smaller than the width of the passage.

[0032] As a result, even if gaps are provided in the diffuse reflection section, the sub-terahertz waves incident on the imaging space are less likely to leak through the gaps.

[0033] Also, for example, the imaging device may further include a lighting device that irradiates visible light into the imaging space through the visible light transmitting area.

[0034] As a result, when the subject of the image capture is a person, the visible light from the lighting device is irradiated onto the person, further reducing the sense of claustrophobia felt by the person.

[0035] In addition, an imaging device according to one aspect of the present disclosure includes a diffuse reflection unit 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 has a reflector that diffusely reflects sub-terahertz waves, a light source that emits sub-terahertz waves toward the reflector, and a detector that receives the sub-terahertz waves that are emitted from the light source and then diffusely reflected by the reflector and reflected by the object to be photographed and detects the intensity of the received reflected waves, wherein the reflector reflects visible light from the side of the shooting space.

[0036] In the imaging device according to this aspect, as in the above-described imaging device, the imaging target can be effectively irradiated with sub-terahertz waves.

[0037] Also, for example, the reflector may have a sheet-shaped sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves, and a visible light diffuse reflecting member that transmits sub-terahertz waves and diffusely reflects visible light, wherein a main surface of the sub-terahertz wave reflecting member facing the shooting space is covered with the visible light diffuse reflecting member, and the visible light diffuse reflecting member has a flat visible light diffuse reflecting surface that diffusely reflects visible light on the side of the visible light diffuse reflecting member opposite the sub-terahertz wave reflecting member side, and the visible light diffuse reflecting surface may constitute the surface of the reflector facing the shooting space.

[0038] This allows the main surface of the sub-terahertz wave reflecting member to be protected by the visible light diffuse reflecting member. Furthermore, since the visible light diffuse reflecting surface is flat, the reflecting plate can be easily cleaned.

[0039] In addition, a projector for projecting an image or a lighting device for emitting illumination light may be further provided on the visible light diffusion reflection surface, and if the subject of the image capture is a person, the person passing through the image capture space can see the image or illumination light, etc. Therefore, it is possible to suppress a feeling of claustrophobia felt by people passing through the image capture space to capture images.

[0040] For example, the visible light diffuse reflection member may include a crystalline resin material.

[0041] This makes it possible to easily manufacture a visible light diffuse reflection member that transmits sub-terahertz waves and diffusely reflects visible light.

[0042] For example, the visible light diffusive reflection member may include visible light diffusive particles.

[0043] This makes it possible to easily manufacture a visible light diffuse reflection member that transmits sub-terahertz waves and diffusely reflects visible light.

[0044] Also, for example, the image capturing device may further include a projector that projects an image onto the visible light diffuse reflection surface.

[0045] As a result, when the object to be photographed is a person, the person passing through the photographing space can see the image projected onto the visible light diffuse reflection surface, thereby reducing the sense of claustrophobia felt by people passing through the photographing space to photograph.

[0046] Furthermore, for example, the reflector may have a sheet-shaped sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves, and a visible light mirror reflecting member that transmits sub-terahertz waves and mirror-reflects visible light, wherein a main surface of the sub-terahertz wave reflecting member facing the shooting space is covered with the visible light mirror reflecting member, and the visible light mirror reflecting member has a flat visible light mirror reflecting surface that mirror-reflects visible light on the side of the visible light mirror reflecting member opposite the sub-terahertz wave reflecting member side, and the visible light mirror reflecting surface may constitute the surface of the reflector facing the shooting space.

[0047] This allows the main surface of the sub-terahertz wave reflecting member to be protected by the visible light specular reflecting member. Furthermore, since the visible light specular reflecting surface is flat, the reflecting plate can be easily cleaned.

[0048] In addition, since the surface of the reflector facing the shooting space is composed of a visible light mirror reflecting surface and a mirror image is reflected on the surface of the reflector facing the shooting space, when the subject to be photographed is a person, the feeling of claustrophobia felt by the person passing through the shooting space to take the photograph can be reduced.

[0049] For example, the visible light specular reflecting member may include a dielectric multilayer film.

[0050] This makes it possible to easily manufacture a visible light specular reflection member that transmits sub-terahertz waves and specularly reflects visible light.

[0051] Also, for example, the reflecting plates may sandwich the photographing space from both sides of the passage.

[0052] 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 toward 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.

[0053] Furthermore, for example, the diffuse reflection section may have a structure in which the width of the passage is narrowest at an opening in the diffuse reflection section that serves as an entrance / exit to the imaging space.

[0054] This makes it difficult for sub-terahertz waves incident on the imaging space to leak from the opening.

[0055] Furthermore, for example, the imaging device may include a door that covers an opening in the diffuse reflector that serves as an entrance to the imaging space, and the door may diffusely reflect sub-terahertz waves and transmit visible light.

[0056] As a result, the door diffusely reflects the sub-terahertz waves, making it difficult for the sub-terahertz waves that enter the imaging space to leak out from the opening.

[0057] In addition, because visible light enters the photography space through the door, if the subject of photography is a person, the sense of claustrophobia felt by the person passing through the photography space to take the photograph can be reduced.

[0058] Also, for example, the killing apparatus may include a door that covers an opening in the diffuse reflector that serves as an entrance to the shooting space, and the door may diffusely reflect sub-terahertz waves and reflect visible light.

[0059] As a result, the door diffusely reflects the sub-terahertz waves, making it difficult for the sub-terahertz waves that enter the imaging space to leak out from the opening.

[0060] Hereinafter, the embodiment will be specifically described with reference to the drawings.

[0061] 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.

[0062] Furthermore, in this specification, terms indicating the relationship between elements, such as "parallel," terms indicating the shape of an element, such as "plate," 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.

[0063] 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.

[0064] (Embodiment 1) First, the imaging device according to the first embodiment will be described.

[0065] 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 diffuse reflection section 20 are omitted.

[0066] 1, the image capturing device 10 is an image capturing device that, for example, irradiates sub-terahertz waves onto the person 100 when the person 100 passes through a space surrounded by a diffuse reflector 20, and captures an image based on the reflected waves of the irradiated sub-terahertz waves by the person 100. The image capturing device 10 also captures an image of a dangerous object, such as a knife, that the person 100 conceals under clothing, etc. The person 100 and the dangerous object, such as a knife, that the person 100 conceals under clothing, etc. are each an example of an object to be captured.

[0067] Hereinafter, the details of each component of the imaging device 10 will be described with reference to FIG. 2 to FIG. 4. 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 is a perspective view of the upper part of the diffuse reflector 20, specifically, a view in which the reflector 33 described below is omitted. FIG. 3 shows a person 100 passing through the inside of the diffuse reflector 20. FIG. 3 also shows an example of the path of the sub-terahertz wave emitted from the light source 50 with an arrow. FIG. 4 is a schematic diagram showing a cross-sectional structure of the diffuse reflector 20. FIG. 4 shows a cross section of the diffuse reflector 20 cut vertically along a line perpendicular to the direction in which the passage 101 extends in a top view. In FIG. 4, the detailed configuration of the reflector 30 is omitted for ease of viewing. This also applies to the reflectors in Figs. 7, 10, 13, 14, 15, 17 and 18 which show the cross-sectional structure of the diffuse reflector used in the following description.

[0068] The photographing device 10 includes a diffuse reflector 20 having reflectors 31, 32, and 33, light sources 51, 52, 53, and 54, detectors 61, 62, 63, and 64, and an image processor 70. In this specification, the reflectors 31, 32, and 33 may be collectively referred to as a reflector 30. The same applies to the reflectors 30a, 30b, 30c, 30d, 30e, 30f, and 30g described below. The light sources 51, 52, 53, and 54 may be collectively referred to as a light source 50. The detectors 61, 62, 63, and 64 may be collectively referred to as a detector 60.

[0069] The diffuse reflector 20 is, for example, a tunnel-like shape through which the person 100 can pass. As shown in FIG. 4, the diffuse reflector 20 has an angular U-shaped cross-sectional shape, but the cross-sectional shape is not particularly limited. The diffuse reflector 20 may be arranged so that the reflector 30 is located on at least one of both sides of the person 100 passing through the passage 101, and the cross-sectional shape of the diffuse reflector 20 may be an I-shape, a J-shape, an L-shape, two I-shapes, a U-shape, a C-shape, a frame shape, a ring shape, or the like. Inside the diffuse reflector 20, a shooting space 102 is formed on the passage 101 through which the person 100 passes, which is a space for shooting the person 100. The shooting space 102 is a space covered by the reflector 30 in the space above the passage 101. The diffuse reflector 20 has a reflector 30. The diffuse reflector 20 also has a visible light transmission region that transmits visible light between the inside and outside of the diffuse reflector 20. In this embodiment, the visible light transmitting region is in the region where the reflector 30 is located. As a result, visible light from outside the diffuse reflector 20 is incident on the shooting space 102. Therefore, it is possible to suppress a sense of claustrophobia felt by the person 100 passing through the shooting space 102 for shooting. In addition, since the visible light transmitting region is in the region where the reflector 30 is located, the region that diffusely reflects the sub-terahertz waves and the visible light transmitting region are located on the same reflector 30. Therefore, it is possible to suppress a sense of claustrophobia felt by the person 100 without reducing the efficiency of irradiation of the sub-terahertz waves to the person 100. In this embodiment, the visible light transmitting region may be the entire region or a part of the region where the reflector 30 is located.

[0070] The reflector 30 of the diffuse reflector 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 diffuse reflector 20 has three reflectors 31, 32, and 33 that diffusely reflect sub-terahertz waves. The reflector 30 (specifically the reflector 31 and the reflector 32) sandwich 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 reflector 30 covers the photographing space 102 from both sides of the passage 101. Moreover, the reflector 30 (specifically, the reflector 33) covers the upper part of the photographing space 102 and surrounds the photographing space 102. The photographing space 102 is, for example, a space sandwiched between the inner surfaces of the reflectors 30 in the space above the passage 101. In this way, the reflectors 30 that diffusely reflect sub-terahertz waves are erected from the floor surfaces on both sides of the passage 101 to sandwich the photographing space 102, so that the sub-terahertz waves that enter the photographing space 102 are repeatedly diffusely reflected by the reflectors 30 on both sides and tend to remain in the photographing space 102, and the sub-terahertz waves are irradiated to the person 100 from various angles. The width and height of the photographing space 102 are constant, but there may be a portion where at least one of the width and height of the photographing space 102 is different.

[0071] The reflecting plate 31 and the reflecting plate 32 are arranged opposite to each other with the photographing space 102 in between. That is, the reflecting plate 31 and the reflecting plate 32 are arranged so as to sandwich the passage 101 when viewed from above. The reflecting plate 31 and the reflecting plate 32 are arranged so as to be parallel to each other. The reflecting plate 31 and the reflecting plate 32 are erected from the floor surface of the side of the passage 101 and constitute the side wall of the diffuse reflection section 20. The height of the upper ends of the reflecting plates 31 and 32 from the passage 101 is not particularly limited, but is, for example, 1.5 m or more and 5.0 m or less. The reflecting plate 33 is located above the photographing space 102. The reflecting plate 33 is joined to the upper ends of the reflecting plates 31 and 32. The reflecting plate 33 constitutes the ceiling of the diffuse reflection section 20. The reflecting plates 31, 32, and 33 are each flat plate-shaped. The reflecting plates 31, 32, and 33 may be curved plate-shaped. The planar shapes of the reflectors 31, 32, and 33 are not particularly limited, and may be, for example, rectangular. The diffuse reflector 20 may further include a reflector 30 located below the shooting space 102, forming a floor of the diffuse reflector 20. The reflector 30 may not cover the upper part of the shooting space 102, and for example, the diffuse reflector 20 may not include the reflector 33. The diffuse reflector 20 may not include the three reflectors 31, 32, and 33, and may include only the reflector 31 or the reflector 32 among the three reflectors 31, 32, and 33.

[0072] The reflector 30 diffusely reflects the sub-terahertz waves. Specifically, the reflector 30 diffusely reflects the sub-terahertz waves incident at least from the shooting space 102 side (i.e., the inside of the diffuse reflection unit 20). As shown in FIG. 3, the sub-terahertz waves emitted from the light source 50 are diffusely reflected at least once by the reflector 30 and irradiated onto the person 100. The reflector 30 also transmits visible light. For example, the reflector 30 transmits 5% or more of the visible light incident from the thickness direction of the reflector 30. The reflector 30 may transmit 30% or more, or may transmit 50% or more of the visible light incident from the thickness direction of the reflector 30.

[0073] Next, the detailed configuration of the reflector 30 will be described.

[0074] Fig. 5 is a schematic diagram showing the cross-sectional structure of the reflector 30. Fig. 5 is an enlarged view of a portion of the cross section of the reflector 30. Note that in Fig. 5, the diagonal hatching indicating the cross section has been omitted for ease of viewing.

[0075] The reflector 30 has a sub-terahertz wave reflecting member 41, a visible light transmitting member 44, and a visible light transmitting member 47. The reflector 30 has a structure in which the visible light transmitting member 44, the sub-terahertz wave reflecting member 41, and the visible light transmitting member 47 are laminated in this order from the imaging space 102 side.

[0076] The sub-terahertz wave reflecting member 41 is a sheet-like member that diffusely reflects sub-terahertz waves. The sub-terahertz wave reflecting member 41 transmits visible light. For example, the sub-terahertz wave reflecting member 41 may transmit 5% or more of the visible light incident from the thickness direction of the reflector 30, or may transmit 50% or more of the visible light.

[0077] The sub-terahertz wave reflecting member 41 is located between the visible light transmitting member 44 and the visible light transmitting member 47. The sub-terahertz wave reflecting member 41 has two main surfaces 42 and 43, which are two surfaces that are the front when viewed from the thickness direction of the sub-terahertz wave reflecting member 41. The main surfaces 42 and 43 are uneven surfaces that diffusely reflect the sub-terahertz wave. When the reflecting plate 30 sandwiches the imaging space 102, the main surfaces 42 and 43 also sandwich the imaging space 102. The main surface 42 is located on the imaging space 102 side of the sub-terahertz wave reflecting member 41, and the main surface 43 is located on the opposite side to the imaging space 102 side of the sub-terahertz wave reflecting member 41. Both of the two main surfaces 42 and 43 of the sub-terahertz wave reflecting member 41 are covered with the visible light transmitting member 44 and the visible light transmitting member 47, respectively. Specifically, the main surface 42 of the sub-terahertz wave reflecting member 41 facing the imaging space 102 is covered with a visible light transmitting member 44, and the main surface 43 of the sub-terahertz wave reflecting member 41 facing the opposite side to the imaging space 102 is covered with a visible light transmitting member 47. Therefore, the main surfaces 42 and 43 do not constitute the surface of the reflecting plate 30 and are not exposed. As a result, if the main surfaces 42 and 43, which are uneven surfaces, are exposed, an object becomes difficult to see when viewed through the reflecting plate 30 due to the influence of the unevenness, but the main surfaces 42 and 43 are covered with the visible light transmitting member 44 and the visible light transmitting member 47, respectively, thereby improving the visibility of the object. In addition, the main surfaces 42 and 43, which are uneven surfaces, are protected.

[0078] In the principal surfaces 42 and 43, which are respectively uneven surfaces, for example, the average length RSm of the roughness curve elements is equal to or greater than the wavelength of the sub-terahertz waves emitted from the light source 50. Specifically, in the principal surfaces 42 and 43, for example, the average length RSm of the roughness curve elements 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 waves to be efficiently diffusely reflected by the principal surfaces 42 and 43. In the illustrated example, the uneven shapes of the principal surfaces 42 and 43 are the same. Note that the uneven shapes of the principal surfaces 42 and 43 may be different. In addition, it is sufficient that the principal surface 42 on the shooting space 102 side of the sub-terahertz wave reflecting member 41 is an uneven surface, and the principal surface 43 may be a flat surface.

[0079] The sub-terahertz wave reflecting member 41 is made of a conductive member that is transparent to visible light. Specifically, the sub-terahertz wave reflecting member 41 is, for example, a conductive thin film, a conductive mesh, or a punched metal. This makes it possible to easily manufacture the sub-terahertz wave reflecting member 41 that diffusely reflects sub-terahertz waves and transmits visible light.

[0080] Examples of materials for the conductive thin film 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.

[0081] The conductive thin film may be a metal thin film made of a pure metal (element metal) or alloy containing at least one metal such as copper, aluminum, nickel, iron, stainless steel, silver, gold, or platinum, and has a thickness that allows visible light to pass through. The thickness of the metal thin film is designed based on the skin depth so as to be a thickness that allows visible light to pass through and reflects sub-terahertz waves.

[0082] The conductive mesh may be a fabric made of a filamentary conductive material such as a metal mesh, or may be a fabric plated with a conductive material such as a metal. The conductive material used for the conductive mesh may be a pure metal (single metal) or an alloy containing at least one metal such as copper, aluminum, nickel, iron, stainless steel, silver, gold, or platinum.

[0083] The conductive mesh has an opening that is, for example, equal to or larger than the wavelength of visible light and equal to or smaller than the wavelength of sub-terahertz waves. Specifically, the conductive mesh has an opening that is, for example, equal to or larger than 500 nm and equal to or smaller than 6 mm.

[0084] As the punched metal, for example, a punched metal in which holes are formed by punching a sheet metal is used. As the metal used for the punched metal, for example, a pure metal (metal element) or an alloy containing at least one metal such as copper, aluminum, nickel, iron, stainless steel, silver, gold, or platinum is used. The holes in the punched metal are, for example, round holes, square holes, or long holes. The hole diameter of the punched metal is, for example, equal to or greater than the wavelength of visible light and equal to or less than the wavelength of sub-terahertz waves. Specifically, the hole diameter of the punched metal is the maximum diameter of the hole, and is, for example, equal to or greater than 500 nm and equal to or less than 6 mm. The pitch of the holes in the punched metal may be designed according to the required transmittance of visible light.

[0085] The visible light transmitting member 44 and the visible light transmitting member 47 each transmit a sub-terahertz wave. The visible light transmitting member 44 and the visible light transmitting member 47 each transmit, for example, 50% or more of the sub-terahertz wave incident from the thickness direction of the reflector 30. The visible light transmitting member 44 and the visible light transmitting member 47 each may transmit 80% or more, or 90% or more of the sub-terahertz wave incident from the thickness direction of the reflector 30. In addition, the visible light transmitting member 44 and the visible light transmitting member 47 each transmit visible light. The visible light transmitting member 44 and the visible light transmitting member 47 each transmit, for example, 50% or more of the visible light incident from the thickness direction of the reflector 30. The visible light transmitting member 44 and the visible light transmitting member 47 each may transmit 80% or more, or 90% or more of the visible light incident from the thickness direction of the reflector 30.

[0086] The visible light transmitting member 44 is located on the imaging space 102 side of the sub-terahertz wave reflecting member 41, and covers the main surface 42. The visible light transmitting member 44 has a flat surface 45 on the side opposite to the sub-terahertz wave reflecting member 41 side of the visible light transmitting member 44. The flat surface 45 constitutes the surface of the reflecting plate 30. The flat surface 45 is the surface of the reflecting plate 30 on the imaging space 102 side (i.e., the inner side). This prevents the person 100 from colliding with the uneven surface (i.e., the main surface 42) of the sub-terahertz wave reflecting member 41 even when the person 100 passing through the imaging space 102 collides with the inner surface of the reflecting plate 30, and the person 100 and the main surface 42 are protected. In addition, since the inner surface of the reflecting plate 30 is the flat surface 45, the reflecting plate 30 can be easily cleaned.

[0087] The visible light transmitting member 47 is located on the opposite side of the sub-terahertz wave reflecting member 41 from the imaging space 102 side, and covers the main surface 43. The visible light transmitting member 47 has a flat surface 48 on the opposite side of the visible light transmitting member 47 from the sub-terahertz wave reflecting member 41 side. The flat surface 48 constitutes the outer surface of the reflecting plate 30 that is opposite the imaging space 102 side. Because the outer surface of the reflecting plate 30 is the flat surface 48, the reflecting plate 30 can be easily cleaned.

[0088] The flat surface 45 and the flat surface 48 are in a parallel positional relationship. In the reflecting plate 30, the flat surface 45, the main surface 42, the main surface 43, and the flat surface 48 are arranged in this order from the shooting space 102 side along the thickness direction of the reflecting plate 30.

[0089] A transparent dielectric material such as a transparent resin material is used as the material of the visible light transmitting member 44 and the visible light transmitting member 47. Examples of the transparent resin material include amorphous resin materials such as polycarbonate-based resin, acrylic-based resin, epoxy-based resin, silicone-based resin, and polystyrene-based resin. A crystalline resin material whose crystal size is equal to or smaller than the wavelength of visible light may be used as the transparent resin material.

[0090] For example, the same material is used for the visible light transmitting member 44 and the visible light transmitting member 47. This makes the refractive indexes of the visible light transmitting member 44 and the visible light transmitting member 47 the same, improving the visibility of the object when viewing the object through the reflector 30. Different materials may be used for the visible light transmitting member 44 and the visible light transmitting member 47.

[0091] When the sub-terahertz wave reflecting member 41 is a conductive thin film, the reflecting plate 30 is formed, for example, by the following method. First, the visible light transmitting member 44 is formed by molding a transparent resin material with a mold having an uneven surface, or by machining a plate-shaped transparent resin material to have unevenness, and the sub-terahertz wave reflecting member 41 is formed on the formed visible light transmitting member 44 by deposition, spraying, or the like. Then, the formed sub-terahertz wave reflecting member 41 is covered with the transparent resin material of the visible light transmitting member 47 by coating or hot melt attachment, or the like, to obtain the reflecting plate 30. When the sub-terahertz wave reflecting member 41 is a metal mesh or a punching metal, the metal mesh or punching metal is processed to have unevenness by machining, and the unevenly processed metal mesh or punching metal is covered with the transparent resin material to be the material of the visible light transmitting member 44 and the visible light transmitting member 47 by coating, hot melt attachment, insert molding, or the like, to obtain the reflecting plate 30. Moreover, the visible light transmitting member 44 and the visible light transmitting member 47 may be formed using a 3D printer.

[0092] 5, the sub-terahertz waves incident on the reflector 30 from the imaging space 102 side penetrate the visible light transmitting member 44, are diffusely reflected by the main surface 42 of the sub-terahertz wave reflecting member 41, and are emitted from the flat surface 45 toward the imaging space 102 at various angles. Visible light incident on the reflector 30 from the outside passes through the visible light transmitting member 47, the sub-terahertz wave reflecting member 41, and the visible light transmitting member 44 in this order, and is emitted from the flat surface 45 toward the imaging space 102. Visible light incident on the reflector 30 from the imaging space 102 side passes through the visible light transmitting member 44, the sub-terahertz wave reflecting member 41, and the visible light transmitting member 47 in this order, and is emitted from the flat surface 48 to the outside of the reflector 30.

[0093] The reflectors 31, 32, and 33 may have the same configuration and material, or at least one of the configuration and material may be different. Instead of the three reflectors 31, 32, and 33, the diffuse reflection unit 20 may have one reflector 30 in which the reflectors 31, 32, and 33 are integrated to sandwich the imaging space 102. Any one of the reflectors 31, 32, and 33 may be a reflector that does not transmit visible light and diffusely reflects sub-terahertz waves.

[0094] 2 and 3 again, the components of the image capturing device 10 other than the diffuse reflection section 20 will be described.

[0095] Light source 50 is a light source that emits sub-terahertz waves to reflector 30. Specifically, light source 50 emits sub-terahertz waves to flat surface 45, which is the inner surface of reflector 30. As a result, the sub-terahertz waves are incident on imaging space 102. Also, as shown in Fig. 3, light source 50 emits sub-terahertz waves to reflector 30 such that a portion of the sub-terahertz waves emitted by light source 50 is diffusely reflected by reflector 30 multiple times. Also, a portion of the sub-terahertz waves emitted by light source 50 may be directly incident on person 100.

[0096] The light source 50 is located near the openings 22 and 23 of the diffuse reflector 20, and is spaced apart from the diffuse reflector 20. The light source 50 is also located between the diffuse reflector 20 and the detector 60. This makes it easier for the sub-terahertz waves irradiated into the shooting space 102 and reflected by the person 100 to enter the detector 60. The light source 50 is supported by, for example, a support member not shown. The light source 50 may be located at any position where it can emit sub-terahertz waves to the reflector 30. The light source 50 may be located, for example, inside the diffuse reflector 20, or on the opposite side of the detector 60 from the diffuse reflector 20 side.

[0097] In this embodiment, the photographing device 10 includes four light sources 51, 52, 53, and 54. The number of light sources 50 is not particularly limited, and may be one or more and three or less, or may be five or more. The light sources 51 and 52 are located in front of the diffuse reflecting unit 20 in the direction in which the passage 101 extends. The light sources 53 and 54 are located behind the diffuse reflecting unit 20 in the direction in which the passage 101 extends. That is, the diffuse reflecting unit 20 is located between the light sources 51 and 52 and the light sources 53 and 54. 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 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 the "front" direction, and the other direction opposite to the one direction is referred to as the "rear" direction.

[0098] The light source 51 and the light source 52 emit sub-terahertz waves from the front of the diffuse reflector 20 toward the reflector 30 , and the light source 53 and the light source 54 emit sub-terahertz waves from the rear of the diffuse reflector 20 toward the reflector 30 .

[0099] Light source 50 is, for example, a point light source that radiates sub-terahertz waves to the periphery of light source 50. Light source 50 may also be a line light source that extends along the end of reflector 30 in the direction in which passage 101 extends and radiates sub-terahertz waves. Light source 50 is realized by, for example, a light source including a known sub-terahertz wave generating element.

[0100] The light source 50 may be a plurality of point light sources arranged along the end of the reflector 30 in the direction in which the passage 101 extends.

[0101] The detector 60 receives the sub-terahertz waves that are emitted from the light source 50 and then diffusely reflected by the reflector 30 and reflected by the person 100. The detector 60 detects the intensity of the received reflected waves. Specifically, the detector 60 generates an image based on the intensity of the received reflected waves. The detector 60 outputs the generated image to the image processing unit 70. The generation of an image by the detector 60 is also referred to as "taking an image". The detectors 60 are located in front of and behind the diffuse reflecting unit 20.

[0102] In this embodiment, the imaging device 10 includes four detectors 61, 62, 63, and 64. The number of detectors 60 is not particularly limited, and may be one or more and three or less, or may be five or more. The detectors 61 and 62 are located in front of the diffuse reflector 20. The detectors 63 and 64 are located behind the diffuse reflector 20. That is, the diffuse reflector 20 is located between the detectors 61 and 62 and the detectors 63 and 64. The detectors 61 and 62 capture an image of the front side of the person 100, and the detectors 63 and 64 capture an image of the rear side of the person 100. The detector 60 is supported by, for example, a support member not shown in the figure.

[0103] The detector 60 includes an image sensor 65 and an optical system 66 .

[0104] The image sensor 65 receives the sub-terahertz waves emitted from the light source 50 and then diffusely reflected by the reflector 30, and reflected by the person 100. The image sensor 65 detects the intensity of the received reflected waves, and generates an image based on the detected intensity. Specifically, the image sensor 65 converts an image of the sub-terahertz waves emitted from the object to be photographed into an electrical signal according to the intensity. The image sensor 65 then generates an image based on the converted electrical signal. The image generated by the image sensor 65 is output to the image processing unit 70.

[0105] Sub-terahertz waves are specularly reflected by the human body, metal, etc., and pass through clothes, bags, etc. Therefore, the image sensor 65 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 65 can receive waves. For example, a wave reflected by the person 100 passing through the area indicated by the dashed line in Fig. 3 is incident on the image sensor 65. Furthermore, if the person 100 is concealing a knife or the like, the image sensor 65 receives a wave reflected specularly by the concealed knife from an area included in the angle range in which the image sensor 65 can receive waves.

[0106] The image sensor 65 is composed of, for example, a plurality of pixels each including a detection element for detecting sub-terahertz waves, and peripheral circuits.

[0107] The optical system 66 forms an image of the sub-terahertz waves, which are emitted from the light source 50 and then diffusely reflected by the reflector 30 and reflected by the person 100, on the image sensor 65. The optical system 66 is configured to include at least one lens, for example. Note that the detector 60 does not necessarily have to include the optical system 66, and the reflected waves may be directly incident on the image sensor 65.

[0108] When the image processing unit 70 receives an image from the detector 60, it 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.

[0109] The image processing performed by the image processing unit 70 may be, for example, a process of determining whether or not an object having a predetermined characteristic (for example, an object having the characteristics of a blade) is included in the image output from the detector 60, and outputting a predetermined detection signal (for example, an alarm indicating that an object having the characteristics of a blade has been photographed) when it is determined that an object having the predetermined characteristic is included. The image processing unit 70 includes, for example, a processor and a memory, and is realized by the processor executing a program stored in the memory.

[0110] The photographing device 10 does not necessarily have to include the image processing unit 70, and the detector 60 may output an image to an external image processing device. Also, the function of the image processing unit 70 may be provided in each detector 60.

[0111] Here, the action and effect of the imaging device 10 according to the present embodiment will be described mainly with reference to FIG. 3. The sub-terahertz waves (arrows in FIG. 3) emitted from the light source 50 to the reflector 30 are diffusely reflected by the reflector 30 and enter the person 100 because the imaging space 102 is covered by the reflector 30 from the side of the imaging space 102. As a result, the surface of the reflector 30 on the imaging space 102 side, that is, the entire flat surface 45, 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 this embodiment, the imaging space 102 is sandwiched between the reflectors 30, so the sub-terahertz waves emitted from the light source 50 are diffusely reflected at least once by the reflector 30 and enter the person 100. Furthermore, the sub-terahertz waves emitted from the light source 50 to the reflector 30 are repeatedly diffusely reflected by the reflectors 30 located on both sides of the passage 101, and tend to remain within the photographing space 102, and are irradiated at various angles to the person 100. Thus, the photographing device 10 can more effectively irradiate the person 100 with the sub-terahertz waves.

[0112] Furthermore, since the sub-terahertz waves are irradiated from various angles over a relatively wide area of ​​the person 100, the reflected waves of the sub-terahertz waves reflected over a relatively wide area of ​​the person 100 are incident on the image sensor 65 of the detector 60. For example, the reflected waves of the sub-terahertz waves reflected over almost the entire surface of the front side of the person 100 are incident on the image sensor 65 of the detector 60 located in front of the diffuse reflection unit 20. In addition, since the sub-terahertz waves emitted from the light source 50 to the reflector 30 tend to remain within the imaging space 102, the amount of reflected waves incident on the image sensor 65 of the detector 60 increases. Therefore, the image quality of the image generated by the detector 60 is improved. As a result, for example, the accuracy of the imaging device 10 in detecting a dangerous object such as a knife concealed by the person 100 is improved.

[0113] In addition, the diffuse reflector 20 has a visible light transmission region that transmits visible light. Since the reflector 30 transmits visible light, the visible light transmission region of the diffuse reflector 20 is in the region where the reflector 30 is located. Since the reflector 30 stands upright from the floor surface on both sides of the passage 101, if the diffuse reflector 20 does not have a visible light transmission region, visible light from outside the diffuse reflector 20 is unlikely to enter the shooting space 102. In addition, the outside of the diffuse reflector 20 cannot be seen from the shooting space 102, and for example, a person 100 passing through the shooting space 102 cannot see the scenery outside the diffuse reflector 20. Therefore, a person 100 passing through the shooting space 102 for shooting is likely to feel a sense of obstruction. In contrast, when the diffuse reflector 20 has a visible light transmission region, visible light from outside the diffuse reflector 20 enters the shooting space 102. In addition, the outside of the diffuse reflecting section 20 can be seen from the shooting space 102, so that, for example, a person 100 passing through the shooting space 102 can see the scenery outside the diffuse reflecting section 20. This allows the shooting device 10 to suppress a sense of claustrophobia felt by the person 100 passing through the shooting space 102 to take a picture. In addition, the shooting device 10 can visually recognize the person 100 passing through the shooting space 102 from outside the diffuse reflecting section 20 through the reflecting plate 30.

[0114] (Embodiment 2) Next, an imaging device according to a second embodiment will be described.

[0115] The imaging device according to the second embodiment is different from that according to the first embodiment in that it includes a reflector that reflects visible light. The following description will focus on the differences from the first embodiment, and descriptions of the commonalities will be omitted or simplified.

[0116] FIG. 6 is a block diagram showing the configuration of the imaging device 10a according to the present embodiment. FIG. 7 is a schematic diagram showing the cross-sectional structure of the diffuse reflector 20a. FIG. 7 shows a cross section of the diffuse reflector 20a cut vertically along a line perpendicular to the direction in which the passage 101 extends in a top view. The imaging device 10a differs from the imaging device 10 according to the first embodiment in that the imaging device 10a includes a diffuse reflector 20a having a reflector 30a instead of the diffuse reflector 20 having a reflector 30. The imaging device 10a also differs from the imaging device 10 according to the first embodiment in that the imaging device 10a further includes a projector 80.

[0117] 6 and 7, the image capturing device 10a includes a diffuse reflector 20a having a reflector 30a, a light source 50, a detector 60, an image processor 70, and a projector 80. The positional relationship of each component of the image capturing device 10a when viewed from above is the same as that of the image capturing device 10, for example.

[0118] The reflector 30a of the diffuse reflector 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 embodiment, the diffuse reflector 20a has three reflectors 31a, 32a, and 33a. The diffuse reflector 20a is, for example, a tunnel-like shape through which the person 100 can pass, similar to the above-mentioned diffuse reflector 20. The reflector 30a (specifically, the reflector 31a and the reflector 32a) sandwich the photographing space 102 on the passage 101 through which the person 100 passes, from both sides of the passage 101. In addition, the reflector 30a (specifically, the reflector 33a) covers the upper side of the photographing space 102 and surrounds the photographing space 102.

[0119] The reflecting plate 31a and the reflecting plate 32a are arranged facing each other across the photographing space 102. The reflecting plate 31a and the reflecting plate 32a are arranged so as to be in a parallel positional relationship. The reflecting plate 31a and the reflecting plate 32a are erected from the floor surface of the side of the passage 101 and constitute the side wall of the diffuse reflecting section 20a. The height of the upper ends of the reflecting plates 31a and 32a from the passage 101 is not particularly limited, but is, for example, 1.5 m or more and 5.0 m or less. The reflecting plate 33a is located above the photographing space 102. The reflecting plate 33a is joined to the upper ends of the reflecting plates 31a and 32a. The reflecting plate 33a constitutes the ceiling of the diffuse reflecting section 20a. The reflecting plates 31a, 32a, and 33a are each flat plate-shaped. The reflecting plates 31a, 32a, and 33a may be curved plate-shaped. The planar shapes of the reflectors 31a, 32a, and 33a are not particularly limited, but may be, for example, rectangular. The diffuse reflector 20a may have a reflector 30a located below the shooting space 102, forming a floor of the diffuse reflector 20a. The reflector 30a may not cover the upper part of the shooting space 102, and for example, the diffuse reflector 20a may not have the reflector 33a. The diffuse reflector 20a may not have the three reflectors 31a, 32a, and 33a, and may have only the reflector 31a or the reflector 32a among the three reflectors 31a, 32a, and 33a.

[0120] The reflector 30a diffusely reflects sub-terahertz waves. Specifically, the reflector 30a diffusely reflects sub-terahertz waves incident at least from the imaging space 102 side (i.e., the inside of the diffuse reflector 20a). The reflector 30a also reflects, specifically, diffusely reflects visible light from the imaging space 102 side.

[0121] Fig. 8 is a schematic diagram showing the cross-sectional structure of the reflector 30a. Fig. 8 is an enlarged view of a part of the cross section of the reflector 30a. Note that in Fig. 8, the diagonal hatching indicating the cross section has been omitted for ease of viewing.

[0122] The reflector 30a includes a sub-terahertz wave reflecting member 41a, a visible light diffuse reflecting member 44a, and a covering member 47a. The reflector 30a has a structure in which the visible light diffuse reflecting member 44a, the sub-terahertz wave reflecting member 41a, and the covering member 47a are laminated in this order from the imaging space 102 side.

[0123] The sub-terahertz wave reflecting member 41a is a sheet-like member that diffusely reflects sub-terahertz waves. The sub-terahertz wave reflecting member 41a may transmit visible light or may not transmit visible light.

[0124] The sub-terahertz wave reflecting member 41a is located between the visible light diffuse reflecting member 44a and the covering member 47a. The sub-terahertz wave reflecting member 41a has two main surfaces 42a and 43a, which are two surfaces that are the front when viewed from the thickness direction of the sub-terahertz wave reflecting member 41a. When the reflecting plate 30a sandwiches the imaging space 102, the main surfaces 42a and 43a also sandwich the imaging space 102. The main surface 42a is located on the imaging space 102 side of the sub-terahertz wave reflecting member 41a, and the main surface 43a is located on the opposite side to the imaging space 102a side of the sub-terahertz wave reflecting member 41a. The main surface 42a on the imaging space 102 side of the sub-terahertz wave reflecting member 41a is covered with the visible light diffuse reflecting member 44a. A main surface 43a of the sub-terahertz wave reflecting member 41a on the side opposite to the imaging space 102 side is covered with a covering member 47a.

[0125] Like the main surface 42 and the main surface 43 according to the first embodiment, the main surface 42a and the main surface 43a are uneven surfaces that diffusely reflect sub-terahertz waves.

[0126] The sub-terahertz wave reflecting member 41a is made of, for example, the same conductive member such as a metal or a conductive oxide as the sub-terahertz wave reflecting member 41 according to embodiment 1. The sub-terahertz wave reflecting member 41a may be made of a metal foil or the like that does not transmit visible light.

[0127] The visible light diffuse reflection member 44a transmits sub-terahertz waves. For example, the visible light diffuse reflection member 44a transmits 50% or more of the sub-terahertz waves incident from the thickness direction of the reflector 30a. The visible light diffuse reflection member 44a may transmit 80% or more, or may transmit 90% or more of the sub-terahertz waves incident from the thickness direction of the reflector 30a. In addition, the visible light diffuse reflection member 44a diffusely reflects visible light from the shooting space 102 side.

[0128] The visible light diffuse reflection member 44a is located on the imaging space 102 side of the sub-terahertz wave reflecting member 41a, and covers the main surface 42a. The visible light diffuse reflection member 44a has a flat visible light diffuse reflection surface 45a that diffusely reflects visible light on the side opposite to the sub-terahertz wave reflecting member 41a side of the visible light diffuse reflection member 44a. The visible light diffuse reflection surface 45a constitutes the surface of the reflector 30a on the imaging space 102 side. This makes it possible to project an image by the projector 80 or the like on the surface of the reflector 30a on the imaging space 102 side. In addition, since the visible light diffuse reflection surface 45a is a flat surface, it is easy to clean the reflector 30a. Furthermore, even if a person 100 passing through the imaging space 102 hits the inner surface of the reflecting plate 30a, the person 100 will not hit the uneven surface (i.e., the main surface 42a) of the sub-terahertz wave reflecting member 41a, and the person 100 and the main surface 42a will be protected.

[0129] The visible light diffuse reflection member 44a may be made of a crystalline resin material that diffusely reflects visible light, such as a fluorine-based resin such as polytetrafluoroethylene or a high-density polyethylene resin. The visible light diffuse reflection member 44a may contain a crystalline resin material as a main component. The visible light diffuse reflection member 44a may also contain visible light diffusing particles such as glass beads. Specifically, the visible light diffuse reflection member 44a may be made of a plate-shaped resin material (such as the above-mentioned amorphous resin material) that does not diffusely reflect visible light, the surface of which facing the shooting space 102 is coated with paint containing visible light diffusing particles such as glass beads, or a resin material in which visible light diffusing particles such as glass beads are dispersed.

[0130] The covering member 47a is located on the side opposite to the imaging space 102 side of the sub-terahertz wave reflecting member 41a, and covers the main surface 43a. The covering member 47a has a flat surface 48a on the side opposite to the sub-terahertz wave reflecting member 41a side of the covering member 47a. The flat surface 48a constitutes the outer surface of the reflecting plate 30a, which is the side opposite to the imaging space 102 side. Since the outer surface of the reflecting plate 30a is the flat surface 48a, the reflecting plate 30a can be easily cleaned.

[0131] The material of the covering member 47a may be any material that can be processed into the shape of the covering member 47a and can maintain the shape. For example, a resin material or a metal may be used as the material of the covering member 47a.

[0132] The reflector 30a is formed, for example, by changing the materials used in the method for forming the reflector 30 according to the first embodiment to the materials described above.

[0133] 8, sub-terahertz waves incident on reflector 30a from the imaging space 102 side enter visible light diffuse reflection member 44a, are diffusely reflected by main surface 42a of sub-terahertz wave reflecting member 41a, and are emitted at various angles from visible light diffuse reflection surface 45a toward imaging space 102. Visible light incident on reflector 30a from the imaging space 102 side is diffusely reflected by visible light diffuse reflection surface 45a.

[0134] The reflectors 31a, 32a, and 33a constituting the reflector 30a may have the same configuration and material, or at least one of the configuration and material may be different. The diffuse reflection unit 20a may have one reflector 30a in which the reflectors 31a, 32a, and 33a are integrated to sandwich the imaging space 102, instead of the three reflectors 31a, 32a, and 33a. Any one of the reflectors 31a, 32a, and 33a may be a reflector that does not diffusely reflect visible light but diffusely reflects sub-terahertz waves.

[0135] Referring again to FIG. 6, the components of the image capturing device 10a other than the diffuse reflection section 20a will be described.

[0136] The projector 80 projects an image onto the visible light diffusion reflecting surface 45a of the reflector 30a. The projector 80 projects an image of, for example, a geometric pattern or a natural scene. The image projected by the projector 80 may be a still image or a moving image. In this way, the projector 80 projects an image onto the visible light diffusion reflecting surface 45a, so that a person 100 passing through the shooting space 102 can see the image projected onto the visible light diffusion reflecting surface 45a. This makes it possible to suppress a sense of claustrophobia felt by the person 100 passing through the shooting space 102 for shooting.

[0137] As described above, in the imaging device 10a according to this embodiment, the imaging space 102 is sandwiched between reflectors 30a, so that sub-terahertz waves are effectively irradiated onto the person 100, similar to the imaging device 10 according to embodiment 1.

[0138] [Variation 1] Next, an imaging device according to Variation 1 of Embodiment 2 will be described.

[0139] The imaging device according to Variation 1 of Embodiment 2 is different from Embodiment 2 mainly in that it includes a reflector that specularly reflects visible light instead of diffusively reflecting it. The following description will focus on the differences from Embodiments 1 and 2, and will omit or simplify the description of the commonalities.

[0140] FIG. 9 is a block diagram showing the configuration of the imaging device 10b according to this modification. FIG. 10 is a schematic diagram showing the cross-sectional structure of the diffuse reflector 20b. FIG. 10 shows a cross section of the diffuse reflector 20b cut vertically along a line perpendicular to the direction in which the passage 101 extends in a top view. The imaging device 10b differs from the imaging device 10a according to the second embodiment in that the imaging device 10b includes a diffuse reflector 20b having a reflector 30b instead of the diffuse reflector 20a having a reflector 30a. The imaging device 10b also differs from the imaging device 10a according to the second embodiment in that the imaging device 10b does not include a projector 80.

[0141] 9 and 10, the image capturing device 10b includes a diffuse reflector 20b having a reflector 30b, a light source 50, a detector 60, and an image processor 70. The positional relationship of each component in the image capturing device 10b when viewed from above is the same as that of the image capturing device 10, for example.

[0142] The reflector 30b of the diffuse reflector 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 diffuse reflector 20b has three reflectors 31b, 32b, and 33b. The diffuse reflector 20b is, for example, a tunnel-like shape through which the person 100 can pass, similar to the above-mentioned diffuse reflector 20 and diffuse reflector 20a. The reflector 30b (specifically, the reflector 31b and the reflector 32b) sandwich the photographing space 102 on the passage 101 through which the person 100 passes from both sides of the passage 101. In addition, the reflector 30b (specifically, the reflector 33b) covers the upper side of the photographing space 102 and surrounds the photographing space 102.

[0143] The reflecting plate 31b and the reflecting plate 32b are arranged facing each other across the photographing space 102. The reflecting plate 31b and the reflecting plate 32b are arranged so as to be in a parallel positional relationship. The reflecting plate 31b and the reflecting plate 32b are erected from the floor surface of the side of the passage 101 and constitute the side wall of the diffuse reflecting section 20b. The height of the upper ends of the reflecting plates 31b and 32b from the passage 101 is not particularly limited, but is, for example, 1.5 m or more and 5.0 m or less. The reflecting plate 33b is located above the photographing space 102. The reflecting plate 33b is joined to the upper ends of the reflecting plates 31b and 32b. The reflecting plate 33b constitutes the ceiling of the diffuse reflecting section 20b. The diffuse reflecting section 20b may have a reflecting plate 30b located below the photographing space 102 so as to constitute the floor part of the diffuse reflecting section 20b. Furthermore, the reflector 30b does not have to cover the upper part of the shooting space 102, and for example, the diffuse reflector 20b does not have to include the reflector 33b. Furthermore, the diffuse reflector 20b does not have to include the three reflectors 31b, 32b, and 33b, and for example, it may include only the reflector 31b or the reflector 32b among the three reflectors 31b, 32b, and 33b.

[0144] The reflector 30b diffusely reflects the sub-terahertz waves. Specifically, the reflector 30b diffusely reflects the sub-terahertz waves incident at least from the imaging space 102 side (i.e., the inside of the diffuse reflector 20b). The reflector 30b also reflects visible light from the imaging space 102 side, specifically, specularly reflects the visible light.

[0145] Fig. 11 is a schematic diagram showing the cross-sectional structure of the reflector 30b. Fig. 11 is an enlarged view of a part of the cross section of the reflector 30b. Note that in Fig. 11, the diagonal hatching indicating the cross section has been omitted for ease of viewing.

[0146] The reflector 30b has a sub-terahertz wave reflecting member 41a, a visible light specular reflecting member 44b, and a covering member 47a. The reflector 30b has a structure in which the visible light specular reflecting member 44b, the sub-terahertz wave reflecting member 41a, and the covering member 47a are laminated in this order from the imaging space 102 side. In other words, the reflector 30b has a configuration including the visible light specular reflecting member 44b instead of the visible light diffuse reflecting member 44a of the reflector 30a according to the second embodiment.

[0147] The visible light mirror reflecting member 44b transmits sub-terahertz waves. For example, the visible light mirror reflecting member 44b transmits 50% or more of the sub-terahertz waves incident from the thickness direction of the reflecting plate 30b. The visible light mirror reflecting member 44b may transmit 80% or more, or may transmit 90% or more of the sub-terahertz waves incident from the thickness direction of the reflecting plate 30b. In addition, the visible light mirror reflecting member 44b mirror-reflects visible light from the shooting space 102 side.

[0148] The visible light specular reflecting member 44b is located on the imaging space 102 side of the sub-terahertz wave reflecting member 41a, and covers the main surface 42a. The visible light specular reflecting member 44b has a flat visible light specular reflecting surface 45b that specularly reflects visible light on the side opposite to the sub-terahertz wave reflecting member 41a side of the visible light specular reflecting member 44b. The visible light specular reflecting surface 45b constitutes the surface of the reflecting plate 30b on the imaging space 102 side. As a result, a mirror image is reflected on the surface of the reflecting plate 30b on the imaging space 102 side, so that a sense of claustrophobia of a person 100 passing through the imaging space 102 for imaging can be suppressed. In addition, since the visible light specular reflecting surface 45b is a flat surface, the reflecting plate 30b can be easily cleaned. Furthermore, even if a person 100 passing through the imaging space 102 hits the inner surface of the reflecting plate 30b, the person 100 will not hit the uneven surface (i.e., the main surface 42a) of the sub-terahertz wave reflecting member 41a, and the person 100 and the main surface 42a will be protected.

[0149] The visible light mirror reflecting member 44b includes, for example, a dielectric multilayer film in which films having different refractive indices are alternately laminated. Specifically, the visible light mirror reflecting member 44b is, for example, a member in which a dielectric multilayer film is laminated on the surface of a plate-shaped resin material on the side of the shooting space 102.

[0150] The reflector 30b is formed, for example, by changing the materials used in the method for forming the reflector 30 according to the first embodiment to the materials described above.

[0151] 11, sub-terahertz waves incident on reflector 30b from the imaging space 102 side enter visible light specular reflecting member 44b, are diffusely reflected by main surface 42a of sub-terahertz wave reflecting member 41a, and are emitted at various angles from visible light specular reflecting surface 45b toward imaging space 102. Visible light incident on reflector 30b from the imaging space 102 side is specularly reflected by visible light specular reflecting surface 45b.

[0152] The reflectors 31b, 32b, and 33b may have the same configuration and material, or at least one of the configuration and material may be different. The diffuse reflection unit 20b may have one reflector 30b in which the reflectors 31b, 32b, and 33b are integrated to sandwich the imaging space 102, instead of the three reflectors 31b, 32b, and 33b. Any one of the reflectors 31b, 32b, and 33b may not specularly reflect visible light but diffusely reflect sub-terahertz waves.

[0153] As described above, in the imaging device 10b according to this modified example, the imaging space 102 is sandwiched between the reflectors 30b, so that the person 100 is effectively irradiated with sub-terahertz waves, similar to the imaging device 10 according to embodiment 1.

[0154] (Embodiment 3) Next, an imaging device according to a third embodiment will be described.

[0155] The imaging device according to embodiment 3 differs from embodiments 1 and 2 mainly in that a gap is provided in the diffuse reflection section. The following description will focus on the differences from embodiments 1 and 2, and descriptions of commonalities will be omitted or simplified.

[0156] Fig. 12 is a block diagram showing the configuration of the imaging device 10c according to the present embodiment. Fig. 13 is a schematic diagram showing the cross-sectional structure of the diffuse reflector 20c. Fig. 13 shows a cross section of the diffuse reflector 20c cut vertically along a line perpendicular to the direction in which the passage 101 extends in a top view. The imaging device 10c differs from the imaging device 10 according to the first embodiment in that the imaging device 10c includes the diffuse reflector 20c having a reflector 30c instead of the diffuse reflector 20 having a reflector 30.

[0157] 12 and 13, the image capturing device 10c includes a diffuse reflector 20c having a reflector 30c, a light source 50, a detector 60, and an image processor 70. The positional relationship of each component in the image capturing device 10c when viewed from above is the same as that of the image capturing device 10, for example.

[0158] The diffuse reflector 20c has two reflectors 31c and 32c. The diffuse reflector 20c has a visible light transmitting region that transmits visible light between the inside and outside of the diffuse reflector 20c.

[0159] In the diffuse reflector 20c, a gap 21c is provided between the reflector 31c and the reflector 32c, specifically, between the upper end of the reflector 31c and the upper end of the reflector 32c. In this embodiment, the visible light transmission region is the region where the gap 21c is located. The gap 21c extends in the direction in which the passage 101 extends. The gap 21c is located above the shooting space 102. The width of the gap 21c is smaller than the height of the diffuse reflector 20c from the passage 101. As a result, even if the gap 21c is provided in the diffuse reflector 20c, the sub-terahertz wave incident on the shooting space 102 is more likely to be diffusely reflected by the reflector 30c of the diffuse reflector 20c than to exit from the gap 21c. Therefore, the sub-terahertz wave incident on the shooting space 102 is less likely to leak from the gap 21c. In addition, the width of the gap 21c is smaller than the width of the passage 101. As a result, even if gap 21c is provided in diffuse reflection unit 20c, sub-terahertz waves incident on imaging space 102 are less likely to leak through gap 21c. Here, the width refers to the length in a direction perpendicular to the extension directions of gap 21c and passage 101 when diffuse reflection unit 20c is viewed from above with passage 101 in mind.

[0160] The reflector 30c of the diffuse reflector 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 embodiment, the reflector 30c (specifically, the reflector 31c and the reflector 32c) sandwich the photographing space 102 on the passage 101 through which the person 100 passes, from both sides of the passage 101. The reflector 30c also covers an upper part of a part of the photographing space 102. The reflector 31c and the reflector 32c are arranged opposite to each other with the photographing space 102 in between. The reflector 31c and the reflector 32c stand upright from the floor surface on the side of the passage 101, and form the side wall of the diffuse reflector 20c. The upper ends of the reflector 31c and the reflector 32c are curved inward so as to approach each other. As a result, the upper ends of the reflectors 31c and 32c cover an upper portion of the shooting space 102. The diffuse reflector 20c may have a reflector 30c located below the shooting space 102 so as to constitute a floor of the diffuse reflector 20c.

[0161] The reflector 30c diffusely reflects the sub-terahertz waves. Specifically, the reflector 30c diffusely reflects the sub-terahertz waves incident at least from the imaging space 102 side (that is, the inside of the diffuse reflector 20c).

[0162] Moreover, the image capturing device 10c according to this embodiment may include another diffuse reflector instead of the diffuse reflector 20c.

[0163] Fig. 14 is a schematic diagram showing a cross-sectional structure of a diffuse reflector 20d, which is another example of the diffuse reflector according to the present embodiment. Fig. 14 shows a cross section of the diffuse reflector 20d cut vertically along a line perpendicular to the direction in which the passages 101 extend in a top view.

[0164] 14, the diffuse reflector 20d has two reflectors 31d and 32d. The reflector 30d covers an upper part of the photographing space 102. The diffuse reflector 20d has a gap 21d between the reflector 31d and the reflector 32d. The gap 21d extends in the direction in which the passage 101 extends. The gap 21d is located above the photographing space 102.

[0165] The reflecting plates 31d and 32d are disposed opposite each other with the photographing space 102 in between. The reflecting plates 31d and 32d stand upright from the floor surface at the side of the passage 101 and form the side walls of the diffuse reflecting section 20d. The reflecting plates 31d and 32d are curved plates that are curved inward so that the upper and lower ends of the reflecting plates 31d and 32d approach each other.

[0166] The reflector 30d diffusely reflects the sub-terahertz waves. Specifically, the reflector 30d diffusely reflects at least the sub-terahertz waves incident from the imaging space 102 side (that is, the inside of the diffuse reflector 20d).

[0167] Fig. 15 is a schematic diagram showing a cross-sectional structure of diffuse reflector 20e, which is yet another example of the diffuse reflector according to the present embodiment. Fig. 15 shows a cross section of diffuse reflector 20e cut vertically along a line perpendicular to the extension direction of passage 101 in top view.

[0168] 15, the diffuse reflector 20e has three reflectors 31e, 32e, and 33e. The diffuse reflector 20e has a gap 21e, which is a slit formed in the reflector 33e. The gap 21e extends in the direction in which the passage 101 extends. The gap 21e is located above the shooting space 102.

[0169] The reflecting plate 31e and the reflecting plate 32e are disposed opposite to each other with the photographing space 102 in between. The reflecting plate 31e and the reflecting plate 32e are erected from the floor surface on the side of the passage 101, and constitute the side wall of the diffuse reflecting section 20e. The reflecting plate 33e is located above the photographing space 102. The reflecting plate 33e is joined to the upper ends of the reflecting plates 31e and 32e. The reflecting plate 33e constitutes the ceiling of the diffuse reflecting section 20. The reflecting plate 33e covers the upper part of the photographing space 102. The reflecting plate 33e has a slit that extends in the direction in which the passage 101 extends as the gap 21e. The extending direction of the slit may be a direction intersecting the extending direction of the passage 101.

[0170] The reflector 30e diffusely reflects the sub-terahertz waves. Specifically, the reflector 30e diffusely reflects the sub-terahertz waves incident at least from the imaging space 102 side (that is, the inside of the diffuse reflector 20e).

[0171] The material and configuration of the reflectors 30c, 30d, and 30e are not particularly limited as long as they are made of a material and have a configuration that can diffusely reflect sub-terahertz waves toward the imaging space 102, and may be, for example, the same material and configuration as the above-mentioned reflector 30, reflector 30a, or reflector 30b.

[0172] As described above, in the imaging device 10c of this embodiment, the imaging space 102 is sandwiched between reflectors 30c, 30d, or 30e, so that sub-terahertz waves are effectively irradiated onto the person 100, as in the imaging device 10 of embodiment 1.

[0173] Further, the diffuse reflecting section 20c, the diffuse reflecting section 20d, and the diffuse reflecting section 20e have a visible light transmitting region that transmits visible light. In the diffuse reflecting section 20c, the diffuse reflecting section 20d, and the diffuse reflecting section 20e, the visible light transmitting region is a region where the gap 21c, the gap 21d, and the gap 21e are located. Therefore, as with the imaging device 10 according to the first embodiment, it is possible to suppress a sense of claustrophobia felt by the person 100 passing through the imaging space 102 for imaging.

[0174] Furthermore, a visible light transmitting region is formed simply by providing gaps 21c, 21d, and 21e in diffuse reflecting section 20c, diffuse reflecting section 20d, and diffuse reflecting section 20e, respectively, and therefore diffuse reflecting section 20c, diffuse reflecting section 20d, and diffuse reflecting section 20e having a visible light transmitting region can be easily manufactured.

[0175] (Embodiment 4) Next, an imaging device according to a fourth embodiment will be described.

[0176] The imaging device according to the fourth embodiment is different from the first embodiment mainly in that it further includes a lighting fixture that irradiates the imaging space with visible light. The following description will focus on the differences from the first to third embodiments, and the description of the commonalities will be omitted or simplified.

[0177] 16 is a block diagram showing a configuration of an image capturing device 10f according to the present embodiment. Image capturing device 10f differs from image capturing device 10 according to the first embodiment in that it further includes a lighting fixture 90.

[0178] 16, the image capturing device 10f includes a diffuse reflector 20, a light source 50, a detector 60, an image processor 70, and a lighting fixture 90. The positional relationship of each component of the image capturing device 10f when viewed from above is the same as that of the image capturing device 10, for example.

[0179] The image capturing device 10f includes the diffuse reflector 20 according to the first embodiment, and a lighting device 90 irradiates the diffuse reflector 20 with visible light from outside.

[0180] Fig. 17 is a schematic diagram showing a cross-sectional structure of the diffuse reflector 20 above which a lighting fixture 90 is provided. Fig. 17 shows a cross section of the diffuse reflector 20 cut vertically along a line perpendicular to the direction in which the passage 101 extends when viewed from above.

[0181] As shown in FIG. 17, a lighting fixture 90 supported by a support member 91 is provided above the diffuse reflector 20, specifically above the reflector 33. The diffuse reflector 20 has a visible light transmission area above the photographing space 102, and the lighting fixture 90 irradiates visible light from above the visible light transmission area through the visible light transmission area into the photographing space 102. As described above, the diffuse reflector 20 has the reflector 30 that transmits visible light. The lighting fixture 90 irradiates visible light into the photographing space 102 through the visible light transmission area in the area where the reflector 30 (specifically the reflector 33) is located. As a result, visible light is irradiated onto the person 100, so that the sense of claustrophobia felt by the person 100 can be further suppressed.

[0182] The lighting device 90 may be provided at a position where it irradiates the shooting space 102 with visible light via the reflector 31 or 32. In other words, the lighting device 90 may be located on the outer lateral side of the diffuse reflector 20.

[0183] Furthermore, the image capturing device 10f may include a diffuse reflector 20e instead of the diffuse reflector 20. Fig. 18 is a schematic diagram showing a cross-sectional structure of the diffuse reflector 20e with a lighting fixture 90 provided above. Fig. 18 shows a cross section of the diffuse reflector 20e cut vertically along a line perpendicular to the extension direction of the passage 101 in a top view.

[0184] 18, above the diffuse reflector 20e, specifically above the reflector 33e, a lighting device 90 supported by a support member 91 is provided. As described above, the diffuse reflector 20e is provided with a gap 21e that transmits visible light. The lighting device 90 irradiates visible light into the shooting space 102 through the gap 21e, which is a visible light transmitting region. As a result, the visible light is irradiated by the person 100, and the sense of claustrophobia felt by the person 100 can be further suppressed.

[0185] In addition, if a gap 21e is also provided in the reflector 31e or 32e of the diffuse reflection unit 20e, a lighting device 90 may be provided in a position where it irradiates visible light into the shooting space 102 through the gap 21e provided in the reflector 31e or 32e.

[0186] Furthermore, the diffuse reflector provided in the photographing device 10f is not limited to the above-mentioned diffuse reflector 20 and diffuse reflector 20e, but may be any diffuse reflector having a visible light transmitting region, such as the diffuse reflector according to the first and third embodiments.

[0187] (Other embodiments) Although the imaging device according to the present disclosure has been described above based on the first to fourth 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 conceivable by a person skilled in the art to these embodiments and configurations constructed by combining components in different embodiments are also included within the scope of one or more aspects of the present disclosure.

[0188] For example, in the above-mentioned embodiment 1, the width of the diffuse reflector 20 when viewed from above is constant, but this is not limited thereto. FIG. 19 is a schematic diagram of an image capturing device 10g according to a modified example when viewed from above. Also, FIG. 19 is a perspective view of the upper part of the diffuse reflector 20g, similar to FIG. 3. As shown in FIG. 19, the image capturing device 10g has a configuration including a diffuse reflector 20g instead of the diffuse reflector 20 of the image capturing device 10. The diffuse reflector 20g has a reflector 30g instead of the reflector 30 of the diffuse reflector 20. Specifically, the diffuse reflector 20g has a reflector 31g and a reflector 32g instead of the reflector 31 and the reflector 32 of the diffuse reflector 20. The diffuse reflector 20g has a structure in which the opening 22g and the opening 23g, which are the entrance and exit to the image capturing space 102, are narrowed. In the diffuse reflector 20g, the distance between the reflector 31g and the reflector 32g is the shortest at the opening 22g and the opening 23g. That is, the diffuse reflector 20g has a structure in which the width of the passage 101 is narrowest at the opening 22g and the opening 23g in the diffuse reflector 20g, which serve as an entrance and exit to the imaging space 102. This makes it difficult for the sub-terahertz waves incident on the imaging space 102 to leak from the opening 22g and the opening 23g. In addition, the structure of the diffuse reflector 20g may be applied to any of the diffuse reflectors of the imaging devices according to the second to fourth embodiments.

[0189] Also, for example, the imaging device 10 according to the above-mentioned first embodiment may further include a door. Fig. 20 is a schematic diagram of an imaging device 10h according to another modified example when viewed from above. As shown in Fig. 20, the imaging device 10h includes a door 25 and a door 26 in addition to the configuration of the imaging device 10. The door 25 and the door 26 cover the opening 22 and the opening 23 in the diffuse reflector 20, which serve as an entrance and exit to the imaging space 102, respectively. The door 25 is located in front of the diffuse reflector 20, and the door 26 is located behind the diffuse reflector 20.

[0190] The doors 25 and 26 each have, for example, the same material and configuration as the reflector 30, and diffusely reflect sub-terahertz waves and transmit visible light. The doors 25 and 26 each have the same material and configuration as the reflector 30a or 30b, and may diffusely reflect sub-terahertz waves and reflect visible light, specifically, diffusely reflect or specularly reflect.

[0191] By providing the doors 25 and 26 to the imaging device 10h, the doors 25 and 26 diffusely reflect the sub-terahertz waves, so that the sub-terahertz waves incident on the imaging space 102 are less likely to leak from the openings 22 and 23.

[0192] The doors 25 and 26 are provided, for example, at positions that do not prevent the detector 60 from receiving waves reflected by the person 100. For example, the height of the doors 25 and 26 from the passage 101 is lower than the height of the detector 60 from the passage 101. The doors 25 and 26 are also arranged to sandwich each detector 60 from both sides in the extending direction of the passage 101, and the reflectors 30 may extend to the doors 25 and 26.

[0193] Moreover, the imaging devices according to the second to fourth embodiments may include a door 25 and a door .

[0194] In the first embodiment, the reflector 30 includes the sub-terahertz wave reflecting member 41, and the visible light transmitting member 44 and the visible light transmitting member 47, but this is not limited thereto. The reflector 30 does not need to include at least one of the visible light transmitting member 44 and the visible light transmitting member 47. In addition, when the sub-terahertz wave reflecting member 41 is made of a material with high mechanical strength such as punching metal, the reflector 30 may be configured to include only the sub-terahertz wave reflecting member 41 out of the sub-terahertz wave reflecting member 41, the visible light transmitting member 44, and the visible light transmitting member 47.

[0195] In addition, in the above-mentioned third embodiment, the gaps 21c, 21d, and 21e are provided so as to be located above the imaging space 102, but this is not limiting. The gaps 21c, 21d, and 21e may be provided so as to be located to the sides of the imaging space 102, or a plurality of gaps may be provided so as to be located both above and to the sides.

[0196] In addition, in the above first to fourth embodiments, the object to be photographed is person 100, but this is not limiting. The object to be photographed may be luggage or the like.

[0197] 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.

[0198] In the above first to fourth embodiments, each component such as the image processing unit 70 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.

[0199] 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.

[0200] 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]

[0201] The present disclosure is widely applicable to imaging devices that capture images of objects. [Explanation of symbols]

[0202] 10, 10a, 10b, 10c, 10f, 10g, 10h Imaging device 20, 20a, 20b, 20c, 20d, 20e, 20g Diffuse reflection part 21c, 21d, 21e gap 22, 22g, 23, 23g opening Doors 25 and 26 30, 30a, 30b, 30c, 30d, 30e, 30g, 31, 31a, 31b, 31c, 31d, 31e, 31g, 32, 32a, 32b, 32c, 32d, 32e, 32g, 33, 33a, 33b, 33e Reflector 41, 41a Sub-terahertz wave reflecting member 42, 42a, 43, 43a Main surface 44, 47 Visible light transmitting material 44a Visible light diffuse reflecting material 44b Visible light mirror reflecting member 45, 48, 48a flat surface 45a Visible light diffuse reflecting surface 45b Visible light specular reflective surface 47a Covering material 50, 51, 52, 53, 54 light source 60, 61, 62, 63, 64 Detectors 65 Image Sensor 66 Optical system 70 Image Processing Section 80 Projector 90 Lighting equipment 100 people Aisle 101 102 Shooting Space

Claims

1. a diffuse reflection unit that covers an imaging space on a passage through which an imaging target passes from at least one of both sides of the passage and has a reflector that diffusely reflects sub-terahertz waves; a light source that emits sub-terahertz waves toward the reflector; a detector that receives a sub-terahertz wave that is emitted from the light source and then diffusely reflected by the reflector, the sub-terahertz wave being reflected by the object to be photographed, and detects an intensity of the received reflected wave; the diffuse reflection portion has a visible light transmission region in an area where the reflector is located, and transmits visible light; The reflector is a sheet-like sub-terahertz wave reflecting member that diffusely reflects sub-terahertz waves and transmits visible light; two visible light transmitting members that transmit sub-terahertz waves and visible light; At least one of the two main surfaces of the sub-terahertz wave reflecting member on the side of the imaging space is an uneven surface, the two main surfaces of the sub-terahertz wave reflecting member are covered with the two visible light transmitting members, respectively; each of the two visible light transmitting members has a flat surface on a side opposite to the sub-terahertz wave reflecting member side of the visible light transmitting member; The flat surfaces of the two visible light transmitting members constitute the surfaces of the reflectors. Filming equipment.

2. the reflector has a structure in which the visible light transmitting member on the imaging space side of the two visible light transmitting members, the sub-terahertz wave reflecting member, and the visible light transmitting member on the opposite side of the imaging space side of the two visible light transmitting members are laminated in this order. The imaging device according to claim 1 .

3. the sub-terahertz wave reflecting member is a conductive thin film, and the conductive thin film is a transparent conductive oxide or a metal thin film.

3. The imaging device according to claim 1.

4. the sub-terahertz wave reflecting member is a conductive mesh, and the mesh size of the conductive mesh is 500 nm or more and 6 mm or less; 3. The imaging device according to claim 1.

5. the sub-terahertz wave reflecting member is a punched metal, and the hole diameter of the punched metal is 500 nm or more and 6 mm or less in terms of the maximum diameter of the hole.

3. The imaging device according to claim 1.

6. The two main surfaces have an average length of roughness curve elements of 0.15 mm or more, and the uneven shapes of the main surface on the shooting space side and the other main surface of the two main surfaces are the same. The imaging device according to claim 1 .

7. The flat surfaces of the two visible light transmitting members are in a parallel positional relationship. The imaging device according to claim 1 .

8. The reflector further covers at least a portion of the photographing space from above. The imaging device according to claim 1 .

9. the diffuse reflector has another visible light transmitting region in a region where the gap provided in the diffuse reflector is located, The gap is located above the photography space, The width of the gap is smaller than the height of the diffuse reflector from the passage. The imaging device according to claim 8.

10. The gap extends in a direction in which the passage extends, The width of the gap is smaller than the width of the passage. The imaging device according to claim 9.

11. Further, a lighting device is provided which irradiates the shooting space with visible light through at least one of the visible light transmitting area and the other visible light transmitting area. The imaging device according to claim 9 or 10.

12. a diffuse reflection unit that covers an imaging space on a passage through which an imaging target passes from at least one of both sides of the passage and has a reflector that diffusely reflects sub-terahertz waves; a light source that emits sub-terahertz waves toward the reflector; a detector that receives a sub-terahertz wave that is emitted from the light source and then diffusely reflected by the reflector, the sub-terahertz wave being reflected by the object to be photographed, and detects an intensity of the received reflected wave; The reflector reflects visible light from the photography space, The reflector is a sheet-like sub-terahertz wave reflecting member that diffusely reflects the sub-terahertz wave; a visible light diffuse reflection member that transmits sub-terahertz waves and diffusely reflects visible light; A coating member, At least one of the two main surfaces of the sub-terahertz wave reflecting member on the side of the imaging space is an uneven surface, the main surface of the sub-terahertz wave reflecting member facing the imaging space is covered with the visible light diffuse reflecting member; the visible light diffuse reflection member has a flat visible light diffuse reflection surface that diffusely reflects visible light on a side of the visible light diffuse reflection member opposite to the sub-terahertz wave reflection member, the main surface of the sub-terahertz wave reflecting member opposite to the imaging space side is covered by the covering member, the covering member has a flat surface on a side of the covering member opposite to the sub-terahertz wave reflecting member, The visible light diffusive reflecting surface and the flat surface constitute the surface of the reflector. Filming equipment.

13. the reflector has a structure in which the visible light diffuse reflecting member, the sub-terahertz wave reflecting member, and the covering member are laminated in this order; The imaging device according to claim 12.

14. The visible light diffuse reflection member includes a crystalline resin material.

14. The imaging device according to claim 12 or 13.

15. The visible light diffusive reflector includes visible light diffusive particles.

14. The imaging device according to claim 12 or 13.

16. Further comprising a projector that projects an image onto the visible light diffuse reflection surface. The imaging device according to any one of claims 12 to 15.

17. a diffuse reflection unit that covers an imaging space on a passage through which an imaging target passes from at least one of both sides of the passage and has a reflector that diffusely reflects sub-terahertz waves; a light source that emits sub-terahertz waves toward the reflector; a detector that receives a sub-terahertz wave that is emitted from the light source and then diffusely reflected by the reflector, the sub-terahertz wave being reflected by the object to be photographed, and detects an intensity of the received reflected wave; The reflector reflects visible light from the photography space, The reflector is a sheet-like sub-terahertz wave reflecting member that diffusely reflects the sub-terahertz wave; a visible light mirror reflecting member that transmits sub-terahertz waves and mirror-reflects visible light; A coating member, At least one of the two main surfaces of the sub-terahertz wave reflecting member on the side of the imaging space is an uneven surface, the main surface of the sub-terahertz wave reflecting member facing the imaging space is covered with the visible light specular reflecting member; the visible light mirror reflecting member has a flat visible light mirror reflecting surface that mirror-reflects visible light on a side of the visible light mirror reflecting member opposite to the sub-terahertz wave reflecting member side, the main surface of the sub-terahertz wave reflecting member opposite to the imaging space side is covered by the covering member, the covering member has a flat surface on a side of the covering member opposite to the sub-terahertz wave reflecting member, The visible light mirror reflecting surface and the flat surface constitute the surface of the reflector. Filming equipment.

18. The visible light mirror reflecting member includes a dielectric multilayer film. The imaging device according to claim 17.

19. The reflectors sandwich the photographing space from both sides of the passage.

19. The imaging device according to any one of claims 1 to 18.

20. The diffuse reflection unit has a structure in which the width of the passage is narrowest at an opening in the diffuse reflection unit which serves as an entrance and exit to the shooting space.

20. The imaging device according to claim 19.

21. a door for covering an opening in the diffuse reflection unit which serves as an entrance to the photography space; The door diffusely reflects sub-terahertz waves and transmits visible light.

21. The imaging device according to claim 19 or 20.

22. a door for covering an opening in the diffuse reflection unit which serves as an entrance to the photography space; The door diffusely reflects sub-terahertz waves and reflects visible light.

21. The imaging device according to claim 19 or 20.

23. The two major surfaces are not exposed. The imaging device according to any one of claims 1 to 11.

Images