Passive Imaging Devices

Abstract

To provide a passive imaging device that suppresses reception of electromagnetic waves radiated from an object other than a subject, and enables stable personal belonging inspection, for example, when used as a walk-through type personal belonging inspection device.SOLUTION: A passive imaging device is configured to generate a subject image by using four sensor units 3A to 3D arranged in a rectangular shape in plan view and receiving electromagnetic waves EW radiated from a subject S moving inside them. Each sensor unit 3A to 3D includes a housing having an electromagnetic wave transmission section and a receiving section that receives, in the housing, the electromagnetic waves that have transmitted through the electromagnetic wave transmission section. The electromagnetic wave transmission sections of the respective sensor units 3A to 3D are facing the sensor units diagonally opposite to them.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a passive imaging device that receives electromagnetic waves emitted from an object to generate an image of the object. [Background technology]

[0002] As an example of this type of passive imaging device, Patent Document 1 describes a millimeter wave passive imaging device that receives thermal noise (electromagnetic waves) in the millimeter wave band radiated from an object to obtain an image.

[0003] Passive imaging devices are also used in security applications such as body scanners (personal item inspection devices) due to their minimally invasive nature and high ability to detect hidden objects. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-36867 Summary of the Invention [Problem to be solved by the invention]

[0005] When a person being inspected (hereinafter referred to as "subject") is carrying a hidden object, the electromagnetic waves emitted from the subject's body are blocked by the object and reduced in areas where the object is present. As a result, the signal strength of the electromagnetic waves received in areas where the object is present is lower than in areas where the object is not present. Therefore, in a passive imaging device applied to a personal belongings inspection device, the shape of the object appears as a dark silhouette in an image corresponding to the subject's body, and it is possible to estimate the type of object (i.e., the subject's possessions) from the shape of the silhouette that appears.

[0006] The inventors are considering using a passive imaging device as a walk-through personal belongings inspection device. In this case, the passive imaging device is configured to include four sensor units Su1 to Su4 arranged in a rectangular shape in a plan view, as shown in Fig. 11. The passive imaging device can be configured so that each of the sensor units Su1 to Su4 receives electromagnetic waves emitted from the body of a subject moving inside the sensor units Su1 to Su4 in the direction of the arrows, and generates an image of the subject.

[0007] However, in a passive imaging device configured as described above, if each sensor unit Su1 to Su4 receives electromagnetic waves emitted from an object other than the subject, an image of the subject may not be generated correctly, making it impossible to perform a stable inspection of personal belongings.

[0008] Therefore, the present invention aims to provide a passive imaging device that suppresses reception of electromagnetic waves emitted from objects other than the subject, and enables stable personal belongings inspection when used, for example, as a walk-through type personal belongings inspection device. [Means for solving the problem]

[0009] According to one aspect of the present invention, a passive imaging device includes four sensor units arranged at the four corners of a rectangular area in a plan view, and is configured so that as a subject moves through a passage inside these four sensor units, each sensor unit receives electromagnetic waves radiated from the left half of the front face, the right half of the front face, the left half of the back face, or the right half of the back face of the subject to generate a subject image. Each sensor unit has an electromagnetic wave transmitting portion extending in the vertical direction with a predetermined width. and a smooth surface portion extending in the vertical direction with a predetermined width. is in front Adjacent in the width direction a receiving section housed in the housing and configured to receive electromagnetic waves transmitted through the electromagnetic wave transmitting section, The two sensor units positioned diagonally opposite each other have the same configuration and are arranged so that the electromagnetic wave transmitting portion of one sensor unit faces the smooth surface portion of the other sensor unit. The smooth surface portion is formed of a material with a lower reflectivity of electromagnetic waves than other portions of the housing. Alternatively, each sensor unit has a temperature adjusting device that maintains the smooth surface portion at a predetermined temperature lower than the normal body temperature of a person. . [Effects of the Invention]

[0010] According to the present invention, a passive imaging device can be provided that suppresses reception of electromagnetic waves emitted from objects other than the subject, and enables stable personal belongings inspection when used, for example, as a walk-through type personal belongings inspection device. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration of a passive imaging device according to an embodiment; [Figure 2] 1 is a perspective view of a main part of a passive imaging device according to an embodiment; [Figure 3] 1 is a plan view of a main part of a passive imaging device according to an embodiment. [Figure 4] 3A and 3B are diagrams illustrating first and fourth sensor units of a passive imaging device according to an embodiment. [Figure 5] 3A and 3B are diagrams illustrating second and third sensor units of a passive imaging device according to an embodiment. [Figure 6] FIG. 3 is a block diagram showing a schematic configuration of first to fourth sensor units. [Figure 7] 10 is a flowchart illustrating an example of an operation of the passive imaging device according to the embodiment. [Figure 8] 10 is a flowchart illustrating an example of an operation of the passive imaging device according to the embodiment. [Figure 9] FIG. 1 shows an example of signal strength of received electromagnetic waves stored as an image (pixel) array. [Figure 10] 10A and 10B are diagrams for explaining the effects of the passive imaging device according to the embodiment. [Figure 11] FIG. 10 is a diagram illustrating a configuration example in which a passive imaging device is used as a walk-through type personal belongings inspection device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] 1 to 3 show a passive imaging device 1 according to one embodiment of the present invention. Fig. 1 is a block diagram showing a schematic configuration of the passive imaging device 1, Fig. 2 is a perspective view of the main part of the passive imaging device 1, and Fig. 3 is a plan view of the main part of the passive imaging device 1.

[0014] A passive imaging device 1 according to the embodiment is a device capable of receiving and imaging electromagnetic waves radiated from an object. In this embodiment, the passive imaging device 1 is configured as a walk-through type personal belongings inspection device, and is installed in a passage P. The passive imaging device 1 is configured to receive electromagnetic waves EW radiated from the body HB of a person (hereinafter referred to as "subject S") walking along the passage P in the direction of the arrow, and to generate and display an image of the subject S (hereinafter referred to as "subject image").

[0015] In addition, the passive imaging device 1 according to the embodiment is configured to determine whether or not the subject S is carrying a specific item (mainly dangerous items such as knives, guns, explosives, etc.) based on the generated subject image.

[0016] In the following description, "front," "back," "left," and "right" mainly refer to directions based on the subject S (as seen from the subject S).

[0017] 1 to 3, the passive imaging device 1 includes four sensor units (first to fourth sensor units 3A to 3D), a processing unit 5, and a display unit .

[0018] Each of the first to fourth sensor units 3A to 3D is configured to receive electromagnetic waves EW emitted from the body HB of the subject S and detect the signal intensity. In this embodiment, the first to fourth sensor units 3A to 3D are arranged in a rectangular shape in a plan view (see FIG. 3). In other words, the first to fourth sensor units 3A to 3D are arranged so as to be located at the four corners of a rectangular area in a plan view (indicated by a two-dot chain line in FIG. 3).

[0019] Specifically, the first sensor unit 3A and the second sensor unit 3B are arranged on either side of the passage P, and the third sensor unit 3C and the fourth sensor unit 3D are installed on either side of the passage P at a position behind the first sensor unit 3A and the second sensor unit 3B in the moving direction of the subject S. In other words, the first sensor unit 3A and the fourth sensor unit 3D are located diagonally opposite each other, and the second sensor unit 3B and the third sensor unit 3C are located diagonally opposite each other. The subject S moving along the passage P moves inside the first to fourth sensor units 3A to 3D.

[0020] Fig. 4 shows a first sensor unit 3A and a fourth sensor unit 3D located diagonally opposite it. Fig. 4(a) is a front view of the first and fourth sensor units 3A and 3D, and Fig. 4(b) is a cross-sectional view taken along line AA in Fig. 4(a). Fig. 5 shows a second sensor unit 3B and a third sensor unit 3C located diagonally opposite it. Fig. 5(a) is a front view of the second and third sensor units 3B and 3C, and Fig. 5(b) is a cross-sectional view taken along line BB in Fig. 5(a).

[0021] 4 and 5, the second and third sensor units 3B and 3C have a shape that is a left-right inversion of the first sensor unit 3A (fourth sensor unit 3D). However, apart from that, the first to fourth sensor units 3A to 3D basically have the same components, so the first to fourth sensor units 3A to 3D will be described collectively below.

[0022] 4 and 5, the first to fourth sensor units 3A to 3D each have a housing 31. An electromagnetic wave transmitting portion 32 that transmits electromagnetic waves and a smooth surface portion 33 that is entirely or mostly formed as a smooth surface are provided on the front surface of the housing 31. The electromagnetic wave transmitting portion 32 is provided in approximately the center of the width direction W of the housing 31 and is formed in a rectangular shape extending in the up-down direction V. The smooth surface portion 33 is provided adjacent to the electromagnetic wave transmitting portion 32 in the width direction W of the housing 31 and is formed in a rectangular shape extending in the up-down direction V. In this embodiment, the length of the smooth surface portion 33 in the up-down direction V is greater (longer) than that of the electromagnetic wave transmitting portion 32.

[0023] Although not particularly limited, in this embodiment, a relatively large opening extending in the vertical direction V is formed in the center of the front surface of the housing 31, and this opening is closed by a plate-shaped closing member 34. The closing member 34 is made of a material having a lower electromagnetic wave reflectivity than other parts of the housing 31. For example, if most of the housing 31 is made of metal, the closing member 34 may be made of a synthetic resin. A rectangular hole extending in the vertical direction V formed in the closing member 34 is covered with an electromagnetic wave transmitting cover or the like to form the electromagnetic wave transmitting portion 32, and a portion adjacent to one side of the rectangular hole in the width direction W (the left side in FIG. 4(a) and the right side in FIG. 5(a)), as indicated by the dashed dotted line in FIGS. 4(a) and 5(a), forms the smooth surface portion 33.

[0024] Furthermore, in this embodiment, each of the first to fourth sensor units 3A to 3D has a temperature adjustment device 35 in the housing 31 for maintaining the temperature of the smooth surface portion 33 at a predetermined temperature (for example, 32°C or lower) that is lower than the normal body temperature of a person. Although not particularly limited, the temperature adjustment device 35 can be configured to include a cooling unit 35a that is installed on the back surface of the smooth surface portion 33 and uses a Peltier element, a temperature sensor 35b that detects the temperature of the smooth surface portion 33, and a control unit 35c that controls the cooling unit 35a (power supply to the Peltier element) based on the temperature detected by the temperature sensor 35b.

[0025] Fig. 6 is a block diagram showing a schematic configuration of the first to fourth sensor units 3A to 3D. Referring to Fig. 6, in this embodiment, each of the first to fourth sensor units 3A to 3D has a polygon mirror 41, a collecting mirror 42, a receiving antenna 43, an amplifier 44, and a signal intensity detection unit 45. These constitute a receiving unit that is housed in a housing 31 and receives electromagnetic waves EW.

[0026] The polygon mirror 41 is disposed inside (directly behind) the electromagnetic wave transmitting portion 32. The polygon mirror 41 is rotated in the vertical direction V by an electric motor (not shown). The polygon mirror 41 is configured to reflect (scan) the electromagnetic waves EW that are emitted from the body HB of the subject S and transmitted through the electromagnetic wave transmitting portion 32 toward (the focusing surface of) the focusing mirror 42.

[0027] The collecting mirror 42 is disposed below the polygon mirror 41. The collecting mirror 42 is configured to collect, onto the receiving antenna 43, the electromagnetic waves EW that are emitted from the body HB of the subject S, transmitted through the electromagnetic wave transmitting portion 32, and reflected by the polygon mirror 41.

[0028] The receiving antenna 43 receives the electromagnetic waves EW collected by the collecting mirror 42. The amplifier 44 amplifies the electromagnetic waves EW received by the receiving antenna 43 and outputs the amplified waves to the signal strength detection unit 45. The signal strength detection unit 45 detects the signal strength of the electromagnetic waves EW input from the amplifier 44. The detection result of the signal strength detection unit 45 is output to the processing unit 5. Note that, although the amplifier 44 and the signal strength detection unit 45 are shown as separate components in this embodiment, the signal strength detection unit 45 may also be configured to include the amplifier 44.

[0029] As described above, the first to fourth sensor units 3A to 3D are arranged in a rectangular shape in a plan view (see FIG. 3), but this is not simply a rectangular shape in a plan view; each electromagnetic wave transmitting portion 32 is arranged so as to face the sensor unit located diagonally. More specifically, the electromagnetic wave transmitting portion 32 of each of the first to fourth sensor units 3A to 3D faces the smooth surface portion 33 of the sensor unit located diagonally. Furthermore, in a plan view, the electromagnetic wave transmitting portion 32 and polygon mirror 41 of each of the first to fourth sensor units 3A to 3D and the smooth surface portion 33 of the sensor unit located diagonally are positioned on a straight line.

[0030] For example, the electromagnetic wave transmitting portion 32 of the first sensor unit 3A faces the smooth surface portion 33 of the fourth sensor unit 3D, and the electromagnetic wave transmitting portion 32 of the fourth sensor unit 3D faces the smooth surface portion 33 of the first sensor unit 3A. Furthermore, the electromagnetic wave transmitting portion 32 of the first sensor unit 3A, the polygon mirror 41 of the first sensor unit 3A, and the smooth surface portion 33 of the fourth sensor unit 3D are positioned on a straight line in a plan view, and the electromagnetic wave transmitting portion 32 of the fourth sensor unit 3D, the polygon mirror 41 of the fourth sensor unit 3D, and the smooth surface portion 33 of the first sensor unit 3A are positioned on a straight line in a plan view.

[0031] Similarly, the electromagnetic wave transmitting portion 32 of the second sensor unit 3B faces the smooth surface portion 33 of the third sensor unit 3C, and the electromagnetic wave transmitting portion 32 of the third sensor unit 3C faces the smooth surface portion 33 of the second sensor unit 3B. Furthermore, the electromagnetic wave transmitting portion 32 of the second sensor unit 3B, the polygon mirror 41 of the second sensor unit 3B, and the smooth surface portion 33 of the third sensor unit 3C are positioned on a straight line in a plan view, and the electromagnetic wave transmitting portion 32 of the third sensor unit 3C, the polygon mirror 41 of the third sensor unit 3C, and the smooth surface portion 33 of the second sensor unit 3B are positioned on a straight line in a plan view.

[0032] In this embodiment, the first sensor unit 3A is configured to receive electromagnetic waves EW emitted mainly from the front left half of the body HB of the subject S as the subject S moves down the passage P in the direction of the arrow and detect the signal intensity thereof, and the second sensor unit 3B is configured to receive electromagnetic waves EW emitted mainly from the front right half of the body HB of the subject S as the subject S moves down the passage P in the direction of the arrow.

[0033] In addition, the third sensor unit 3C is configured to receive electromagnetic waves EW emitted mainly from the left half of the back of the body HB of the subject S as the subject S moves down the passage P in the direction of the arrow, and the fourth sensor unit 3D is configured to receive electromagnetic waves EW emitted from the right half of the back of the body HB of the subject S as the subject S moves down the passage P.

[0034] In this embodiment, the third sensor unit 3C and the fourth sensor unit 3D are provided with an entry detection sensor 51 that detects the entry of the subject S, and the first sensor unit 3A and the second sensor unit 3B are provided with an exit detection sensor 52 that detects the exit of the subject S (see FIG. 3). The entry detection sensor 51 is, for example, a transmission-type optical sensor, and includes a light-emitting element 51A on the third sensor unit 3C side and a light-receiving element 51B on the fourth sensor unit 3D side. Similarly, the exit detection sensor 52 is, for example, a transmission-type optical sensor, and includes a light-emitting element 52A on the first sensor unit 3A side and a light-receiving element 52B on the second sensor unit 3B side. Each of the first to fourth sensor units 3A to 3D also has a mirror angle detection sensor 53 that detects the mirror angle of the polygon mirror 41 (see FIG. 6).

[0035] Returning to FIG. 1, the processing unit 5 receives the detection results of the first to fourth sensor units 3A to 3D (signal intensity detection units 45 thereof). Based on the detection results of the first sensor unit 3A and the second sensor unit 3B, which will be positioned diagonally in front of the subject S moving through the passage P, the processing unit 5 generates a front image of the body HB of the subject S as a subject image, and based on the detection results of the third sensor unit 3C and the fourth sensor unit 3D, which will be positioned diagonally behind the subject S moving through the passage P, the processing unit 5 generates a back image of the body HB of the subject S as a subject image. The subject images generated by the processing unit 5 (i.e., the front image and back image of the body HB of the subject S) are output to and displayed on the display unit 7.

[0036] The subject image generated by the processing unit 5 (subject image displayed on the display unit 7) is an image corresponding to the body HB of the subject S. Here, if the subject S is carrying a hidden object, as described above, the electromagnetic waves EW emitted from the body of the subject S are blocked by the object in the area where the object is present, and therefore the signal strength of the electromagnetic waves EW received in the area where the object is present is lower than in the area where the object is not present. As a result, the shape of the object (personal effects) carried by the subject S appears as a dark silhouette in the subject image.

[0037] Furthermore, in this embodiment, the processing unit 5 determines whether or not the subject S is carrying the specific item based on the generated subject image, and more specifically, based on the (shape of) a dark silhouette that appears in the subject image. If the processing unit 5 determines that the subject S is carrying the specific item, it notifies a host device (not shown) and / or notifies an inspector via a notification unit (not shown).

[0038] In other words, in this embodiment, the processing unit 5 has the function of an image generation unit that generates an image of the subject, and the function of a judgment unit that determines whether the subject S is carrying the specific item.

[0039] However, this is not a limitation. The processing unit 5 does not have to determine whether or not the subject S is carrying the specific item. In this case, the processing unit 5 functions as an image generating unit, and an examiner or the like determines whether or not the subject S is carrying the specific item based on the subject image (the shape of a dark silhouette appearing in the subject image) displayed on the display unit 7.

[0040] Next, a description will be given of an example of the operation of the passive imaging device 1. Figures 7 and 8 are flowcharts for explaining an example of the operation of the passive imaging device 1.

[0041] When the entrance of the subject S is detected by the entrance detection sensor 51 (step S1; YES), the passive imaging device 1 operates the first to fourth sensor units 3A to 3D (step S2). Specifically, the passive imaging device 1 rotates the polygon mirror 41 of each of the first to fourth sensor units 3A to 3D and activates the signal intensity detection section 45. This enables the first to fourth sensor units 3A to 3D to receive the electromagnetic waves EW radiated from the body HB of the subject S moving through the passage P and detect the signal intensity SI.

[0042] Next, the passive imaging device 1 receives, using the first to fourth sensor units 3A to 3D, electromagnetic waves EW radiated from the body HB of the subject S moving through the passage P and detects the signal intensity SI. Specifically, the passive imaging device 1 detects, in each of the first to fourth sensor units 3A to 3D, the signal intensity SI of the electromagnetic waves EW received at each predetermined angle while the mirror angle of the polygon mirror 41 changes from the lower limit to the upper limit of the set range, that is, the signal intensity SI of the electromagnetic waves EW received at each mirror angle (steps S3 to S8). Note that, although not particularly limited, the predetermined angle can be set appropriately depending on the number of pixels of the image generated by the passive imaging device 1, etc.

[0043] Here, in this embodiment, the setting range (lower and upper limits) of the mirror angle of each of the polygon mirrors 41 of the first to fourth sensor units 3A to 3D, in other words, the receiving range of the electromagnetic waves in the vertical direction V of the first to fourth sensor units 3A to 3D (the receiving parts thereof), is set based on the size in the vertical direction V of the smooth surface portion 33 of the diagonally opposite sensor unit.

[0044] Specifically, for example, with regard to the polygon mirror 41 of the first sensor unit 3A, the mirror angle at which electromagnetic waves radiated from the top or near the smooth surface portion 33 of the fourth sensor unit 3D diagonally opposite the first sensor unit 3A can be reflected (scanned) toward the focusing mirror 42 (of the focusing surface) of the first sensor unit 3A can be set as the lower limit of the setting range, and the mirror angle at which electromagnetic waves radiated from the bottom or near the smooth surface portion 33 of the fourth sensor unit 3D can be reflected (scanned) toward the focusing mirror 42 (of the focusing surface) of the first sensor unit 3A can be set as the upper limit of the setting range.

[0045] Furthermore, with regard to the polygon mirror 41 of the second sensor unit 3B, the mirror angle at which electromagnetic waves radiated from the top or near the smooth surface portion 33 of the third sensor unit 3C diagonally opposite the second sensor unit 3B can be reflected (scanned) toward the focusing mirror 42 (of the focusing surface) of the second sensor unit 3B can be set as the lower limit of the setting range, and the mirror angle at which electromagnetic waves radiated from the bottom or near the smooth surface portion 33 of the third sensor unit 3C can be reflected (scanned) toward the focusing mirror 42 (of the focusing surface) of the second sensor unit 3B can be set as the upper limit of the setting range.

[0046] Although the description will be omitted, the same applies to the polygon mirror 41 of the third sensor unit 3C and the polygon mirror 41 of the fourth sensor unit 3D.

[0047] Next, the passive imaging device 1 stores the signal strength SI of the electromagnetic wave EW received for each mirror angle in each of the first to fourth sensor units 3A to 3D in the current time column of the image (pixel) array (step S9).

[0048] 9 shows an example of the signal strength SI of the electromagnetic waves EW received for each mirror angle, which is stored in step S9. In the example shown in Fig. 9, the signal strength SI of the electromagnetic waves EW received for each mirror angle is already stored in the column for the time "t-1" a predetermined time before the current time and the column for the time "t-2" a predetermined time before that, and thereafter, the signal strength SI of the electromagnetic waves EW received for each mirror angle can be stored in the column for the time "t+1" a predetermined time after the current time, the column for the time "t+2" a predetermined time after that, ..., the column for "t+n."

[0049] Next, the passive imaging device 1 determines whether or not the entrance of the subject S is detected by the entrance detection sensor 52 (step S10). If the entrance of the subject S is not detected (step S10; NO), the passive imaging device 1 returns to step S3 and repeats the processes of steps S3 to S11. As a result, as the subject S moves through the passage P, the first to fourth sensor units 3A to 3D receive electromagnetic waves EW radiated from different parts in the left and right directions of the body HB of the subject S and detect the signal intensities SI thereof.

[0050] On the other hand, if the subject S's advance is detected (step S10; YES), the passive imaging device 1 generates subject images (front and back images of the subject S's body HB) based on the signal intensity SI of the electromagnetic waves EW received for each stored mirror angle (step S11).

[0051] Specifically, in this embodiment, the passive imaging device 1 generates an image of the front left half of the body HB of the subject S based on the signal strength SI of the electromagnetic waves EW received for each mirror angle by the first sensor unit 3A, and generates an image of the front right half of the body HB of the subject S based on the signal strength SI of the electromagnetic waves EW received for each mirror angle by the second sensor unit 3B. Then, the passive imaging device 1 synthesizes (combines) the generated front left half image and front right half image to generate a front side image of the subject's body HB.

[0052] The passive imaging device 1 also generates an image of the left half of the back surface of the body HB of the subject S based on the signal strength SI of the electromagnetic waves EW received for each mirror angle by the third sensor unit 3C, and generates an image of the right half of the back surface of the body HB of the subject S based on the signal strength SI of the electromagnetic waves EW received for each mirror angle by the fourth sensor unit 3D. The passive imaging device 1 then synthesizes the generated left half and right half back surface images to generate a back side image of the body HB of the subject S.

[0053] Next, the passive imaging device 1 performs edge extraction processing on the generated images (front-side image and back-side image) of the human body HB of the subject S to generate an edge image (step S12), and displays the generated edge image on the display unit 7 (step S13).

[0054] Next, the passive imaging device 1 determines whether or not the subject S is carrying the specific item based on the generated edge images (the edge image of the front-side image and the edge image of the back-side image) (personal item determination), and if the subject S is carrying the specific item, notifies the host device or notifies the inspector of that fact (step S14). Thereafter, the passive imaging device 1 stops the first to fourth sensor units 3A to 3D (step S15), and ends this flow.

[0055] The passive imaging device 1 according to the embodiment provides the following advantages.

[0056] In the passive imaging device 1 according to the embodiment, the electromagnetic wave transmitting portions 32 of the first to fourth sensor units 3A to 3D, which are arranged in a rectangular shape in a plan view, face the sensor unit at the diagonal corner. Therefore, the presence of the diagonal sensor units prevents the first to fourth sensor units 3A to 3D from receiving electromagnetic waves emitted from objects outside the first to fourth sensor units 3A to 3D. Therefore, the passive imaging device 1 can generate a subject image with little noise, enabling stable and accurate baggage inspection.

[0057] 10(a), the passive imaging device 1 according to the embodiment prevents the first to fourth sensor units 3A to 3D of each passive imaging device 1 from receiving electromagnetic waves emitted from the body of the subject of an adjacent passive imaging device 1. Therefore, each passive imaging device 1 can generate a subject image with less noise of its own subject without being affected by the subject of an adjacent passive imaging device 1, and as a result, the possessions of many people can be inspected stably and accurately.

[0058] On the other hand, if the first to fourth sensor units 3A' to 3D' of the passive imaging device 1' are arranged arbitrarily, there is a risk that the first to fourth sensor units 3A' to 3D' of each passive imaging device 1' may receive electromagnetic waves emitted from the body of the subject of the adjacent passive imaging device 1', as shown as a comparative example in Fig. 10(b). In this case, the subject image generated by each passive imaging device will contain noise, making it impossible to perform stable and accurate personal belongings inspection.

[0059] In this way, the passive imaging device 1 according to the embodiment can generate images of subjects with less noise, not only when used alone but also when used in a row, thereby contributing to stable and accurate inspection of personal belongings.

[0060] Furthermore, in the passive imaging device 1 according to the embodiment, the electromagnetic wave transmitting portion 32 of each of the first to fourth sensor units 3A to 3D faces the smooth surface portion 33 of the sensor unit diagonally opposite it. This prevents the first to fourth sensor units 3A to 3D from inadvertently receiving unnecessary electromagnetic waves other than those emitted from the body HB of the subject S, and allows for the generation of a subject image with less noise.

[0061] Furthermore, in the passive imaging device 1 according to the embodiment, the smooth surface portion 33 is formed of a material having a lower reflectivity of electromagnetic waves than other portions of the housing 31. This further prevents the first to fourth sensor units 3A to 3D from inadvertently receiving unnecessary electromagnetic waves other than those emitted from the body HB of the subject S.

[0062] Furthermore, in the passive imaging device 1 according to the embodiment, the first to fourth sensor units 3A to 3D have a temperature adjustment device 35 that maintains the smooth surface portion 33 at a predetermined temperature that is lower than a person's normal body temperature. As a result, the image of the portion other than the subject image in the image generated by the passive imaging device 1 is stabilized, and the difference between the subject image and the image of the portion other than the subject image increases, resulting in a clear subject image.

[0063] In particular, in the passive imaging device 1 according to the embodiment, the electromagnetic wave reception ranges of the first to fourth sensor units 3A to 3D in the vertical direction V are set based on the size in the vertical direction V of the smooth surface portions 33 of the diagonally disposed sensor units. This more effectively prevents the first to fourth sensor units 3A from receiving electromagnetic waves radiated from objects outside the first to fourth sensor units 3A to 3D, more effectively prevents the first to fourth sensor units 3A to 3D from inadvertently receiving unnecessary electromagnetic waves other than those radiated from the body HB of the subject S, and / or further stabilizes portions of the image generated by the passive imaging device 1 other than the subject image, thereby enabling a clearer subject image to be obtained.

[0064] In the above-described embodiment, the first to fourth sensor units 3A to 3D receive the electromagnetic waves EW radiated from the body HB of the subject S using the polygon mirror 41. However, this is not limited to this. The first to fourth sensor units 3A to 3D may use a mirror (scan mirror) having the same function as the polygon mirror 41 instead of the polygon mirror 41, or may receive the electromagnetic waves EW radiated from the body HB of the subject S using an array antenna.

[0065] Furthermore, in the above-described embodiment, the passive imaging device 1 determines whether or not the subject S is carrying the specific item based on an edge image obtained by performing edge extraction processing on images (front-side image and back-side image) of the subject S's body HB. However, this is not limited to this. The passive imaging device 1 may omit the edge extraction processing (step S12) and determine whether or not the subject S is carrying the specific item based on images of the subject S's body HB.

[0066] The above describes the embodiments and modifications of the present invention, but the present invention is not limited to the above-described embodiments and modifications, and it goes without saying that further modifications and changes are possible based on the technical concept of the present invention. [Explanation of symbols]

[0067] 1...passive imaging device, 3A to 3D...first to fourth sensor units, 5...processing unit, 7...display unit, 31...casing, 32...electromagnetic wave transmitting unit, 33...smooth surface unit, 35...temperature adjusting device, 41...polygon mirror, 42...condensing mirror, 43...receiving antenna, 44...amplifier, 45...signal strength detecting unit, 51...entrance detection sensor, 52...exit detection sensor, 53...mirror angle detection sensor, P...passageway, S...subject, HB...subject's body

Claims

1. The system includes four sensor units arranged at four corners of a rectangular area in a plan view, and is configured such that as the subject moves through these inner passages, each sensor unit receives an electromagnetic wave radiated from the front left half, the front right half, the back left half, or the back right half of the subject to generate a subject image; Each sensor unit has a housing having an electromagnetic wave transmitting portion extending in the vertical direction with a predetermined width and a smooth surface portion extending in the vertical direction with a predetermined width, the smooth surface portion being provided adjacent to the front in the width direction, and a receiving portion accommodated in the housing and receiving electromagnetic waves that have transmitted through the electromagnetic wave transmitting portion; the two sensor units positioned diagonally opposite each other have the same configuration and are arranged such that the electromagnetic wave transmitting portion of one sensor unit faces the smooth surface portion of the other sensor unit; A passive imaging device, wherein the smooth surface portion is formed of a material having a lower reflectivity of electromagnetic waves than other portions of the housing.

2. The invention includes four sensor units arranged at the four corners of a rectangular area in a plan view, and as the subject moves through these inner passages, each sensor unit is configured to receive electromagnetic waves emitted from the front left half, front right half, back left half or back right half of the subject to generate an image of the subject, Each sensor unit has a housing having an electromagnetic wave transmitting portion extending in the vertical direction with a predetermined width and a smooth surface portion extending in the vertical direction with a predetermined width, the smooth surface portion being provided adjacent to the front in the width direction, and a receiving portion accommodated in the housing and receiving electromagnetic waves that have transmitted through the electromagnetic wave transmitting portion; the two sensor units positioned diagonally opposite each other have the same configuration and are arranged such that the electromagnetic wave transmitting portion of one sensor unit faces the smooth surface portion of the other sensor unit; A passive imaging device, wherein each sensor unit has a temperature adjusting device that maintains the smooth surface portion at a predetermined temperature that is lower than a person's normal body temperature.

3. the vertical length of the smooth surface portion is greater than the vertical length of the electromagnetic wave transmitting portion, 3. The passive imaging device according to claim 1, wherein the electromagnetic wave receiving range in the vertical direction of each sensor unit is set based on the uppermost and lowermost points of the flat surface portion of a diagonally adjacent sensor unit.

4. the subject image includes a front side image and a back side image of the subject, the front side image of the subject is an image obtained by combining an image of the left front half of the subject generated based on electromagnetic waves radiated from the left front half of the subject and an image of the right front half of the subject generated based on electromagnetic waves radiated from the right front half of the subject, the rear-side image of the subject is an image obtained by combining an image of the left half of the back side of the subject generated based on electromagnetic waves radiated from the left half of the back side of the subject and an image of the right half of the back side of the subject generated based on electromagnetic waves radiated from the right half of the back side of the subject, 4. The passive imaging device according to claim 1, wherein the subject image is used to determine whether or not the subject is carrying a specific item.

5. The receiving unit A polygon mirror that is rotated in the vertical direction; a signal intensity detection unit that detects a signal intensity of the electromagnetic wave radiated from the subject, transmitted through the electromagnetic wave transmitting unit, and reflected by the polygon mirror; Including, generating a front left half image of the subject, a front right half image of the subject, a back left half image of the subject, and a back right half image of the subject based on the detection results of the signal intensity detection units of the respective sensor units; 5. The passive imaging device of claim 4.

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