Passive Imaging Devices

Abstract

To provide a passive imaging device that can reduce overlooking of personal belongings in, for example, an inspection of personal belongings.SOLUTION: A passive imaging device is configured to receive electromagnetic waves (F1+F2) in a plurality of frequency bands different from each other that are emitted from a human body 2 of a subject being an analyte and scanned by a polygon mirror 11 as a scan mirror, detect the signal intensity of the received electromagnetic waves for every frequency band and every mirror angle (scan angle) of the polygon mirror 11, add up the signal intensities at corresponding scan angle in the frequency bands, and create an image for the human body 2 of the subject based on the signal intensity after the addition.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] As an example of this type of passive imaging device, Patent Document 1 describes a millimeter-wave passive imaging device that obtains an image by receiving millimeter-wave thermal noise emitted from an object. Passive imaging devices are mainly used in security body scanners (personal item inspection devices) because they are non-invasive and have a high ability to detect hidden objects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-36867 Summary of the Invention [Problem to be solved by the invention]

[0004] In a passive imaging device applied to a personal belongings inspection device, when a subject is carrying a hidden object, the electromagnetic waves emitted from the subject's body are blocked by the object and reduced, resulting in a lower reception level of the electromagnetic waves in the area where the object is located compared to areas where the object is not present. As a result, the shape of the object appears as a dark silhouette in the image with the human body in the background, and from this silhouette it is possible to determine whether the subject is carrying an object and to estimate the type of the object (i.e., the possession).

[0005] However, depending on the object, the electromagnetic waves emitted from the object may offset the drop in reception level caused by the electromagnetic waves radiated from the human body being blocked by the object. In such cases, there is no difference in the reception level of the electromagnetic waves between areas where there is an object and areas where there is no object, and the shape of the object does not appear as a silhouette. This can lead to, for example, personal belongings being overlooked during a personal belongings inspection.

[0006] Therefore, an object of the present invention is to provide a passive imaging device that can reduce the chance of personal belongings being overlooked during personal belongings inspection, for example. [Means for solving the problem]

[0007] According to one aspect of the present invention, a passive imaging device includes: Move The apparatus is configured to receive electromagnetic waves of a plurality of different frequency bands emitted from an object and scanned by a scan mirror, detect signal strengths of the received electromagnetic waves for each frequency band and for each scan angle of the scan mirror, sum up the signal strengths at the corresponding scan angles in each frequency band, and generate an image of the object based on the summed signal strengths, wherein the plurality of frequency bands are spaced apart from each other. The image of the subject includes a front side image of the subject and a back side image of the subject. .

[0008] According to another aspect of the present invention, a passive imaging device includes: Move The apparatus is configured to receive electromagnetic waves of a plurality of different frequency bands radiated from an object to be examined and scanned by a scan mirror, detect the signal strength of the received electromagnetic waves for each frequency band and for each scan angle of the scan mirror, generate an image of the object for each frequency band based on the detected signal strength, and generate a composite image by combining the generated images for each frequency band, wherein the plurality of frequency bands are spaced apart from each other. the images of the subject for each frequency band include a first front-side image of the subject based on electromagnetic waves of a first frequency band, a second front-side image of the subject based on electromagnetic waves of a second frequency band, a first back-side image of the subject based on electromagnetic waves of the first frequency band, and a second back-side image of the subject based on electromagnetic waves of the second frequency band, and the composite image includes a front-side image of the subject obtained by combining the first front-side image and the second front-side image, and a back-side image of the subject obtained by combining the first back-side image and the second back-side image. .

[0009] According to yet another aspect of the present invention, a passive imaging device includes: MoveThe apparatus is configured to receive electromagnetic waves of a plurality of different frequency bands radiated from an object and scanned by a scan mirror, detect the signal strength of the received electromagnetic waves for each frequency band and for each scan angle of the scan mirror, generate an image of the object for each frequency band based on the detected signal strength, perform edge enhancement processing on the generated image for each frequency band to generate an edge-enhanced image for each frequency band, and synthesize the generated edge-enhanced images for each frequency band to generate a synthesized edge-enhanced image, wherein the plurality of frequency bands are spaced apart from each other. the images for each frequency band of the subject include a first front-side image of the subject based on electromagnetic waves in a first frequency band, a second front-side image of the subject based on electromagnetic waves in a second frequency band, a first back-side image of the subject based on electromagnetic waves in the first frequency band, and a second back-side image of the subject based on electromagnetic waves in the second frequency band, and the composite edge-enhanced image includes a front-side image of the subject obtained by combining the edge-enhanced image of the first front-side image and the edge-enhanced image of the second front-side image, and a back-side image of the subject obtained by combining the edge-enhanced image of the first back-side image and the edge-enhanced image of the second back-side image. . [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a passive imaging device that can reduce the risk of personal belongings being overlooked during personal belongings inspection, for example. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a 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] FIG. 2 is a diagram showing a schematic configuration of a sensing unit of a passive imaging device according to an embodiment. [Figure 5] 10 is a flowchart illustrating an example of an operation of the passive imaging device according to the embodiment. [Figure 6] 10 is a flowchart illustrating an example of an operation of the passive imaging device according to the embodiment. [Figure 7] FIG. 10 is a diagram showing an example of the reception level of electromagnetic waves in the first frequency band for each mirror angle (scanning angle), which is saved as an image (pixel) array. [Figure 8] FIG. 10 is a diagram showing an example of the reception level of electromagnetic waves in the second frequency band for each mirror angle (scanning angle), which is saved as an image (pixel) array. [Figure 9] FIG. 10 is a diagram showing an example of a result of adding together the reception levels of electromagnetic waves in a first frequency band and electromagnetic waves in a second frequency band at corresponding mirror angles (corresponding scanning angles). [Figure 10] 1 is a diagram schematically illustrating a portion of an image (edge-enhanced image) of a human body of a subject generated by a passive imaging device according to an embodiment. [Figure 11] FIG. 1 is a diagram showing an example of frequency characteristics of electromagnetic wave transmittance of an article. [Figure 12] FIG. 10 is a diagram illustrating another example of the configuration of the sensing unit of the passive imaging device according to the embodiment. [Figure 13] 10 is a flowchart illustrating another example of the operation of the passive imaging device according to the embodiment. [Figure 14] 10 is a flowchart illustrating another example of the operation of the passive imaging device according to the embodiment. 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 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] The passive imaging device 1 receives electromagnetic waves emitted from a subject or the like to generate an image. In this embodiment, the passive imaging device 1 is configured as a walk-through personal belongings inspection device, and is configured to detect a human body 2 of a person (hereinafter referred to as "subject") walking down a passage 50 in the direction of the arrow, receive electromagnetic waves 3 emitted from the subject's body (i.e., subject) 2 to generate an image of the subject's body 2, and determine whether the subject is carrying a specific item (mainly a dangerous object such as a knife, gun, or explosive). In the following description, "front," "back," "left," and "right" refer to directions relative to the subject (as seen from the subject).

[0015] As shown in FIG. 1, the passive imaging device 1 according to the embodiment includes four sensing units (first to fourth sensing units) 10A to 10D, a processing unit 20, and a display unit 30.

[0016] As shown in Fig. 3, the first to fourth sensing units 10A to 10D receive electromagnetic waves 3 radiated from a human body 2 of the subject and detect the signal intensity (reception level of the electromagnetic waves). Fig. 4 shows a schematic configuration of the first to fourth sensing units 10A to 10D.

[0017] As shown in FIG. 4, each of the first to fourth sensing units 10A to 10D includes a polygon mirror 11 as a scan mirror, a collecting mirror 12, a receiving antenna 13, a splitter 14, a first amplifier 15A, a second amplifier 15B, a first detector 16A, and a second detector 16B.

[0018] The polygon mirror 11 is driven to rotate, and reflects the electromagnetic wave 3 emitted from the subject's body 2 by the mirror surface, thereby scanning the electromagnetic wave 3 in a predetermined direction (for example, the vertical direction).

[0019] The condenser mirror 12 condenses onto the receiving antenna 13 the electromagnetic waves 3 that are emitted from the subject's body 2 and scanned by the polygon mirror 11 (reflected by the mirror surface of the polygon mirror 11 ).

[0020] The receiving antenna 13 is configured to receive electromagnetic waves in a plurality of predetermined frequency bands (bands) that are different from each other. Specifically, in this embodiment, the receiving antenna 13 is configured to receive electromagnetic waves F1 in a first frequency band and electromagnetic waves F2 in a second frequency band that is different from the first frequency band. The first frequency band and the second frequency band may be set, for example, according to the specific item, but are not limited to this and can be set arbitrarily. Furthermore, the first frequency band and the second frequency band may be adjacent to each other, but it is preferable that they are separated from each other. Although not particularly limited, for example, the first frequency band may be 75-110 GHz and the second frequency band may be 110-170 GHz. Alternatively, the first frequency band may be 75-110 GHz and the second frequency band may be 140-220 GHz.

[0021] The branching filter 14 branches the electromagnetic waves (F1+F2) received by the receiving antenna 13 into electromagnetic waves F1 of the first frequency band and electromagnetic waves F2 of the second frequency band, and outputs the electromagnetic waves F1 of the first frequency band to a first amplifier 15A, while outputting the electromagnetic waves F2 of the second frequency band to a second amplifier 15B. The electromagnetic waves F1 of the first frequency band are amplified by the first amplifier 15A and then input to a first detector 16A, and the electromagnetic waves F2 of the second frequency band are amplified by the second amplifier 15B and then input to a second detector 16B.

[0022] The first detector 16A detects the signal strength of the input electromagnetic wave F1 of the first frequency band (in other words, the reception level of the electromagnetic wave F1 of the first frequency band), and the second detector 16B detects the signal strength of the electromagnetic wave F2 of the second frequency band (in other words, the reception level of the electromagnetic wave F2 of the second frequency band).

[0023] In this embodiment, the first to fourth sensing units 10A to 10D are disposed on the sides of the passage 50, as shown in Figures 2 and 3. Specifically, the first sensing unit 10A is installed on the left side of the passage 50, and the second sensing unit 10B is installed on the opposite side of the passage 50 from the first sensing unit 10A, i.e., on the right side of the passage 50. The third sensing unit 10C is installed on the left side of the passage 50 and behind the first sensing unit 10A, and the fourth sensing unit 10D is installed on the opposite side of the passage 50 from the third sensing unit 10C, i.e., on the right side of the passage 50 and behind the second sensing unit 10B. In addition, the first to fourth sensing units 10A to 10D face approximately the center of a rectangular area (shown by a two-dot chain line in Figure 3) formed by connecting the centers of these units in a plan view.

[0024] The first sensing unit 10A is configured to receive electromagnetic waves radiated mainly from the front left half of the subject's body 2 as the subject moves and detect their signal strength (reception level), and the second sensing unit 10B is configured to receive electromagnetic waves radiated mainly from the front right half of the subject's body 2 as the subject moves and detect their signal strength.

[0025] On the other hand, the third sensing unit 10C is configured to receive electromagnetic waves emitted mainly from the left half of the back of the subject's body 2 as the subject moves and detect the signal strength thereof, and the fourth sensing unit 10D is configured to receive electromagnetic waves emitted from the right half of the back of the subject's body 2 as the subject moves and detect the signal strength thereof.

[0026] Each of the first to fourth sensing units 10A to 10D has an angle detection sensor 41 that detects the angle of the mirror surface (mirror angle) of the polygon mirror 11, i.e., the scanning angle of the polygon mirror 11 (see FIG. 4). Furthermore, the third sensing unit 10C and the fourth sensing unit 10D are provided with a pair of entry detection sensors 42, 42 that detect the entry of the subject, and the first sensing unit 10A and the second sensing unit 10B are provided with a pair of exit detection sensors 43, 43 that detect the exit of the subject (see FIG. 3).

[0027] Returning to FIG. 1, the processing unit 20 receives the detection results of the first to fourth sensing units 10A to 10D (first detector 16A and second detector 16B). The processing unit 20 generates a front image of the subject's body 2 based on the detection results of the first sensing unit 10A and the second sensing unit 10B, and generates a back image of the subject's body 2 based on the detection results of the third sensing unit 10C and the fourth sensing unit 10D. The processing unit 20 then outputs the generated front image and back image of the subject's body 2 to the display unit 30, causing the display unit 30 to display them.

[0028] The image generated by the processing unit 20 (the image displayed on the display unit 30) is an image with the subject's body 2 as the background. Here, if the subject is carrying a hidden object, as described above, the electromagnetic waves emitted from the subject's body are blocked by the object in the area where the object is present. Therefore, the signal strength of the received electromagnetic waves (the reception level of the electromagnetic waves) is lower in the area where the object is present than in the area where the object is not present. As a result, the shape of the object appears as a dark silhouette in the image.

[0029] In this embodiment, the processing unit 20 determines whether the subject is carrying the specific item based on the detection results of the first to fourth sensing units 10A to 10D or based on a generated image of the subject's body 2. If the processing unit 20 determines that the subject is carrying the specific item, it notifies a higher-level device (not shown) and / or notifies an inspector via a notification unit (not shown).

[0030] However, this is not a limitation. The processing unit 20 does not have to determine whether the subject is carrying the specific item. In this case, an inspector or the like will determine whether the subject is carrying the specific item based on the image displayed on the display unit 30, or more specifically, based on a dark silhouette that appears in the generated image.

[0031] Here, we will explain the operation of the passive imaging device 1. Figures 5 and 6 are flowcharts for explaining an example of the operation of the passive imaging device 1.

[0032] When the passive imaging device 1 detects the entry of a subject (person) using the entry detection sensors 42 (step S1), it operates the first to fourth sensing units 10A to 10D (step S2). Specifically, the passive imaging device 1 rotates the polygon mirrors 11 of the first to fourth sensing units 10A to 10D. This enables the first to fourth sensing units 10A to 10D to receive the electromagnetic waves F1 of the first frequency band and the electromagnetic waves F2 of the second frequency band emitted from the subject's body 2 and detect their signal intensities (reception levels).

[0033] Next, the passive imaging device 1 acquires the signal strength (reception level) of the electromagnetic waves F1 in the first frequency band and the signal strength (reception level) of the electromagnetic waves F2 in the second frequency band detected by each of the first to fourth sensing units 10A to 10D for each mirror angle (scanning angle) of the polygon mirror 11. Specifically, for each of the first to fourth sensing units 10A to 10D, the passive imaging device 1 acquires the signal strength (reception level) B1 of the electromagnetic waves F1 in the first frequency band received at each predetermined angle while the mirror angle (scanning angle) of the polygon mirror 11 varies from the upper limit to the lower limit, and the signal strength (reception level) B2 of the electromagnetic waves F2 in the second frequency band received at each predetermined angle (steps S3 to S8). Note that the predetermined angle is set in advance depending on the number of pixels of the image generated by the passive imaging device 1, etc.

[0034] Next, the passive imaging device 1 stores, for each of the first to fourth sensing units 10A to 10D, the reception level B1 of the electromagnetic wave F1 of the first frequency band for each of the predetermined angles while the mirror angle (scanning angle) changes from the upper limit to the lower limit, i.e., for each of the mirror angles (scanning angles), in the current time column of the image (pixel) array (step S9). Note that Fig. 7 shows an example of the reception level B1 of the electromagnetic wave F1 of the first frequency band stored here (i.e., in step S9).

[0035] Furthermore, the passive imaging device 1 stores, for each of the first to fourth sensing units 10A to 10D, a reception level B2 of the electromagnetic wave F2 of the second frequency band for each of the predetermined angles while the mirror angle (scanning angle) changes from the upper limit to the lower limit, i.e., for each of the mirror angles (scanning angles), at the current time of the image (pixel) array (step S10). Note that Fig. 8 shows an example of the reception level B2 of the electromagnetic wave F2 of the second frequency band stored here (i.e., in step S10).

[0036] Furthermore, the passive imaging device 1 sums up the reception level B1 of the electromagnetic wave F1 in the first frequency band and the reception level B2 of the electromagnetic wave F2 in the second frequency band at the corresponding mirror angle (corresponding scan angle) for each of the first to fourth sensing units 10A to 10D (step S11). Note that Fig. 9 shows an example of the summation result.

[0037] Next, the passive imaging device 1 determines whether or not the subject's entry is detected by the entry detection sensors 43 (step S12). If the subject's entry is not detected, the passive imaging device 1 repeats the processes of steps S3 to S11.

[0038] On the other hand, if the subject's advancement is detected, the passive imaging device 1 generates an image (hereinafter referred to as the "first image") of the subject's body 2 based on the reception level B1 (see Figure 7) of the electromagnetic wave F1 in the first frequency band for each mirror angle (scanning angle) (step S13).

[0039] Specifically, in this embodiment, the passive imaging device 1 generates an image of the front left half of the subject's body 2 based on the reception level B1 of the electromagnetic waves F1 in the first frequency band for each mirror angle (scanning angle) in the first sensing unit 10A, generates an image of the front right half of the subject's body 2 based on the reception level B1 of the electromagnetic waves F1 in the first frequency band for each mirror angle (scanning angle) in the second sensing unit 10B, and synthesizes (combines) the generated front left half image and front right half image to generate a first front side image of the subject's body 2. In addition, the passive imaging device 1 generates an image of the left half of the back side of the subject's body 2 based on the reception level B1 of the electromagnetic waves F1 in the first frequency band for each mirror angle (scanning angle) in the third sensing unit 10C, generates an image of the right half of the back side of the subject's body 2 based on the reception level B1 of the electromagnetic waves F1 in the first frequency band for each mirror angle (scanning angle) in the fourth sensing unit 10D, and generates a first back side image of the subject's body 2 by combining the generated left half and right half back side images.

[0040] Furthermore, the passive imaging device 1 generates a second image of the subject's body 2 based on the reception level B2 (see FIG. 8) of the electromagnetic wave F2 in the second frequency band for each mirror angle (scanning angle) (step S14).

[0041] Specifically, in this embodiment, the passive imaging device 1 generates an image of the front left half of the subject's body 2 based on the reception level B2 of the electromagnetic waves F2 of the second frequency band for each mirror angle (scanning angle) in the first sensing unit 10A, generates an image of the front right half of the subject's body 2 based on the reception level B2 of the electromagnetic waves F2 of the second frequency band for each mirror angle (scanning angle) in the second sensing unit 10B, and generates a second front side image of the subject's body 2 by combining the generated front left half image and front right half image. In addition, the passive imaging device 1 generates an image of the left half of the back side of the subject's body 2 based on the reception level B2 of the electromagnetic waves F2 of the second frequency band for each mirror angle (scanning angle) in the third sensing unit 10C, generates an image of the right half of the back side of the subject's body 2 based on the reception level B2 of the electromagnetic waves F2 of the second frequency band for each mirror angle (scanning angle) in the fourth sensing unit 10D, and generates a second back side image of the subject's body 2 by combining the generated left half and right half back side images.

[0042] Furthermore, the passive imaging device 1 generates a third image of the subject's body 2 based on the sum of the reception level B1 of the electromagnetic wave F1 in the first frequency band and the reception level B2 of the electromagnetic wave F2 in the second frequency band at the corresponding mirror angle (corresponding scanning angle) (see Figure 9) (step S15).

[0043] Specifically, in this embodiment, the passive imaging device 1 generates an image of the left front half of the subject's body 2 based on the sum of the reception level B1 of the electromagnetic waves F1 in the first frequency band and the reception level B2 of the electromagnetic waves F2 in the second frequency band at the corresponding scanning angle in the first sensing unit 10A, generates an image of the right front half of the subject's body 2 based on the sum of the reception level B1 of the electromagnetic waves F1 in the first frequency band and the reception level B2 of the electromagnetic waves F2 in the second frequency band at the corresponding scanning angle in the second sensing unit 10B, and generates a third front side image of the subject's body 2 by combining the generated left front half image and right front half image. In addition, the passive imaging device 1 generates an image of the left half of the back side of the subject's body 2 based on the sum of the reception level B1 of the electromagnetic waves F1 in the first frequency band and the reception level B2 of the electromagnetic waves F2 in the second frequency band at the corresponding scanning angle in the third sensing unit 10C, generates an image of the right half of the back side of the subject's body 2 based on the sum of the reception level B1 of the electromagnetic waves F1 in the first frequency band and the reception level B2 of the electromagnetic waves F2 in the second frequency band at the corresponding scanning angle in the fourth sensing unit 10D, and generates a third back side image of the subject's body 2 by combining the generated left half and right half back images.

[0044] Next, the passive imaging device 1 performs edge enhancement processing on each of the generated first to third images (first to third front-side images and first to third back-side images) of the subject's body 2 to generate respective edge-enhanced images (step S16), and displays the generated edge-enhanced images on the display unit 30 (step S17).

[0045] Figure 10 is a diagram showing a schematic representation of a portion of an edge-enhanced image displayed on the display unit 30, where Figure 10(a) shows an example of an edge-enhanced image of the first front-side image, Figure 10(b) shows an example of an edge-enhanced image of the second front-side image, and Figure 10(c) shows an example of an edge-enhanced image of the third front-side image.

[0046] Next, the passive imaging device 1 determines whether or not the subject is carrying the specific item based on the generated edge-enhanced images, i.e., the edge-enhanced image of the first image, the edge-enhanced image of the second image, and the edge-enhanced image of the third image (determination of whether or not the subject is carrying the specific item), and if the subject is carrying the specific item, notifies a host device or notifies an inspector of that fact (step S18). Thereafter, the passive imaging device 1 stops the first to fourth sensing units 10A to 10D (step 19), and ends this flow.

[0047] Here, advantages of the passive imaging device 1 according to the embodiment compared to conventional devices of the same type will be described.

[0048] As described above, when the subject is carrying an object, the electromagnetic waves radiated from the subject's body 2 are blocked and reduced in the area where the object is located. For example, if the signal strength of the electromagnetic waves radiated from the subject's body 2 is "1" and the electromagnetic wave transmittance of the object is 0.5, the signal strength of the electromagnetic waves radiated from the subject's body 2 in the area where the object is located will be "0.5." In this case, if the signal strength of the electromagnetic waves radiated from the object is "0.5," the signal strength (reception level) of the electromagnetic waves received by the passive imaging device in the area where the object is located will be "0.5" + "0.5" = "1," which is no different from the "1" in the area where the object is not located. In this case, the shape of the object will not appear as a silhouette in the image generated by the passive imaging device with the subject's body 2 in the background. As a result, the passive imaging device and / or the inspector may erroneously determine that the subject is not carrying an object, even though the subject is actually carrying an object.

[0049] Incidentally, the electromagnetic wave transmittance of an article varies depending on the frequency band of the electromagnetic wave, and generally tends to be lower as the frequency band of the electromagnetic wave increases, as shown in Fig. 11. Therefore, if a passive imaging device receives electromagnetic waves of multiple different frequency bands emitted from the subject's body and generates images of the subject's body for each frequency band, it is thought that it will be possible to reduce the above-mentioned erroneous determinations.

[0050] In this regard, the passive imaging device 1 according to the embodiment receives electromagnetic waves of different frequency bands (electromagnetic waves F1 of the first frequency band and electromagnetic waves F2 of the second frequency band) emitted from the subject's body 2, and generates, as images of the subject's body 2, a first image based on the reception level of the electromagnetic waves F1 of the first frequency band, a second image based on the reception level of the electromagnetic waves F2 of the second frequency band, and a third image based on the sum of the reception levels of the electromagnetic waves F1 of the first frequency band and the electromagnetic waves F2 of the second frequency band, as well as edge-enhanced images of these images. Therefore, for example, even if the shape of an item held by the subject does not appear as a silhouette in the first image, the shape of the item held by the subject may appear as a silhouette in the second image and the third image. Alternatively, even if the silhouette of the shape of the item held by the subject that appears in the first image and the second image is unclear, the silhouette of the shape of the item held by the subject may appear relatively clearly in the third image. Therefore, the passive imaging device 1 according to the embodiment can significantly reduce the oversight of a subject's belongings during a personal belongings inspection compared to conventional similar devices, and also improves the detection rate of the specific items.

[0051] In the above-described embodiment, the passive imaging device 1 receives electromagnetic waves of two different frequency bands (electromagnetic waves F1 of the first frequency band and electromagnetic waves F2 of the second frequency band) emitted from the subject's body 2 to generate an image of the subject's body 2. However, this is not limited to this. The passive imaging device 1 may receive electromagnetic waves of three or more different frequency bands emitted from the subject's body 2 to generate an image of the subject's body 2 for each frequency.

[0052] Furthermore, in the above-described embodiment, the passive imaging device 1 determines whether the subject possesses the specific item based on the edge-enhanced image of the first image, the edge-enhanced image of the second image, and the edge-enhanced image of the third image of the subject. However, this is not limited to this. The passive imaging device 1 may omit edge enhancement processing and determine whether the subject possesses the specific item based on the first image, the second image, and the third image. Alternatively, the passive imaging device 1 may determine whether the subject possesses the specific item based on the first image or the edge-enhanced image of the first image, or the second image or the edge-enhanced image of the second image, and the third image or the edge-enhanced image of the third image. Furthermore, the passive imaging device 1 may determine whether the subject possesses the specific item based only on the third image or the edge-enhanced image of the third image.

[0053] In the above-described embodiment, each of the first to fourth sensing units 10A to 10D separates the electromagnetic waves (F1+F2) received by the receiving antenna 13 into the electromagnetic waves F1 of the first frequency band and the electromagnetic waves F2 of the second frequency band using the branching filter 14. However, this is not limited to this. For example, as shown in FIG. 12, each of the first to fourth sensing units 10A to 10D may be configured to separate the electromagnetic waves (F1+F2) received by the receiving antenna 13 into the electromagnetic waves F1 of the first frequency band and the electromagnetic waves F2 of the second frequency band by using a distributor 17, a first bandpass filter (first BPF) 18A that passes the first frequency band, and a second bandpass filter (second BPF) 18B that passes the second frequency band, instead of the branching filter 14.

[0054] In the above-described embodiment, the passive imaging device 1 adds up the reception level B1 of the electromagnetic waves F1 in the first frequency band and the reception level B2 of the electromagnetic waves F2 in the second frequency band at the corresponding mirror angle (corresponding scan angle), and generates a third image of the subject's body 2 based on the addition result, and also generates an edge-enhanced image of this third image. However, this is not limited to this. The passive imaging device 1 may also generate a composite edge-enhanced image by combining (overlapping) the edge-enhanced image of the first image based on the reception level of the electromagnetic waves F1 in the first frequency band and the edge-enhanced image of the second image based on the reception level of the electromagnetic waves F2 in the second frequency band. In this case, the passive imaging device 1 operates, for example, as follows.

[0055] Figures 13 and 14 are flowcharts for explaining another example of the operation of the passive imaging device 1. In Figures 13 and 14, the processing of steps S21 to S33 is the same as the processing of steps S1 to S10 and S12 to S14 in Figures 5 and 6, so the explanation will be omitted and only the processing from step S34 onwards will be explained.

[0056] The passive imaging device 1 generates the first image (first front-side image and first back-side image) of the subject's body 2 (step S32), and then generates the second image (second front-side image and second back-side image) of the subject's body 2 (step S33), and then performs edge enhancement processing on each of the first image and the second image to generate respective edge-enhanced images (step S34).

[0057] Next, the passive imaging device 1 generates a composite edge-enhanced image by combining (overlapping) the edge-enhanced image of the first image and the edge-enhanced image of the second image (step S35), and displays the edge-enhanced image of the first image, the edge-enhanced image of the second image, and the composite edge-enhanced image on the display unit 30 (step S36).

[0058] Next, the passive imaging device 1 determines whether the subject is carrying the specific item (personal item presence determination) based on the edge-enhanced image of the first image, the edge-enhanced image of the second image, and the combined edge-enhanced image, and if the subject is carrying the specific item, notifies a host device or notifies an inspector of that fact (step S37). Thereafter, the passive imaging device 1 stops the first to fourth sensing units 10A to 10D (step 38), and ends this flow.

[0059] In this way, the same effects as those of the above-described embodiment can be obtained.

[0060] The passive imaging device 1 may generate a composite image of the first image and the second image, and then perform edge enhancement processing on the generated composite image to generate a composite edge-enhanced image. The passive imaging device 1 may also omit the edge enhancement processing and determine whether the subject is carrying the specific item based on the first image, the second image, and the composite image. Alternatively, the passive imaging device 1 may determine whether the subject is carrying the specific item based on the first image or an edge-enhanced image of the first image, or the second image or an edge-enhanced image of the second image, and the composite image or the composite edge-enhanced image. Furthermore, the passive imaging device 1 may determine whether the subject is carrying the specific item based only on the composite image or the composite edge-enhanced image.

[0061] The above describes the embodiments of the present invention and their modifications. However, 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]

[0062] 1...passive imaging device, 2...(subject's) human body, 3...electromagnetic wave, 10A-10D...first to fourth sensing units, 11...polygon mirror (scan mirror), 12...collecting mirror, 13...receiving antenna, 14...branching filter, 15A, 15B...first and second amplifiers, 16A, 16B...first and second detectors, 17...distributor, 18A, 18B...first and second band-pass filters, 20...processing unit, 30...display unit, 41...angle detection sensor

Claims

1. A device configured to receive electromagnetic waves of multiple different frequency bands emitted from a moving subject and scanned by a scan mirror, detect the signal strength of the received electromagnetic waves for each frequency band and for each scan angle of the scan mirror, add up the signal strengths at the corresponding scan angles in each frequency band, and generate an image of the subject based on the added signal strengths; the plurality of frequency bands are spaced apart from one another; A passive imaging device, wherein the images of the subject include a front-side image of the subject and a back-side image of the subject.

2. 2. The passive imaging device of claim 1, wherein an edge-enhanced image is generated by performing edge enhancement processing on the image of the subject.

3. 3. The passive imaging device according to claim 2, wherein the subject is a human body of a subject, and whether or not the subject is carrying a specific item is determined based on the edge-enhanced image.

4. A device configured to receive electromagnetic waves of multiple different frequency bands emitted from a moving subject and scanned by a scan mirror, detect the signal strength of the received electromagnetic waves for each frequency band and for each scanning angle of the scan mirror, generate images of the subject for each frequency band based on the detected signal strength, and synthesize the generated images for each frequency band to generate a composite image; the plurality of frequency bands are spaced apart from one another; the images of the subject for each frequency band include a first front-side image of the subject based on electromagnetic waves in a first frequency band, a second front-side image of the subject based on electromagnetic waves in a second frequency band, a first back-side image of the subject based on electromagnetic waves in the first frequency band, and a second back-side image of the subject based on electromagnetic waves in the second frequency band; The composite image is a front-side image of the subject obtained by combining the first front-side image and the second front-side image; a rear-side image of the subject obtained by combining the first rear-side image and the second rear-side image; 1. A passive imaging device comprising:

5. 5. The passive imaging device according to claim 4, wherein edge enhancement processing is performed on each of the images for each frequency band to generate an edge-enhanced image for each frequency band, and edge enhancement processing is performed on the composite image to generate a composite edge-enhanced image.

6. A device configured to receive electromagnetic waves of multiple different frequency bands emitted from a moving subject and scanned by a scan mirror, detect the signal strength of the received electromagnetic waves for each frequency band and for each scanning angle of the scan mirror, generate images of the subject for each frequency band based on the detected signal strength, perform edge enhancement processing on the generated images for each frequency band to generate edge-enhanced images for each frequency band, and synthesize the generated edge-enhanced images for each frequency band to generate a composite edge-enhanced image, the plurality of frequency bands are spaced apart from one another; the images of the subject for each frequency band include a first front-side image of the subject based on electromagnetic waves in a first frequency band, a second front-side image of the subject based on electromagnetic waves in a second frequency band, a first back-side image of the subject based on electromagnetic waves in the first frequency band, and a second back-side image of the subject based on electromagnetic waves in the second frequency band; The synthesized edge-enhanced image is a front-side image of the subject obtained by combining an edge-enhanced image of the first front-side image and an edge-enhanced image of the second front-side image; a back-side image of the subject obtained by combining an edge-enhanced image of the first back-side image and an edge-enhanced image of the second back-side image; 1. A passive imaging device comprising:

7. 7. The passive imaging device according to claim 5, wherein the subject is a human body of a subject, and whether or not the subject is carrying a specific item is determined based on the edge-enhanced images for each frequency band and the composite edge-enhanced image.

8. 8. The passive imaging device according to claim 3, wherein a plurality of frequency bands are set according to the specific article.

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