Radar system and inspection method

Abstract

To provide a radar system that can accurately inspect an inspection target in a short time.SOLUTION: A radar system comprises a plurality of transmission antennas, a plurality of receiving antennas, and a processing portion connected to the plurality of transmission antennas and the plurality of receiving antennas. The processing portion includes a detection portion that detects the shape of an inspection target. The processing portion selects one first transmission antenna of the plurality of transmission antennas and at least one first receiving antenna of the plurality of receiving antennas on the basis of the shape detected by the detection portion, causes the one first transmission antenna to transmit an electromagnetic wave, causes at least one first receiving antenna to receive the electromagnetic wave, and inspects the inspection target on the basis of a signal from at least one first receiving antenna.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to radar systems and inspection methods. [Background technology]

[0002] Radar systems are expected to be applied to inspections in a variety of fields, including automobiles, non-destructive testing, medicine, and security. Inspection accuracy is proportional to the number of antennas that transmit and receive radio waves. To improve inspection accuracy, it is necessary to increase the number of antennas. However, the larger the number of antennas, the larger the size of the received signal. The received signal is sent to a signal processing circuit. The signal processing circuit obtains information indicating the inspection result. If the size of the received signal is large, it takes a long time to transmit the received signal from the antenna's receiving circuit to the signal processing circuit. If the size of the received signal is large, the signal processing time also takes a long time. If inspections are to be performed periodically, the large size of the received signal makes it impossible to shorten the inspection period. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 078627 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a radar system that can perform inspections with high accuracy in a short time. [Means for solving the problem]

[0005] The radar system according to the embodiment includes: Placed on the board a plurality of transmitting antennas; disposed on the substrate The apparatus includes a plurality of receiving antennas, and a processing unit connected to the plurality of transmitting antennas and the plurality of receiving antennas. The surface of the substrate side shape is convex toward the substrate in one direction, among the plurality of transmitting antennas a portion disposed at the center of the substrate in the one direction a transmitting antenna, and a receiving antenna among the plurality of receiving antennas. a portion disposed at the center of the substrate in the one direction Select the receiving antenna of If the shape of the surface of the inspection target on the side of the substrate is not convex toward the substrate in the one direction, all of the plurality of transmitting antennas and all of the plurality of receiving antennas are selected, and The transmitting antenna transmits radio waves, Selected above The radio wave signal received from the receiving antenna is acquired and the inspection object is inspected. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a diagram for explaining an example of the layout of the radar system according to the first embodiment. [Figure 2] FIG. 4 is a diagram for explaining another example of the arrangement of the radar system according to the first embodiment. [Figure 3] FIG. 2 is a diagram for explaining an example of a cluster according to the first embodiment. [Figure 4] FIG. 2 is a diagram for explaining an example of transmission and reception of a cluster according to the first embodiment. [Figure 5] FIG. 2 is a block diagram illustrating an example of a circuit configuration of the radar system according to the first embodiment. [Figure 6] FIG. 2 is a diagram for explaining an example of a shape construction unit of the radar system according to the first embodiment. [Figure 7] FIG. 2 is a diagram for explaining an example of cluster selection in the radar system according to the first embodiment. [Figure 8] FIG. 2 is a diagram for explaining an example of cluster selection in the radar system according to the first embodiment. [Figure 9] FIG. 4 is a diagram for explaining another example of cluster selection in the radar system according to the first embodiment. [Figure 10] FIG. 4 is a diagram for explaining another example of cluster selection in the radar system according to the first embodiment. [Figure 11] FIG. 3 is a diagram for explaining a normal to an inspection object in the radar system according to the first embodiment. [Figure 12] FIG. 2 is a diagram for explaining the origin of radar coordinates in the radar system according to the first embodiment. [Figure 13]FIG. 4 is a diagram for explaining another example of antenna selection in the radar system according to the first embodiment. [Figure 14] FIG. 6 is a diagram for explaining an allowable angle in another example of antenna selection in the radar system according to the first embodiment. [Figure 15] FIG. 4 is a block diagram for explaining another example of the controller in the radar system according to the first embodiment. [Figure 16] FIG. 4 is a block diagram for explaining yet another example of the controller in the radar system according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments will be described with reference to the drawings. The following description exemplifies devices and methods embodying the technical concepts of the embodiments. The technical concepts of the embodiments are not limited to the structures, shapes, arrangements, materials, etc. of the components described below. Modifications that can be easily conceived by those skilled in the art are naturally included within the scope of the disclosure. For clarity of explanation, the drawings may schematically depict elements with different sizes, thicknesses, planar dimensions, shapes, etc., compared to the actual embodiment. Elements with different dimensional relationships or ratios may be included in multiple drawings. Corresponding elements may be designated by the same reference numerals in multiple drawings, and redundant description may be omitted. Some elements may be designated by multiple names, but these designations are merely examples and do not exclude the use of other names for these elements. Furthermore, elements that do not have multiple names may also be designated by other names. In the following description, "connection" may include not only direct connection but also connection via other elements.

[0008] Hereinafter, the present embodiment will be described in detail with reference to the drawings.

[0009] First embodiment FIG. 1 is a diagram illustrating an example of the layout of a radar system according to the first embodiment. The example radar system relates to a security system installed in facilities where many people gather, such as train stations, bus terminals, airports, shopping malls, concert halls, and exhibition halls. FIG. 1 illustrates an example of inspecting whether a walking inspection target 10 possesses a predetermined object. The predetermined object is a dangerous object that is not permitted to be possessed at the location where the radar system is installed. Examples of dangerous objects include metal objects such as handguns and knives, powders such as explosives, and liquids such as gasoline. Examples of dangerous objects include powders such as narcotics and illegally brought-in goods such as gold bars. The first embodiment is not limited to inspecting a walking inspection target 10, but can also inspect a stationary inspection target 10. The inspection target may be, for example, a person or luggage. If the inspection target is a person, the inspection target may also include clothing, items in the clothing, and items carried or carried by the person. If the inspection target is luggage, the inspection target may also include the luggage packaging.

[0010] A panel 16, a near-infrared camera 20, and a near-infrared light projector 22 are installed on one side wall 14 of a passage 12 of the inspection object 10. The passage 12 may include a station ticket gate, a room entrance / exit control gate, etc. The passage 12 may also be an area where many people can pass through or stay. A panel 18 is installed on the other side wall of the passage 12. The longitudinal direction of the passage 12 is referred to as the x-direction. The height direction of the passage 12 is referred to as the y-direction. The width direction of the passage 12 is referred to as the z-direction.

[0011] The panels 16 and 18 are parallel to each other. The radio wave transmitting and receiving areas of the panels 16 and 18 are called the inspection areas. It is not essential to provide two panels 16 and 18, and only one panel may be provided.

[0012] An example of the shape of the panels 16, 18 is rectangular. One side on the front side and one side on the back side of the panels 16, 18 may be bent toward the center. In this case, radio waves from the panels 16, 18 are efficiently irradiated onto the inspection object 10 located in the center of the inspection area.

[0013] The panels 16, 18 each include a plurality of clusters 30. A cluster 30 is a transmitting / receiving unit that serves as a single unit of transmission / reception control. The number and arrangement of the clusters 30 are determined so that the panels 16, 18 can transmit radio waves to the entire area of ​​a standard-sized inspection object 10 and receive reflected waves from the entire area of ​​the inspection object 10. This size corresponds to the two-dimensional shape (also referred to as the outline) of the inspection object 10 when it is projected onto the panel surface.

[0014] An example of radio waves is radio waves with wavelengths of 1 millimeter to 1 centimeter (frequency of 30 GHz to 300 GHz), also known as millimeter waves. Another example of radio waves is radio waves with wavelengths of 100 micrometers to 1 millimeter (frequency of 300 GHz to 3 THz), also known as submillimeter waves or terahertz waves.

[0015] These radio waves irradiated onto the inspection object 10 are reflected by the skin of the inspection object 10. These radio waves are also reflected by metal objects such as handguns and knives. The reflectivity of metal is higher than that of skin. The intensity of the waves reflected by metal is higher than that of skin. These radio waves are also absorbed by powder such as explosives. The reflectivity of powder is lower than that of skin. The intensity of the reflected waves is determined by the type of material at the point where the radio waves are reflected, such as skin, metal, or powder. A radar system can determine the type of material at the reflection point from the intensity of the reflected waves (the intensity of the received signal), and can inspect for dangerous items concealed in clothing.

[0016] The near-infrared light projector 22 projects a near-infrared light pattern onto the inspection area. Examples of the pattern include a grid and stripes. The near-infrared camera 20 captures a near-infrared image of the inspection area. The near-infrared light pattern projected onto the inspection object 10 is distorted according to the three-dimensional shape of the inspection object 10. Three-dimensional shape data of the inspection object 10 is obtained based on the distortion of the near-infrared light pattern captured by the near-infrared camera 20. The three-dimensional shape data also represents the position of the inspection object 10 relative to the radar system. The near-infrared camera 20 can be replaced with various detection units capable of acquiring the shape of the inspection object 10. For example, a three-dimensional shape can be acquired. For example, a 3D camera using a ToF (Time of Flight) method or a stereo method can be used. In this case, the near-infrared light projector 22 is not required.

[0017] For a standard-sized inspection target 10, the panels 16 and 18 transmit radio waves to the entire area of ​​the inspection target 10 and receive reflected waves from the entire area of ​​the inspection target 10. However, depending on the body shape, posture, and position of the inspection target 10, some of the clusters 30 on the panels 16 and 18 may not transmit radio waves to the inspection target 10, or some of the clusters 30 on the panels 16 and 18 may not receive radio waves from the inspection target 10. It is pointless to operate some of the clusters that do not contribute to transmitting and receiving radio waves for the inspection target 10. The radar system according to the embodiment selects clusters to be used for transmitting and receiving radio waves based on the three-dimensional shape and position of the inspection target 10.

[0018] When the near-infrared camera 20 captures an image of the inspection object 10, the radar system recognizes that the inspection object 10 is present in the inspection area and starts emitting radio waves. The radar system radiates radio waves and obtains received signals only when the inspection object 10 is present in the inspection area, so there is no need to process unnecessary received signals that do not contribute to the inspection.

[0019] 2 is a diagram illustrating another example of the layout of the radar system according to the first embodiment. A panel 26 is installed at one end of the floor 13 of the inspection area. The inspection object 10 stands on the floor 13 of the inspection area with its front surface facing the panel 26. The panel 26 irradiates radio waves onto the front of the inspection object 10, and the front surface of the inspection object 10 is inspected. As with the panels 16 and 18, one right side and one left side of the panel 26 may also be bent toward the center.

[0020] After inspecting the front side, the inspection object 10 is turned 180 degrees so that the back side faces the panel 16. This allows the back side of the inspection object 10 to be inspected as well. Note that two panels may be placed in front of and behind the floor surface 13 so that the front and back sides of the inspection object 10 can be inspected simultaneously.

[0021] 3 is a diagram illustrating an example of a cluster 30 according to the first embodiment. One cluster 30 includes at least one transmitting module 42 and at least one receiving module 52. The at least one transmitting module 42 and the at least one receiving module 52 are arranged on one substrate of the cluster 30. An example of the shape of the substrate of the cluster 30 is rectangular.

[0022] The transmitting module 42 includes a plurality of transmitting circuits 46. Each transmitting circuit 46 is connected to a plurality of transmitting antennas 44. The plurality of transmitting antennas 44 configure one transmitting array antenna. For example, one transmitting module 42 includes four transmitting circuits 46. One transmitting circuit 46 includes one transmitting array antenna consisting of four transmitting antennas 44. One transmitting module 42 includes four transmitting array antennas. The transmitting circuits 46 may be configured using integrated circuits.

[0023] The multiple transmitting antennas 44 and the multiple transmitting circuits 46 are arranged on a single substrate of the transmitting module 42. An example of the shape of the substrate of the transmitting module 42 is rectangular. All of the transmitting antennas 44 may be arranged in a line or in a two-dimensional manner. All of the transmitting antennas 44 may be arranged at equal intervals, for example, at intervals of one wavelength. The multiple transmitting antennas 44 may also be arranged at uneven intervals. An example of an unevenly spaced array antenna is a minimum redundancy array (MRA) antenna. An MRA antenna achieves the maximum aperture length with the same number of antennas by minimizing the redundancy of antenna spacing.

[0024] By constructing a non-uniformly spaced array antenna, a virtual array antenna can be efficiently generated and the array aperture length can be increased, which enables high resolution in direction-of-arrival estimation and image generation by synthetic aperture processing.

[0025] The transmitting circuit 46 includes a reference signal generator, an amplifier, and a phase shifter. The reference signal generator generates a Linear Frequency Modulated Continuous Wave (L-FMCW) signal (hereinafter referred to as a chirp signal) whose frequency increases linearly over time. The amplifier amplifies the chirp signal to a predetermined power. The amplifier transmits the amplified chirp signal to a phase shifter. The phase shifter adjusts the phase of the amplified chirp signal to a predetermined phase. The phase shifter supplies an output to the transmitting antenna 44. At least one of the multiple transmitting antennas 44 connected to the transmitting circuit 46, or all of the multiple transmitting antennas 44, transmits a single chirp wave. One transmitting circuit 46 transmits a single chirp wave at a certain timing, and another transmitting circuit 46 transmits the next chirp wave at a subsequent timing. In this manner, multiple chirp waves are sequentially transmitted by the multiple transmitting circuits 46.

[0026] The receiving module 52 includes a plurality of receiving circuits 56. Each receiving circuit 56 is connected to a plurality of receiving antennas 54. The plurality of receiving antennas 54 constitute one receiving array antenna. For example, one receiving module 52 includes four receiving circuits 56. One receiving circuit 56 includes one receiving array antenna made up of four receiving antennas 54. One receiving module 52 includes four receiving array antennas. The receiving circuits 56 may be configured as integrated circuits.

[0027] The multiple receiving antennas 54 and the multiple receiving circuits 56 are arranged on a single substrate of the receiving module 52. An example of the shape of the substrate of the receiving module 52 is rectangular. All of the receiving antennas 54 may be arranged in a line or in a two-dimensional manner. All of the receiving antennas 54 may be arranged at equal intervals, for example, at intervals of one wavelength. The multiple receiving antennas 54 may also be arranged at uneven intervals. An example of an unevenly spaced array antenna is an MRA antenna.

[0028] The receiving circuit 56 includes an amplifier, a frequency conversion unit, and an analog-to-digital converter (ADC). Radio waves radiated to the test object 10 are reflected by the test object 10. The multiple receiving circuits 56 simultaneously receive the reflected waves. The receiving circuit 56 receives the reflected waves using at least one transmitting antenna among the multiple receiving antennas 56, or using all of the multiple receiving antennas 56. The amplifier amplifies the received signal from the receiving antenna to a predetermined power. The amplifier transmits the amplified received signal to the frequency conversion unit. The frequency conversion unit mixes the transmitted signal input to the transmitting antenna with the received signal to generate a received intermediate frequency signal (received IF signal). The frequency conversion unit transmits the received IF signal to the ADC. The ADC converts the received IF signal into a digital signal.

[0029] The arrangement of the transmitting module 42 and the receiving module 52 on the substrate of the cluster 30 is arbitrary. When the transmitting antennas 44 and the receiving antennas 54 are both arranged in a line, the transmitting module 42 is arranged on the substrate of the cluster 30 so that the arrangement direction of the transmitting antennas 44 is along one of the two directions that define the rectangle of the substrate of the cluster 30, for example, the y-axis direction. The receiving module 52 is arranged on the substrate of the cluster 30 so that the arrangement direction of the receiving antennas 54 is along the other of the two directions that define the rectangle of the substrate of the cluster 30, for example, the x-axis direction. Since transmission and reception are interchangeable, "transmission" in FIG. 3 may be replaced with "reception," and "reception" in FIG. 3 may be replaced with "transmission."

[0030] FIG. 4 is a diagram illustrating an example of transmission and reception in the cluster 30 according to the first embodiment. It is assumed that there are two transmission modules 42 and two reception modules. Two rows of transmission antennas 44 provided by the two transmission modules 42 are arranged along the x-axis direction. The element spacing between the transmission antennas 44 in each row is one wavelength (λ). The positions of the transmission antennas 44 in the first row in the x-axis direction are not the same as the positions of the transmission antennas 44 in the second row in the x-axis direction, but are shifted by half a wavelength (λ / 2). Two rows of reception antennas 54 provided by the two reception modules 52 are arranged along the y-axis direction. The element spacing between the reception antennas 54 in each row is one wavelength. The positions of the reception antennas 54 in the first row in the y-axis direction are not the same as the positions of the reception antennas 54 in the second row in the y-axis direction, but are shifted by half a wavelength. A virtual array antenna 60 is realized by the transmission antennas 44 and reception antennas 54 arranged in this manner. The element spacing between each antenna in the virtual array antenna 60 is half a wavelength.

[0031] 5 is a block diagram for explaining an example of the circuit configuration of the radar system of the first embodiment. A controller 102 is connected to a panel 16 (or 18 or 26) that includes a plurality of clusters 30. The controller 102 includes a shape construction unit 112 and a selection unit 114. A near-infrared light projector 22 and a near-infrared camera 20 are connected to the shape construction unit 112.

[0032] 6 is a diagram illustrating an example of the shape construction unit 112 in the radar system according to the first embodiment. A near-infrared light projector 22 projects a near-infrared light pattern (here, a grid pattern) 23 onto the inspection object 10 in the inspection area. A near-infrared camera 20 captures a near-infrared image of the inspection area. The near-infrared light pattern projected onto the inspection object 10 is distorted according to the three-dimensional shape of the inspection object 10.

[0033] The shape construction unit 112 receives the grid pattern 23 projected by the near-infrared light projector 22 and the near-infrared light pattern captured by the near-infrared camera 20. Based on the coordinates of each grid point of the projected pattern 23 and the coordinates of each grid point of the captured pattern on the camera image, the shape construction unit 112 calculates three-dimensional coordinates of the grid points on the surface of the inspection object 10 according to the principles of triangulation, and generates three-dimensional shape data of the inspection object 10. The shape construction unit 112 transmits the three-dimensional shape data to the selection unit 114. The three-dimensional shape data represents the two-dimensional body shape and posture related to the contours of the inspection object 10, as well as the three-dimensional body shape and posture related to the contours of the inspection object 10. The body shape may be obese, thin, etc., and the posture may be upright, leaning forward, bending forward, leaning backward, etc. Because the three-dimensional shape data is the coordinates of the grid points, the position of the inspection object 10 relative to the radar system can also be determined from the three-dimensional shape data.

[0034] An example of generating 3D shape data is the technique described in Hiroshi Kawasaki, Ryo Furukawa, Ryusuke Sagawa and Yasushi Yagi, "Dynamic scene shape reconstruction using a single structured light pattern," 2008 IEEE Conference on Computer Vision and Pattern Recognition, 2008, pp. 1-8, doi: 10.1109 / CVPR.2008.4587702.

[0035] High angular resolution is required for radar systems to detect multiple adjacent targets inside clothing. The angular resolution for estimating the direction of arrival is determined by the aperture length of the array antenna. If the element spacing is longer than half the wavelength, grating lobes will occur, so the multiple antennas that make up the array antenna must be closely spaced. When multiple antennas are closely spaced, a large amount of data transfer and processing occurs.

[0036] The selection unit 114 selects one transmission cluster 30 that transmits radio waves to the inspection object 10 and at least one reception cluster 30 that receives reflected waves, according to the three-dimensional shape data of the inspection object 10. The selection unit 114 selects one transmission module 42 from all the transmission modules 42 of the selected transmission cluster 30. The selection unit 114 selects one transmission circuit 46 from all the transmission circuits 46 of the selected transmission module 42. The selected one transmission circuit 46 transmits radio waves. When the transmission of the selected transmission circuit 46 is completed, the selection unit 114 selects another transmission circuit 46.

[0037] The selection unit 114 selects at least one receiving module 52 from all the receiving modules 52 in at least one receiving cluster 30. The selection unit 114 selects at least one receiving circuit 56 from all the receiving circuits 56 in the at least one receiving module 52. The selected at least one receiving circuit 56 operates simultaneously and receives reflected waves simultaneously.

[0038] This eliminates the need to send or receive radio waves that are not involved in the inspection, and eliminates the need to collect received signals that are not involved in the inspection, thereby minimizing the size of the received signal and minimizing the transfer time and signal processing time of the received signal between the panel 16 and the signal processing unit 104.

[0039] 7 and 8 are diagrams illustrating an example of cluster selection in the radar system according to the first embodiment. FIGS. 7 and 8 show how a cluster is selected according to the body shape of the inspection target 10. FIGS. 7(a) and 8(a) show plan views of the inspection target 10 as viewed from above the radar system. Rotating FIGS. 7(a) and 8(a) counterclockwise by 90 degrees results in side views of the inspection target 10 as viewed from the side of the radar system. The shapes of the inspection target 10 in FIGS. 7(a) and 8(a) show the shapes of the three-dimensional shape data projected onto the xz plane or yz plane.

[0040] FIG. 7(a) shows a slim-type inspection target 10. The surface of the slim-type inspection target 10 facing the panel 16, i.e., the surface that reflects radio waves, is substantially flat. All transmitting antennas on the panel 16 transmit radio waves to all points on the surface of the inspection target 10 that are parallel to the panel 16. All receiving antennas on the panel 16 receive reflected waves from all points on the surface of the inspection target 10 that are parallel to the panel 16. Therefore, when the cross-sectional shape or side shape of the inspection target 10 is the shape shown in FIG. 7(a), the selection unit 114 selects all clusters 30 as transmitting / receiving clusters 31A, as shown in FIG. 7(b). That is, each cluster 30 is selected sequentially as a transmitting cluster, and all clusters 30 are selected as receiving clusters.

[0041] FIG. 8(a) shows an obese test subject 10. The surface of the obese test subject 10 facing the panel 16, i.e., the radio wave reflecting surface, is convex toward the panel 16. A transmitting antenna on one peripheral portion of the panel 16 in the x direction transmits radio waves to one peripheral portion of the surface of the test subject 10 in the x direction, but does not transmit radio waves to the other peripheral portion. Therefore, when the cross-sectional shape or side shape of the test subject 10 is the shape shown in FIG. 8(a), the selector 114 selects the cluster group in the center in the x direction as the transmitting / receiving cluster 31B, as shown in FIG. 8(b). That is, each cluster 30 included in the cluster group 31B in the center in the x direction is sequentially selected as a transmitting cluster, and all clusters 30 included in the cluster group 31B in the center in the x direction are selected as receiving clusters.

[0042] 9 and 10 are diagrams illustrating another example of cluster selection in the radar system according to the first embodiment. FIGS. 9 and 10 show how a cluster is selected depending on the position of the inspection target 10 in the direction of travel (x direction) relative to the radar system. FIGS. 9(a) and 10(a) show plan views of the inspection target 10 as viewed from above the radar system. When inspecting a walking inspection target 10, the state shown in FIG. 10 first occurs over time, followed by the state shown in FIG. 9. In FIGS. 9 and 10, the viewing angle of the panel 16 is assumed to be a certain angle. The directivity of the antenna is determined by the width and length of the antenna. The viewing angle can be adjusted by adjusting the directivity. In the explanation of FIGS. 9 and 10, the viewing angle of the panel 16 is assumed to be 30 degrees.

[0043] FIG. 9(a) shows a case where the x-coordinate of the center of the panel 16 is close to the x-coordinate of the inspection target 10. In this case, the incident angle of the reflected wave from the inspection target 10 relative to the panel 16 is small. When the antenna element spacing is one wavelength, if the absolute value of the incident angle is within 30 degrees, grating lobes appear at angles of 30 degrees or more. When the inspection target 10 is positioned as shown in FIG. 9(a), setting the viewing angle of the panel 16 to ±30 degrees can suppress grating lobes incident from outside the viewing angle. Therefore, the selector 114 selects a group of clusters in the center in the x-direction as the transmitting / receiving cluster 31C, as shown in FIG. 9(b).

[0044] 10(a) shows a case where the x coordinate of the center of the panel 16 is far from the x coordinate of the inspection target 10. In this case, the incident angle of the reflected wave with respect to the panel 16 is large. Therefore, when the inspection target 10 is positioned as shown in FIG. 10(a), a grating lobe falls within the field of view of the panel 16, and the selector 114 selects all clusters 3 as the transmitting / receiving cluster 31D, as shown in FIG. 10(b).

[0045] As described above, depending on the body shape or position of the subject 10, there may be a combination of transmitting clusters and receiving clusters to which no reflected waves are incident. Transmitting and receiving radio waves using such a useless combination results in redundant data transfer time and processing time. The selection unit 114 adaptively selects transmitting and receiving clusters that contribute to the examination based on the body shape or position of the subject 10, and operates only the selected clusters. This prevents unnecessary transfer of received signals and reduces processing time.

[0046] Depending on the arrangement of the transmitting modules 42 within a cluster 30, there may be transmitting modules 42 that do not contribute to testing, even within the same cluster 30. Depending on the arrangement of the receiving modules 52 within a cluster 30, there may be receiving modules 52 that do not contribute to testing, even within the same cluster 30. Furthermore, depending on the arrangement of the transmitting antennas 44 within a transmitting module 42, there may be transmitting antennas 44 that do not contribute to testing, even within the same transmitting module 42. Depending on the arrangement of the receiving antennas 54 within a receiving module 52, there may be receiving antennas 54 that do not contribute to testing, even within the same receiving module 52.

[0047] Therefore, the selection unit 114 may cause all of the transmitting modules 42 and receiving modules 52 of the selected cluster to transmit and receive, or may select some of the transmitting modules 42 and receiving modules 52 that contribute to the test and cause the selected transmitting modules 42 and receiving modules 52 to transmit and receive. The selection unit 114 may cause all of the transmitting circuits 46 of the transmitting modules 42 to transmit sequentially, or may select some of the transmitting circuits 46 (i.e., transmitting antennas 44) that contribute to the test and cause the selected some of the transmitting circuits 46 to transmit sequentially. The selection unit 114 may cause all of the receiving circuits 56 of the receiving module 52 to receive simultaneously, or may select some of the receiving circuits 56 (i.e., receiving antennas 54) that contribute to the test and cause the selected some of the receiving circuits 56 to transmit simultaneously.

[0048] The selection unit 114 selects some of the transmitting modules 42 and receiving modules 52 that will contribute to the test, and selects the transmitting circuits 46 and receiving circuits 56 that will contribute to the test, in accordance with the criteria shown in FIGS.

[0049] Next, another example of antenna selection by the selector 114 will be described. Fig. 11 is a diagram for explaining the normal to the inspection target 10 in the radar system according to the first embodiment. Fig. 12 is a diagram for explaining the radar coordinate origin in the radar system according to the first embodiment. Fig. 13 is a diagram for explaining the allowable angle in another example of antenna selection in the radar system according to the first embodiment.

[0050] The selection unit 114 determines the normal of a certain grid point among the grid points indicated by the three-dimensional shape data of the object of inspection 10. Here, it is assumed that the selection unit 114 determines the normal of the grid point having the shortest Euclidean distance to the radar system (e.g., panel 16) among the grid points indicated by the three-dimensional shape data of the object of inspection 10. The selection unit 114 determines the angle between the normal of the determined grid point and the origin of the radar coordinate system. The selection unit 114 determines whether or not to operate the transmitting and receiving antennas based on the determined angle. The normal of the grid point depends on the shape and position of the object of inspection 10. The angle between the normal and the origin of the radar coordinate system also depends on the shape and position of the object of inspection 10. Therefore, the selection unit 114 selects the transmitting and receiving antennas depending on the shape and position of the object of inspection 10.

[0051] Although the normal of the grid point with the shortest Euclidean distance to the radar system is used, the normals of all grid points of the three-dimensional shape data or a part of a plurality of grid points may be used.

[0052] 11, the coordinate origin of the three-dimensional shape data is the camera coordinate origin, which is the installation position of the near-infrared camera 20. The radar coordinate origin is the reference point of a certain cluster and is defined as (xrad, yrad, zrad) (camera coordinates). The transmitting antenna and receiving antenna are assumed to exist on the xy plane.

[0053] FIG. 12 shows an example of the radar coordinate origin (x rad, y rad, z rad) of a certain cluster. Assume that the transmitting antennas 44 are arranged along the y direction, and the receiving antennas 54 are arranged along the x direction. The y coordinate of the receiving antenna 54 coincides with the y coordinate of the midpoint of the arrangement of the multiple transmitting antennas 44. The y coordinate of the midpoint of the arrangement of the transmitting antennas 44 is defined as the y coordinate yrad of the radar coordinate origin. Assume that the distance between the side of the transmitting module 42 board closest to the receiving module 52 and the side of the receiving module 52 board closest to the transmitting module 42 is 2×d1. The x coordinate of a point at a distance d1 from the transmitting module 42 or a point at a distance d1 from the receiving module 52 is defined as the x coordinate xrad of the radar coordinate origin. The z coordinate zrad of the radar coordinate origin is the depth of the inspection object 112 as seen from the cluster.

[0054] Let point s be the grid point with the shortest Euclidean distance to the radar system, and the coordinates of point s be (xs, ys, zs) (camera coordinate system). Let vector U be the vector between grid point s and grid point u, the shortest distance from grid point s. Let vector V be the vector between grid point s and grid point v, which is adjacent to grid point u in the counterclockwise direction.

[0055] The normal vector N of the lattice point s can be calculated from the vectors U and V as follows:

[0056] N=(U×V) / (||U×V||) The normal vector N is expressed as follows using the unit vectors Xo, Yo, and Zo of the x-, y-, and z-axes:

[0057] N=xnXo+ynYo+znZo xn, yn, and zn are coefficients.

[0058] The azimuth angle θn and elevation angle φn of the normal vector N in the radar coordinate system are expressed by Equation 1 and Equation 2, respectively.

[0059]

number

[0060] The azimuth angle θs and elevation angle φs between the grid point s and the origin of the radar coordinate system are expressed by Equation 3 and Equation 4, respectively.

[0061]

number

[0062] The selection unit 114 selects an antenna to operate according to the azimuth angle θs and the elevation angle φs.

[0063] If the absolute value of the azimuth angle θs is less than 30 degrees and the absolute value of the elevation angle φs is less than 30 degrees, the selector 114 selects the transmitting module and receiving module included in the cluster that includes the radar coordinate origin.

[0064] A case where the absolute value of the azimuth angle θs is 30 degrees or more will be described.

[0065] The selection unit 114 compares the angular difference θd=|θn|−|θs| between the azimuth angle θn and the azimuth angle θs with the allowable angle α to select an antenna and change the antenna to be operated.

[0066] Fig. 13(a) shows an example of the angle difference θd when the azimuth angle θs is a negative angle and its absolute value is 30 degrees or more. Fig. 13(b) shows an example of the angle difference θd when the azimuth angle θs is a positive angle and its absolute value is 30 degrees or more.

[0067] FIG. 14 is a diagram illustrating an example of the acceptable angle α. FIG. 14(b) shows the results of theoretical calculations of the radar cross section (RCS [dB]) of a 10 mm × 10 mm metal plate 130 for the radar incident angle θ shown in FIG. 14(a). The horizontal axis in FIG. 14(b) represents the absolute value of the incident angle. An example of theoretical calculations is shown in Table 14-1 in Chapter 14.2 of M.I. Skolnik, “Radar Handbook,” 2nd Edition, McGraw-Hill Publishing Company, New York, 1990. The acceptable angle α is defined as the incident angle (approximately 8 degrees) at which the radar cross section is lower than the maximum value by a predetermined value, e.g., −10 dB. From FIG. 14(b), it can be seen that no side lobes are generated if the incident angle is less than the acceptable angle α. The acceptable angle is not limited to 8 degrees and may be other angles.

[0068] When the azimuth angle θs is a negative angle, if 0<θd<α, the selector 114 operates all antennas in the cluster.

[0069] When the azimuth angle θs is a negative angle, θd<0 or θd>α, the selector 114 does not operate any antennas and does not irradiate the radar.

[0070] When the azimuth angle θs is 0 degrees or a positive angle, if −α<θd<0, the selector 114 operates all antennas in the cluster.

[0071] When the azimuth angle θs is 0 degrees or a positive angle, if θd<−α or θd>0, the selector 114 does not operate any antennas and does not perform radar irradiation.

[0072] Next, the case where the absolute value of the elevation angle φs is 30 degrees or more will be described.

[0073] The selection unit 114 compares the angle difference φd=|φn|−|φs| between the elevation angle φn and the elevation angle φs with the allowable angle α to select an antenna and change the antenna to be operated.

[0074] When the elevation angle θs is a negative angle, if 0<φd<α, the selector 114 activates all antennas in the cluster.

[0075] When the azimuth angle φs is a negative angle, θd<0 or θd>α, the selector 114 does not operate any antennas and does not irradiate the radar.

[0076] When the azimuth angle φs is 0 degrees or a positive angle, if −α<φd<0, the selector 114 operates all antennas in the cluster.

[0077] When the azimuth angle φs is 0 degrees or a positive angle, if φd<−α or φd>0, the selector 114 does not operate any antennas and does not irradiate the radar. The above explanation relates to antenna selection on a cluster-by-cluster basis, but if the radar coordinate origin (xrad, yrad, zrad) is the position of each antenna, it is possible to control whether each antenna operates or not according to the azimuth angle θs and elevation angle φs. Here is an example.

[0078] 5, the received IF signals (digital signals) of all the selected receiving circuits 56 are output from the cluster 30 and transmitted to the signal processing unit 104. The signal processing unit 104 includes a distance estimation unit 116 and an arrival direction estimation unit 118.

[0079] The distance estimation unit 116 includes a fast Fourier transform circuit (FFT circuit). The FFT circuit calculates the intensity of the reflected wave received by the receiving antenna 54. In a radar system using chirp waves, the received IF signal oscillates at a frequency corresponding to the distance between the radar and the target (reflection point). Therefore, the distance estimation unit 116 calculates a range spectrum based on the output signal of the FFT circuit and estimates the range distance (distance to the target) in descending order of power frequency. The distance estimation unit 116 transmits the estimation result to the direction of arrival estimation unit 118.

[0080] The direction of arrival estimation unit 118 estimates the direction of arrival for a specific range distance. The direction of arrival estimation unit 118 extracts a range spectrum corresponding to the frequency at which peak power occurs for each receiving antenna. The received signal of each receiving array antenna in the far field is expressed as follows: Here, it is assumed that the receiving antenna 54 in one receiving module 52 configures a two-dimensional array antenna.

[0081]

number

[0082] Direction of arrival estimation estimates the angle of arrival of the reflected wave from the phase difference based on the element spacing. The direction of arrival estimation method may also use beamforming, Capon, MUSIC, or ESPRIT methods. In this example, beamforming is used. The beamforming method controls the weight for each sweep angle (θi, φk), scans the main beam of the array antenna, and calculates the output power for the received signal of the array antenna. The weights used here are prepared for the number PQ, which is the number of virtual receiving arrays. The weights are expressed in Equation 7.

[0083]

number

[0084] The beamforming output power BF(θi,φk) for the angle (θi,φk) is expressed by Equation 9.

[0085]

number

[0086] The display unit 106 performs aperture synthesis processing based on the output power BF(θi, φk) and displays an image of the inspection object 10. An operator views the image and determines whether or not the inspection object 10 is carrying a hazardous material. Instead of the display unit 106, a machine learning device may be provided, and the machine learning device may determine whether or not the inspection object 10 is carrying a hazardous material based on the output power BF(θi, φk).

[0087] The radar system according to the first embodiment selects an effective combination of a receiving cluster / receiving module / transmitting circuit (i.e., transmitting antenna) and a transmitting cluster / transmitting module / transmitting circuit (i.e., transmitting antenna) based on three-dimensional shape data of the inspection object 10, and transmits and receives radio waves using the selected combination. Since received data that does not contribute to the inspection is not collected, the size of the received data can be kept to the minimum necessary. Therefore, even if the number of antennas is increased, the size of the received data does not increase, making it possible to perform highly accurate inspection. Since the size of the received data is small, the data transfer time and processing time are also short. Furthermore, since the processing time for one radio wave irradiation is short, inspection can be repeated at short intervals.

[0088] 15 is a block diagram illustrating another example of the controller 102A in the radar system according to the first embodiment. The controller 102A does not include the near-infrared light projector 22, the camera 20, and the shape construction unit 112 that are included in the controller 102. This radar system includes a shape sensor 140. The controller 102A includes a communication unit 142 that receives data from the shape sensor 140. The shape sensor 140 detects the three-dimensional shape of the inspection object 10 and outputs three-dimensional shape data. The communication unit 142 acquires the three-dimensional shape from the shape sensor 140 and transmits the three-dimensional shape data to the selection unit 114.

[0089] 16 is a block diagram illustrating another example of the controller 102B in the radar system according to the first embodiment. The controller 102B does not include the near-infrared light projector 22, the camera 20, and the shape construction unit 112 that are included in the controller 102. The controller 102B includes a camera 150 and an image analysis unit 152. The camera 150 captures an image of the inspection object 10 within the inspection area. The image analysis unit 152 analyzes the image captured by the camera 150 by image processing and obtains three-dimensional shape data of the inspection object 10. The image analysis unit 152 transmits the three-dimensional shape data to the selection unit 114.

[0090] The controller 102A shown in FIG. 15 or the controller 102B shown in FIG. 16 also allows the selection unit 114 to select a combination of receiving cluster / receiving module / transmitting circuit (i.e., transmitting antenna) and transmitting cluster / transmitting module / transmitting circuit (i.e., transmitting antenna) that contributes to the inspection, depending on the shape, posture, or position of the inspection object 10.

[0091] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0092] 10...inspection object, 16, 18, 26...panel, 20...near-infrared camera, 22...near-infrared light projector, 30...cluster, 42...transmitting module, 44...transmitting antenna, 52...receiving module, 54...receiving antenna, 102...controller, 104...processing unit, 106...display unit, 112...shape construction unit, 114...selection unit, 116...distance estimation unit, 118...arrival direction estimation unit

Claims

1. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; a processing unit connected to the plurality of transmitting antennas and the plurality of receiving antennas; The processing unit When the shape of the surface of the inspection target facing the substrate is convex toward the substrate in one direction, some of the transmitting antennas that are arranged in a central portion of the substrate in the one direction are selected from the plurality of transmitting antennas, and some of the receiving antennas that are arranged in a central portion of the substrate in the one direction are selected from the plurality of receiving antennas, If the shape of the surface of the object to be inspected that faces the board is not convex toward the board in the one direction, selecting all of the plurality of transmitting antennas and all of the plurality of receiving antennas; transmitting radio waves from the selected transmitting antenna; A radar system that acquires radio wave signals received from the selected receiving antenna and inspects the inspection object.

2. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; a processing unit connected to the plurality of transmitting antennas and the plurality of receiving antennas; The processing unit detecting an incident angle of the reflected wave of the inspection object relative to the center of the substrate based on a position of the inspection object in one direction parallel to the substrate; If the incident angle is within a first angle, selecting some of the transmitting antennas that are disposed in a center portion of the substrate in the one direction from among the plurality of transmitting antennas, and selecting some of the receiving antennas that are disposed in a center portion of the substrate in the one direction from among the plurality of receiving antennas; if the incident angle is not within a first angle, selecting all of the plurality of transmitting antennas and all of the plurality of receiving antennas; transmitting radio waves from the selected transmitting antenna; A radar system that acquires radio wave signals received from the selected receiving antenna and inspects the inspection object.

3. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; a processing unit connected to the plurality of transmitting antennas and the plurality of receiving antennas; The processing unit a normal vector of a point on the surface of the object to be inspected is obtained, and when the absolute value of the angle formed by the normal vector as viewed from the origin on the substrate is within a specific range, some of the transmitting antennas are selected from the plurality of transmitting antennas, and some of the receiving antennas are selected from the plurality of receiving antennas; transmitting radio waves from the selected transmitting antenna; acquiring a radio wave signal received from the selected receiving antenna and inspecting the inspection object; If the absolute value of the angle is not within the specific range, the radar system does not operate the plurality of transmitting antennas and the plurality of receiving antennas.

4. A radar system as described in claim 3, further comprising a detection unit that detects the shape of the object to be inspected and a point on the surface of the object to be inspected.

5. A plurality of transmission modules disposed on the substrate; a plurality of receiving modules disposed on the substrate; Further comprising: each of the plurality of transmitting modules includes one or more transmitting antennas that are part of the plurality of transmitting antennas; each of the plurality of receiving modules includes one or more receiving antennas that are part of the plurality of receiving antennas; The processing unit selecting one or more first transmitting modules that are part of the plurality of transmitting modules, and selecting at least a part of the one or more transmitting antennas included in each of the selected one or more first transmitting modules; 4. The radar system according to claim 1, wherein one or more first receiving modules that are part of the plurality of receiving modules are selected, and at least some of the one or more receiving antennas included in each of the selected one or more first receiving modules are selected.

6. Further comprising a plurality of clusters, each of the plurality of clusters comprises at least one transmitting module and at least one receiving module; each of the at least one transmitting module includes one or more transmitting antennas that are part of the plurality of transmitting antennas; each of the at least one receiving module includes one or more receiving antennas that are part of the plurality of receiving antennas; The processing unit selecting one transmission cluster from the plurality of clusters, selecting one or more first transmission modules from the at least one transmission module included in the selected one transmission cluster, and selecting at least a portion of the one or more transmission antennas included in each of the selected one or more first transmission modules; 4. The radar system according to claim 1, wherein at least one receiving cluster is selected from the plurality of clusters, one or more first receiving modules are selected from at least one receiving module included in each of the at least one selected receiving cluster, and at least a portion of the one or more receiving antennas included in each of the selected one or more first receiving modules is selected.

7. 5. The radar system according to claim 4, wherein the detection unit comprises: a projector that projects a grid pattern onto the inspection object; a camera that captures an image of the grid pattern projected onto the inspection object; and a calculation unit that generates three-dimensional shape data of the inspection object from the image of the grid pattern captured by the camera.

8. The radar system according to claim 4 , wherein the detection unit receives the three-dimensional shape data from a first sensor that acquires the three-dimensional shape data of the inspection object.

9. 5. The radar system according to claim 4, wherein the detection unit comprises: a camera that photographs the inspection object; and a calculation unit that analyzes the image of the inspection object photographed by the camera and generates three-dimensional shape data of the inspection object.

10. The plurality of transmitting antennas are equally spaced apart, 4. The radar system according to claim 1, wherein the plurality of receiving antennas are spaced apart at equal intervals.

11. The plurality of transmitting antennas are spaced apart at irregular intervals, 4. The radar system according to claim 1, wherein the plurality of receiving antennas are not spaced apart from one another.

12. the plurality of transmitting antennas constitute a minimum redundant array antenna; 4. The radar system according to claim 1, wherein the plurality of receiving antennas constitute a minimum redundancy array antenna.

13. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; An inspection method using a radar system including the plurality of transmitting antennas and a processing unit connected to the plurality of receiving antennas, comprising: Detect the shape of the inspection object, When the shape of the surface of the inspection target facing the substrate is convex toward the substrate in one direction, some of the transmitting antennas that are arranged in a central portion of the substrate in the one direction are selected from the plurality of transmitting antennas, and some of the receiving antennas that are arranged in a central portion of the substrate in the one direction are selected from the plurality of receiving antennas, If the shape of the surface of the object to be inspected that faces the board is not convex toward the board in the one direction, selecting all of the plurality of transmitting antennas and all of the plurality of receiving antennas; transmitting radio waves from the selected transmitting antenna; causing the selected receiving antenna to receive radio waves; an inspection method for inspecting the inspection object based on a signal from the selected receiving antenna;

14. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; An inspection method using a radar system including the plurality of transmitting antennas and a processing unit connected to the plurality of receiving antennas, comprising: detecting an incident angle of the reflected wave of the inspection object relative to the center of the substrate based on a position of the inspection object in one direction parallel to the substrate; If the incident angle is within a first angle, selecting some of the transmitting antennas that are disposed in a center portion of the substrate in the one direction from among the plurality of transmitting antennas, and selecting some of the receiving antennas that are disposed in a center portion of the substrate in the one direction from among the plurality of receiving antennas; if the incident angle is not within a first angle, selecting all of the plurality of transmitting antennas and all of the plurality of receiving antennas; transmitting radio waves from the selected transmitting antenna; An inspection method for inspecting the inspection object by acquiring a radio wave signal received from the selected receiving antenna.

15. A plurality of transmitting antennas disposed on a substrate; a plurality of receiving antennas disposed on the substrate; An inspection method using a radar system including the plurality of transmitting antennas and a processing unit connected to the plurality of receiving antennas, comprising: Calculate the normal vector of a point on the surface of the object to be inspected, selecting some of the transmitting antennas from the plurality of transmitting antennas and some of the receiving antennas from the plurality of receiving antennas when the absolute value of the angle formed by the normal vector as viewed from the origin on the substrate is within a specific range; transmitting radio waves from the selected transmitting antenna; acquiring a radio wave signal received from the selected receiving antenna and inspecting the inspection object; If the absolute value of the angle is not within the specific range, the plurality of transmitting antennas and the plurality of receiving antennas are not operated.

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