Coil structure of a through-type probe and through-type probe

Abstract

The application discloses a coil structure of a through-type detector and the through-type detector, which comprises double-side oppositely arranged transmitting coil groups, and an intermediate channel is formed between the double-side transmitting coil groups for passing through a measured object; different frequency currents are alternately flowed in single-side transmitting coils of the double-side transmitting coil groups, so that a magnetic field of a measured area distribution is alternately changed in a time when the different frequency currents are flowed. The single-side transmitting coils alternately flow the different frequency currents, the double-side transmitting coil groups generate different magnetic field distributions of the measured area under different frequencies, and the magnetic induction intensity of a same point in a space of the measured area is changed by using the alternate change of the different magnetic fields, so that the missing detection caused by the weak magnetic induction intensity of a certain area or some areas in the single magnetic field distribution of the space of the measured area is avoided.

Description

Technical Field

[0001] This invention relates to the field of walk-through detector technology, and more particularly to a coil structure for a walk-through detector and a walk-through detector. Background Technology

[0002] Walk-through detectors are widely used in various fields. In metal processing plants or raw material smelting plants, walk-through detectors are often installed to prevent workers from carrying metal panels or scrap materials produced on-site out of the factory. Similarly, in government offices, examination venues, and other similar locations, walk-through detectors are also used to prohibit personnel from carrying mobile phones. In the application of walk-through detectors, the large and rapid flow of people necessitates highly efficient and reliable detection. However, in existing traditional detection technologies, transmitting coils are placed inside the side panels of the detector. The magnetic lines of force inside the detector are distributed horizontally from one side panel to the other. When a person carrying a metal panel or mobile phone passes through the detector while keeping the maximum cross-section of the metal panel or mobile phone parallel to the horizontal magnetic lines of force, the cross-section of the metal panel or mobile phone passing through the horizontal magnetic lines of force is very small, resulting in fewer magnetic lines passing through. Therefore, the generated eddy current effect is small, and the detected eddy current signal is weak, which may lead to missed detections by the detector. This significantly reduces the reliability of the detection results. In other words, traditional walk-through detectors cannot guarantee that metal panels or mobile phones will be detected in any posture. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a coil structure for a through-type detector and a through-type detector, thereby improving the detection reliability of the through-type detector and reducing missed detections.

[0004] The present invention adopts the following technical solution:

[0005] On one hand, the present invention provides a coil structure for a through-type detector, characterized in that it includes two opposing sets of transmitting coils, with an intermediate channel formed between the two sets of transmitting coils for the passage of the object being measured;

[0006] Different frequencies of current flow alternately through the single-sided transmitting coil of the double-sided transmitting coil group, so that the magnetic field distributed in the measured area is constructed and alternately changed during the time that the different frequency currents flow.

[0007] In this scheme, the single-sided transmitting coil alternately carries currents of different frequencies, and the double-sided transmitting coil group constructs different magnetic field distributions in the measured area during the time when currents of different frequencies flow. By using the alternating changes of different magnetic fields to change the magnetic induction intensity at the same point in the measured area, the scheme avoids the possibility of a single magnetic field distribution in the measured area having a weak magnetic induction intensity in a certain area or some areas, which would cause missed detection.

[0008] Electromagnetic fields generated by currents of different frequencies cooperate to form a spatial electromagnetic field in the x, y, and z directions. By using the information received from the three directions, the three-dimensional metal information of the object under test can be obtained, and a rough judgment can be made on the shape of the object under test.

[0009] Alternatively, in another scheme, the single-sided transmitting coil alternately carries currents of different frequencies, and the double-sided transmitting coil group constructs the same magnetic field distribution in the measured area during the time when the currents of different frequencies flow. If the magnetic field distribution of the measured area generated by the first frequency can already generate a three-dimensional first magnetic field, the magnetic field distribution of the measured area generated by the second frequency does not need to be different from the first magnetic field.

[0010] That is, the magnetic field distributed in the measured area can be the same or different when current of different frequencies flows for different periods of time.

[0011] As an improvement to the above scheme, the current frequencies of the two-sided transmitting coil groups are the same. The phase difference of the current signals of the two-sided transmitting coil groups is 0 degrees or 180 degrees. In this scheme, when the phase difference of the current signals of the two-sided transmitting coils is 0 degrees, the magnetic field is horizontally distributed along the x-axis. When the phase difference of the current signals of the two-sided transmitting coils is 180 degrees, the normals of the two-sided transmitting coils are relatively compressed, resulting in magnetic field offsets in the y-axis and z-axis. Under the alternating transformation of the two different magnetic fields, a spatial electromagnetic field in the x, y, and z directions is formed, which increases the spatial magnetic induction intensity and avoids missed detection.

[0012] As an improvement to the above scheme, the current frequencies of the bilateral transmitting coil groups are different. According to the coil structure of the through-type detector as described in claim 4, the phase difference of the current signals of the bilateral transmitting coil groups is 0 degrees or 180 degrees. In this scheme, when the phase difference of the current signals of the bilateral transmitting coils is 0 degrees, the magnetic field is horizontally distributed along the x-axis; when the phase difference of the current signals of the bilateral transmitting coils is 180 degrees, the normals of the bilateral transmitting coils are relatively compressed, resulting in magnetic field offsets along the y-axis and z-axis. Under the alternating transformation of the two different magnetic fields, a spatial electromagnetic field in the x, y, and z directions is formed, increasing the spatial magnetic induction intensity and avoiding missed detections.

[0013] Optionally, the current flow paths within the bilateral transmitting coils may be the same or different. In this design, one side of the bilateral transmitting coil is equipped with a U-shaped coil, while the other side is equipped with an upper coil and a lower coil, resulting in different current flow paths within the bilateral transmitting coils; if the bilateral coil structures are the same, then the current flow paths are the same.

[0014] Preferably, the duration of current flow at different frequencies can be preset.

[0015] Preferably, a preset switching pause time is provided between the times when current flows at different frequencies to ensure that the system remains stable when switching between different frequencies.

[0016] Preferably, the single-sided transmitting coil assembly includes an upper coil and a lower coil wound in opposite directions. The upper coil and the lower coil are electrically connected or disconnected. Currents of different frequencies within the single-sided transmitting coil flow through the same or different current-carrying loops. In this embodiment, when the upper coil and the lower coil are electrically connected, currents of different frequencies within the single-sided transmitting coil flow through the same current-carrying loop; when the upper coil and the lower coil are electrically disconnected, both the upper coil and the lower coil simultaneously flow through the current-carrying loop of frequency 1, only the upper coil flows through the current-carrying loop of frequency 2, and only the lower coil flows through the current-carrying loop of frequency 3. Therefore, currents of different frequencies within the single-sided transmitting coil flow through different current-carrying loops.

[0017] Preferably, the coils of the bilateral transmitting coil group have the same shape and size, and their orthographic projections overlap.

[0018] Optionally, the coils of the bilateral transmitting coil group have different shapes and sizes, and the orthographic projections of the coils overlap.

[0019] Optionally, at least two pairs of the bilateral transmitting coil groups are provided.

[0020] Optionally, the coil positions of at least two pairs of said bilateral transmitting coil groups are staggered.

[0021] As an improvement to the above solution, the transmitting coil unit structure, consisting of an upper coil and a lower coil on both sides or one side, has a coil located at its upper and / or bottom. The frequency of this coil is different from the frequency of the transmitting coil unit structure. This solution can increase the magnetic induction intensity of the magnetic field in the measured area, improve the detection rate, and prevent cross-regional detection of the measured object.

[0022] Optionally, the number of coil turns in the bilateral transmitting coil group may be equal or unequal.

[0023] On the other hand, the present invention provides a pass-through detector, including a main body structure, wherein a host and a coil structure for the pass-through detector are disposed within the main body structure, characterized in that the coil structure for the pass-through detector is the coil structure of the pass-through detector.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: In the middle channel of the detector, the current in the coil is an alternating current, and different frequencies of current flow alternately through the bilateral transmitting coils to generate the same or different electromagnetic fields. The electromagnetic fields generated by the different frequency currents cooperate with each other to form a spatial electromagnetic field in three directions: x, y, and z. By using the information received in the three directions, the three-dimensional metal information of the tested item is obtained, and the shape of the tested item is roughly judged. No matter what posture the tested item passes through the detector, it can be detected by the system, which greatly improves the reliability of metal detection, effectively avoids the phenomenon of missed or wrong detection by walk-through detectors, and ensures the smooth progress of security inspection work. Attached Figure Description

[0025] Figure 1a This is a schematic diagram of a first example of the coil structure of the through-type detector of the present invention at a first frequency;

[0026] Figure 1b This is a schematic diagram of a first example of the coil structure of the through-type detector of the present invention at a second frequency;

[0027] Figure 2a This is a front view of a first example of the coil structure of the through-type detector of the present invention at a first frequency;

[0028] Figure 2b This is a front view of a first example of the coil structure of the through-type detector of the present invention at a second frequency;

[0029] Figure 3a This is a top view of a first example of the coil structure of the through-type detector of the present invention at a first frequency;

[0030] Figure 3b This is a top view of a first example of the coil structure of the through-type detector of the present invention at a second frequency;

[0031] Figure 4a This is a bottom view of a first example of the coil structure of the through-type detector of the present invention at a first frequency;

[0032] Figure 4b This is a bottom view of a first example of the coil structure of the through-type detector of the present invention at a second frequency;

[0033] Figure 5a This is a schematic diagram of the first frequency current flow direction of the coil structure of the through-type detector of the present invention in a first example;

[0034] Figure 5b This is a schematic diagram of the first frequency current flow direction in a second example of the coil structure of the through-type detector of the present invention;

[0035] Figure 5cThis is a schematic diagram of the second frequency current flow direction in a first example of the coil structure of the through-type detector of the present invention;

[0036] Figure 5d This is a schematic diagram of the second frequency current flow direction of a second example of the coil structure of the through-type detector of the present invention;

[0037] Figure 6 This is a schematic diagram of a third example of the coil structure of the through-type detector of the present invention;

[0038] Figure 7 This is a schematic diagram of the fourth example of the coil structure of the through-type detector of the present invention;

[0039] Figure 8 This is a schematic diagram of the fifth example of the coil structure of the through-type detector of the present invention;

[0040] Figure 9 This is a schematic diagram of the sixth example of the coil structure of the through-type detector of the present invention;

[0041] Figure 10 This is a schematic diagram of the seventh example of the coil structure of the through-type detector of the present invention. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0043] The coil structure for a through-type detector described in various embodiments of the present invention includes a transmitting coil 1, a transmitting coil 2, and a receiving coil (not shown). Transmitting coil 1 and transmitting coil 2 are respectively connected to the receiving coil via electromagnetic coupling. Transmitting coil 1 and transmitting coil 2 are located on opposite sides of the door panel of the through-type detector 300, forming an intermediate channel for the passage of the object to be measured. The coil current of transmitting coils 1 and 2 is an alternating current. When an excitation signal is sent through the transmitting coil, the receiving coil generates an induced signal. The alternating current in the transmitting coil group allows the receiving coil to detect the object by inducing a voltage value.

[0044] The coil structure of the through-type detector and all embodiments thereof conform to the following rules:

[0045] In terms of current flow rules, current of multiple frequencies flows through transmitting coil 1 (or transmitting coil 2).

[0046] Regarding the flow path rules, there are multiple ways for the current to flow through the transmitting coil 1 (or transmitting coil 2). Currents of different frequencies can use the same flow path or different flow paths.

[0047] Regarding the timing rule of alternating current flow at different times, the time for currents of different frequencies to flow in transmitting coil 1 (or transmitting coil 2) can be the same or different.

[0048] Regarding the time interval rules for current switching at different times, there may or may not be a time interval when different frequencies of current switch within transmitting coil 1 (or transmitting coil 2).

[0049] Regarding the magnetic field generated by the current at different times, the magnetic fields generated by currents of different frequencies in transmitting coil 1 (or transmitting coil 2) can be the same or different.

[0050] Regarding the rules for the shape and size of the coils, the shape and size of transmitting coil 1 and transmitting coil 2 can be the same or different.

[0051] Regarding the number of turns, the number of turns of transmitting coil 1 and transmitting coil 2 can be equal or unequal.

[0052] In terms of positioning rules, the positions of transmitting coil 1 and transmitting coil 2 can be symmetrical about left and right along the middle channel, or they can be asymmetrical.

[0053] Regarding wiring rules, different parts of the transmitting coils within a single-sided transmitting coil group may or may not have actual electrical connections.

[0054] In terms of coil type and quantity rules, there can be multiple sets of identical or different transmitting coils.

[0055] refer to Figure 1a and Figure 1b , Figure 1a This is a schematic diagram of a first example of the coil structure of the through-type detector of the present invention at a first frequency. Figure 1b This is a schematic diagram of a first example of the coil structure of the through-type detector of the present invention at a second frequency. The transmitting coil 1 of this through-type detector consists of an upper coil 111 and a lower coil 112, both wound in opposite directions on the same conductor. The transmitting coil 2 consists of an upper coil 211 and a lower coil 212, both wound in opposite directions on the same conductor. The transmitting coils 1 and 2 have the same shape and size, with their centers overlapping, meaning their coil projections overlap. The transmitting coils 1 and 2 have the same frequency, and the alternating flow of currents at the first and second frequencies generates different magnetic fields.

[0056] like Figure 1aA rectangular coordinate system is established as shown. Transmitting coil 1 and transmitting coil 2 are parallel to the y-axis and z-axis, and perpendicular to the x-axis. The y-axis is the channel through which the object being measured passes. Transmitting coil 1 and transmitting coil 2 are equidistant from the z-axis and y-axis. At a certain moment when a current of the first frequency flows through transmitting coil 1 and transmitting coil 2, viewed along the positive x-axis, the current in the upper coil 111 of transmitting coil 1 flows counterclockwise, and the current in the lower coil 112 of transmitting coil 1 flows clockwise. Similarly, the current in the upper coil 211 of transmitting coil 2 flows counterclockwise, and the current in the lower coil 212 of transmitting coil 2 flows clockwise. According to the right-hand rule, at this moment, the magnetic field lines generated by the upper coil 111 are parallel to the negative x-axis, the magnetic field lines generated by the upper coil 211 are parallel to the negative x-axis, and the magnetic field lines generated by the lower coil 112 are parallel to the positive x-axis.

[0057] like Figure 1b A rectangular coordinate system is established as shown. Transmitting coil 1 and transmitting coil 2 are parallel to the y-axis and z-axis, and perpendicular to the x-axis. The y-axis is the channel through which the object being measured passes. Transmitting coil 1 and transmitting coil 2 are equidistant from the z-axis and y-axis. At a certain moment when the second frequency current flows through transmitting coil 1 and transmitting coil 2, looking along the positive x-axis, the current in the upper coil 111 of transmitting coil 1 flows counterclockwise, and the current in the lower coil 112 of transmitting coil 1 flows clockwise. Similarly, the current in the upper coil 211 of transmitting coil 2 flows clockwise, and the current in the lower coil 212 of transmitting coil 2 flows counterclockwise. According to the right-hand rule, at this moment, the magnetic field lines generated by the upper coil 111 are parallel to the negative x-axis, the magnetic field lines generated by the upper coil 211 are parallel to the positive x-axis, the magnetic field lines generated by the lower coil 112 are parallel to the positive x-axis, and the magnetic field lines generated by the lower coil 212 are parallel to the negative x-axis.

[0058] Please refer to Figure 2a , Figure 2a This is a front view of the first frequency of the first example of the coil structure of the through-type detector of the present invention; at a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with the first frequency current, the magnetic field lines of the left and right coils on the same horizontal plane are in the same direction, so a magnetic field in the x-axis direction is generated in this region; in the vertical direction near the junction area of ​​the upper and lower coils of the transmitting coil, the magnetic field lines surround the junction segment in a counterclockwise direction, so a magnetic field in the z-axis direction is generated in this region.

[0059] Please refer to Figure 2b , Figure 2b This is a front view of the second frequency of the first example of the coil structure of the through-type detector of the present invention; at a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with the second frequency current, the magnetic field lines of the left and right coils on the same level are opposite in direction, and the magnetic field lines in the middle channel are deflected in the direction parallel to the y-axis, so a magnetic field in the y-axis direction is generated in this region.

[0060] Please refer to Figure 3a , Figure 3a This is a top view of the first frequency of the first example of the coil structure of the through-type detector of the present invention; at a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with the first frequency current, the magnetic field lines of the left and right coils are in the same direction, so a magnetic field in the x-axis direction is generated in this region.

[0061] Please refer to Figure 3b , Figure 3b This is a top view of the coil structure of the through-type detector of the present invention at a second frequency, representing a first example. At a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with a second frequency current, the magnetic field lines of the left and right coils are in opposite directions, and the magnetic field lines in the middle channel deflect in the z-axis direction, thus generating a magnetic field in the z-axis direction in this region.

[0062] Please refer to Figure 4a , Figure 4a This is a bottom view of the first frequency of the first example of the coil structure of the through-type detector of the present invention; at a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with the first frequency current, the magnetic field lines of the left and right coils are in the same direction, so a magnetic field in the x-axis direction is generated in this region.

[0063] Please refer to Figure 4b , Figure 4b This is a bottom view of the coil structure of the through-type detector of the present invention at a second moment in the first example; at a certain moment when the transmitting coil 1 and the transmitting coil 2 are flowing with the second frequency current, the magnetic field lines of the left and right coils are in opposite directions, and the magnetic field lines in the middle channel are deflected in the direction parallel to the z-axis, so a magnetic field in the z-axis direction is generated in this region.

[0064] The time that the transmitting coil 1 and the transmitting coil 2 have the first frequency current flowing through them and the second frequency current flowing through them can be the same or different. There is a switching pause time between the two times, and the length of the switching pause time can be set to ensure stability when switching between different frequencies. During the period when transmitting coils 1 and 2 are energized by the first frequency current, the signal phase difference between their two sides is 0 degrees, and the normals of the two coils are in the same direction. The magnetic field in the measured area between transmitting coils 1 and 2 is mainly a horizontal magnetic field along the x-axis, as well as a ring-shaped magnetic field at the junction of the upper and lower coils, with the magnetic induction intensity being the greatest along the x-axis. During the period when transmitting coils 1 and 2 are energized by the second frequency current, the signal phase difference between their two sides is 180 degrees, and the normals of the two coils are opposite. This results in the magnetic field lines of the upper coils being relatively compressed, causing the magnetic field lines to shift towards the y and z axes in the middle channel. The normals of the lower coils are opposite, forming a larger ring-shaped magnetic field in the middle channel, with the magnetic induction intensity being the greatest in the y and z axis directions of the middle channel. By alternating the magnetic field distributed in the measured area during the period when transmitting coils 1 and 2 are energized by the first frequency current and the second frequency current, the magnetic field in the measured area is maximized. This method alters the magnetic field strength at the same point within the measured area, essentially performing two tests on the same point. When the metal plate and the phone's maximum cross-section are parallel to the x-axis, the magnetic field lines in the measured area pass through the sides of the metal plate and phone when the first frequency current flows through the coil, resulting in a small eddy current effect and making it difficult to detect the object, leading to missed detections. After the alternation, when the second frequency current flows through the coil, the magnetic field strength generated in the z-axis direction of the middle channel is at its maximum. The magnetic field lines in the measured area pass through the maximum cross-section of the metal plate and phone, resulting in a maximum eddy current effect and enabling the detection of the object. However, when the metal plate and the phone's maximum cross-section are parallel to the z-axis, the magnetic field lines in the measured area, parallel to the x-axis, pass through the maximum cross-section of the metal plate and phone when the first frequency current flows through the coil, resulting in a maximum eddy current effect and enabling the detection of the object. Conversely, when the second frequency current flows through the coil, the magnetic field lines in the measured area, parallel to the z-axis, pass through the sides of the metal plate and phone, resulting in a small eddy current effect and making it difficult to detect the object, leading to missed detections. By alternating and complementing different magnetic fields distributed in the space under test at different times, a magnetic field is formed that exists simultaneously in the x, y, and z axes. Therefore, regardless of the posture in which the metal plate or mobile phone passes through the detector, an effective eddy current magnetic field can be generated at its maximum cross-sectional area, which greatly improves the detection rate of the tested items and enhances the reliability of the pass-through detector.

[0065] Further analysis of the information collected along the x, y, and z axes can determine the three-dimensional metal information of the object being measured, thereby making a rough judgment on the metal shape of the object.

[0066] The second embodiment of the coil structure of the through-type detector of the present invention differs from the first embodiment in that the current flow direction is different, but the working principle is the same.

[0067] Please refer to Figure 5a , Figure 5a This is a schematic diagram of the first frequency current flow direction of the coil structure of the through-type detector of the present invention. Looking along the positive x-axis, the upper coil 111 and the upper coil 211 have a counterclockwise current flow, while the lower coil 112 and the lower coil 212 have a clockwise current flow.

[0068] Please refer to Figure 5b , Figure 5b This is a schematic diagram of the first frequency current flow direction in a second example of the coil structure of the through-type detector of the present invention. Looking along the positive x-axis, the upper coil 111 and upper coil 211 both have a clockwise current flow, while the lower coil 112 and lower coil 212 both have a counter-clockwise current flow.

[0069] Please refer to Figure 5c , Figure 5c This is a schematic diagram of the second frequency current flow direction in a first embodiment of the coil structure of the through-type detector of the present invention. Looking along the positive x-axis, the upper coil 111 flows counterclockwise, the upper coil 211 flows clockwise, the lower coil 112 flows clockwise, and the lower coil 212 flows counterclockwise.

[0070] Please refer to Figure 5d , Figure 5d This is a schematic diagram of the second frequency current flow direction of the coil structure of the through-type detector of the present invention in a second example. Viewed along the positive x-axis, the upper coil 111 has a clockwise current flow, the upper coil 211 has a counterclockwise current flow, the lower coil 112 has a counterclockwise current flow, and the lower coil 212 has a clockwise current flow.

[0071] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the third example of the coil structure of the through-type detector of the present invention. The third embodiment is based on the first embodiment, the only difference being that: the transmitting coil 1 and the transmitting coil 2 have the same shape but different sizes, the coil centers coincide, and the projected portions of the bilateral coils overlap.

[0072] Please refer to Figure 7 , Figure 7 This is a schematic diagram of the fourth example of the coil structure of the through-type detector of the present invention. Example 4 is based on Example 1, the only difference being that: the transmitting coil 1 and the transmitting coil 2 have the same shape and size, the coil centers do not coincide, and the projected portions of the bilateral coils overlap; that is, the transmitting coil 1 and the transmitting coil 2 are asymmetrical about the y-axis, but the projected portions of the coils overlap.

[0073] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the fifth embodiment of the coil structure of the through-type detector of the present invention. The difference between embodiment five and embodiment one is only that: the upper coil 111 and the lower coil 112 of the transmitting coil 1 are not actually electrically disconnected, while the upper coil 211 and the lower coil 212 of the transmitting coil 2 are electrically disconnected. The two embodiments operate on the same principle.

[0074] Please refer to Figure 9 , Figure 9 This is a schematic diagram of the sixth embodiment of the coil structure of the through-type detector of the present invention. Embodiment Six is ​​based on Embodiment One, with the only difference being that two pairs of transmitting coil groups are arranged on the side panels: transmitting coil 1 and transmitting coil 2 form one pair, and transmitting coil 1' and transmitting coil 2' form another pair. The two pairs of transmitting coil groups can be identical or staggered. The number of transmitting coil pairs in this embodiment can be set as needed.

[0075] refer to Figure 10 , Figure 10 This is a schematic diagram of the seventh example of the coil structure of the through-type detector of the present invention. Example seven is based on example one, with the only difference being that, in addition to transmitting coil 1 and transmitting coil 2, this example also includes transmitting coils 3, 4, 5, and 6 with different coil structures in other areas. The frequencies of coils 3, 4, 5, and 6 are different from the frequencies of transmitting coils 1 and 2. The different frequencies are set to prevent cross-regional detection of the object under test and to strengthen the magnetic field distributed in the x, y, and z directions along the middle channel.

[0076] The eighth embodiment of the coil structure of the through-type detector provided by the present invention includes a transmitting coil 1 comprising an upper coil 111 and a lower coil 112, and a transmitting coil 2 comprising a U-shaped coil. The orthographic projections of the upper coil 111 and the lower coil 112 overlap with the transmitting coil 2. Multiple frequencies of current flow through the transmitting coil 1 (or transmitting coil 2).

[0077] On the other hand, a walk-through detector is provided, including a detector housing and an X-ray coil assembly, a receiving coil, and a main unit mounted on a controller housing. A security checkpoint is located in the middle of the detector housing. Transmitting coil assembly 1 and transmitting coil assembly 2 are respectively located on both sides of the security checkpoint. The transmitting coil assembly and the receiving coil are connected by electromagnetic coupling. Both the transmitting coil assembly and the receiving coil are electrically connected to the main unit. The current in the coils of the transmitting coil assembly is alternating current. Transmitting coil 1 consists of an upper coil 111 and a lower coil 112, which are coils wound in opposite directions on the same conductor. Transmitting coil 2 consists of an upper coil 211 and a lower coil 212, which are coils wound in opposite directions on the same conductor. Transmitting coil 1 and transmitting coil 2 have the same shape and size, and the centers of the two coils coincide. The same or different magnetic fields flow alternately through transmitting coil 1 and transmitting coil 2, forming electromagnetic fields in the x, y, and z directions. The two different magnetic field distributions complement each other, improving the detection rate of the tested item and enhancing the reliability of the through-type detector. Using the information received from the three directions, the three-dimensional metallic information of the tested item is obtained, and a rough judgment of the shape of the tested item is made.

[0078] The through-type detector includes a coil structure, and its specific implementation is described in Examples 1 to 8, which will not be repeated here.

[0079] Using the coil structure of this invention to construct a through-type detector can effectively solve the problem of high false negative rate in through-type detectors, and greatly improve the reliability and detection efficiency of through-type detectors.

[0080] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A coil structure for a through-type detector, characterized in that, It includes opposing double-sided transmitting coil groups, with an intermediate channel formed between the double-sided transmitting coil groups for the object to be measured to pass through; Different frequencies of current flow alternately through the single-sided transmitting coil group of the double-sided transmitting coil group, so that the magnetic field distributed in the measured area is constructed and alternately changed during the time when the different frequency currents flow; the single-sided transmitting coil group includes an upper coil and a lower coil wound in opposite directions. During the time that current flows at different frequencies, the phase difference of the current signal of the bilateral transmitting coil group is 0 degrees or 180 degrees.

2. The coil structure of the through-type detector as described in claim 1, characterized in that, The current frequencies of the two-sided transmitting coil groups are the same.

3. The coil structure of the through-type detector as described in claim 1, characterized in that, The current frequencies of the two-sided transmitting coil groups are different.

4. The coil structure of the through-type detector as described in claim 1, characterized in that, The current flow paths within the bilateral transmitting coil groups may be the same or different.

5. The coil structure of the through-type detector as described in claim 1, characterized in that, The duration of current flow at different frequencies can be preset.

6. The coil structure of the through-type detector as described in claim 1, characterized in that, A preset pause time is set between the time when currents of different frequencies flow.

7. The coil structure of the through-type detector as described in any one of claims 1-6, characterized in that, The upper coil and the lower coil are electrically connected or disconnected.

8. The coil structure of the through-type detector as described in claim 7, characterized in that, The currents of different frequencies within the single-sided transmitting coil group flow through the same or different current loops.

9. The coil structure of the through-type detector as described in any one of claims 1-6, characterized in that, The coils in the bilateral transmitting coil group have the same shape and size, and their orthographic projections overlap.

10. The coil structure of the through-type detector as described in any one of claims 1-6, characterized in that, The coils of the bilateral transmitting coil group have different shapes and sizes, and their orthographic projections overlap.

11. The coil structure of the through-type detector as described in claim 1, characterized in that, At least two pairs of the bilateral transmitting coil groups are provided.

12. The coil structure of the through-type detector as described in claim 11, characterized in that, The coil positions of at least two pairs of said bilateral transmitting coil groups are staggered.

13. The coil structure of the through-type detector as described in any one of claims 1-6, characterized in that, The transmitting coil unit structure, consisting of an upper coil and a lower coil on both sides or one side, has a coil on its upper and / or bottom sides, the frequency of which is different from the frequency of the transmitting coil unit structure.

14. The coil structure of the through-type detector as described in any one of claims 1-6, characterized in that, The number of turns in the bilateral transmitting coil groups may be equal or unequal.

15. A pass-through detector, comprising a main body structure, wherein a main unit and a coil structure for the pass-through detector are disposed within the main body structure, characterized in that, The coil structure of the pass-through detector is as described in any one of claims 1-14.

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