Millimeter-wave imaging device, security inspection device, and security inspection method

Abstract

A millimeter-wave imaging device, comprising: a first millimeter-wave transceiving array (100), which comprises a row of first millimeter-wave transmitting antennas (100T) and a row of first millimeter-wave receiving antennas (100R); and a second millimeter-wave transceiving array (200), which comprises a row of second millimeter-wave transmitting antennas (200T) and a row of second millimeter-wave receiving antennas (200R), wherein the first millimeter-wave transceiving array (100) and the second millimeter-wave transceiving array (200) are respectively configured to transmit and receive millimeter waves to construct a first holographic image and a second holographic image of an object to be inspected. The millimeter-wave imaging device is further configured such that the second millimeter-wave receiving antenna (200R) receives millimeter waves of the first millimeter-wave transmitting antenna (100T) to form a first transmission image, or such that the first millimeter-wave receiving antenna (100R) receives millimeter waves of the second millimeter-wave transmitting antenna (200T) to form a second transmission image. The present application further relates to a security inspection device and a security inspection method.

Description

Millimeter wave imaging device, security inspection device, and security inspection method

[0001] This application claims priority to Chinese patent application No. 202311810579.3, filed on December 26, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the field of security inspection technology, and in particular to a millimeter wave imaging device, a security inspection device, and a security inspection method. Background Art

[0003] In my country, the application of millimeter-wave body imaging security equipment is constantly expanding, playing a positive role in occasions involving personnel security checks and inspections, including civil aviation airports, customs and ports, important places, and major events.

[0004] Millimeter-wave body inspection equipment has a wide inspection range, fast speed, good user experience, and non-contact, digital working mode, making it the preferred choice for various types of smart security.

[0005] There is a need to further improve millimeter wave security inspection equipment and methods, improve inspection accuracy, and reduce missed detections. Summary of the Invention

[0006] The present disclosure aims to provide a millimeter wave imaging device, comprising:

[0007] a first millimeter-wave transceiver array, comprising a row of first millimeter-wave transmitting antennas and a row of first millimeter-wave receiving antennas, wherein the first millimeter-wave transceiver array is configured such that the row of first millimeter-wave receiving antennas corresponds one-to-one with the row of first millimeter-wave transmitting antennas to respectively receive millimeter waves transmitted by the row of first millimeter-wave transmitting antennas;

[0008] a second millimeter-wave transceiver array, comprising a row of second millimeter-wave transmitting antennas and a row of second millimeter-wave receiving antennas, wherein the second millimeter-wave transceiver array is configured such that the row of second millimeter-wave receiving antennas corresponds one-to-one with the row of second millimeter-wave transmitting antennas to respectively receive millimeter waves transmitted by the row of second millimeter-wave transmitting antennas, and the second millimeter-wave transceiver array is arranged substantially opposite to the first millimeter-wave transceiver array to define an inspection channel;

[0009] wherein the first millimeter wave transceiver array is configured to transmit millimeter waves toward the inspected object on the inspection channel and receive reflected millimeter waves to construct a first holographic image of the inspected object, and the second millimeter wave transceiver array is configured to transmit millimeter waves toward the inspected object on the inspection channel and receive reflected millimeter waves to construct a second holographic image of the inspected object; and

[0010] The millimeter wave imaging device is further configured so that the second millimeter wave receiving antenna receives the millimeter waves of the first millimeter wave transmitting antenna to form a first transmission image, and the first millimeter wave receiving antenna receives the millimeter waves of the second millimeter wave transmitting antenna to form a second transmission image.

[0011] In one embodiment, the millimeter wave imaging device is configured to reconstruct a scattering image of the inspected object based on the constructed first holographic image and the second holographic image, and to determine whether the inspected object contains a suspect item by combining the scattering image of the inspected object with at least one of the first transmission image and the second transmission image.

[0012] In one embodiment, the millimeter wave imaging device is configured such that at least part of the row of first millimeter wave transmitting antennas of the first millimeter wave transceiver array transmits millimeter waves toward the inspected object on the inspection channel in a time sequence, and

[0013] At least part of the row of second millimeter wave transmitting antennas of the second millimeter wave transceiver array transmits millimeter waves toward the inspected object on the inspection channel in a time sequence.

[0014] In one embodiment, the millimeter wave imaging device is configured such that at least a portion of the row of first millimeter wave transmitting antennas of the first millimeter wave transceiver array transmits millimeter waves of a frequency of a first group of frequencies toward the inspected object on the inspection channel in a time sequence so that the row of first millimeter wave receiving antennas receives the millimeter waves reflected by the inspected object to construct a first holographic image, and at the same time, at least a portion of the row of second millimeter wave transmitting antennas of the second millimeter wave transceiver array transmits millimeter waves of a different frequency of a second group of frequencies toward the inspected object on the inspection channel in a time sequence so that the row of second millimeter wave receiving antennas receives the millimeter waves reflected by the inspected object to construct a second holographic image.

[0015] In one embodiment, the millimeter wave imaging device is configured such that at least part of the row of first millimeter wave transmitting antennas of the first millimeter wave transceiver array transmits millimeter waves of one frequency of a third group of frequencies toward the inspected object on the inspection channel in a time sequence so that corresponding receiving antennas of the row of second millimeter wave receiving antennas receive the millimeter waves transmitted through the inspection channel to construct a first transmission image, and / or

[0016] At least part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array transmits millimeter waves of a frequency of the fourth group of frequencies toward the inspected object on the inspection channel in a time sequence so that the corresponding receiving antennas in the row of first millimeter-wave receiving antennas receive the millimeter waves transmitted through the inspection channel to construct a second transmission image.

[0017] In one embodiment, the millimeter wave imaging device is configured such that, within one scanning cycle, a portion of the row of first millimeter wave transmitting antennas of the first millimeter wave transceiver array transmits millimeter waves of one frequency of a first group of frequencies toward the inspected object on the inspection channel in a time sequence, and a portion of the row of second millimeter wave transmitting antennas of the second millimeter wave transceiver array transmits millimeter waves of one frequency of a second group of frequencies toward the inspected object on the inspection channel in a time sequence; and

[0018] The remaining parts of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array transmit millimeter waves of a frequency of the third group of frequencies toward the inspected object on the inspection channel in a time sequence, and the millimeter waves are received by the corresponding receiving antennas of the remaining parts of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array, and / or the remaining parts of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array transmit millimeter waves of a frequency of the fourth group of frequencies toward the inspected object on the inspection channel in a time sequence, and the millimeter waves are received by the corresponding receiving antennas of the remaining parts of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array.

[0019] In one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously.

[0020] In one embodiment, the millimeter wave imaging device is configured such that the first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged in a horizontal direction and move in a vertical direction; or

[0021] The first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged in a vertical direction and move in a horizontal direction; or

[0022] The first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged in a vertical direction and move along an arc around the object to be inspected.

[0023] One aspect of the present disclosure provides a security inspection device, including the aforementioned millimeter wave imaging device.

[0024] One aspect of the present disclosure provides a security inspection method, comprising:

[0025] Scanning the inspected object in the inspection channel using the millimeter wave imaging device to construct a first holographic image and a second holographic image as well as a first transmission image and a second transmission image;

[0026] Based on the constructed first holographic image and second holographic image, a scattering image of the inspected object is reconstructed, and the scattering image of the inspected object is combined with at least one of the first transmission image and the second transmission image to determine whether the inspected object contains other items.

[0027] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure, wherein:

[0029] Figure 1 shows a device explaining the principle of millimeter wave holographic measurement;

[0030] FIG2 shows a schematic diagram of plane scanning millimeter wave holographic imaging;

[0031] FIG3 shows a schematic diagram of identifying suspicious objects according to the present disclosure;

[0032] FIG4 shows a schematic diagram of a millimeter wave imaging device according to an embodiment of the present disclosure;

[0033] FIG5 shows a schematic diagram of the working timing of the millimeter wave imaging device according to an embodiment of the present disclosure, which includes four groups of frequencies;

[0034] FIG6 shows a schematic diagram of the working timing of the millimeter wave imaging device according to an embodiment of the present disclosure, which includes three groups of frequencies. DETAILED DESCRIPTION

[0035] To more clearly illustrate the purpose, technical solutions and advantages of the present disclosure, embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the following description of the embodiments is intended to explain and illustrate the overall concept of the present disclosure and should not be understood as limiting the present disclosure. In the specification and drawings, the same or similar reference numerals refer to the same or similar parts or structures. For the sake of clarity, the drawings are not necessarily drawn to scale, and some well-known parts and structures may be omitted in the drawings.

[0036] Unless otherwise defined, technical or scientific terms used in this disclosure should have the ordinary meaning understood by a person of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and similar expressions used in this disclosure do not denote any order, quantity, or importance, but are simply used to distinguish different components. The terms "a" or "an" do not exclude a plurality. "Include" or "comprising" and similar expressions mean that the element or object preceding the word includes the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects. "Connected" or "connected" and similar expressions are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," "top," or "bottom" are used only to indicate relative positional relationships; if the absolute position of the described object changes, the relative positional relationship may also change accordingly. When an element, such as a layer, film, region, or substrate, is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element, or intervening elements may be present.

[0037] Millimeter-wave electromagnetic radiation, with wavelengths ranging from 1 to 10 mm and corresponding frequencies from 30 to 300 GHz, has widespread applications in radar, guidance, remote sensing, communications, perception, and nondestructive testing. Many materials impenetrable at optical frequencies are nearly transparent to millimeter waves, making millimeter-wave imaging inherently advantageous in many situations, making it suitable for contactless, non-invasive security inspections.

[0038] Millimeter waves, with wavelengths on the millimeter scale, lack ionizing properties compared to X-rays and have difficulty penetrating human skin, making low-power millimeter wave signals harmless. Furthermore, millimeter waves can achieve high-resolution imaging at half the wavelength. For wavelengths between 1 and 10 mm, millimeter waves can resolve objects 0.5 to 5 mm in size, enabling inspections of prohibited items such as firearms, knives, explosives, and even lighters and small bags of drugs during body inspections.

[0039] Millimeter waves have strong penetration ability on common clothing. When the frequency is less than 300GHz, the penetration rate of millimeter waves on clothing is greater than -3dB, and decreases with increasing frequency. When the frequency approaches mid-infrared, the penetration rate drops to a level close to -30dB.

[0040] The reflectivity of human skin for millimeter waves is close to that of metal, so the signal-to-noise ratio of the millimeter wave signal reflected by the human surface is relatively high. At the same time, against the bright background of the human body, the outlines of low-brightness powdery suspicious objects and various other suspicious objects will stand out.

[0041] Millimeter-wave imaging can be divided into active millimeter-wave imaging and passive millimeter-wave imaging. Passive millimeter-wave imaging does not transmit millimeter waves, but only uses a receiving antenna to receive millimeter waves emitted by the inspected object, such as the human body. Therefore, it has the advantages of not irradiating the human body with millimeter waves at all and fast imaging speed, but is relatively susceptible to environmental influences. Active millimeter-wave imaging uses a transmitting antenna to transmit millimeter waves to illuminate an object, such as the human body, and uses a receiving antenna to receive the returned millimeter waves. Therefore, the cost is relatively high and the acquisition time is relatively long, but it is less affected by the environment and has good image quality.

[0042] Active millimeter-wave imaging can achieve holographic imaging. "Holography" refers to all the information required to reconstruct the image of an object, including amplitude and phase information. Millimeter-wave holographic imaging systems are usually array-based, without lens-based focusing devices, and focus imaging is achieved through signal processing algorithms. Active millimeter-wave holographic imaging and optical holographic imaging have in common in that both acquire three-dimensional images by recording the amplitude and phase information of the wave. The difference is that millimeter-wave holography directly demodulates and records the amplitude and phase information. Due to the higher optical frequency band, optical holography is more difficult to directly demodulate and record phase information, and usually uses an indirect method to record phase information. Optical holographic imaging generally includes a recording process and a reproduction process. During the recording process, reference light is introduced to interfere with the object light wave emitted on the holographic interferometer, forming interference fringes and recording the object light wavefront information. During the reproduction process, the reference light is used to illuminate the holographic interferometer to reproduce the object light wave, so that a three-dimensional image of the object can be seen.

[0043] Unlike optical holographic imaging, millimeter-wave holographic imaging relies on heterodyne mixing technology. Instead of measuring millimeter-wave intensity, it measures a complex signal containing amplitude and phase information. The millimeter-wave holographic measurement principle is shown in Figure 1. The millimeter-wave signal emitted by the millimeter-wave source is split into two paths by a coupler. One path is illuminated by the transmitting antenna onto the imaging object, while the other path is input into an I / Q demodulator as a reference signal. The millimeter-wave signal reflected from the object is received by the receiving antenna, passes through a power amplifier, and is input into the I / Q demodulator as the measurement signal. The I / Q demodulator uses the reference signal to extract the phase of the measurement signal.

[0044] Without considering the signal amplitude, assume that the millimeter wave signal emitted by the millimeter wave source is cosωt, ω is the angular frequency of the millimeter wave signal, and t is time. The millimeter wave signal received by the receiving antenna has experienced the process of being incident on the surface of the object and reflected back, which introduces the phase to be measured. So the signal can be expressed as The mixer mainly includes a multiplier and a bandpass filter. The product of the two signals input to mixer 1 is:

[0045] Mixer 1 performs low-pass filtering on the above signal to obtain the real part I of the complex signal to be measured. The reference signal input to mixer 2 is first phase-shifted by 90 degrees and then passes through the multiplier to obtain:

[0046] Similarly, low-pass filtering the above signal can obtain the imaginary part Q of the complex signal to be measured. In actual measurement, the output signal of the I / Q demodulator also contains amplitude information:

[0047] In the above formula, A is the amplitude of the complex signal to be measured, is the phase of the complex signal to be measured.

[0048] Millimeter-wave holographic imaging can directly extract phase information using the above-mentioned measurement circuit, so no reference wave illumination is required, which greatly simplifies the imaging device and facilitates imaging of any field of view.

[0049] In one embodiment of the present disclosure, referring to FIG2 , the transceiver antennas RX and TX of the millimeter-wave direct holographic imaging system are arranged adjacent to each other and are approximately considered to be in the same position. A pair of transceiver antennas is called a channel. For an array, the transceiver array includes a group of transceiver antenna pairs, for example, n pairs of transceiver antennas, i.e., n channels. During the inspection, the first pair of transceiver antennas starts transmitting and receiving signals, for example, for a few milliseconds. Then, the second pair of transceiver antennas starts transmitting and receiving signals, for a few milliseconds. The n pairs of transceiver antennas operate in sequence, completing a scan of the transceiver antenna array, where the transmitted signal is at a fixed frequency (so-called fixed-frequency scan). The transceiver antenna array can perform a second scan, operating similarly to the first scan, but with the transmitted signal at another fixed frequency. The transceiver antenna array can perform multiple scans of a set of frequencies. The transmitting antenna TX emits a spherical wave exp(-jkr) / r (r is the distance) onto the imaging object. Each point on the object scatters the millimeter-wave signal, and the scattered signal received by the receiving antenna will be a superposition of the scattered signals at various locations on the object's surface. Under the assumption of Born single-scattering approximation and isotropic scattering, the millimeter wave signal received by the receiving antenna can be expressed as:

[0050] Where (x0, y0) is the position of the transmitting and receiving antennas, f(x, y) is the complex reflectivity image of the object at the position (x, y), is the distance between a point on the object and the transceiver antenna (assuming the imaging object is two-dimensional, and the distance between the object and the scanning aperture is Z0). In the above formula, s(x0, y0) is the complex signal measured by heterodyne mixing technology. By scanning the entire planar aperture, the hologram to be measured is obtained. The rich reflectivity image f(x, y) of the object is then inverted using an image reconstruction algorithm.

[0051] According to the present disclosure, during actual security inspections, missed detections may occur. For example, as shown in FIG3 , a person carrying a foreign object (located on the person's shoulder) may cast a shadow under visible light, similar to the person's shadow, resulting in the shadow shown in FIG3 , making it observable. However, in holographic imaging, the transmitting antenna transmits millimeter waves toward the person, and the person strongly reflects these waves, resulting in the person appearing bright in the image, while the space (background) outside the person appears black. If the foreign object carried by the person has a strong absorption of millimeter waves, the millimeter waves are absorbed and reflected in the image as black, the same color as the background image. As a result, the contrast of the foreign object in the resulting image is weak (or the image containing the foreign object is invisible). While such a foreign object can be distinguished within the imaging area of ​​the person, if it is outside or near the person, such as in the position shown in FIG3 , the foreign object and the background both appear black in the image, making it difficult to distinguish, potentially leading to missed detections.

[0052] According to an embodiment of the present disclosure, a millimeter wave imaging device is provided, comprising two millimeter wave transceiver arrays, for example, a first millimeter wave transceiver array 100 and a second millimeter wave transceiver array 200. The first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200 are arranged generally opposite each other to define an inspection channel. In other embodiments, the millimeter wave imaging device may include more than two millimeter wave transceiver arrays.

[0053] In an embodiment of the present disclosure, a first millimeter-wave transceiver array 100 includes a row of first millimeter-wave transmitting antennas 100T and a row of first millimeter-wave receiving antennas 100R, wherein the first millimeter-wave transceiver array 100 is configured such that each receiving antenna in the row of first millimeter-wave receiving antennas 100R corresponds one-to-one with a first millimeter-wave transmitting antenna in the row of first millimeter-wave transmitting antennas 100T, respectively receiving millimeter waves transmitted by the row of first millimeter-wave transmitting antennas 100T. A second millimeter-wave transceiver array 200 includes a row of second millimeter-wave transmitting antennas 200T and a row of second millimeter-wave receiving antennas 200R, wherein the second millimeter-wave transceiver array 200 is configured such that each receiving antenna in the row of second millimeter-wave receiving antennas 200R corresponds one-to-one with a second millimeter-wave transmitting antenna in the row of second millimeter-wave transmitting antennas 200T, respectively receiving millimeter waves transmitted by the row of second millimeter-wave transmitting antennas 200T. In other embodiments of the present disclosure, the first or second millimeter-wave transceiver array 200 may include more than one row of millimeter-wave transmitting antennas and more than one row of first millimeter-wave receiving antennas 100R.

[0054] In the present disclosure, the receiving antennas of a row of millimeter-wave receiving antennas T correspond one-to-one with the transmitting antennas of a row of millimeter-wave transmitting antennas R to respectively receive the millimeter waves transmitted by the millimeter-wave transmitting antennas. For example, each millimeter-wave transmitting antenna in a row of millimeter-wave transmitting antennas is paired with the closest millimeter-wave receiving antenna, and the paired transmitting antenna and receiving antenna start working at the same time, thereby ensuring that the receiving antenna receives the millimeter-wave signal transmitted by the paired transmitting antenna, rather than the millimeter-wave signal transmitted by other transmitting antennas.

[0055] In the disclosed embodiment, the first millimeter wave transceiver array 100 is configured to transmit millimeter waves toward the object being inspected in the inspection channel and receive reflected millimeter waves to construct a first holographic image of the object. The second millimeter wave transceiver array 200 is configured to transmit millimeter waves of a different frequency toward the object being inspected in the inspection channel and receive reflected millimeter waves to construct a second holographic image of the object. The principle of forming the holographic image here is the same as the principle of holographic imaging described above and will not be repeated here.

[0056] In an embodiment of the present disclosure, the millimeter wave imaging device is further configured such that the second millimeter wave receiving antenna 200R receives the millimeter waves of the first millimeter wave transmitting antenna 100T to form a first transmission image, and the first millimeter wave receiving antenna 100R receives the millimeter waves of a different frequency from the second millimeter wave transmitting antenna 200T to form a second transmission image. Specifically, the first millimeter wave transmitting antenna 100T transmits millimeter waves of a certain frequency, which are reflected by the human body or other inspected objects when passing through the inspection channel. If there are other objects, such as suspected objects, that absorb the millimeter waves, the millimeter waves reflected by the human body or other inspected objects and the millimeter waves absorbed by the suspected objects will not be received by the second millimeter wave receiving antenna 200R at this time. The outlines of the human body and the suspected objects will appear in the first transmission image, as shown in FIG3 . That is, the projection area blocked by the human body or other inspected objects and the suspected objects does not detect the millimeter wave signal, while the millimeter wave signal is detected in other areas. It should be noted that because suspected objects absorb millimeter waves, the millimeter wave signals reflected by them are weak. Consequently, the signal reflected by the suspected object in a holographic image constructed based on the signal reflected by a person carrying the suspected object is weak. Consequently, the suspected object may be overlooked or missed after the holographic image is reconstructed. In this embodiment, by receiving the millimeter wave signal from the first millimeter wave transmitting antenna 100T via the second millimeter wave receiving antenna 200R, or by receiving the millimeter wave signal from the second millimeter wave transmitting antenna 200T via the first millimeter wave receiving antenna 100R, the outline of the suspected object can be clearly displayed after being obscured, thus preventing missed detection of the suspected object.

[0057] In an embodiment of the present disclosure, the millimeter wave imaging device is configured to reproduce the scattered image of the inspected object based on the constructed first holographic image and the second holographic image, and to determine whether the inspected object contains other items by combining the scattered image of the inspected object with at least one of the first transmission image and the second transmission image. For example, the difference between the two can be compared to determine whether the inspected object contains other items; or, for example, in a deep learning neural network, the scattered image and the transmission image are used as training samples to train the model, thereby achieving a judgment on whether the inspected object carries suspicious items. It should be noted that during the scattering or reflection of the millimeter waves by the surface of the inspected object, the millimeter waves can penetrate the human body's clothing, and thus the resulting image can reflect suspicious items hidden in the clothing.

[0058] For example, in some cases, the inspected object carries a suspected item that absorbs millimeter waves. When the first millimeter-wave transmitting antenna 100T transmits millimeter waves to illuminate the inspected object carrying the suspected item, the suspected item absorbs the millimeter waves, resulting in no echo from the suspected item to the first millimeter-wave receiving antenna 100R. Consequently, the first holographic image constructed by the first millimeter-wave transceiver array 100 does not include the echo signal reflected by the suspected item. As a result, the item is not displayed in the three-dimensional image of the inspected object reconstructed by the first holographic image, potentially leading to missed detection. According to an embodiment of the present disclosure, the first millimeter-wave transmitting antenna 100T illuminates the inspected object, and the second millimeter-wave receiving antenna 200R, located opposite the first millimeter-wave transmitting antenna 100T, receives the millimeter-wave signal. This millimeter-wave signal does not include the millimeter-wave signal reflected by the inspected object or the millimeter-wave signal absorbed by the suspected item. As a result, the first transmission image can depict the outline of the suspected item. Combining the three-dimensional image of the inspected object reconstructed by the first holographic image with the detected first transmission image of the inspected object can determine whether the inspected object is carrying an item, thereby mitigating the risk of missed detection.

[0059] In one embodiment of the present disclosure, not all millimeter wave transceiver arrays need to be operational during a single scan. For example, the millimeter wave imaging device is configured so that a portion of a row of first millimeter wave transmit antennas 100T in the first millimeter wave transceiver array 100 sequentially transmits millimeter waves toward the object being inspected in the inspection channel, and a portion of a row of second millimeter wave transmit antennas 200T in the second millimeter wave transceiver array 200 sequentially transmits millimeter waves toward the object being inspected in the inspection channel. In this embodiment, although not all millimeter wave transceiver arrays are operational, this does not affect the acquisition of the first and second holographic images.

[0060] In an embodiment of the present disclosure, the millimeter wave imaging device is configured such that a row of first millimeter wave transmitting antennas 100T of a first millimeter wave transceiver array 100 transmits millimeter waves of a frequency of a first group of frequencies toward the inspected object on the inspection channel at least partially in sequence so that the row of first millimeter wave receiving antennas 100R receives the millimeter waves reflected by the inspected object so as to construct a first holographic image, and at the same time, the row of second millimeter wave transmitting antennas 200T of the second millimeter wave transceiver array 200 transmits millimeter waves of a frequency of a second group of frequencies toward the inspected object on the inspection channel at least partially in sequence so that the row of second millimeter wave receiving antennas 200R receives the millimeter waves reflected by the inspected object so as to construct a second holographic image. It can be understood here that part of a row of first millimeter wave transmitting antennas 100T transmits millimeter waves in sequence, the first transmitting antenna in a row of first millimeter wave transmitting antennas 100T transmits the first frequency of the first group of frequencies, the second transmitting antenna in a row of first millimeter wave transmitting antennas 100T transmits the second frequency of the first group of frequencies, and so on. A row of first millimeter wave transmitting antennas 100T transmits millimeter waves one by one at the frequencies in the first group of frequencies, so that the corresponding receiving antennas in a row of millimeter wave receiving antennas receive millimeter waves one by one to construct a first holographic image; for a row of second millimeter wave transmitting antennas 200T, similarly, each frequency in the second group of frequencies is transmitted in sequence to construct a second holographic image.

[0061] In one embodiment of the present disclosure, a row of first millimeter-wave transmitting antennas 100T of the first millimeter-wave transceiver array 100 can sequentially transmit millimeter waves of one frequency from a third group of frequencies toward an object under inspection in the inspection channel. This allows the row of second millimeter-wave receiving antennas 200R to receive the millimeter waves transmitted through the inspection channel and construct a first transmission image. This first transmission image can then be combined with a scattered image of the object under inspection reconstructed from a holographic image to determine whether the object contains an object.

[0062] In one embodiment of the present disclosure, a row of second millimeter-wave transmitting antennas 200T in the second millimeter-wave transceiver array 200 can sequentially transmit millimeter waves of one frequency from a fourth group of frequencies toward the inspected object in the inspection channel, so that the row of first millimeter-wave receiving antennas 100R receives the millimeter waves transmitted through the inspection channel to construct a second transmission image. This second transmission image can then be combined with a scattered image of the inspected object reconstructed from a holographic image to determine whether the inspected object contains an object. It should be noted that while a first transmission image and a second transmission image can be obtained, this is not necessary. Acquiring only one of the first and second transmission images can also determine whether the inspected object is carrying a suspected object.

[0063] In one embodiment of the present disclosure, a millimeter wave imaging device is configured to acquire a first holographic image, a second holographic image, and a first transmission image and a second transmission image within a single scanning cycle. This is advantageous because the images can be acquired of approximately the same portion of the inspected object, providing more complete, accurate, and easily completed image information.

[0064] For example, a portion of the first millimeter-wave transmitting antennas 100T in the row of the first millimeter-wave transceiver array 100 sequentially transmits millimeter waves of one frequency of the first group of frequencies toward the object being inspected on the inspection channel, and a portion of the second millimeter-wave transmitting antennas 200T in the row of the second millimeter-wave transceiver array 200 sequentially transmits millimeter waves of one frequency of the second group of frequencies toward the object being inspected on the inspection channel. At this point, a scan cycle of the millimeter-wave imaging device has completed (holographic imaging). The remaining portion (transmitting antennas) of the row of the first millimeter-wave transmitting antennas 100T in the first millimeter-wave transceiver array 100 sequentially transmits millimeter waves of one frequency of the third group of frequencies toward the object being inspected on the inspection channel, and the millimeter waves are received by the corresponding receiving antennas of the remaining portion of the row of the second millimeter-wave transmitting antennas 200T in the second millimeter-wave transceiver array 200. When all the remaining portion of the row of the first millimeter-wave transmitting antennas 100T has transmitted millimeter waves, a scan cycle is complete. In this embodiment, optionally, the remaining portion of the row of second millimeter-wave transmitting antennas 200T in the second millimeter-wave transceiver array 200 sequentially transmits millimeter waves at one frequency of the fourth frequency group toward the object under inspection on the inspection channel, and the millimeter waves are received by corresponding receiving antennas in the remaining portion of the row of first millimeter-wave transmitting antennas 100T in the first millimeter-wave transceiver array 100. However, according to embodiments of the present disclosure, only one of the remaining portion of the row of first millimeter-wave transmitting antennas 100T and the remaining portion of the row of second millimeter-wave transmitting antennas 200T sequentially transmits millimeter waves to acquire one of the first and second transmission images, or both portions may be used to acquire the first and second transmission images.

[0065] In an embodiment of the present disclosure, the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200 of the millimeter wave imaging device move synchronously. Thus, the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200 can acquire images of the front and back sides, or the front and back sides, of the inspected object to form a complete three-dimensional surface image of the inspected object. Furthermore, the millimeter wave signal emitted by the first millimeter wave transmitting antenna 100T can be received by the second millimeter wave receiving antenna 200R facing it, and the millimeter wave signal emitted by the second millimeter wave transmitting antenna 200T can be received by the first millimeter wave receiving antenna 100R facing it. However, it should be understood that this is not necessary. Through algorithmic processing, a holographic image of the inspected object and a transmission image can be constructed without the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200 of the millimeter wave imaging device moving synchronously.

[0066] In one embodiment of the present disclosure, as shown in Figure 4, a millimeter wave imaging device is configured such that a first millimeter wave transceiver array 100 and a second millimeter wave transceiver array 200 are arranged horizontally and move vertically. For example, a vertical column 300 can be provided, and the first millimeter wave transceiver array 100 moves up and down on the vertical column via a slider, while the second millimeter wave transceiver array 200 also moves up and down on the vertical column via a slider. This allows the entire body of the subject to be scanned through multiple scanning cycles of the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200.

[0067] In one embodiment of the present disclosure, the millimeter wave imaging device is configured such that the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200 are arranged in a vertical direction and move in a horizontal direction.

[0068] In one embodiment of the present disclosure, the millimeter wave imaging device is configured such that a first millimeter wave transceiver array 100 and a second millimeter wave transceiver array 200 are arranged in a vertical direction and move in an arc in a horizontal direction around the object to be inspected, thereby completely scanning the entire body of the object to be inspected through multiple scanning cycles of the first millimeter wave transceiver array 100 and the second millimeter wave transceiver array 200.

[0069] A specific scanning operation of the millimeter wave imaging device is described in the following example.

[0070] Taking the millimeter wave imaging device shown in Figure 4 as an example, a first millimeter wave transceiver array 100 and a second millimeter wave transceiver array 200 are positioned opposite each other. The first and second millimeter wave transceiver arrays 100 and 200 move simultaneously and perform scanning synchronously. The transmission and reception frequencies are shown in Figure 5, transmitting millimeter waves at four different frequencies.

[0071] In the time period t0 to t1, the first millimeter wave transmitting antenna 100T transmits millimeter waves of the first frequency group, wherein at T 1-1 , the first millimeter wave transmitting antenna 100T transmits a millimeter wave of the first frequency of the first group of frequencies; at T 1-2 , the second first millimeter wave transmitting antenna 100T transmits a millimeter wave of a second frequency of the first frequency group; ... at T 1-m , the mth first millimeter wave transmitting antenna 100T transmits the millimeter wave of the mth frequency of the first group of frequencies. At the same time, the first millimeter wave receiving antenna 100R receives the millimeter wave of the first group of frequencies, wherein at T 1-1 , the first first millimeter wave receiving antenna 100R receives the millimeter wave of the first frequency of the first group of frequencies; at T 1-2 , the second first millimeter wave receiving antenna 100R receives the millimeter wave of the second frequency of the first frequency group; ... at T 1-m The m-th first millimeter wave receiving antenna 100R receives the millimeter wave of the m-th frequency of the first frequency group. The first hologram image is formed through the above operation.

[0072] At the same time, in the time period t0 to t1, the second millimeter wave transmitting antenna 200T transmits millimeter waves of the second frequency group, wherein at T 2-1 , the first second millimeter wave transmitting antenna 200T transmits the millimeter wave of the first frequency of the second group of frequencies; at T 2-2 , the second millimeter wave transmitting antenna 200T transmits a millimeter wave of a second frequency of a second group of frequencies; ... at T 2-m , the mth second millimeter wave transmitting antenna 200T transmits the millimeter wave of the mth frequency of the second group of frequencies. At the same time, the second millimeter wave receiving antenna 200R receives the millimeter wave of the second group of frequencies, wherein at T 2-1 , the first second millimeter wave receiving antenna 200R receives the millimeter wave of the first frequency of the second group of frequencies; at T 2-2 , the second second millimeter wave receiving antenna 200R receives the millimeter wave of the second frequency of the second group of frequencies; ... at T 2-m The m-th second millimeter wave receiving antenna 200R receives the millimeter wave of the m-th frequency of the second frequency group. The second hologram image is generated through the above operation.

[0073] During the time period t1 to t2, the first millimeter wave transmitting antenna 100T transmits millimeter waves of the third frequency group, wherein during the time period T 3-1 , the first (for a row of millimeter wave transceiver arrays, it can also be the m+1th, at this time a row scan completes the sequential transmission of the first group of frequencies and the third group of frequencies) first millimeter wave transmitting antenna 100T transmits the first frequency of the third group of frequencies; at T 3-2, the second first millimeter wave transmitting antenna 100T transmits a millimeter wave of a second frequency of the third frequency group; ... at T 3-n , the nth first millimeter wave transmitting antenna 100T transmits the millimeter wave of the nth frequency of the third group of frequencies. At the same time, the second millimeter wave receiving antenna 200R can be operated to receive the millimeter wave of the third group of frequencies, wherein R 3-1 , the first second millimeter wave receiving antenna 200R receives the millimeter wave of the first frequency of the third group of frequencies; 3-2 , the second second millimeter wave receiving antenna 200R receives the millimeter wave of the second frequency of the third frequency group; ... at R 3-m The m-th second millimeter wave receiving antenna 200R receives the millimeter wave of the m-th frequency of the third frequency group. The first transmission image is acquired through the above operation.

[0074] In the embodiment shown in FIG5 , during the time period t1 to t2, the second millimeter wave transmitting antenna 200T transmits millimeter waves of the fourth frequency group, wherein during the time period T 4-1 , the first second millimeter wave transmitting antenna 200T transmits the millimeter wave of the first frequency of the fourth group of frequencies; at T 4-2 , the second second millimeter wave transmitting antenna 200T transmits the millimeter wave of the second frequency of the fourth frequency group; ... at T 4-n , the nth second millimeter wave transmitting antenna 200T transmits the millimeter wave of the nth frequency of the fourth group of frequencies. At the same time, the first millimeter wave receiving antenna 100R can be operated to receive the millimeter wave of the fourth group of frequencies, wherein R 4- 1. The first first millimeter wave receiving antenna 100R receives the millimeter wave of the first frequency of the fourth group of frequencies; 4-2 , the second first millimeter wave receiving antenna 100R receives the millimeter wave of the second frequency of the fourth frequency group; ... at R 4-m The mth first millimeter wave receiving antenna 100R receives the millimeter wave of the mth frequency of the fourth frequency group. The second transmission image is acquired through the above operation.

[0075] In another embodiment of the present disclosure, during the time period t0 to t1, the first millimeter wave transmitting antenna 100T transmits a millimeter wave of one frequency in the first group of frequencies. 1-1 、T 1-2 ,…T 1-m The millimeter wave of the frequency is transmitted in sequence, and the echo signal is received in sequence through the receiving antenna; in the time period t1 to t2, the first millimeter wave transmitting antenna 100T transmits a millimeter wave of a frequency in the third group of frequencies, and a row of the first millimeter wave transmitting antennas 100T are at T 3-1 、T 3-2 ,…T 3- mMillimeter waves of this frequency are sequentially transmitted. Correspondingly, the second millimeter-wave receiving antenna receives the millimeter waves transmitted through the inspection channel, generating a transmission image. Similarly, the second millimeter-wave transmitting antenna 200T performs a similar scan, with the 1-m transmitting antennas transmitting millimeter waves of the same (fixed) frequency, but at a different frequency than the millimeter waves transmitted by the first millimeter-wave transmitting antenna 100T.

[0076] In the embodiment shown in FIG6 , other parts are the same as those in the embodiment shown in FIG5 . In the time period t1 to t2 , the second millimeter wave transmitting antenna 200T and the first millimeter wave receiving antenna 100R are turned off. At this time, no second transmission image is acquired.

[0077] After the scan is completed, four sets of valid echo data, for example, as shown in FIG. 5 , or three sets of valid echo data, as shown in FIG. 6 , are acquired.

[0078] Taking the embodiment shown in FIG5 as an example, the four sets of valid echo data obtained are respectively denoted as S 1 (first group of frequencies), S 2 (second frequency group), S 3 (the third frequency group), S 4 (Fourth frequency group).

[0079] Targeting S 1 and S 2 , use formula 1 and formula 2 to construct the holographic image and obtain a set of three-dimensional data:

[0080] Among them, σ(x, y, z) is the reconstructed three-dimensional holographic data, σ(x, y, z i ) is the z position of a certain layer along the z direction in the reconstructed 3D holographic data. i data, s(x′, y′, f) is the echo signal sampled at different positions, x′ is the horizontal sampling position, y′ is the vertical sampling position, and f is the electromagnetic wave frequency; the exponential term In the equation, e is a natural constant, j is an imaginary unit, k is a wave number, and k x and k y are the components of the wave number k in the x and y directions, and R0 is the distance from the array surface to the imaging center. is the three-dimensional inverse Fourier transform, FT 2D is the two-dimensional Fourier transform, and STOLT{} is the interpolation operator.

[0081] Calculate the amplitude of the 3D holographic data and perform maximum projection along the z direction to obtain the scanning scattering image I1 of the inspected object: I1(x, y) = max(abs(σ(x, y, z)), z)…Formula 3

[0082] Echo data S for the object under inspection 3 and S 4 Before scanning the object to be inspected, a complete scan of the air can be performed to obtain echo data S bkg 3 、S bkg 4 Formula 4 is used to construct a set of two-dimensional data, which directly generates the transmission image I2 of the inspected object.

[0083] The above calculation principle is essentially no different from the principle introduced earlier in this article.

[0084] Another aspect of the present disclosure provides a security inspection device, comprising the aforementioned millimeter wave imaging device.

[0085] Another aspect of the present disclosure provides a security inspection method, comprising:

[0086] Scanning the inspected object in the inspection channel using the aforementioned millimeter wave imaging device to construct a first holographic image and a second holographic image as well as a first transmission image and a second transmission image;

[0087] Based on the constructed first holographic image and second holographic image, a scattering image of the inspected object is reconstructed, and the scattering image of the inspected object is combined with at least one of the first transmission image and the second transmission image to determine whether the inspected object contains other items.

[0088] According to the method disclosed in the present invention, an all-round inspection of the inspected object, such as the surface of the human body, can be performed, and suspicious items carried by the human body that are absorbent to millimeter waves and difficult to inspect can be detected at the same time, providing convenient, fast and accurate inspection results.

[0089] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions provided by this disclosure can be achieved. This is not limited herein.

[0090] In the technical solutions disclosed herein, the collection, storage, use, processing, transmission, provision and disclosure of user personal information involved comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0091] The above specific embodiments do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions may be made to the disclosed embodiments or examples based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure shall be included within the scope of protection of this disclosure.

Claims

1. A millimeter-wave imaging device, comprising: A first millimeter-wave transceiver array, including a row of first millimeter-wave transmitting antennas and a row of first millimeter-wave receiving antennas, wherein the first millimeter-wave transceiver array is configured such that the row of first millimeter-wave receiving antennas corresponds one-to-one with the row of first millimeter-wave transmitting antennas to respectively receive millimeter-waves transmitted by the row of first millimeter-wave transmitting antennas; A second millimeter-wave transceiver array, including a row of second millimeter-wave transmitting antennas and a row of second millimeter-wave receiving antennas, wherein the second millimeter-wave transceiver array is configured such that the row of second millimeter-wave receiving antennas corresponds one-to-one with the row of second millimeter-wave transmitting antennas to respectively receive millimeter-waves transmitted by the row of second millimeter-wave transmitting antennas, and the second millimeter-wave transceiver array is arranged substantially opposite to the first millimeter-wave transceiver array to define an inspection channel; Wherein the first millimeter-wave transceiver array is configured to emit millimeter-waves towards an object to be inspected on the inspection channel and receive the reflected millimeter-waves to construct a first holographic image of the object to be inspected, and the second millimeter-wave transceiver array is configured to emit millimeter-waves towards an object to be inspected on the inspection channel and receive the reflected millimeter-waves to construct a second holographic image of the object to be inspected; And Wherein the millimeter-wave imaging device is further configured such that the second millimeter-wave receiving antennas receive the millimeter-waves of the first millimeter-wave transmitting antennas to form a first transmission image, and the first millimeter-wave receiving antennas receive the millimeter-waves of the second millimeter-wave transmitting antennas to form a second transmission image.

2. The millimeter-wave imaging device according to claim 1, configured to reproduce a scattering image of the object to be inspected based on the constructed first holographic image and second holographic image, and combine the scattering image of the object to be inspected with at least one of the first transmission image and the second transmission image to determine whether the object to be inspected contains a suspicious item.

3. The millimeter-wave imaging device according to claim 1, configured to At least part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array sequentially emits millimeter-waves towards an object to be inspected on the inspection channel, and At least part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array sequentially emits millimeter-waves towards an object to be inspected on the inspection channel.

4. The millimeter-wave imaging device according to claim 3, configured to At least part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array sequentially emits millimeter-waves of a frequency in a first group of frequencies towards an object to be inspected on the inspection channel so that the row of first millimeter-wave receiving antennas receives the millimeter-waves reflected by the object to be inspected to construct a first holographic image, while at least part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array sequentially emits millimeter-waves of a different frequency in a second group of frequencies towards an object to be inspected on the inspection channel so that the row of second millimeter-wave receiving antennas receives the millimeter-waves reflected by the object to be inspected to construct a second holographic image.

5. The millimeter-wave imaging device according to claim 3, configured to At least part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a third set of frequencies toward an object to be inspected on the inspection channel, so that the corresponding receiving antennas of the row of second millimeter-wave receiving antennas receive the millimeter waves transmitted through the inspection channel, so as to construct a first transmission image, and / or At least part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a fourth set of frequencies toward an object to be inspected on the inspection channel, so that the corresponding receiving antennas of the row of first millimeter-wave receiving antennas receive the millimeter waves transmitted through the inspection channel, so as to construct a second transmission image.

6. The millimeter-wave imaging device according to claim 1, configured such that, within one scanning cycle, part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a first set of frequencies toward an object to be inspected on the inspection channel, and part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a second set of frequencies toward an object to be inspected on the inspection channel; and The remaining part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a third set of frequencies toward an object to be inspected on the inspection channel, and the millimeter waves are received by the corresponding receiving antennas of the remaining part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array, and / or the remaining part of the row of second millimeter-wave transmitting antennas of the second millimeter-wave transceiver array sequentially emits millimeter waves of one frequency in a fourth set of frequencies toward an object to be inspected on the inspection channel, and the millimeter waves are received by the corresponding receiving antennas of the remaining part of the row of first millimeter-wave transmitting antennas of the first millimeter-wave transceiver array.

7. The millimeter-wave imaging device according to claim 1, wherein the first millimeter-wave transceiver array and the second millimeter-wave transceiver array move synchronously.

8. The millimeter-wave imaging device according to claim 7, configured such that The first millimeter-wave transceiver array and the second millimeter-wave transceiver array are arranged in a horizontal direction and move in a vertical direction; or The first millimeter-wave transceiver array and the second millimeter-wave transceiver array are arranged in a vertical direction and move in a horizontal direction; or The first millimeter-wave transceiver array and the second millimeter-wave transceiver array are arranged in a vertical direction and move along an arc around the object to be inspected.

9. A security inspection device, comprising the millimeter-wave imaging device according to any one of the foregoing claims.

10. A security inspection method, comprising:[[]] Scanning an object to be inspected in the inspection channel using the millimeter-wave imaging device according to any one of claims 1-8, and constructing a first holographic image, a second holographic image, a first transmission image, and a second transmission image. Based on the constructed first holographic image and second holographic image, reproduce the scattering image of the object to be inspected, and combine the scattering image of the object to be inspected with at least one of the first transmission image and the second transmission image to determine whether the object to be inspected contains other items.

Images