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

Abstract

The invention provides millimeter wave imaging equipment, security inspection equipment and a security inspection method. A millimeter wave imaging device includes a millimeter wave transmit-receive array and a plate. The plate can reflect millimeter waves incident on the plate to the detected object and the at least one millimeter wave transmit-receive array. The millimeter wave imaging device is configured to reconstruct a holographic image of the object based on a first portion of the millimeter waves emitted from the millimeter wave transmit-receive array incident on the object and a portion of the millimeter waves reflected from the object back to the millimeter wave transmit-receive array through an algorithm, and further reconstruct the holographic image of the object through the algorithm. An enhanced holographic image of the portion of the object close to the plate is reconstructed based on the additional millimeter waves reflected back from the three-dimensional region close to the plate.

Description

Technical Field

[0001] The present invention 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

[0002] In my country, the application of millimeter-wave body imaging security equipment is constantly expanding, playing an active role in occasions involving personnel security checks and inspections, including civil aviation airports, customs and ports, important places and major events.

[0003] Millimeter-wave human imaging equipment is harmless to the human body and has strong penetrating power. Its transmission power is less than one thousandth of the electromagnetic radiation of a mobile phone. It can accurately identify items carried by the human body, effectively improve the objectivity, accuracy, and pertinence of inspections, reduce the labor intensity of security inspectors, and improve security inspection efficiency.

[0004] 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

[0005] The object of the present invention is to provide a millimeter wave imaging device, comprising:

[0006] at least one millimeter wave transceiver array, configured to transmit millimeter waves and receive reflected millimeter waves; and

[0007] at least one board;

[0008] The millimeter wave imaging device is configured to construct a holographic image of the inspected object by transmitting millimeter waves toward the inspected object through the at least one millimeter wave transceiver array and receiving reflected millimeter waves;

[0009] The at least one plate is capable of reflecting at least a portion of the millimeter wave incident on the at least one plate toward the object under inspection and the at least one millimeter wave transceiver array;

[0010] The millimeter wave imaging device is configured to reconstruct a holographic image of the object under inspection based on a first part of the millimeter waves emitted from at least one millimeter wave transceiver array being incident on the object under inspection, and a part of the first part of the emitted millimeter waves being reflected from the object under inspection back to the millimeter waves of the at least one millimeter wave transceiver array, and also to reconstruct an enhanced holographic image of a portion of the object under inspection close to the at least one plate based on additional millimeter waves reflected back from a three-dimensional area close to the at least one plate.

[0011] In one embodiment, the additional millimeter waves reflected back from the three-dimensional region proximate to the at least one plate include:

[0012] A first portion of the millimeter waves emitted by the at least one millimeter-wave transceiver array toward the object under test is incident on the object under test, wherein another portion of the emitted first portion of the millimeter waves is reflected by the object under test to the at least one plate, and then reflected by the at least one plate back to the millimeter waves of the at least one millimeter-wave transceiver array.

[0013] In one embodiment, the additional millimeter waves reflected back from the three-dimensional region proximate to the at least one plate include:

[0014] The second part of the millimeter wave emitted by the at least one millimeter wave transceiver array toward the object under test is incident on the at least one plate, and a part of the second part of the emitted millimeter wave is reflected by the at least one plate to the object under test, and then reflected by the object under test back to the millimeter wave of the at least one millimeter wave transceiver array.

[0015] In one embodiment, the at least one plate is configured to support the object under inspection or to support the vicinity of the location of the object under inspection.

[0016] In one embodiment, the at least one plate comprises a reflective surface capable of reflecting at least part of the millimeter waves.

[0017] In one embodiment, the at least one millimeter wave transceiver array includes at least one row of transmitting antennas and receiving antennas, each transmitting antenna and one receiving antenna can be arranged adjacent to each other to form a pair of transmitting antennas-receiving antennas, and multiple pairs of transmitting antennas-receiving antennas are arranged in one dimension; or

[0018] The at least one millimeter wave transceiver array includes at least one row of transmitting antenna-receiving antenna pairs, and the transmitting antenna and receiving antenna of each pair of transmitting antenna-receiving antennas are arranged laterally along the extension direction of the millimeter wave transceiver array, with the transmitting antennas arranged in one row and the receiving antennas arranged in another row.

[0019] In one embodiment, the millimeter wave imaging device further includes: at least one column, the at least one millimeter wave transceiver array is supported by the at least one column, wherein the at least one millimeter wave transceiver array is arranged in a horizontal direction and moves along the at least one column.

[0020] In one embodiment, the at least one millimeter wave transceiver array includes a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged toward the object to be inspected;

[0021] At least one column includes a first column and a second column, the first millimeter wave transceiver array is supported by the first column and moves along the first column, and the second millimeter wave transceiver array is supported by the second column and moves along the second column.

[0022] In one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in the vertical direction; or

[0023] The first millimeter wave transceiver array and the second millimeter wave transceiver array move asynchronously in a vertical direction.

[0024] In one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction along the vertical direction; or

[0025] The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move in opposite directions along the vertical direction.

[0026] In one embodiment, the at least one millimeter wave transceiver array extends in a vertical direction.

[0027] In one embodiment, at least one millimeter wave transceiver array includes a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in a horizontal direction; or

[0028] The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move asynchronously in a horizontal direction.

[0029] In one embodiment, the at least one millimeter wave transceiver array includes a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction along the horizontal direction; or

[0030] The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move in opposite directions along the horizontal direction.

[0031] Another aspect of the present invention provides a security inspection device, comprising:

[0032] Such as the millimeter wave imaging device mentioned above.

[0033] Another aspect of the present invention provides a security inspection method, comprising:

[0034] The aforementioned millimeter wave imaging device is used to emit millimeter waves to illuminate the inspected object in the inspection channel, and receive the reflected millimeter wave echo signal, thereby constructing an overall holographic image of the inspected object and an enhanced holographic image of the part close to the plate, so as to construct a partially enhanced overall holographic image.

[0035] 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 invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are used to better understand the present invention and do not constitute a limitation of the present invention, wherein:

[0037] Figure 1 A device is shown to explain the principle of millimeter wave holographic measurement;

[0038] Figure 2 A schematic diagram of plane scanning millimeter wave holographic imaging is shown;

[0039] Figure 3 A millimeter wave imaging device according to the present invention is shown, wherein the plate arrangement is removed for illustration;

[0040] Figure 4 A millimeter wave imaging device according to the present invention is shown, wherein the plate arrangement is removed for illustration;

[0041] Figure 5 The holographic imaging principle of the millimeter wave imaging device according to the present invention is shown;

[0042] Figure 6 A schematic diagram of the transmission and reflection paths of millimeter waves at the foot and its vicinity according to the present invention is shown;

[0043] Figure 7 The holographic measurement principle of the foot and its vicinity according to the present invention is shown;

[0044] Figure 8 The figure shows the feet and the vicinity of the human body whose image is to be enhanced according to the present invention;

[0045] Fig. 9 A full-body holographic image of a human body using a millimeter wave imaging device according to the present invention is shown, wherein enhanced signals of the feet and nearby parts are not included;

[0046] Fig.10 A full-body holographic image of a human body using the millimeter wave imaging device of the present invention is shown, wherein the image signals of the feet and nearby parts are enhanced. DETAILED DESCRIPTION

[0047] In order to more clearly explain the purpose, technical solutions and advantages of the present invention, the embodiments of the present invention will be described in detail below in conjunction with 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 invention, and should not be understood as limiting the present invention. In the specification and the drawings, the same or similar reference numerals refer to the same or similar parts or components. 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.

[0048] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. The wording "one" or "an" does not exclude multiple. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right", "top" or "bottom" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. When an element such as a layer, a film, a region or a substrate substrate is referred to as being "on" or "under" another element, the element may be "directly" located "on" or "under" another element, or there may be an intermediate element.

[0049] Millimeter-wave electromagnetic radiation has a wavelength range of 1 to 10 mm, corresponding to a frequency range of 30 to 300 GHz, and is widely used in radar, guidance, remote sensing, communications, perception, and nondestructive testing. Many materials that are impenetrable in the optical frequency band are nearly transparent to millimeter waves, so millimeter-wave imaging has a natural advantage in many cases and is suitable for contactless, non-invasive security inspections.

[0050] The wavelength of millimeter waves is in the millimeter range. Compared with X-rays, they do not have ionizing properties and are difficult to penetrate the surface of human skin, so low-power millimeter wave signals are harmless to the human body. At the same time, millimeter waves can achieve half-wavelength high-resolution imaging. For millimeter waves with a wavelength between 1 and 10 mm, objects of 0.5 to 5 mm can be distinguished, thus meeting the requirements for the inspection of prohibited items such as guns, knives, explosives, and even lighters and small bags of drugs in human security inspections.

[0051] Millimeter waves have a strong ability to penetrate common clothing. When the frequency is less than 300GHz, the penetration rate of millimeter waves through 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.

[0052] The reflectivity of human skin to millimeter waves is close to that of metal, so the signal-to-noise ratio of the millimeter-wave signal reflected from the human body surface is relatively high. At the same time, against the bright human background, the outlines of low-brightness powdery suspicious objects and various other suspicious objects will stand out.

[0053] 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.

[0054] Active millimeter wave imaging can achieve holographic imaging. "Holography" refers to all the information required to reconstruct the image of the object, including amplitude and phase information. The millimeter wave holographic imaging system is usually in the form of an array, without a lens focusing device, and focusing imaging is achieved through signal processing algorithms. The commonality between active millimeter wave holographic imaging and optical holographic imaging is that both obtain 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 high optical frequency band, it is difficult to directly demodulate and record the phase information of optical holography, and the phase information is usually recorded indirectly. Optical holographic imaging generally includes a recording process and a reproduction process: in the recording process, a reference light is introduced to interfere with the object light wave emitted on the holographic interference plate to form interference fringes and record the object light wavefront information: in the reproduction process, the reference light is used to illuminate the holographic interference plate to reproduce the object light wave, so that a three-dimensional image of the object can be seen.

[0055] Unlike optical holographic imaging, millimeter-wave holographic imaging relies on heterodyne mixing technology. What is measured is no longer the millimeter-wave intensity, but a complex signal containing amplitude and phase information. Figure 1 As shown in the figure, the millimeter wave signal emitted by the millimeter wave source is divided into two paths through the coupler. One signal is irradiated on the imaging object through the transmitting antenna, and the other signal is input into the I / Q demodulator as a reference signal. The millimeter wave signal reflected by the object is received by the receiving antenna, and after passing through the power amplifier, it is input into the I / Q demodulator as a measurement signal. The I / Q demodulator uses the reference signal to extract the phase of the measurement signal.

[0056] Without considering the signal amplitude, assume that the millimeter wave signal emitted by the millimeter wave source is cosωt, where 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 φ to be measured, so the signal can be expressed as cos(ωt+φ). The mixer mainly includes a multiplier and a bandpass filter. The product of the two signals input to mixer 1 is:

[0057]

[0058] 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:

[0059]

[0060] Similarly, the imaginary part Q of the complex signal to be measured can be obtained by low-pass filtering the above signal. In actual measurement, the output signal of the I / Q demodulator also contains amplitude information:

[0061]

[0062] In the above formula, A is the amplitude of the complex signal to be measured, and φ is the phase of the complex signal to be measured.

[0063] Millimeter-wave holographic imaging can directly extract phase information using the above-mentioned measurement circuit, so no reference wave irradiation is required, which greatly simplifies the imaging device and facilitates imaging of any field of view.

[0064] In one embodiment of the present invention, reference Figure 2 , 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, such as n pairs of transceiver antennas, that is, n channels; when implementing the inspection, the first pair of transceiver antennas starts to transmit and receive signals, for example, for a few milliseconds, and then the second pair of transceiver antennas starts to transmit and receive signals, which lasts for a few milliseconds. The n pairs of transceiver antennas work in sequence to complete a scan of the transceiver antenna array, in which the transmission signal is a fixed frequency (the so-called fixed frequency scan). The transceiver antenna array can perform a second scan, which operates similarly to the first scan, but the transmission signal is 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) to illuminate the imaging object. Each point on the object scatters the millimeter wave signal, and the scattered signal received by the receiving antenna will be the superposition of the scattered signals at various positions on the surface of the object. Under the assumption of Born single scattering approximation and isotropic scattering, the millimeter wave signal received by the receiving antenna can be expressed as:

[0065]

[0066] 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 that the imaging object is two-dimensional, the distance between the object and the scanning aperture is Z0), j is the imaginary unit, and k is the wave number. In the above formula, s(x0,y0) is the complex signal measured by heterodyne mixing technology. The hologram to be measured can be obtained by scanning the entire plane aperture, and then the rich reflectivity image f(x,y) of the object is inverted by the image reconstruction algorithm.

[0067] The inventors have found that in the actual security inspection process, the signals in some parts are often weak, and some areas of the final holographic image are not very clear. Regardless of whether it is cylindrical scanning, plane scanning or area array scanning, the position of the transceiver antenna at the bottom of the array is usually a certain distance from the plane where the feet of the person being inspected stand. Limited by the imaging principle, when the person being inspected stands in the security inspection channel and is scanned by the millimeter-wave security scanner, the signal received at the calf, especially the ankle, is very weak, and the signal reflected back to the millimeter-wave transceiver array is also very weak, resulting in poor imaging of the area near the calf and ankle, causing the suspicious objects in this area to be missed.

[0068] like Figure 3 and 4 Two inspection devices are shown, in which the transceiver antenna array is moved to the lower part of the object to be inspected, such as a human body, close to the ground. The transceiver antenna array cannot move downward further, the illumination angle is limited, and the information obtained by illumination is limited, so the following will occur Fig. 9 In the schematically shown full-body image, the images of the human body's feet and some parts above the feet often appear unclear or have significantly weak signals.

[0069] Figure 5 The coordinate diagram of the three-dimensional holographic data quickly reconstructed according to the present invention is shown. Figure 5 , the present invention gives the formula 1 of the principle of the present invention as follows.

[0070] , Formula 1

[0071] In formula 1, To reconstruct a layer z along the z direction in the 3D holographic data i The data at are echo signals sampled at different positions, is the horizontal sampling position, is the vertical sampling position, the coordinates of the transmitting and receiving antennas are equivalent to the same. is the frequency of electromagnetic waves; exponential term In this example, e is a natural constant, j is an imaginary unit, k is a wave number, and k x and k x k y is the component of wave number k in the x and y directions, R0 is the distance from the array surface to the imaging center, zi is the distance from the reconstructed image of this layer to the imaging center is the two-dimensional inverse Fourier transform, is the two-dimensional Fourier transform, take part of the data.

[0072] In the present invention, a board is provided for imaging the part of the object close to the ground, such as the foot and nearby parts of the human body, and the millimeter waves are reflected by the board to enhance the collection of millimeter waves reflecting information of the foot and nearby parts of the human body.

[0073] Figure 6 It is shown that the present invention enhances the millimeter wave return signal of the part of the inspected object close to the ground by providing a millimeter wave route increased by the plate design, thereby enhancing the image of the part of the inspected object close to the ground.

[0074] In the present invention, the millimeter wave imaging device includes at least one millimeter wave transceiver array for transmitting millimeter waves and receiving reflected millimeter waves. The millimeter wave transceiver array is formed by arranging a pair of transmitting antennas TX and receiving antennas RX.

[0075] In one embodiment, the millimeter wave transceiver array has at least one row of transmitting antennas TX and receiving antennas RX, and each transmitting antenna TX and one receiving antenna RX can be arranged adjacent to each other to form a pair of transmitting antenna TX-receiving antenna RX, and multiple pairs of transmitting antenna TX-receiving antenna RX are arranged in one dimension. The millimeter wave transceiver array may include one row of transmitting antenna TX-receiving antenna RX pairs, or may include two or more rows of transmitting antenna TX-receiving antenna RX pairs.

[0076] In one embodiment, the millimeter wave transceiver array can be as follows Figure 3 As shown, the millimeter wave imaging device is arranged in the horizontal direction and can move in the vertical direction on the pillar to scan the object to be inspected, such as the human body as shown in the figure. In another embodiment, the millimeter wave imaging device includes a plurality of millimeter wave transceiver arrays supported by a plurality of corresponding pillars, and each millimeter wave transceiver array is arranged in the horizontal direction and moves along the corresponding pillar to scan the human body.

[0077] In one embodiment, the millimeter wave imaging device includes a first millimeter wave transceiver array and a second millimeter wave transceiver array, the first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged toward the object to be inspected; at least one column includes a first column and a second column, the first millimeter wave transceiver array is supported by the first column and moves along the first column, and the second millimeter wave transceiver array is supported by the second column and moves along the second column. However, it should be known that the millimeter wave imaging device may also include other numbers of millimeter wave transceiver arrays, which can be provided according to actual application scenarios.

[0078] In one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in the vertical direction; in another embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move asynchronously in the vertical direction.

[0079] In one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction along the vertical direction; in another embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move in opposite directions along the vertical direction.

[0080] In another embodiment, the transmitting antenna TX and the receiving antenna RX of each pair of the transmitting antenna TX and the receiving antenna RX can be arranged transversely along the extension direction of the millimeter wave transceiver array, for example, the millimeter wave transceiver array is as follows: Figure 3 The horizontal direction shown extends, and the transmitting antenna TX and the receiving antenna RX of each pair of transmitting antenna TX and receiving antenna RX are arranged up and down. In this case, all transmitting antennas TX are arranged in one row and all receiving antennas RX are arranged in another row; in other embodiments, each pair of transmitting antenna TX and receiving antenna RX can be arranged along other directions.

[0081] In another embodiment, the millimeter wave transceiver array can be as follows Figure 4 The scanning object to be inspected is arranged in the vertical direction as shown, such as the human body as shown in the figure. In another embodiment, the vertically arranged millimeter wave transceiver array can move around a circular or rectangular or other shaped track in the horizontal plane to scan around the human body. In other embodiments, the millimeter wave transceiver array can have other arrangements and corresponding scanning methods. In one embodiment, the millimeter wave imaging device includes a first millimeter wave transceiver array and a second millimeter wave transceiver array, which are directed toward the inspected object such as a human body, and the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction in the horizontal direction; in another embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the opposite direction in the horizontal direction; in one embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in the horizontal direction; in another embodiment, the first millimeter wave transceiver array and the second millimeter wave transceiver array move asynchronously in the horizontal direction.

[0082] In the present invention, the transmitting antenna of the millimeter wave transceiver array transmits, for example, millimeter waves toward the human body. After the millimeter waves are incident on the human body, they are directly reflected back to the receiving antenna of the millimeter wave transceiver array. The reflected millimeter waves are also called echo signals. After being processed by an algorithm, a holographic image of the human body can be obtained. Figure 6(1) shows a schematic diagram of the path of the millimeter wave. According to the above principle of holographic imaging, for example, the surface of the human body directly reflects the millimeter wave emitted by the transmitting antenna back to the receiving antenna, thereby constructing a surface image of the human body. The present invention notes that the transmission signal emitted by the transmitting antenna is not entirely irradiated to the human body, but only a part of it is irradiated to the human body and a part of it is irradiated to other spaces. Here, the part of the transmission signal irradiated to the human body is referred to as the first part of the transmission signal, and the part of the transmission signal irradiated to the board is referred to as the second part of the transmission signal.

[0083] In an embodiment of the present invention, a millimeter wave imaging device is provided with a board, a part (first part) of the transmission signal emitted by the transmitting antenna directly irradiates the human body, and a part (second part) of the transmission signal irradiates the board, and the board reflects the transmission signal to the human body, and then the human body reflects it back to the receiving antenna. The path diagram of the millimeter wave in this case is as follows: Figure 6 As shown in (2), the echo signal reflected back to the receiving antenna is processed by the millimeter wave imaging device to construct the corresponding part of the human body, such as the enhanced holographic image of the foot.

[0084] Figure 6 (3) in the figure shows the third situation. After a part of the transmission signal (the first part) emitted by the transmitting antenna hits the human body, a part is reflected to the plate, and then reflected back to the receiving antenna by the plate. The path diagram of the millimeter wave is shown in Figure 6 As shown in (3). The echo signal reflected back to the receiving antenna is processed by the millimeter wave imaging device to construct the corresponding part of the human body, such as the enhanced holographic image of the foot. The present invention notes that after a part (the first part) of the transmission signal emitted by the transmitting antenna directly irradiates the human body, it will not be fully reflected back to the receiving antenna, but part of it will be reflected back to the human body and the other part will be reflected to the board. The part scattered to other spaces is not discussed here.

[0085] Figure 6 (4) in the figure shows the fourth situation. The plate reflects the millimeter wave reflected by the human body to the receiving antenna, and at the same time reflects the millimeter wave emitted by the transmitting antenna to the plate to the human body, and then reflects back to the receiving antenna. The path diagram of the millimeter wave is shown in Figure 6 As shown in (4), the echo signal reflected back to the receiving antenna is processed by the millimeter wave imaging device to construct the corresponding part of the human body, such as the enhanced holographic image of the foot.

[0086] The plate can be set at the position where the human body is supported or near the position where the human body stands when being examined. The plate can be any plate-shaped object with a reflective surface. The reflective surface can include materials that can reflect millimeter waves, such as aluminum foil and indium tin oxide (ITO) film.

[0087] In the present invention, the millimeter wave imaging device is configured to have at least one millimeter wave transceiver array so as to be able to transmit millimeter waves toward the object to be inspected and receive reflected millimeter waves to construct a holographic image of the object to be inspected. In the present invention, as described in the above embodiment, multiple echoes can be obtained by setting the board.

[0088] First, like the inspection equipment in the prior art, the echo obtained by the millimeter wave imaging device of the present invention includes a first part of the millimeter wave emitted from the millimeter wave transceiver array incident on the human body, and a part of the millimeter wave reflected from the human body (such as the foot) back to the millimeter wave transceiver array. This echo is used to reconstruct a holographic image of the inspected object based on an algorithm, such as Fig. 9 Full body image shown.

[0089] Figure 6 (2) shows the second situation of the echo obtained by the millimeter wave imaging device of the present invention, the echo includes the second part of the millimeter wave emitted by the millimeter wave transceiver array toward the human body incident on the board, part of the second part of the emitted millimeter wave is reflected by the board to the human body, and then the human body reflects the millimeter wave back to the millimeter wave transceiver array.

[0090] Figure 6 (3) shows the third situation of the echo obtained by the millimeter wave imaging device of the present invention, wherein the echo includes the first part of the millimeter wave emitted by the millimeter wave transceiver array toward the human body, which is incident on the human body, and part of the first part of the emitted millimeter wave is reflected from the human body to the plate, and then reflected by the plate back to the millimeter wave of the millimeter wave transceiver array.

[0091] Figure 6 (4) shows a situation in which the millimeter wave imaging device of the present invention is actually applied, wherein the echo obtained by the millimeter wave imaging device of the present invention includes Figure 6 (2) and (3) of millimeter wave.

[0092] The present invention reconstructs an enhanced holographic image of the portion of the human body near the plate based on an algorithm based on additional echo signals reflected from a three-dimensional area near the plate. This enhanced holographic image is superimposed on Figure 6 (1) Holographic image of the human body constructed using the echo signal.

[0093] The following briefly describes how to use an algorithm to construct, for example, a full-body holographic image of a human body and a partially enhanced holographic image, thereby constructing a final enhanced full-body holographic image.

[0094] The present invention uses the back projection algorithm (Formula 2) according to Figure 5 The path shown and Figure 6 The coordinate system shown in the figure reconstructs two rectangular areas where the feet of a person stand (such as Figure 8 ).

[0095] , formula 2

[0096] in, Echo data The last few rows of data (e.g. 100 rows) are strictly based on the actual coordinates of the transmitting and receiving antennas. is the receiving antenna coordinate, are the transmitting antenna coordinates. This is the reconstructed three-dimensional holographic data of the rectangular area where the two legs stand.

[0097] The amplitude of the 3D holographic data is calculated to obtain a 3D amplitude image, and the final 3D amplitude image is obtained by amplitude correction and superposition (Formula 3).

[0098] , formula 3

[0099] is the final three-dimensional amplitude image calculated, The overall three-dimensional holographic data is quickly reconstructed in the wave number domain. The 3D holographic data of the local area of ​​the leg calculated by the BP reconstruction algorithm. is the correction factor, usually an empirical constant.

[0100] The overall image obtained by rapid reconstruction in the wavenumber domain (such as Fig. 9 As shown in the figure, the image of the foot and nearby parts is weak) and the enhanced image of the leg, as shown in the figure Fig.10 shown.

[0101] The millimeter wave imaging device may also include other auxiliary devices.

[0102] In an embodiment of the present invention, an operation and display terminal may be provided for imaging system operation, display of a full-body image of a millimeter-wave holographic image and a partially enhanced full-body image, and the like.

[0103] One aspect of the present invention further provides a security inspection device, comprising the above-mentioned millimeter wave imaging device.

[0104] The security inspection equipment may include other components or devices, which are not described in detail here.

[0105] One aspect of the present invention also provides a security inspection method. In the present invention, a method is provided to enhance the image clarity of the foot and its vicinity. The method comprises: using the above-mentioned millimeter wave imaging device to emit millimeter waves to illuminate the inspected object, and receiving the reflected millimeter wave echo signal, constructing an overall holographic image of the inspected object and an enhanced holographic image of the part close to the plate, so as to construct a partially enhanced overall holographic image.

[0106] In this embodiment, the echo signal includes: a first part of the millimeter wave emitted from at least one millimeter wave transceiver array is incident on the object under inspection, wherein a portion of the millimeter wave is reflected from the object under inspection back to the millimeter wave of the at least one millimeter wave transceiver array; a first part of the millimeter wave emitted by at least one millimeter wave transceiver array toward the object under inspection is incident on the object under inspection, a portion of the first part of the emitted millimeter wave is reflected from the object under inspection to the at least one plate, and then reflected by the at least one plate back to the millimeter wave of the at least one millimeter wave transceiver array; and a second part of the millimeter wave emitted by at least one millimeter wave transceiver array toward the object under inspection is incident on the at least one plate, a portion of the second part of the emitted millimeter wave is reflected by the at least one plate to the object under inspection, and then the object under inspection reflects the millimeter wave back to the at least one millimeter wave transceiver array.

[0107] The device and method of the present invention can also be applied to other scenarios, such as inspecting other objects.

[0108] The method according to the present invention can perform an all-round inspection on the human body surface, and can inspect the holographic image of parts of the human body with weak echo signals, such as feet, and provide accurate inspection results.

[0109] 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 the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0110] In the technical solution of the present disclosure, the collection, storage, use, processing, transmission, provision and disclosure of user personal information involved are in compliance with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0111] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made to the disclosed embodiments or examples according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A millimeter wave imaging device, comprising: At least one millimeter wave transceiver array, used for transmitting millimeter waves and receiving reflected millimeter waves; and at least one board; The millimeter wave imaging device is configured to construct a holographic image of the inspected object by transmitting millimeter waves toward the inspected object through the at least one millimeter wave transceiver array and receiving reflected millimeter waves; The at least one plate is capable of reflecting at least a portion of the millimeter wave incident on the at least one plate toward the object under inspection and the at least one millimeter wave transceiver array; The millimeter wave imaging device is configured to reconstruct a holographic image of the object under inspection based on a first part of the millimeter waves emitted from at least one millimeter wave transceiver array being incident on the object under inspection, and a part of the first part of the emitted millimeter waves being reflected from the object under inspection back to the millimeter waves of the at least one millimeter wave transceiver array, and also to reconstruct an enhanced holographic image of a portion of the object under inspection close to the at least one plate based on additional millimeter waves reflected back from a three-dimensional area close to the at least one plate.

2. The millimeter wave imaging device of claim 1, wherein the additional millimeter waves reflected back from a three-dimensional area near the at least one plate include: A first portion of the millimeter waves emitted by the at least one millimeter-wave transceiver array toward the object under test is incident on the object under test, wherein another portion of the emitted first portion of the millimeter waves is reflected by the object under test to the at least one plate, and then reflected by the at least one plate back to the millimeter waves of the at least one millimeter-wave transceiver array.

3. The millimeter wave imaging device of claim 1 , wherein the additional millimeter waves reflected back from a three-dimensional region proximate to the at least one plate include: The second part of the millimeter wave emitted by the at least one millimeter wave transceiver array toward the object under test is incident on the at least one plate, and a part of the second part of the emitted millimeter wave is reflected by the at least one plate to the object under test, and then reflected by the object under test back to the millimeter wave of the at least one millimeter wave transceiver array. 4 . The millimeter wave imaging apparatus according to claim 1 , wherein the at least one plate is configured to support the object to be inspected or to support the vicinity of a position of the object to be inspected. 5 . The millimeter wave imaging device according to claim 1 , wherein the at least one plate comprises a reflective surface capable of reflecting at least a portion of the millimeter waves.

6. The millimeter wave imaging device according to claim 1, wherein the at least one millimeter wave transceiver array comprises at least one row of transmitting antennas and receiving antennas, each transmitting antenna and one receiving antenna can be arranged adjacent to each other to form a pair of transmitting antennas and receiving antennas, and multiple pairs of transmitting antennas and receiving antennas are arranged in one dimension; or The at least one millimeter wave transceiver array includes at least one row of transmitting antenna-receiving antenna pairs, and the transmitting antenna and receiving antenna of each pair of transmitting antenna-receiving antennas are arranged laterally along the extension direction of the millimeter wave transceiver array, with the transmitting antennas arranged in one row and the receiving antennas arranged in another row.

7. The millimeter wave imaging device according to claim 1, further comprising: At least one column, the at least one millimeter wave transceiver array is supported by the at least one column, wherein the at least one millimeter wave transceiver array is arranged in a horizontal direction and moves along the at least one column.

8. The millimeter wave imaging device according to claim 7, wherein the at least one millimeter wave transceiver array comprises a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array are arranged toward the object to be inspected; At least one column includes a first column and a second column, the first millimeter wave transceiver array is supported by the first column and moves along the first column, and the second millimeter wave transceiver array is supported by the second column and moves along the second column.

9. The millimeter wave imaging device according to claim 8, wherein the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in the vertical direction; or The first millimeter wave transceiver array and the second millimeter wave transceiver array move asynchronously in a vertical direction.

10. The millimeter wave imaging device according to claim 8, wherein the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction along the vertical direction; or The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move in opposite directions along the vertical direction.

11. The millimeter wave imaging device according to claim 1, wherein the at least one millimeter wave transceiver array extends in a vertical direction.

12. The millimeter wave imaging device according to claim 10, wherein the at least one millimeter wave transceiver array comprises a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array move synchronously in the horizontal direction; or The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move asynchronously in a horizontal direction.

13. The millimeter wave imaging device according to claim 10, wherein the at least one millimeter wave transceiver array comprises a first millimeter wave transceiver array and a second millimeter wave transceiver array, and the first millimeter wave transceiver array and the second millimeter wave transceiver array move in the same direction along the horizontal direction; or The first millimeter wave transceiver array and the second millimeter wave transceiver array are configured to move in opposite directions along the horizontal direction.

14. A security inspection device, comprising: Millimetre wave imaging apparatus as claimed in any preceding claim.

15. A security inspection method, comprising: The millimeter wave imaging device described in claim 1 is used to emit millimeter waves to illuminate the object under inspection in the inspection channel, and receive the reflected millimeter wave echo signal, thereby constructing an overall holographic image of the object under inspection and an enhanced holographic image of the part close to the plate, so as to construct a partially enhanced overall holographic image.

Images