A hand-held security inspection device and security inspection method based on terahertz technology

Abstract

The present invention provides a handheld security inspection device and a security inspection method based on terahertz technology, which relates to the technical field of terahertz applications. A terahertz detection component detects and receives terahertz waves radiated by a target, converts the terahertz waves into electrical signals and sends them to a signal acquisition and processing module; a laser ranging module measures the distance from the handheld security inspection device to the target in real time; the signal acquisition and processing module acquires the electrical signals at intervals, calculates the difference in terahertz radiation intensity between the previous moment and the current moment, compares the intensity difference with a target threshold corresponding to the distance, and determines whether there are prohibited items.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz applications, and particularly to a handheld security inspection device and a security inspection method based on terahertz technology. Background Art

[0002] Terahertz is an electromagnetic wave with a wavelength of 3 mm to 30 μm, and its frequency range is 0.1 THz to 10 THz. Due to the special position of terahertz waves in the electromagnetic spectrum, it has many excellent characteristics different from other bands, such as high penetrability, large bandwidth, low photon energy, fingerprint spectrum characteristics, etc. Based on the unique properties of terahertz, terahertz technology has been widely applied in fields such as space exploration, communication, biomedicine, and public security in recent years.

[0003] There are a large number of people in public places and the situation is complex. There are often lawbreakers carrying prohibited items such as knives, guns, and various explosives to commit crimes, resulting in heavy casualties and property losses, and also causing extremely bad negative impacts on society. It is urgent to conduct security checks on people entering public places.

[0004] At present, the means of human body security inspection in public places include handheld metal detectors, metal security gates, X-ray backscatter imaging security inspection equipment, millimeter-wave human body security inspection equipment, and passive terahertz human body security inspection equipment, but each means has certain limitations.

[0005] 1. Handheld metal detectors and metal security gates:

[0006] Handheld metal detectors and metal security gates can detect whether the passing people carry metal items, but they cannot detect dangerous items made of non-metal materials, such as ceramic knives, explosives, etc. At the same time, the false alarms of metal detection are relatively high, and manual touch recheck is required, which has a certain degree of invasiveness.

[0007] 2. X-ray backscatter security inspection equipment:

[0008] X-ray backscatter imaging technology is used for security inspection, which can effectively detect metal prohibited items hidden under human clothes, as well as non-metal prohibited items such as ceramic knives, plastic guns, hybrid weapons, liquid bombs, and drugs. However, when this equipment works, it will generate X-rays, which have ionizing radiation and great harm to the human body.

[0009] 3. Millimeter-wave human body security inspection equipment:

[0010] Millimeter-wave human body security inspection equipment is based on the principle of radar imaging for security inspection imaging. The millimeter-wave human body security inspection equipment has high resolution, up to the millimeter level; and good environmental adaptability. However, during security inspection, the person to be inspected needs to stay still for 2 to 3 seconds, and real-time non-stop security inspection cannot be achieved. It occupies a large space and is relatively difficult to deploy.

[0011] 4. Passive terahertz human body security inspection equipment:

[0012] Passive terahertz body security inspection equipment is based on the principle of passive terahertz imaging technology, which can detect prohibited items such as metals, ceramics, liquids, powders, etc. carried by people. However, the terahertz equipment currently used in the market is channel terahertz equipment, which occupies a large space and is difficult to deploy. Summary of the invention

[0013] In order to solve the above technical problems, the present invention proposes a security inspection method of a handheld security inspection device based on terahertz technology, comprising the following steps:

[0014] The terahertz detection component detects the terahertz waves radiated by the receiving target, converts the terahertz waves into electrical signals and sends them to the signal acquisition and processing module;

[0015] The laser ranging module measures the distance from the handheld security inspection device to the target in real time;

[0016] The signal acquisition and processing module acquires the electrical signal at intervals, calculates the terahertz radiation intensity difference between the current moment and the previous moment, compares the intensity difference with the target threshold corresponding to the distance at the current moment measured by the laser ranging module, and determines whether there are contraband.

[0017] Furthermore, the maximum detection distance L is divided into m distance segments: 0~L1, L1~L2, ..., L m-1 ~L m ; Define the intensity difference threshold corresponding to each distance segment j as TH j , j=1,2,3,…,m, the intensity difference threshold TH j Exist in the threshold array TH;

[0018] The terahertz detection component has N detection channels, and the difference in terahertz radiation intensity between the current moment and the previous moment of the nth detection channel is calculated and stored in the nth position in the array DC;

[0019] According to the distance measured by the laser rangefinder at the current moment, determine the distance segment and the corresponding intensity difference threshold, and assign it to the target threshold TH a ;

[0020] The intensity difference stored at each position in the array DC is compared with the target threshold TH a By comparison, if the N intensity differences stored in the array DC are all less than the target threshold TH a , then it is judged that there is no contraband at the target; if there is at least one intensity difference not less than the target threshold TH a , then it is determined that there are contraband at the target.

[0021] Further, each detection channel is calibrated at fixed time intervals. The i-th polynomial fitting method is used to calibrate the detection channels, and for the terahertz radiation intensity P detected by each detection channel n n Through the calibration polynomial Calibration is performed to obtain the calibrated terahertz radiation intensity , and the coefficients in the calibration polynomial , ,…, , are solved using the least gradient descent method.

[0022] Further, the terahertz radiation intensity data of each calibrated detection channel n is stored in a one-dimensional array D0 with a size of 1*N. After an interval time , the newly obtained terahertz radiation intensity data of each detection channel n is stored in a one-dimensional array D1 with a size of 1*N. The terahertz signal intensity difference is obtained by taking the absolute value of the difference between the intensity values corresponding to the same detection channel n in arrays D0 and D1, and is stored in an array DC with a size of 1*N. When the next interval time arrives, the terahertz radiation intensity of array D1 is assigned to array D0, and array D1 is used to store the terahertz radiation intensity collected in the next interval time .

[0023] The present invention also proposes a handheld security inspection device based on terahertz technology for implementing the security inspection method, including: a terahertz detection component, a signal acquisition and processing module, and a laser ranging module;

[0024] The terahertz detection component is used to detect and receive the terahertz wave radiated by the target, convert the terahertz wave into an electrical signal, and send it to the signal acquisition and processing module;

[0025] The laser ranging module is used to measure the distance from the handheld security inspection device to the target in real time;

[0026] The signal acquisition and processing module is used to collect the electrical signal at interval times, calculate the terahertz radiation intensity difference between the previous moment and the current moment, determine the distance segment to which the distance measured by the laser ranging module belongs and the corresponding intensity difference threshold, and assign it to the target threshold; compare the intensity difference with the target threshold to determine whether there are prohibited items.

[0027] Further, the handheld security inspection device further includes an optical camera, a display and control module, and an audible and visual alarm module;

[0028] The optical camera is used to perform real-time optical imaging on the target and output an optical video stream;

[0029] The display and control module is used to control the handheld security inspection device, match the judgment result of the signal acquisition and processing module with the optical video stream output by the optical camera, display it on the display screen, and control the acoustic-optic alarm module to give an alarm.

[0030] Further, the terahertz detection component includes: a plurality of receiving antennas and a plurality of detectors. The receiving antennas are used to receive the terahertz waves radiated by the target, and the detectors are used to convert the terahertz waves into electrical signals. The plurality of receiving antennas and the plurality of detectors form N detection channels.

[0031] Further, the signal acquisition and processing module includes: a signal acquisition module and a signal processing module;

[0032] The signal acquisition module is used to complete the sampling of the output signal of the terahertz detection component;

[0033] The signal processing module is used to perform noise reduction, channel calibration and parsing processing on the acquired output signal, and judge whether there are prohibited items.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] The handheld security inspection device of the present invention is used for security inspection of targets in the security inspection spaces of rail transit, airports, railways, courts, and large-scale events. The handheld security inspection device has the advantages of being small and easy to operate, and can detect prohibited items of various materials (such as metals, ceramics, liquids, powders, etc.); it uses the passive terahertz security inspection principle and has no radiation; the results are visualized and there is an acoustic-optic alarm. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic diagram of the use of the handheld security inspection device of the present invention;

[0038] Figure 2 It is a schematic structural diagram of the handheld security inspection device of the present invention;

[0039] Figure 3 It is a schematic diagram of the terahertz detection component of the present invention receiving human body radiation;

[0040] Figure 4 It is a schematic diagram of the threshold array of the present invention;

[0041] Figure 5Schematic diagram of the terahertz radiation intensity array of the present invention. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0043] In the accompanying drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the components in the system and show the connection relationships of the various parts of the device, only the relative positional relationships between the components are clearly distinguished, which cannot constitute a limitation on the signal transmission direction, connection sequence, and the sizes, dimensions, and shapes of the various parts of the structure within the component or structure.

[0044] Schematic diagram of the use of the handheld security inspection device is as Figure 1 shown. The working principle of the handheld security inspection device is that the staff holds the security inspection device and scans the person to be inspected from top to bottom, passively receiving the terahertz waves radiated by the person to be inspected and the contraband target. If the person is carrying contraband, which blocks or absorbs the terahertz waves radiated by the person, then the signal intensity at the position of the contraband is different from the terahertz signal intensity of the person. Through signal processing and analysis, it can be determined whether it is contraband. An optical camera is integrated inside the security inspection device for real-time imaging. When the terahertz technology determines that the target is contraband, it will be marked on the optical image corresponding to the position of the target and output to the display screen.

[0045] Schematic diagram of the structure of the handheld security inspection device is as Figure 2 shown. The handheld security inspection device includes: a terahertz detection component, a signal acquisition and processing module, a laser ranging module, an optical camera, a display and control module, an audible and visual alarm module, and a power supply module.

[0046] The terahertz detection component is used to detect and receive the terahertz waves radiated by the human body and convert them into electrical signals for use by the subsequent signal acquisition and processing module.

[0047] The terahertz detection component includes: a plurality of receiving antennas and a plurality of detectors. Among them, the receiving antennas are used to receive the terahertz waves radiated by the human body and the contraband target, and the detectors convert the terahertz waves into electrical signals and send them to the subsequent signal acquisition and processing module. The plurality of receiving antennas and the plurality of detectors are designed in an array form. One receiving antenna and one detector form one detection channel, and the plurality of receiving antennas and the plurality of detectors form N detection channels.

[0048] The terahertz waves radiated by the human background and contraband targets received by the terahertz detection component are as follows Figure 3 shown. The terahertz receiving antenna is a directional antenna with a certain beam width. Looking out from the antenna aperture, the beam is conical. At different distances from the antenna, the receiving field of view of the antenna is different. As shown in Figure 3 the figure, the closer to the antenna, the smaller the human body area entering the receiving field of view of the antenna. Ignoring the attenuation of electromagnetic waves at relatively close distances, the human body area is proportional to the terahertz radiation intensity, that is, the larger the human body area entering the receiving field of view of the terahertz antenna, the greater the terahertz radiation intensity.

[0049] The signal acquisition and processing module includes: a signal acquisition module and a signal processing module.

[0050] The signal acquisition module is used to complete the sampling of the signals output by the terahertz detection component, and the collected data is output to the signal processing module for processing. The signal acquisition module includes: N A / D chips and conditioning circuits, and each detection channel is configured with 1 A / D channel.

[0051] The signal processing module is used to perform processing such as noise reduction, channel calibration, and parsing on the signals output by the signal acquisition module, and judge whether there is contraband according to the parsing results. The signal processing module includes: a microprocessor and peripheral circuits.

[0052] Signal noise reduction processing: The terahertz waves radiated by the human body and contraband targets are weak signals, and the system operates in a passive mode, which introduces noise. Therefore, noise reduction processing is required after the terahertz signals are collected.

[0053] Channel calibration: The current production process level of terahertz detection components cannot guarantee the response consistency between channels, and the response of terahertz detection components will change with the temperature environment. Therefore, each channel needs to be calibrated at intervals.

[0054] The specific channel calibration method is as follows. Let the same excitation S, for example, the terahertz radiation of the inspected person without carrying the target be used as the excitation. Let the terahertz radiation intensity of the inspected person output by the nth channel of the terahertz detection component be , where n = 1, 2,..., N; let be the calibrated terahertz radiation intensity of the inspected person; it is necessary to calibrate the of each channel of the terahertz detection component to .

[0055] Use the method of -order polynomial fitting to calibrate the detection channels, that is, , where the coefficients in the calibration polynomial , ,..., , The solution of is implemented using the minimum gradient descent method.

[0056] During the operation of the handheld security inspection device, each collected signal is calibrated after noise reduction processing, and then parsing processing is performed.

[0057] For signal parsing, when the human body is used as the background and a prohibited item target is carried, due to the shielding or absorption of terahertz radiation by the prohibited item target, the intensity of terahertz radiation at the position of the prohibited item received by the detector decreases. Target parsing is performed by detecting the decrease in the intensity of terahertz radiation.

[0058] By obtaining the radiation intensities of the inspected persons and the carried prohibited item targets in different distance ranges through preliminary tests, calculating the difference in terahertz radiation intensities between the inspected persons carrying prohibited item targets and not carrying targets within the set distance range, the intensity difference threshold of terahertz radiation intensities in different distance ranges is obtained accordingly, and it is stored as a threshold array for subsequent signal parsing for target detection.

[0059] The laser ranging module is used to measure the distance from the surface of the security inspection device to the human body in real time, providing data support for selecting the intensity difference threshold for subsequent signal parsing.

[0060] The optical camera is used for real-time optical imaging of the target and outputs an optical video stream.

[0061] The display and control module is used to control the working logic of the whole machine, match the result of terahertz signal processing with the optical video stream output by the optical camera, and finally display it on the display screen, and control the sound and light alarm module to give an alarm.

[0062] After receiving the "prohibited item" command, the display and control module performs the following three operations:

[0063] 1. Control the optical camera to intercept the optical picture at the current moment, mark it, and display it on the display screen;

[0064] 2. Store the intercepted and marked optical picture;

[0065] 3. Synchronously control the indicator light of the sound and light alarm module to flash and emit an alarm sound.

[0066] The sound and light alarm module is used for sound and light alarm prompts. It mainly includes an LED indicator light and a speaker.

[0067] The power supply module is used for power supply and distribution management of the whole machine. The power supply module supports charging and discharging.

[0068] The working principle of the handheld security inspection device is as follows:

[0069] During the mobile detection process of the handheld security inspection device, at fixed intervals of time, the laser ranging module measures the distance from the inspected person to the security inspection device in real time.

[0070] The signal acquisition and processing module is used to acquire the electrical signal at intervals, calculate the difference in terahertz radiation intensity between the previous moment and the current moment, determine the distance segment to which the distance measured by the laser ranging module belongs and the corresponding intensity difference threshold, and assign it to the target threshold; compare the intensity difference with the target threshold to determine whether there are contraband items.

[0071] The handheld security inspection device has N detection channels; the maximum detection distance during operation is L. The radiation intensities of the inspected persons and the contraband targets carried within different distance ranges are obtained through preliminary tests. The terahertz radiation intensity differences between the cases where the inspected persons carry contraband targets and do not carry targets within the set distance range are calculated, and the intensity difference thresholds for different distance ranges are obtained accordingly. The detection distance L is divided into m segments 0-L1, L1-L2,..., L m-1 ~L m . According to the test results, the terahertz radiation intensity difference threshold corresponding to each distance segment is defined as TH j , where j = 1, 2, 3,..., m. The target threshold TH j is present in the threshold array TH. The structure of the threshold array TH is as Figure 4 shown.

[0072] After the security inspection device is powered on, the staff moves the security inspection device. The detection component detects the terahertz waves radiated by the human body and the contraband targets carried. After the signal acquisition module collects the data and performs noise reduction and averaging, the data of each channel is calibrated through a calibration polynomial , where n = 1, 2,..., N; the calibrated terahertz intensity data of each channel is stored in a one-dimensional array . The size of the array is 1*N;

[0073] At the interval time , the terahertz signals output by the detection component are collected, noise reduction and averaging are performed, and after the data of each channel is calibrated through a calibration polynomial , a one-dimensional array with a size of 1*N is output; at the adjacent interval time , the change in the terahertz signal intensity can be obtained by taking the absolute difference of the intensity values corresponding to the same detection channel n in the arrays D0 and D1, and is stored in an array DC with a size of 1*N. Among them, DC n is the nth position in the array DC, where the intensity difference between adjacent moments of the nth detection channel is stored. Among them, n = 1, 2,..., N. When the next interval time arrives, the data of D1 is assigned to D0, and D1 is ready to store the newly collected and processed data after the next interval time .

[0074] The display and control module controls the laser rangefinder to measure the distance between the human body and the security inspection device, determines the corresponding distance segment and the intensity difference threshold according to the distance measured by the laser rangefinder at the current moment, and assigns it to the target threshold TH a ;

[0075] Compare each position DC in the intensity difference array DC n The stored intensity differences with the target threshold TH a If there is an intensity difference not less than the target threshold TH among the N intensity differences stored in the array DC a , it is determined that there are contraband items at this target. The signal processing module sends a "contraband" command to the display and control module;

[0076] The display and control module controls the optical camera to capture the current optical picture, marks it and outputs it to the display screen; controls the indicator light of the sound and light module to flash and the speaker to emit an alarm sound; stores the picture; loops through steps a) to e) until the security inspection of the person being inspected is completed;

[0077] If all the N intensity differences stored in the array DC are less than the intensity difference of the target threshold TH a , it is determined that there are no contraband items at this target, and steps a) to e) are looped through until the security inspection of the person being inspected is completed.

[0078] The functions that the handheld security inspection device of the present invention can achieve are as follows:

[0079] The handheld device can passively detect whether a person is carrying contraband without radiation; it can detect metal and non-metal contraband, such as controlled knives and guns, ceramic knives, liquid poisons, powder explosives, etc.; the device is light and easy to operate; the results are visual and there is a sound and light alarm; it has a charging function.

[0080] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state disk (SSD)), etc.

[0081] As described above, the foregoing is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A security inspection method for a handheld security inspection device based on terahertz technology, characterized in that, It includes the following steps: The terahertz detection component detects and receives the terahertz wave radiated by the target, and converts the terahertz wave into an electrical signal and sends it to the signal acquisition and processing module; The laser ranging module measures the distance from the handheld security inspection device to the target in real time; The signal acquisition and processing module acquires the electrical signal at intervals, calculates the difference in terahertz radiation intensity between the current moment and the previous moment, compares the intensity difference with the target threshold corresponding to the distance measured by the laser ranging module at the current moment, and determines whether there are contraband items; Through preliminary tests, the radiation intensities of the inspected persons and the contraband targets in different distance ranges are obtained, and the difference in terahertz radiation intensity between the inspected persons carrying contraband targets and those not carrying targets within the set distance range is calculated, and the intensity difference thresholds for different distance ranges are obtained accordingly; Divide the maximum detection distance L into m distance segments: 0 to L1, L1 to L2, ……, L m-1 ~L m ; Define the intensity difference threshold corresponding to each distance segment j as TH j , j = 1, 2, 3, …, m, and store the intensity difference threshold TH j in the threshold array TH; The terahertz detection component has N detection channels, calculates the difference in terahertz radiation intensity between the current moment and the previous moment of the nth detection channel, and stores it in the nth position of the array DC; The terahertz radiation intensity data of each calibrated detection channel n are stored in a one-dimensional array D0 with a size of 1*N. After an interval time , the newly obtained terahertz radiation intensity data of each detection channel n are stored in a one-dimensional array D1 with a size of 1*N. The terahertz signal intensity difference is obtained by taking the absolute value of the difference between the intensity values corresponding to the same detection channel n in arrays D0 and D1, and is stored in an array DC with a size of 1*N. At the arrival of the next interval time , the terahertz radiation intensity of array D1 is assigned to array D0, and array D1 is used to store the terahertz radiation intensity collected in the next interval time ; Determine the distance segment to which it belongs and the corresponding intensity difference threshold according to the distance at the current moment measured by the laser rangefinder, and assign it to the target threshold TH a ; Compare the intensity differences stored at each position in the array DC with the target threshold TH a respectively. If all N intensity differences stored in the array DC are less than the target threshold TH a , it is determined that there is no contraband at this target; if there is at least one intensity difference not less than the target threshold TH a , it is determined that there is contraband at this target.

2. The security inspection method according to claim 1, wherein Calibrate each detection channel at fixed intervals, use the i-th polynomial fitting method to calibrate the detection channels, and for the terahertz radiation intensity P detected by each detection channel n n Through the calibration polynomial Perform calibration to obtain the calibrated terahertz radiation intensity , the coefficients in the calibration polynomial , ,…, , Solve using the least gradient descent method.

3. A handheld security inspection device based on terahertz technology, characterized in that, For implementing the security inspection method described in any one of claims 1-2, it includes: a terahertz detection component, a signal acquisition and processing module, and a laser ranging module; The terahertz detection component is used to detect and receive the terahertz wave radiated by the target, convert the terahertz wave into an electrical signal, and send it to the signal acquisition and processing module; The terahertz detection component includes: a plurality of receiving antennas and a plurality of detectors. The receiving antennas are used to receive the terahertz wave radiated by the target, and the detectors are used to convert the terahertz wave into an electrical signal. The plurality of receiving antennas and the plurality of detectors form N detection channels; The laser ranging module is used to measure the distance from the handheld security inspection device to the target in real time; The signal acquisition and processing module is used to acquire the electrical signal at intervals, calculate the difference in terahertz radiation intensity between the previous moment and the current moment, determine the distance segment to which the distance measured by the laser ranging module belongs and the corresponding intensity difference threshold, assign it to the target threshold; compare the intensity difference with the target threshold to determine whether there are contraband items.

4. The handheld security inspection device according to claim 3, characterized in that, The handheld security inspection device further includes an optical camera, a display and control module, and an audible and visual alarm module; The optical camera is used to perform real-time optical imaging on the target and output an optical video stream; The display and control module is used to control the handheld security inspection device, match the judgment result of the signal acquisition and processing module with the optical video stream output by the optical camera, display it on the display screen, and control the audible and visual alarm module to give an alarm.

5. The handheld security inspection device according to claim 3, characterized in that, The signal acquisition and processing module includes: a signal acquisition module and a signal processing module; The signal acquisition module is used to complete the sampling of the output signal of the terahertz detection component; The signal processing module is used to perform noise reduction, channel calibration and analysis processing on the acquired output signal to determine whether there are contraband items.

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