Low-cost portable millimeter wave radiation imaging system and method

Abstract

The invention provides a portable low-cost millimeter wave radiation imaging system and system. The system comprises a millimeter wave radiometer, an IMU module, a range finder, an optical camera, an acquisition module, a wireless transceiver module, a power supply module, an equipment appearance tool, client equipment and a detachable portable support rod. The millimeter wave radiometer is used for acquiring a millimeter wave radiation brightness temperature value of an observation scene, the IMU module is used for acquiring azimuth angle and pitch angle information of the meter wave radiometer, the range finder is used for acquiring the distance to the observation scene or a target, and the optical camera is used for acquiring an optical image of the observation scene; synchronously acquiring the data through an acquisition module; the collected data is transmitted to client equipment through the wireless receiving and transmitting module; performing two-dimensional uniform interpolation on the non-uniform azimuth angle and pitch angle on the client device; performing corresponding interpolation processing on the millimeter wave radiation brightness temperature value to generate a homogenized millimeter wave radiation image; and performing registration and fusion display on the millimeter wave radiation image and the optical image.

Description

Technical Field

[0001] This invention relates to the field of passive millimeter-wave radiation imaging and detection, and more particularly to a portable, low-cost millimeter-wave radiation imaging technology solution. Background Technology

[0002] Remote sensing technology involves receiving electromagnetic waves reflected from or radiated by a target (scene) from a distance, then interpreting and analyzing these waves to obtain rich information about the target, including its material, size, dielectric constant, reflectivity, etc., and using this information for target classification and identification. From a platform perspective, remote sensing technology can be divided into three main categories: ground-based remote sensing, air-based remote sensing, and spaceborne remote sensing. From the perspective of the observed object, it can be divided into land remote sensing, atmospheric remote sensing, and ocean remote sensing. Currently, from the perspective of electromagnetic wave wavelength, the main remote sensing technologies include visible light, infrared, and microwave remote sensing. Visible light imaging technology has the advantage of high resolution, but generally has a narrow field of view and is easily affected by low-visibility weather conditions such as clouds, fog, smoke, and rain. Infrared detection technology also has high spatial resolution, but similarly has a narrow field of view and is greatly affected by the Earth's background. Although it has stronger penetrating power than optical imaging, it also cannot penetrate clouds and rain areas and is greatly affected by low-visibility weather conditions such as clouds and rain. Currently, microwave remote sensing primarily relies on active radar, which is the mainstream sensor in microwave remote sensing. Active radar imaging technology offers all-weather, 24 / 7 imaging capabilities, but it requires active signal transmission, resulting in high power consumption, poor stealth, and susceptibility to interference from land and sea clutter. Millimeter-wave radiation imaging technology, on the other hand, is attracting significant attention due to its numerous advantages, including all-weather, 24 / 7 capability, strong stealth due to no signal transmission, minimal interference from land and sea clutter, and good detection capabilities against stealth and electromagnetically silent targets. Millimeter-wave radiation imaging technology can penetrate the Earth's surface, vegetation, and even human bodies to a certain depth, providing information that visible light, infrared, hyperspectral, and active radar remote sensing methods cannot provide. It has strong practical application value in fields such as Earth remote sensing, security and inspection, precision guidance, and target detection.

[0003] In millimeter-wave radiation imaging application research, many representative companies, such as RPG, Millivision, TRW, Andrew, and QinetiQ, have developed millimeter-wave imaging systems that can be applied to civilian fields such as security inspection, ground imaging, marine surveillance, and marine oil spill monitoring (see passive millimeter-wave imaging). Among them, target detection and passive microwave remote sensing are two important application directions of millimeter-wave radiation imaging technology. In particular, in recent years, millimeter-wave radiation imaging technology has received much attention in the field of target detection.

[0004] In the field of millimeter-wave radiation imaging technology and its applications, millimeter-wave radiation imaging experiments on various types of targets and scenarios are a crucial research area. Millimeter-wave radiation imaging primarily involves acquiring millimeter-wave radiation images of targets. Analyzing these images reveals the millimeter-wave radiation characteristics of the targets, providing vital support for the demonstration of millimeter-wave radiation imaging systems and the feasibility analysis of target detection. The primary equipment for acquiring millimeter-wave radiation images of targets is the millimeter-wave radiometer. Currently, the main types of millimeter-wave radiometers used for millimeter-wave radiation imaging include real-aperture millimeter-wave radiometers, focal-plane millimeter-wave radiometers, and synthetic aperture millimeter-wave radiometers. Real-aperture millimeter-wave radiometers (MWRTs) have a simple structure and high resolution, but they generally require a bulky, high-precision two-dimensional mechanical scanning platform. These platforms are cumbersome, costly, and inconvenient for field operation. Focal-plane millimeter-wave radiometers (FWRTs) consist of multiple real-aperture MWRTs; while they may not require a two-dimensional scanning platform, they still necessitate multiple radiometers, leading to high costs. Synthetic aperture MWRTs, composed of multiple radiometers, acquire millimeter-wave radiation images of the target through interferometric imaging. However, synthetic aperture MWRTs are also costly and require additional acquisition equipment. Although they offer advantages such as instantaneous imaging, this comes at the cost of increased system and signal processing complexity. In conclusion, low-cost, lightweight, and simple-to-process millimeter-wave radiometers represent a crucial future development path for millimeter-wave radiometers, and the development of corresponding practical technical solutions is urgently needed in this field. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing millimeter-wave radiation imaging systems, such as high cost, bulky size, and complex operation, and to provide a portable, low-cost millimeter-wave radiation imaging system and method. Its specific objectives include: 1) Solving the cost problem: Through innovative system architecture, the expensive and bulky high-precision 2D mechanical scanning platform is abandoned, and low-cost module combination is adopted, which significantly reduces the manufacturing cost of the entire system.

[0006] 2) Solving the portability problem: Through lightweight design and integrated packaging, the system weight and size are greatly reduced, and wireless data transmission and portable support rods are introduced, making it easy to carry, deploy and operate, and suitable for various scenarios such as the field and mobile platforms.

[0007] 3) Solving the usability problem: Provides an easy-to-operate imaging method that supports both manual and support rod-assisted scanning modes, and combines real-time data feedback, enabling non-professional users to quickly obtain the coverage of the scanning area and ensure the integrity of the imaging.

[0008] 4) Enhance image usability: Through data fusion technology, the obtained millimeter-wave radiation images are accurately matched and superimposed with high-resolution optical images to provide users with more intuitive and information-rich fused images, which facilitates the analysis of the millimeter-wave radiation characteristics of targets and scenes.

[0009] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions: A portable, low-cost millimeter-wave radiation imaging system includes a millimeter-wave radiometer, an IMU module, a rangefinder, an optical camera, an acquisition module, a wireless transceiver module, a power module, an external fixture, a client device, and a detachable portable support rod. The millimeter-wave radiometer is used to obtain the millimeter-wave radiation brightness temperature of the observed scene; The IMU module is used to acquire the azimuth, elevation and yaw angle information of the millimeter-wave radiometer; The rangefinder is used to measure the distance from the millimeter-wave radiometer to the observation scene or target; The optical camera is used to acquire optical images of the observed scene; The acquisition module is used to acquire the output signals of the millimeter-wave radiometer, IMU module, rangefinder and optical camera; The wireless transceiver module is used to transmit control commands and collected data to the client device; The power module is used to supply power to the various modules of the system; The device's external tooling is used to integrate the millimeter-wave radiometer, IMU module, rangefinder, optical camera, data acquisition module, wireless transceiver module, and power supply module, and is equipped with a handle and a circular rotating joint. The detachable portable support rod is connected to the equipment's external tooling via the circular rotary joint, supporting manual 2D scanning.

[0010] Furthermore, the millimeter-wave radiometer includes a Cassegrain antenna, a millimeter-wave low-noise amplifier, a millimeter-wave filter, a millimeter-wave power amplifier, a millimeter-wave detector, and an integrator connected in sequence, for outputting a voltage signal corresponding to the brightness temperature of the scene's millimeter-wave radiation.

[0011] Furthermore, the IMU module is used to measure the azimuth, pitch, yaw, three-axis velocity, and acceleration information of the millimeter-wave radiometer in real time during the scanning process.

[0012] Furthermore, the acquisition module simultaneously acquires the voltage signal of the millimeter-wave radiometer, the attitude information of the IMU module, the distance information of the rangefinder, and the image data of the optical camera.

[0013] Furthermore, the wireless transceiver module uses wireless transmission to enable data interaction between the acquisition module and the client device, supporting real-time display and control.

[0014] Furthermore, the device's external tooling is equipped with handles on the top and sides for easy hand operation and angle adjustment.

[0015] Moreover, the detachable portable support rod enables manual two-dimensional scanning of azimuth and pitch angles through a circular rotary joint, replacing the traditional two-dimensional mechanical scanning platform.

[0016] On the other hand, the present invention provides a portable, low-cost millimeter-wave radiation imaging method, characterized by comprising the following steps: The millimeter-wave radiation brightness temperature value of the observation scene is obtained using a millimeter-wave radiometer, the azimuth and elevation angle information of the millimeter-wave radiometer is obtained using an IMU module, the distance to the observation scene or target is obtained using a rangefinder, and the optical image of the observation scene is obtained using an optical camera. The above data is collected synchronously through the acquisition module; The collected data is transmitted to the client device via a wireless transceiver module; On the client device, two-dimensional uniform interpolation is performed on the non-uniform azimuth and elevation angles; the millimeter-wave radiation brightness temperature value is interpolated accordingly to generate a uniform millimeter-wave radiation image; the millimeter-wave radiation image is registered and fused with the optical image for display.

[0017] Moreover, the two-dimensional uniform interpolation is implemented by dividing the non-uniform azimuth and elevation angles obtained by the IMU module into a uniform grid within a preset scanning range; and averaging or interpolating the millimeter-wave radiation brightness temperature values ​​falling within each uniform grid to obtain the brightness temperature values ​​under uniform angular coordinates.

[0018] Furthermore, when performing image registration and fusion display, based on the consistent reference positions of the IMU module and the millimeter-wave radiometer, the pixels of the millimeter-wave radiation image are mapped to the optical image coordinate system according to the angular resolution and ranging information, thereby achieving resolution matching and superimposed display.

[0019] In summary, this invention proposes a portable, low-cost millimeter-wave radiation imaging scheme to acquire millimeter-wave radiation images of a scene. By combining observation information (azimuth and elevation information) provided by an IMU module, distance information provided by a rangefinder, and optical images acquired by an optical camera, a two-dimensional millimeter-wave radiation image that precisely matches the optical images of the target and the scene is ultimately obtained. Furthermore, the system has a simple structure, is lightweight, supports manual scanning to acquire two-dimensional millimeter-wave radiation images of the scene, and is easy to operate. It can also transmit the acquired information to a computer via a wireless module to achieve real-time imaging observation. This provides a portable, low-cost millimeter-wave radiation imaging scheme for various types of scenes and targets.

[0020] This invention provides an effective means for engineers to measure the millimeter-wave radiation characteristics of various types of scenes and targets, and provides important support for passive microwave remote sensing algorithm inversion, target millimeter-wave radiation modeling, and millimeter-wave radiation system design. At the same time, this invention can be applied to UAV ground observation, security inspection and other application fields, and has high practical value and market economic value.

[0021] Compared with the prior art, the present invention has the following advantages: 1. Significantly reduced cost and weight: This invention proposes to use a low-cost commercial IMU module to acquire the observation angle information of a millimeter-wave radiation imaging system, replacing the two-dimensional scanning turntable, thereby effectively reducing the hardware cost and size / weight of the high-resolution millimeter-wave radiation imaging system. This invention proposes a detachable portable support rod that is connected to a millimeter-wave radiometer system via a circular rotating joint, replacing a high-precision two-dimensional scanning platform. This significantly reduces the cost, size, and weight of the two-dimensional scanning platform while still providing a certain level of accuracy in two-dimensional scanning.

[0022] 2. Excellent operational flexibility and convenience: This invention proposes incorporating a wireless transceiver module and a lithium battery power supply into a millimeter-wave radiation imaging system, further reducing the cost, weight, and size of the high-resolution millimeter-wave radiation imaging system and improving its convenience. Wireless data transmission separates the acquisition and processing ends, allowing operators greater freedom of movement.

[0023] This invention proposes a real-time synchronous display of voltage or brightness temperature values ​​from a millimeter-wave radiometer at different observation angles, as well as information such as the azimuth, elevation, and yaw angles observed by the millimeter-wave radiometer. Furthermore, the proposed solution's backend data processing capabilities, by fusing information such as the millimeter-wave radiometer's voltage values, observation azimuth, and observation distance, acquire a millimeter-wave radiation image superimposed with a lower-level optical image. The combination of manual scanning mode and real-time image trajectory display enables rapid system deployment and intuitive operation, greatly improving the convenience of field experiments.

[0024] 3. Enhanced Image Quality and Information Content: High-quality two-dimensional millimeter-wave images are reconstructed from non-uniform manual scanning data. Precise fusion with optical images effectively compensates for the blurred outlines of millimeter-wave images, providing more intuitive and information-rich observation results.

[0025] 4. Wide Range of Applications: The portable, low-cost millimeter-wave radiation imaging system proposed in this invention has a simple structure and strong practicality. It can provide millimeter-wave radiation imaging equipment for various scenarios and can be used on ground platforms and airborne platforms. It primarily supports millimeter-wave radiation imaging of various ground scenes and targets, research on passive microwave remote sensing inversion models, and research on passive millimeter-wave radiation detection methods. It can be applied to target detection, security inspection, and ground reconnaissance. The implementation of this invention is simple and convenient, with strong practicality. It solves the problems of low practicality and inconvenience in actual application of related technologies, improves user experience, and has significant market value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the composition and layout of a portable low-cost millimeter-wave imaging system in an embodiment of the present invention; Figure 2 This is a schematic diagram of the external structure of the portable low-cost millimeter-wave radiation imaging system in an embodiment of the present invention; Figure 3 This is a schematic diagram of the millimeter-wave radiometer receiver structure in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the distance calculation of the millimeter-wave radiometer in an embodiment of the present invention; Figure 5 This is a schematic diagram of the two-dimensional scanning trajectory and algorithm of the portable low-cost millimeter-wave radiometer in an embodiment of the present invention; Figure 6 This is a schematic diagram of the uniform interpolation result of the azimuth and elevation coordinates in the detection method implemented by the portable low-cost millimeter-wave radiometer in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] This invention provides a portable, low-cost millimeter-wave radiation imaging system and corresponding detection method. Its core design lies in the collaborative work of the hardware system and software algorithms. The hardware system mainly includes a millimeter-wave radiometer, an IMU (Inertial Measurement Unit) module, a rangefinder, an optical camera, a data acquisition module, a wireless transceiver module, a power supply module, a device mounting fixture, a client device (such as a laptop computer), and a detachable portable support rod. The software mainly includes real-time display and data processing software for the millimeter-wave radiometer imaging system running on the client device. This software combines the voltage values ​​measured by the millimeter-wave radiometer system with the azimuth information obtained from the IMU module, the distance information measured by the rangefinder, and the optical image obtained by the optical camera. By uniformly interpolating the azimuth information from the IMU and the brightness temperature value measured by the millimeter-wave radiometer, and combining this with the optical image obtained from the optical camera, a high-resolution fused image of optical and millimeter-wave radiation is finally displayed.

[0029] The key to this invention lies in using the azimuth and elevation angle information acquired in real time by the IMU module to replace the function of a traditional two-dimensional scanning turntable, recording the spatial orientation of each millimeter-wave radiation sampling point. A stable and low-cost manual two-dimensional scanning mechanism is provided by utilizing a detachable portable support rod combined with a circular rotary joint on the equipment fixture. The acquisition module synchronously acquires radiometer voltage, IMU attitude, ranging distance, and optical image data, which are then transmitted to the client via a wireless transceiver module. At the client, data processing software performs two-dimensional uniform interpolation on the non-uniformly sampled angle and brightness temperature data to reconstruct a high-quality millimeter-wave radiation image, and uses distance information to perform pixel-level fusion display with the optical image.

[0030] The following is combined Figures 1-6 This invention introduces an unmanned aerial vehicle (UAV)-borne multi-purpose dual-frequency millimeter-wave radiation imaging system provided by an embodiment of the present invention.

[0031] Example 1 Figure 1 This is a schematic diagram of the composition and layout of a portable, low-cost millimeter-wave imaging system in an embodiment of the present invention.

[0032] See Figure 1The portable, low-cost millimeter-wave radiation imaging system provided in this embodiment includes a millimeter-wave radiometer, a rangefinder, an IMU module, an optical camera, an acquisition module, a wireless transceiver module, a power module, and a client device (preferably a commercially available laptop computer with an integrated wireless module). The low-cost millimeter-wave radiation imaging method based on the aforementioned portable low-cost millimeter-wave radiation imaging system combines the brightness temperature value of the millimeter-wave radiometer with the elevation and azimuth information from the IMU module, the distance measured by the rangefinder, and the optical image obtained by the optical camera. Through uniform interpolation and image matching, the millimeter-wave radiation image and the optical image are fused and displayed on the client device. This scheme cleverly utilizes the spatial attitude information provided by the IMU to compensate for the inherent low spatial resolution of the millimeter-wave radiometer, thereby generating a high-resolution millimeter-wave image, which is then fused with the optical image.

[0033] The millimeter-wave radiometer mainly consists of a Cassegrain antenna, a feed, and a millimeter-wave radiometer receiver. Its primary function is to receive thermal radiation signals from targets and scenes in the millimeter-wave band. The range of received thermal radiation signals depends mainly on the antenna pattern of the Cassegrain antenna, and the final output voltage... ; Rangefinders are primarily used to measure the distance from millimeter-wave radiometers to targets or scenes. ; The IMU module primarily measures the azimuth angle pointed to by the millimeter-wave radiometer. Pitch angle and yaw angle Attitude information and status information such as the platform's three-axis velocity and acceleration signals; The camera mainly acquires optical images of the observed scene and target, providing matching optical images for the voltage signal output by the millimeter-wave radiometer; The acquisition module mainly collects voltage information output by the millimeter-wave radiometer, attitude signals and status information of the IMU module, optical data from the camera, and distance information from the rangefinder; the millimeter-wave radiometer, rangefinder, IMU module, and optical camera are respectively connected to the acquisition module; The wireless transceiver module is mainly responsible for sending and receiving control commands and transmitting information from the acquisition module. The wireless transceiver module connects to the acquisition module and establishes a remote connection with the client device. Specifically, the wireless transmitting module sends out the information from the acquisition module wirelessly, and the wireless receiving module receives the information sent by the wireless transmitting module and transmits it to the laptop. The wireless transceiver module can greatly improve the convenience of the system. The laptop computer is mainly used for controlling modules such as millimeter-wave radiometers, as well as processing, storing, and displaying the acquired data. Other types of client devices can also be used in specific implementations. The power module primarily connects to and supplies power to the millimeter-wave radiometer, rangefinder, IMU module, camera, data acquisition module, and wireless module. In practical implementations, a battery module (such as a lithium battery) can also be included, along with an integrated power management module to provide power storage and protection against power outages. The power management module provides power and power monitoring management for the millimeter-wave radiometer, IMU module, rangefinder, and optical equipment.

[0034] In practical operation, the control software on the client device sends start / stop acquisition commands to the acquisition module via a wireless link. The acquisition module then transmits the packaged sensor data (voltage, attitude, distance, video stream) to the client device in real time via the wireless link, achieving physical separation between the acquisition end and the processing and display end, greatly improving the flexibility and convenience of field operations.

[0035] To effectively achieve the goals of low cost and portability of this invention, multiple modules in the system can preferably be commercially available, mature, low-cost modules. For example: IMU module: A commercially available inertial measurement unit based on MEMS technology can be selected, which is inexpensive, compact, and can provide sufficient attitude measurement accuracy.

[0036] Rangefinder: Commercially available rangefinder sensor modules based on laser or ultrasound can be used. These modules are affordable and can meet the measurement needs for short to medium distances.

[0037] Optical camera: A regular USB webcam or mobile phone camera module can be used, which greatly reduces the cost of the image acquisition part.

[0038] Acquisition module: A data acquisition card based on an open-source hardware platform can be used, along with necessary signal conditioning circuits, to achieve low-cost, multi-channel synchronous data acquisition.

[0039] Wireless transceiver module: A general-purpose Wi-Fi or Bluetooth module can be selected to realize wireless data transmission.

[0040] By flexibly selecting and integrating the aforementioned low-cost commercial modules, the overall cost is effectively controlled while ensuring the realization of the core functions of the system, demonstrating the low-cost advantage of this invention.

[0041] Example 2 Based on Embodiment 1, the present invention further includes a detachable support rod and an external fixture structure. The external fixture integrates the millimeter-wave radiometer system, IMU module, rangefinder, optical camera, acquisition module, power module, and wireless transceiver module. The fixture also provides a handle for easy measurement and can be connected to the detachable portable support rod.

[0042] Furthermore, the detachable portable support rod is connected to the portable millimeter-wave radiometer system via a circular rotary joint. The circular rotary joint can provide fixed support for manual two-dimensional scanning, which has higher stability than purely manual scanning, thereby reducing system cost and weight.

[0043] Figure 2 This is a schematic diagram of the external structure of the portable low-cost millimeter-wave radiation imaging system of the present invention, including a top view and a side view.

[0044] See Figure 2 The portable low-cost millimeter-wave radiation imaging system provided in Example 2 includes a millimeter-wave radiometer, a rangefinder, an IMU module, a camera, an acquisition module, a wireless transceiver module, a power module, a detachable support rod, and an external tooling structure, etc. The external tooling structure houses a millimeter-wave radiometer receiver, a Cassegrain antenna, a wireless module, a data acquisition module, a camera, a power supply module, and other components. The external tooling features three handles and a circular rotating joint. Three handles are installed, one on the top of the tooling housing and the other on the sides of the tooling housing. The top handle is convenient for lifting, and the side handles are convenient for adjusting the orientation and tilt angles. The detachable support rod is connected to the tooling housing via a circular rotary joint to support the millimeter-wave radiation imaging system. The circular rotary joint enables rotational scanning of the azimuth and elevation angles, thereby realizing manual two-dimensional scanning imaging based on the millimeter-wave radiometer.

[0045] Example 3 Based on Examples 1 and 2, the present invention further realizes a detection method based on a low-cost portable millimeter-wave radiation imaging system. The voltage value measured by the millimeter-wave radiometer system is combined with the IMU module, rangefinder and optical camera, and assigned to the corresponding scene to obtain an overlay image of optical image and millimeter-wave radiation image for display.

[0046] In practical implementation, the processing software can be deployed on a laptop computer, providing real-time data display and back-end data processing functions. The real-time display function primarily allows for the selection and display of information such as the voltage information received by the wireless module from the millimeter-wave radiometer, the observation information (azimuth, elevation, yaw) from the IMU module, and the distance information from the rangefinder. The back-end data processing function, based on the acquired millimeter-wave radiometer voltage and IMU module observation information, processes the data to obtain a high-resolution millimeter-wave radiation image, and, with the assistance of the rangefinder's distance information, projects the millimeter-wave radiation image onto an optical image according to the spatial resolution, combining the radiometer's angular resolution.

[0047] The processing procedure of the embodiment first homogenizes the non-uniform azimuth and elevation coordinates, and then interpolates the sampled millimeter-wave radiation voltage according to the homogenized azimuth and elevation coordinates to obtain the voltage values ​​of the homogenized azimuth and elevation coordinates, thereby obtaining the two-dimensional scanning image of the portable millimeter-wave radiometer.

[0048] Furthermore, uniform interpolation is performed in two dimensions based on the non-uniform azimuth and elevation angles obtained from the IMU module. At the same time, based on the relationship between the non-uniform azimuth and elevation angles and the interpolated uniform azimuth and elevation angles, the brightness temperature value output by the millimeter-wave radiometer is differentiated and matched with the uniformly interpolated azimuth and elevation angles. Furthermore, image matching is based on keeping the IMU basic reference position (0,0) consistent with the reference position (0,0) pointed to by the millimeter-wave radiometer, thereby ensuring that the IMU azimuth and elevation angles are consistent with those of the millimeter-wave radiometer. Furthermore, the fusion display is achieved by keeping the basic reference position (0,0) of the optical camera consistent with the reference position (0,0) pointed to by the millimeter-wave radiometer, and by matching the positions of the two images according to the resolution of the optical camera and the resolution of the millimeter-wave radiometer.

[0049] Figure 3 This is a schematic diagram of a millimeter-wave radiometer receiver.

[0050] In this embodiment, the feed source is located at the focal point of the Cassegrain antenna, receiving the strong signal focused by the reflector and performing mode conversion before guiding it to the transmission line. The millimeter-wave radiometer receiver is connected to the feed source of the Cassegrain antenna, receiving millimeter-wave radiation signals from the natural scene and target collected by the Cassegrain antenna. See [link to relevant documentation]. Figure 3 The millimeter-wave radiometer receiver includes, in sequence, a millimeter-wave low-noise amplifier, a millimeter-wave radio frequency filter, a millimeter-wave power amplifier, a millimeter-wave detector, and an integrator. The millimeter-wave low-noise amplifier amplifies the signal from the Cassegrain antenna receiver, which is then filtered by the millimeter-wave radio frequency filter. The filtered signal is then amplified again by the millimeter-wave power amplifier, and the amplified signal enters the millimeter-wave detector. The detector outputs to the integrator, which outputs a voltage signal within the corresponding bandwidth. This voltage signal enters the data acquisition unit. The mathematical relationship between the voltage signal and the brightness temperature of the natural scene is as follows: (1) in, Indicates in The voltage in the direction, where k represents the Boltzmann constant. B represents the apparent brightness temperature of the antenna, and B represents the effective bandwidth of the system.

[0051] Figure 4 This is a schematic diagram of the distance calculation for the millimeter-wave radiometer in this invention.

[0052] See Figure 4 The rangefinder in the portable, low-cost millimeter-wave radiometric imaging system provided by this invention is used to measure the distance from the center point of the millimeter-wave radiometer to the scene or target, obtaining the distance at different pitch and observation angles. Distance to the observation scene or target Based on the detection distance and the angular resolution of the radiometer The size of a single cell is calculated. The specific calculation formula is as follows: (2) Millimeter-wave radiation images inherently have low resolution and blurred outlines. By calculating the pixel size, millimeter-wave data can be mapped onto high-resolution optical images more accurately, solving the registration problem caused by the huge difference in resolution between the two.

[0053] The two-dimensional angular resolution of the radiometer is The angular resolution of the optical image is Furthermore, the angular resolution of optical images is much higher than that of radiometers, and the elevation and observation angles obtained through IMU measurements are significantly higher. It matches the observation angle of the optical image and is unified under the same azimuth and observation angle reference coordinate system.

[0054] Under the same coordinate system with the same pitch and observation angle established above, the millimeter-wave radiation image and the optical image are mapped to this unified coordinate system to obtain a fused image of the two images, providing a more convenient fused image for the millimeter-wave image and characteristic analysis of various types of targets.

[0055] Figure 5 This is a schematic diagram of the two-dimensional scanning trajectory of the portable, low-cost millimeter-wave radiometer in this invention.

[0056] See Figure 5The IMU module in a portable, low-cost millimeter-wave radiometer can simultaneously and accurately measure the azimuth and elevation information of the radiometer. During measurement, there are two modes: a purely manual scanning mode and a support rod-assisted scanning mode. In the purely manual scanning mode, the user holds the handle on top of the radiometer with one hand and performs a manual two-dimensional scan. Simultaneously, the wireless transceiver module displays the acquired azimuth, elevation, and corresponding voltage information on a laptop screen. The operator can then identify which observation areas were not scanned based on the displayed image trajectory and perform supplementary scanning. In the support rod-assisted scanning mode, the radiometer is fixed to a support rod via a rotating joint. The operator uses the handles on both sides of the radiometer fixture to perform a two-dimensional scene scan. Again, the wireless transceiver module simultaneously acquires azimuth, elevation, and corresponding voltage information and displays it on a laptop screen. The operator can then identify which observation areas were not scanned based on the displayed image trajectory and perform supplementary scanning.

[0057] Figure 6 This is a schematic diagram of the uniform interpolation result of the azimuth and elevation coordinates in the detection method implemented by the portable low-cost millimeter-wave radiometer in this invention.

[0058] Although uniform elevation and azimuth angle information cannot be directly obtained through either manual scanning mode or rod-assisted scanning mode, the detection method based on a millimeter-wave radiometer in this invention can obtain uniformly interpolated elevation and azimuth angles from the non-uniform elevation and azimuth angles observed in manual scanning mode or rod-assisted scanning mode through uniform interpolation. At the same time, using the same method, the voltage signal output by the millimeter-wave radiometer is subjected to the same interpolation to obtain the voltage values ​​under uniform azimuth and elevation coordinates. Based on this, a two-dimensional voltage distribution map (brightness temperature distribution map) based on the millimeter-wave radiometer can be drawn and superimposed with optical images to provide a fused display of optical and millimeter-wave radiation brightness temperature images.

[0059] The specific steps are as follows: Let the scanning range of the manual turntable be M1*M2 (°), where M1 represents the azimuth scanning angle range and M2 represents the pitch scanning angle range. This indicates the angular resolution of the millimeter-wave radiometer; the input voltage of the millimeter-wave radiometer is... , This represents the azimuth angle of the nth sampling point. This represents the elevation angle of the nth sampling point. Based on the scanning range and the angular resolution of the millimeter-wave radiometer, the azimuth angle is divided into... Equal portions, with pitch angles of all Divide it into equal parts, then the voltage (brightness temperature) values ​​of the m1-th pixel in the azimuth direction and the m2-th pixel in the pitch direction after equal division. for (3) in, This indicates that it falls within the range of azimuth angles. and pitch angle range All sampled voltage values ​​are represented by S, and i is the sampled voltage value label. Finally, based on the averaged values, high-quality azimuth and elevation two-dimensional voltage or brightness temperature distribution maps are plotted.

[0060] The millimeter-wave radiation imaging system designed using the method of this invention mainly consists of a millimeter-wave radiometer (receiver and antenna), an IMU module, a rangefinder, an optical camera, an acquisition module, a wireless transceiver module, equipment fixtures, client equipment, and a detachable portable support rod. Traditional solid-aperture millimeter-wave radiometer systems with a two-dimensional scanning platform mainly consist of a millimeter-wave radiometer (receiver and antenna), a two-dimensional scanning platform, an acquisition module, equipment fixtures, and client equipment. Compared to traditional solid-aperture microwave radiometer systems with a two-dimensional scanning platform, the millimeter-wave radiation imaging system proposed by the method of this invention reduces system weight and cost by eliminating the two-dimensional scanning platform. Furthermore, the inclusion of a wireless transmission module provides greater convenience for the entire millimeter-wave radiation imaging system, facilitating measurement implementation.

[0061] To facilitate understanding of the technical effects of this invention, based on a survey of domestic and international manufacturers and commonly used modules, assuming a 94G millimeter-wave radiation imaging system with a diameter of 300mm, the manufacturing costs and weights of the two schemes are statistically analyzed, as shown in the table below: Table 1

[0062] Table 1 shows that, under the same spatial resolution requirements, the manufacturing cost of the present invention is 35,062 yuan, and the weight is 15.979 kg. Compared with the traditional system's 219,219 yuan and 39.725 yuan, the present invention significantly reduces hardware costs, approximately one-sixth of the traditional real-aperture millimeter-wave radiation imaging system, and weighs less than half the weight. Therefore, the present invention greatly reduces the cost and weight of the traditional real-aperture microwave radiation imaging system. Furthermore, the present invention employs a wireless module for data transmission, giving the millimeter-wave radiation imaging system high flexibility and greatly improving its ease of use.

[0063] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A portable, low-cost millimeter-wave radiation imaging system, characterized in that: It includes a millimeter-wave radiometer, IMU module, rangefinder, optical camera, data acquisition module, wireless transceiver module, power supply module, equipment exterior tooling, client equipment, and detachable portable support rod; The millimeter-wave radiometer is used to obtain the millimeter-wave radiation brightness temperature of the observed scene; The IMU module is used to acquire the azimuth, elevation and yaw angle information of the millimeter-wave radiometer; The rangefinder is used to measure the distance from the millimeter-wave radiometer to the observation scene or target; The optical camera is used to acquire optical images of the observed scene; The acquisition module is used to acquire the output signals of the millimeter-wave radiometer, IMU module, rangefinder and optical camera; The wireless transceiver module is used to transmit control commands and collected data to the client device; The power module is used to supply power to the various modules of the system; The device's external tooling is used to integrate the millimeter-wave radiometer, IMU module, rangefinder, optical camera, data acquisition module, wireless transceiver module, and power supply module, and is equipped with a handle and a circular rotating joint. The detachable portable support rod is connected to the equipment's external tooling via the circular rotary joint, supporting manual 2D scanning.

2. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The millimeter-wave radiometer includes a Cassegrain antenna, a millimeter-wave low-noise amplifier, a millimeter-wave filter, a millimeter-wave power amplifier, a millimeter-wave detector, and an integrator connected in sequence, for outputting a voltage signal corresponding to the brightness temperature of the scene's millimeter-wave radiation.

3. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The IMU module is used to measure the azimuth, pitch, yaw, three-axis velocity, and acceleration information of the millimeter-wave radiometer in real time during the scanning process.

4. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The acquisition module simultaneously acquires the voltage signal of the millimeter-wave radiometer, the attitude information of the IMU module, the distance information of the rangefinder, and the image data of the optical camera.

5. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The wireless transceiver module uses wireless transmission to enable data interaction between the acquisition module and the client device, supporting real-time display and control.

6. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The equipment is equipped with handles on the top and sides for easy hand operation and angle adjustment.

7. The portable, low-cost millimeter-wave radiation imaging system according to claim 1, characterized in that: The detachable portable support rod enables manual two-dimensional scanning of azimuth and elevation angles via a circular rotary joint, replacing the traditional two-dimensional mechanical scanning platform.

8. A portable, low-cost millimeter-wave radiation imaging method, characterized in that, Includes the following steps: The millimeter-wave radiation brightness temperature value of the observation scene is obtained using a millimeter-wave radiometer, the azimuth and elevation angle information of the millimeter-wave radiometer is obtained using an IMU module, the distance to the observation scene or target is obtained using a rangefinder, and the optical image of the observation scene is obtained using an optical camera. The above data is collected synchronously through the acquisition module; The collected data is transmitted to the client device via a wireless transceiver module; Two-dimensional uniform interpolation is performed on non-uniform azimuth and elevation angles on the client device; The millimeter-wave radiation brightness temperature value is interpolated accordingly to generate a uniform millimeter-wave radiation image; the millimeter-wave radiation image is then registered and fused with the optical image for display.

9. The portable, low-cost millimeter-wave radiation imaging method according to claim 8, characterized in that: The two-dimensional uniform interpolation is implemented by dividing the non-uniform azimuth and elevation angles obtained by the IMU module into a uniform grid within a preset scanning range; averaging or interpolating the millimeter-wave radiation brightness temperature values ​​falling within each uniform grid to obtain the brightness temperature value under uniform angular coordinates.

10. The portable, low-cost millimeter-wave radiation imaging method according to claim 8, characterized in that: When performing image registration and fusion display, based on the fact that the reference positions of the IMU module and the millimeter-wave radiometer are consistent, the pixels of the millimeter-wave radiation image are mapped to the optical image coordinate system according to the angular resolution and ranging information, so as to achieve resolution matching and superimposed display.

Images