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2021 Vol. 43, No. 6

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Materials & Devices
Influence of Cd-rich Annealing on Position-dependent Conductivity Transition in Cd1-xZnxTe Crystal
YUAN Shouzhang, ZHAO Wen, KONG Jincheng, JIANG Jun, ZHAO Zenglin, JI Rongbin
2021, 43(6): 517-522.
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Abstract:
In this study, Cd1-xZnxTe(x=0.04) crystals were grown using the Te-rich Vertical Bridgman(VB) method. A position-dependent conductivity transition was found in some of the as-grown Cd1-xZnxTe ingots, which caused significant nonuniformity in the Hg1-yCdyTe(MCT) focal plane array(FPA) response map. Cd-rich annealing experiments were performed on Cd1-xZnxTe ingots with position-dependent conductivity transition, and the relationships between the position-dependent conductivity transition and annealing conditions, including annealing time, temperature, and Cd partial pressure, were studied. Furthermore, by understanding the formation mechanism of Cd vacancies and Cd interstitials, we found that Cd vacancies can be reduced during Cd1-xZnxTe ingot growth.
Systems & Designs
Fuzzy Adaptive PID Control of Large Aperture Fast Steering Mirror
CAI Yusheng, ZHU Jun, SHI Lei, ZHANG Jingzhong
2021, 43(6): 523-531.
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Abstract:
The ability of a fast-steering mirror (FSM) to track a target accurately and steadily depends on its servo control performance. The larger the aperture of the FSM is, the more difficult it is to design the flexible supporting hinge and the driver; in addition, it will also demand greater requirements on the servo control. To solve this problem, this paper proposes a fuzzy adaptive tune(FAT) proportional integral derivative (PID) control algorithm, which not only uses fuzzy theory for adaptively tuning the control parameters, but also inherits the classic PID controller for engineering realization. In this study, we designed a controller for the ϕ500 mm FSM driven by a voice coil motor, conducted simulation experiments, and compared the results with the simulation results based on classic PID control. According to the results, the overshoot was 5.4%, the settling time was 51.0 ms based on FAT PID control, and the capacity of resisting disturbance was stronger than that of the classical PID control. In addition, compared with traditional PID control, the proposed control method improved the ϕ500 mm FSM response speed, decreased the tracking error, and improved ϕ500 mm FSM system tracking performance and robustness.
Terahertz
Research on Terahertz Band Demultiplexer Based on Metamaterials
ZHANG Xuewen, PAN Wu, SHEN Tao, LI Yi
2021, 43(6): 532-536.
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Abstract:
This paper proposes a terahertz demultiplexer based on metamaterials; its unit cell is composed of two layers of "one" shaped metal wires and a quartz substrate in the middle. The terahertz demultiplexer works in the terahertz communication window and demultiplexes two beams of terahertz waves with center frequencies of 0.225 THz and 0.300 THz. The isolation of the terahertz demultiplexer is 34 dB and 47 dB, and its insertion loss is 0.19 dB and 0.04 dB, respectively. The group delay of the demultiplexer was relatively stable. Finally, the influence of the effective and structural parameters of the demultiplexer on its performance are discussed. This terahertz demultiplexer has low insertion loss, large isolation, and stable group delay, and its performance is less affected by parameter changes. It has significant application prospects in practical terahertz communication systems.
Low-light-level
Direct Coupling of Low Light Image Intensifier with Large Size CMOS
GAO Tianyang, CAO Fengmei, WANG Xia, CUI Zhigang
2021, 43(6): 537-542.
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Abstract:
The large size direct coupling technology was studied by coupling a 40 mm diameter image intensifier with a full-frame CMOS. To solve the problems of large-size ICCD/ICMOS made by lens coupling, such as large volume, large light energy loss, and large number of moiré fringes in optical cone coupling devices, a direct coupling process is proposed to make ICCD/ICMOS. The large-size ICMOS developed in this study can obtain more information in the field of view. The resolution of the entire device is up to 3600×1800, the picture is clear, there is no obvious moiré fringe, and the structure is compact. The entire device has the size of a handheld digital camera and has strong concealability, which is conducive to obtaining target information more accurately and quickly in a complex environment.
Image Processing & Simulation
Snow Information Recognition based on GF-6 PMS Images
WANG Guangyuan, DENG Zhengdong, LU Zhao, WANG Daqing, SHI Yue, XU Haoli, ZHAO Xiaoning
2021, 43(6): 543-556.
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Abstract:
From the perspective of limited research on snow recognition in high spatial resolution optical remote sensing images, considering Daowai District of Harbin City as the research area, this paper systematically discusses and analyzes the application of different methods in snow information recognition. First, ground feature types and snow distribution characteristics were mastered through visual interpretation of GF-6 PMS images of two phases in the study area. Second, based on the results of visual interpretation, eight typical surface feature types were selected, and the spectral characteristics of "snow"and "non-snow"pixels were obtained. Third, the application of the six methods in snow recognition was discussed and analyzed. Accuracy was evaluated using three indexes: positive predictive value, recall rate, and F-score. Finally, a final recognition result judgment method based on voting results was developed, and the final recognition result of snow information in the study area was obtained. The results showed that, owing to the influence of the underlying surface and shadow, the phenomenon of "same spectrum foreign matter"and "same object different spectrum"was common in the study area, which interfered with the snow recognition process to a large extent. The recognition effect of the deep learning algorithm was the best, while that of the decision tree method was relatively poor; the recognition accuracy was higher for the farmland area than that for the pond area, and the phenomenon of false and missing recognitions was relatively less. The final recognition result judgment method based on voting results can effectively improve the phenomenon of false and missing recognitions in a single recognition method. This paper has important guiding significance for snow recognition based on high-spatial-resolution optical remote sensing images.
A Survey of Uncooled Infrared Image Denoising Algorithms
WANG Jia, ZHOU Yongkang, LI Zemin, WANG Shijin, ZENG Bangze, ZHAO Deli, HU Jianchuan
2021, 43(6): 557-565.
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In infrared image processing, owing to technical issues with the infrared detector, the original infrared image includes a variety of noise, especially salt and pepper noise, fixed noise, or random stripe noise. Currently, there are many filtering algorithms for infrared image denoising, but they emphasize time, space, denoising effect, maintaining detail, and so on differently; therefore, it is difficult to achieve a perfect combination. Identifying methods to filter noise information more quickly, efficiently, and accurately and retain more details is an important future research direction for noise reduction in infrared image processing. This study investigated and compared the current mainstream infrared image denoising algorithms from three categories: traditional filter denoising, transform domain filter denoising, and image layered processing filter denoising, and a combination of a traditional algorithm and image layered adaptive denoising algorithm is proposed to provide a reference for future studies in related fields.
A Visible and Infrared Image Fusion Method based on Generative Adversarial Networks and Attention Mechanism
LUO Di, WANG Congqing, ZHOU Yongjun
2021, 43(6): 566-574.
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Abstract:
A new fusion method for visible and infrared images based on generative adversarial networks is proposed to solve the problem of recognizing targets in low-light images; the method can be directly applied to the fusion of RGB three-channel visible images and infrared images. In generative adversarial networks, the generator adopts a U-Net structure with encoding and decoding layers. The discriminator adopts a Markovian discriminator, and the attention mechanism is introduced to force the fused image to pay more attention to the high-intensity information on infrared images. The experimental results show that the proposed method not only maintains the detailed texture information of visible images but also introduces the main target information of infrared images to generate fusion images with good visual effects and high target identification, and it performs well in information entropy, structural similarity, and other objective indexes.
Infrared Pedestrian Detection in Complex Night Scenes
ZHAO Shuang, CHEN Shuyue, WANG Qiaoyue
2021, 43(6): 575-582.
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Abstract:
An infrared pedestrian detection algorithm is proposed to solve the problem of small differences between pedestrians and backgrounds in gray scale images and the occurrence of occlusion in infrared images at night. First, a significant graph with the full coverage of the target is generated by the pedestrian semantic fusion method, and the region of interest is obtained by combining it with the original graph. Then, a two-branch classifier based on the improved histogram of the gradient feature is constructed. The fuzzy score of the classifier is used to determine the occurrence of occlusion and call the head template for the final detection. Experiments based on the LSI far infrared pedestrian dataset and independent datasets of pedestrians captured at night in winter and summer prove that the proposed method is robust and quick in detecting pedestrians under different environments. It can significantly reduce the rate of missed detection and realize a detection rate of 94.20%.
Fast Focal Length Measurement Method based on Infrared Lens Images
ZHONG Jianbo, LI Maozhong, XIA Qingsong, LUO Yongfang, JIA Yuchao, WANG Caiping, LI Hongbin, LUO Hong, HUANG Pan
2021, 43(6): 583-586.
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Abstract:
Accurately measuring the focal length of an infrared lens is a crucial issue in infrared lens parameter measurement. This paper proposes a practical focal length estimation method based on a target knife image. First, the target image is captured in the focused state and a binary image is obtained, then the edge of the target is extracted, the vertex coordinates of the minimum external rectangle are obtained, and the corresponding focal length of the infrared lens is estimated. Experimental results show that the algorithm can measure the focal length of the infrared lens quickly and accurately, and the average absolute error percentage is less than 1.48. This method lays the foundation for the rapid measurement of infrared lens parameters.
Guidance & Countermeasure
Numerical Simulation of Radiation Characteristics of Aircraft Exhaust Systems with Different Nozzles
HUANG Zhangbin, GUAN Liu, LI Xiaoxia, FENG Yunsong
2021, 43(6): 587-591.
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Abstract:
The exhaust system is the most important infrared radiation source of an aircraft, and the shape of the nozzle contributes to the infrared radiation characteristics of the exhaust system. Three types of 3D nozzles were built, and the temperature field of the plume was simulated using ANSYS14.5. Then, the spectral infrared radiation characteristics of the plume were obtained using the single band Curtis-Godson (C-G) approximation method. The results show that under the same exit area, the core area of the S-shaped nozzle plume is minimum and is approximately 60% of the axisymmetric circular nozzle plume; in the rectangular nozzle wide edge detection surface, the infrared radiation of the dual rectangular nozzle is minimum, and among the three types of nozzles, the stealthy performance of the two-element rectangular S curved nozzle is the best, the two-element rectangular nozzle takes the second place, and the axial symmetrical circular nozzle is the worst.
Method of LOS Rate Extraction for Roll-Pitch Infrared Seekers
WANG Shuaiwei, LIANG Yiming, ZHENG Jianqiang, YANG Shujun, MA Jirong
2021, 43(6): 592-596.
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Abstract:
Roll-pitch seekers adopt the polar coordinate control form of rolling and pitching two axes. The outer frame is the rolling frame, the inner frame is the pitching frame, and the field of view can cover the entire front hemisphere. They have a simple structure, light weight, small volume, and low cost; therefore, they are very suitable for short-range infrared air defense missiles. This paper discusses the difference between the line-of-sight rates of roll–pitch seekers and pitch–yaw seekers and expounds the reason why roll–pitch seekers rotate around the x axis. The method of obtaining the line-of-sight rate of the roll–pitch seeker is given, the simplified form is deduced, and the conditions for using the simplified formula are analyzed. The simulation results show that the simplified formula has good approximation accuracy and certain engineering application prospects.
IR Applications
Design of Portable Infrared thermometer and Temperature Compensation Technology
YANG Qingzhi, WANG Yuxiang, XU Hong
2021, 43(6): 597-606.
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Infrared thermometers are popular because of their safety, hygiene, and high efficiency. However, commercial infrared thermometers have large measurement errors and high cost, so their application is limited. Considering this, this paper first analyzes various factors that affect the measurement accuracy of an infrared thermometer and gives the calculation results of the specific influence degree. Then, using STM32F407 MCU as the control core, an MLX90615 infrared sensor, DS18B20 integrated temperature sensor, and HC-SR04 ultrasonic sensor to obtain information, a cheap and reliable portable infrared thermometer for hospitals and families is designed, and a method of temperature compensation is provided. Finally, the reliability of the system design was verified by testing. The test results show that the maximum comprehensive error is less than 0.15℃, which has definite practical value and reference value.
Refrigeration
Effect of Orifice Size on Flow Stability of Shape Memory Alloy Self-Regulated Cryocoolers
GUO Xiangxiang, HAN Penglei
2021, 43(6): 607-613.
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Abstract:
The flow stability of shape memory alloy (SMA) self-regulated cryocoolers with different orifice sizes is analyzed via theoretical calculation and experimental study. The theoretical calculation demonstrates that the smaller the orifice diameter, the more stable is the flow rate when the cryocoolers are influenced by the same disturbance factors. The change in flow rate increases linearly with the increase in orifice diameter. In the experimental investigation, two types of SMA self-regulated cryocoolers, equipped with 0.15 mm and 0.25 mm orifices, respectively, were developed. Fatigue and vibration tests were introduced as disturbance factors. The flow rates of cryocoolers were evaluated at 29 and 22 MPa. The results show that the cryocoolers with a 0.15 mm orifice have smaller flow rate variance than those with a 0.25 mm orifice. Both the theoretical and experimental results verified that narrowing the diameter of the orifice is conducive to the flow stability of SMA self-regulated cryocoolers.

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