Infrared technology and application

Advance in high operating temperature HgCdTe infrared detector
Chen Jun, Xi Zhongli, Qin Qiang, Deng Gongrong, Luo Yun, Zhao Peng
2023, 52(1): 20220462. doi: 10.3788/IRLA20220462
[Abstract](54) [FullText HTML] (14) [PDF 2475KB](35)
High operating temperature (HOT) infrared detector technology is an important branch of the third-generation infrared detector technology. The basic materials that can be used for high operating temperature infrared detectors are mainly Sb based and HgCdTe based. This paper introduces the lasest research progress of high operating temperature infrared focal plane module in Kunming Institute of Physics (KIP). The high operating temperature MCT based detectors developed based on p-on-n technology have reached good performance in the temperature range of 150 K with the NETD less than 20 mK. The weight of MCT 640×512 IDDCA module adapted with high efficiency moving magnet split linear cooler is less than 270 g with the detector length in optical axis direction less than 70 mm (F4). At ambient temperature, the steady power consumption of the module is less than 2.5 Wdc while the cool down time is less than 80 s, audible noise is less than 27 dB and self induced vibration force is less than 1.1 N. MCT HOT modules are now under environmental adaptability and reliability verification and commercial mass production of this detector will be realized after the verification test.
Simulation research on IR radiation space distribution characteristic of fight plane
Tong Zhongcheng, Wang Liang, Wu Jun
2023, 52(1): 20220264. doi: 10.3788/IRLA20220264
[Abstract](47) [FullText HTML] (14) [PDF 5195KB](23)
Considering the IR radiation space distribution research of fight plane is very little, in order to deeply understand IR radiation space distribution characteristics of fight plane in 3-5 μm, the infrared radiation ellipsoid model of tail flare is established, IR radiation characteristics of fight plane in different directions in 3-5 μm are simulated and calculated with the fight plane skin IR radiation model and the tail nozzle IR radiation model, and space distribution curves of IR radiation is given. The calculation shows that the infrared radiation of the aircraft is symmetrical with respect to the wing plane and the longitudinal symmetry plane of the fuselage. There are 4 extremes each in the tail and nose. The maximum value of infrared radiation is 5 177 W when the radiation direction is (\begin{document}$ \pm $\end{document}150°, \begin{document}$ \pm $\end{document}32°) in the tail and the maximum value is 3 461 W when the radiation direction is (\begin{document}$ \pm $\end{document}68°, \begin{document}$ \pm $\end{document}64°) in the nose. By analyzing the distribution rule of IR radiation of fight plane in the wing plane, the fuselage longitudinal symmetrical plane and the peak value plane, the IR radiation is very low when the radiation direction is positive direction of the plane axis, and the IR radiation grows rapidly when the angle between the radiation direction and the plane axis increases and the radiation direction is not positive direction of the plane axis. The research also shows the direction of peak value of IR radiation is closer to the plane axis in longitudinal symmetrical plane if the angle between the projection of radiation direction in wing plane and the plane axis becomes small. Similarly, the direction of peak value of IR radiation is closer to the plane axis in wing plane if the angle between the projection of radiation direction in longitudinal symmetrical plane and the plane axis becomes small.
Influence of the discharge port structure on infrared characteristics of underwater vehicle thermal jet
Gao Chengzhe, Du Yongcheng, Yang Li
2023, 52(1): 20220333. doi: 10.3788/IRLA20220333
[Abstract](33) [FullText HTML] (10)
The circulating cooling water of the underwater vehicle power system discharged from the discharge port, mixed with the environmental water for heat exchange and formed the thermal jet. The thermal jet diffused and floated in the environmental water and forms infrared characteristics on the surface of the water. In order to explore the influence of the structure of the discharge port on the infrared characteristics of the underwater vehicle thermal jet, this paper used the method of simulation analysis and experimental verification. Based on the CFD calculation software platform, the motion model of underwater vehicle was established, the structure of different radius-ratio oval discharge ports was designed, and the infrared characteristics of thermal jet were compared. The influence of the radius ratio of the oval discharge port on the infrared characteristics of the thermal jet was verified by the scale tank experiment, and the authenticity of the simulation calculation method and design parameters was verified at the same time. On the basis of oval discharge ports, the number and distribution position of discharge ports were further designed to suppress the infrared characteristics of thermal jet and improve the thermal stealth performance of underwater vehicles. According to the simulation calculation and experimental results, under the condition of the same discharge flow, the smaller the radius ratio was, the better the mixed heat transfer effect of the oval discharge port was, and the less obvious the infrared characteristics were. At the same time, increasing the number of discharge ports and adopting the symmetrical arrangement of discharge ports could further strengthen the temperature attenuation of thermal jet and reduce the surface maximum temperature.
Process development and characteristic evaluation of micro-bolometer device
Liu Wei, He Bing, Ma Te, Liu Gang
2023, 52(1): 20220279. doi: 10.3788/IRLA20220279
[Abstract](37) [FullText HTML] (9) [PDF 2417KB](21)
Based on MEMS micro-bridge structure, micro-bolometer device was developed on standard semiconductor production line. Chemical Vapor Deposition (CVD) technology was used to deposit amorphous silicon (α-Si) film as sensing material. The within wafer thickness uniformity and the resistance uniformity of 1000 Å α-Si film can be controlled to be less than 2%, and the Temperature Coefficient of Resistance (TCR) of 1000 Å α-Si film can reach at about −2.5%. Contact module of MEMS micro-bridge structure was developed by trench first approach, and electrical connection between MEMS and readout circuit was achieved by thin electrode layer on sidewall and bottom of the anchor and contact structure. Ti/TiN thin metal layer was used as electrode layer, and sensing resistor device was defined by the electrode layer patterns. Sensing material resistor device was fabricated by optimized integration scheme, which can achieve better process control on the sensing material loss and electrical layer sidewall recess etch amount. After device fabrication, room temperature resistance of device was about 250 kΩ with good ohmic contact. Device level TCR was measured at about −2%, and slightly lower than the data of thin film on blanket wafer. And the resistance data during the temperature raising up and down indicated that there was no hysteresis effect. Finally the MEMS device was released, and the optical and SEM data showed good physical performance, which can match the technical requirements of micro-bolometer production.
Study on large-area array SW HgCdTe infrared focal plane device
Gong Xiaodan, Li Hongfu, Yang Chaowei, Yuan Shouzhang, Feng Yuanqing, Huang Yuanjin, Hu Xu, Li Lihua
2022, 51(9): 20220079. doi: 10.3788/IRLA20220079
[Abstract](231) [FullText HTML] (55) [PDF 1929KB](96)
With the development of infrared focal plane technology, large-area infrared focal plane devices have been widely used in remote sensing, meteorology, resource surveys and high-resolution earth observation satellites. Therefore, based on the third-generation infrared focal plane technology ultra-large-scale focal plane devices are called research hotspots at home and abroad. The short wave (SW) 2 k (18 μm, pixel pitch) mercury cadmium telluride(MCT) infrared focal plane device was reported, which was successfully developed by Kunming Institute of Physics using n-on-p technology. The SW 2 k MCT infrared focal plane device has broken through the preparation of large-size cadmium zinc telluride (CdZnTe) substrates and the growth of large-area liquid phase epitaxy thin film materials. The substrate size was increased from Φ75 mm to Φ90 mm, and a highly uniform large-area Mercury Cadmium Telluride (HgCdTe) thin film material was obtained. By tackling key technologies such as large array device technology and large area array flip-chip interconnect, a high-performance SW 2 k×2 k (18 μm) MCT infrared focal plane device with an operability over 99.9%, average peak detection rate (D*) greater than 4×1012 (cm·Hz1/2)/W and dark current density of 1 nA/cm2 was finally obtained.
Design and fabrication of short and middle wavelength infrared dual band-pass filter at cryogenic temperature
Zhou Sheng, Liu Dingquan, Wang Kaixuan, Li Yaopeng, Hu Jinchao, Wang Shuguang, Zhu Haoxiang
2022, 51(9): 20210964. doi: 10.3788/IRLA20210964
[Abstract](93) [FullText HTML] (19) [PDF 2081KB](46)
Dual band-pass filter can simultaneously form two spectral channels to transmit at any position of the element, so as to realize simultaneous detection of dual spectral channels. In this paper, an infrared dual band-pass filter used at 100 K temperature was developed. Sapphire (Al2O3) was used as substrate, and Ge and SiO were used as high (H) and low (L) refractive index thin films respectively. An infrared dual band-pass filter combined with a shorter wavelength channel (2.60-2.85 μm) and a longer wavelength channel (4.10-4.40 μm) was designed and fabricated. Based on Fabre-Perot (F-P) filter structure, Ge and SiO thin films were deposited by electron beam evaporation and resistance thermal evaporation on the two sides of the substrate. At the working temperature (100 K), the filter transmittance of shorter channel is 91.2%, and the top ripple amplitude is 2.1%; the average transmittance of longer channel is 87.7%, and the top ripple amplitude is 3.8%. Between the two channels (wavelength 3.00-3.95 μm), the cut-off depth is less than 0.1%. The optical performance of the infrared dual band-pass filter can meet the spectral requirements and contribute to more accurate infrared remote sensing and detection.
Numerical study of fluid flow, heat transfer and infrared signature of 2D exhaust system model with full shielded guide vane combined with rear body
Cheng Wen, Ji Honghu, Shi Xiaojuan, Wang Hao
2022, 51(9): 20210965. doi: 10.3788/IRLA20210965
[Abstract](70) [FullText HTML] (19) [PDF 3412KB](30)
In order to reduce the contribution of the last-stage turbine of the infrared radiation in backward of the exhaust system, the full shielding guide vane(FSGV) is designed to achieve full shielding of the low-pressure turbine. Numerical simulation methods are used to study fluid flow heat transfer and infrared signature of three exhaust system (including baseline axisymmetric exhaust system,2D exhaust system and 2D exhaust system with FSGV) models combined with aircraft rear body, revealing the general rule of infrared radiation characteristics in the 3-5 μm band in backward of the three different combined models; the results show that compared with the baseline axisymmetric exhaust system model combined with aircraft rear body, whether it is a 2D exhaust system model combined with aircraft rear body or 2D exhaust system model with FASG model combined with aircraft rear body, the infrared radiation intensity has been reduced, and the drop rates are 22.1% and 46.9% respectively at a detection angle of 0°. If the cooling technology is adopted for the FSGV, as long as cooling efficiency reaches 0.282 and 0.482, compared to uncooled state of the exhaust system, the infrared radiation in backward of the exhaust system can be reduced by 20.4% and 35.45%.
Quality assessment of FY-4 A’s geostationary interferometric infrared sounder observations data
Wang Yurun, Guan Li
2022, 51(9): 20210838. doi: 10.3788/IRLA20210838
[Abstract](90) [FullText HTML] (46) [PDF 1917KB](23)
The quality assessment of FY-4A Geostationary Interferometric Infrared Sounder (GIIRS) observation data can promote its application in numerical weather forecast. Using FY-4A Geostationary Interferometric Infrared Sounder (GIIRS) observation data in July 2020, this paper not only analyzes the dependence on FOV and latitude of noise for all channels of GIIRS, but also analyzes the distribution of bias (observation minus model) with time, FOV, latitude and zenith angle to evaluate the quality of GIIRS observation data. The results show that the noise of GIIRS exceeded the sensitivity index in the bands 727.5-733.8 cm−1, 1107.5-1130 cm−1, 1650-1776.9 cm−1, and the biases and standard deviation of biases of these three bands are obviously larger than other channels. Except for the channels with large noise in long wave, the noise of each column is small in the middle and larger on both two sides when the noise of all bands is arranged in a 32×4 area array. Besides, the distribution of NEdT does not vary with latitude and FOR. So, when GIIRS data assimilation or variational inversion is carried out, the observation error can just consider the NEdT distribution of different channels in 32×4 array. The surface temperature of the numerical prediction model is underestimated in the daytime, which makes the underestimation of simulated radiation, reduces the absolute value of the bias, and makes the bias have obvious diurnal variation. The bias characteristics of middle-wave channels basically do not vary with the columns of 32×4 array, and are mainly related to the rows in the array. The bias correction can be carried out for the rows of 32×4 array, and the correction of latitude band and satellite zenith angle is basically not needed.
Research on early warning and detection capability of scanning camera of space-based infrared system
Lei Ping, Xing Hui, Wang Juanfeng, Wang Bing, Huang Ligang, Wang Jinsuo
2022, 51(9): 20210977. doi: 10.3788/IRLA20210977
[Abstract](165) [FullText HTML] (31) [PDF 1241KB](55)
With the completion of the deployment of the fifth geostationary satellite in May 2021, all satellites of the entire space-based infrared system are nearly depolyed, and the system's ability to monitor the ground is greatly improved. Based on a large number of relevant literature and public reports, a comprehensive performance analysis of the scanning cameras of all 9 orbiting satellites of the space-based infrared system is carried out. First of all, according to the detector system of the scanning camera and flight-trace characteristics, this paper analyzes its scanning imaging system and calculates estimated values of such key parameters as optical system parameters, detector parameters, ground resolution and sensitivity of all 9 orbiting satellites' scanning cameras. Secondly, to comprehensively analysis and research on the flight characteristics of space-based infrared system satellites in large elliptical orbits and their ground surveillance missions, this paper proves that the optimal in-orbit operation mode is pairwise synchronization, and the difference between the two satellites in a single orbit is 1/4 period. A comprehensive analysis of the flight characteristics and ground monitoring missions of the space-based infrared system geostationary satellites shows that at least two satellites are in good ground observation positions in the mid-latitudes of the northeastern hemisphere. Finally, according to the radiation characteristics of the ballistic missile plume and the detection parameters of the space-based infrared system scanning cameras, the minimum observation height of the missile plume by all orbiting satellites is calculated and analyzed. The results show that the 40°N latitude area in the Eastern Hemisphere can be monitored by more than 4 satellites at the same time, and some satellite-borne cameras have the ability to detect the ignition timing of ballistic missiles.
Effect of baffle configuration on aerodynamic and infrared radiation characteristics of helicopter infrared suppressor
Chen Suqi, Shan Yong, Zhang Jingzhou, Yang Zongyao
2022, 51(8): 20210659. doi: 10.3788/IRLA20210659
[Abstract](87) [FullText HTML] (16) [PDF 3303KB](22)
In this paper, a baffle with an ejector structure is designed to block the high-temperature parts in the infrared suppressor. At the same time, the baffle structure injects ambient cold air to cool its own surface to significantly reduce the infrared radiation of the infrared suppressor. The effects of bow-shaped baffle configuration on the aerodynamic performance, temperature field, and spatial distribution of infrared radiation intensity of the infrared suppressor are studied by numerical simulation. The results show that compared with the nonbaffle structure (Case 0), the baffle structure increases the pumping coefficient of the two-dimensional ejector nozzle by 115% and the thermal mixing efficiency of the infrared suppressor by 273%. Nevertheless, the total pressure recovery coefficient of the infrared suppressor decreases by 7%, and the peak values of the wall and gas infrared radiation intensity are reduced by 46% and 72% within the 3-5 μm band, respectively. Compared with the single bow-shaped baffle (Case 1) structure, the better-designed double bow-shaped baffle (Case 3) can eject ambient cold air with a pumping coefficient of approximately 0.1 and reduce the average surface temperature of its cold side from 638 K to 415 K. The peak values of the wall and gas radiation intensity decrease by 84% and 80% within the 3-5 μm band. In general, the surface temperature of the bow-shaped baffle cold side is affected by the internal eject flow of the double bow-shaped baffle, the stagnation vortex downstream of the bow-shaped baffle cold side, and the cold backflow at the narrow edge end face of the two-dimensional mixing duct.
Study of testing the detecting SNR of point target imaging infrared remote sensing systems
Li Xiaoman, Hu Bin, He Jialiang, Ge Jianyun, Zhou Ji, Xu Bing
2022, 51(8): 20210929. doi: 10.3788/IRLA20210929
[Abstract](75) [FullText HTML] (4) [PDF 1283KB](55)
According to the vacuum and cryogenic test requirements of remote sensors, a set of infrared target background simulators that could work stably in low temperature and vacuum environments was designed and built. The simulator is mainly composed of cold diaphragm, vacuum and low temperature surface source blackbody and three-dimensional electric moving table. The cold diaphragm simulates the detection background, and the micro holes distributed on the cold diaphragm are used to simulate the detection point targets. By effectively controlling the thermal insulation and temperature control between the target simulator and the background simulator and the thermal insulation between the background simulator and the remote sensor to be tested, the stable test is realized. In addition, combining simulation optimization with practical experience, the influence of the thickness of the cold stop plate, the target phase and the collimator of the simulator is removed through simulation calculation, which effectively reduces the measurement uncertainty of the system. The simulation analysis method and the verification results in this paper have reference significance for the detection experiment of signal-to-noise ratio of infrared remote sensor point target detection.
Application of automatic target recognition in image terminal guidance
Chen Xianzhi, Luo Zhenbao, Li Yiqiang, Chen Tao
2022, 51(8): 20220391. doi: 10.3788/IRLA20220391
[Abstract](120) [FullText HTML] (36) [PDF 2996KB](55)
The engineering application of automatic target recognition is the key technology to realize the long-range and precise strike after the image terminal-guided missile is launched. The development history, identification method, technical level and application effect of automatic target recognition of precision-guided weapons at home and abroad are summarized. The recognition methods and application scenes based on target features and template matching are analysed, and two types of engineering verification effective methods are identified. The automatic target recognition method combines the automatic target recognition process, such as task planning, main execution content, and the impact of planning quality on different recognition methods. To meet the needs of intelligent development of precision guided weapons in the future, the engineering application of deep learning recognition technology has become a new trend. To solve the balance problem between the efficiency and application accuracy of deep learning algorithms, this paper focuses on the analysis of network pruning, weight quantization, and low rank. The key technologies of real-time acceleration inference such as approximation and knowledge distillation; for network model training, ideas for effectively solving problems such as insufficient training samples or difficulty in obtaining military target samples are proposed. With the wide application of multiband and multimode composite guidance technology, information fusion provides a new technical approach for the engineering application of target recognition. How to adapt to various complex scenes and artificial active interference is a major challenge for image terminal guidance. The robustness of target recognition under interference conditions is expounded, which is an engineering problem that needs to be urgently solved in the application of automatic target recognition technology in image terminal guidance.
Dynamic infrared cloud scene simulation based on time series smoothing multiscale superposition
Wu Shuang, Li Chao, Gao Chuanwei, Tong Qi
2022, 51(8): 20220656. doi: 10.3788/IRLA20220656
[Abstract](54) [FullText HTML] (11) [PDF 2494KB](22)
The cloud scene in the space-based infrared observation scene has the characteristics of geometric structure dynamic change, scale dynamic change, radiation dynamic change and is coupled with the space-based dynamic detection link, which will have a great impact on the detection efficiency of the system. Therefore, it is very important to carry out research on cloud scene simulation methods for the design of space-based infrared optical satellite systems. This paper proposes a dynamic cloud image simulation method based on the time series smoothing multiscale superposition method to solve the problems of low computational efficiency and large memory usage of traditional simulation methods in large-scale dynamic cloud image simulation applications. The interframe interpolation method is used to realize the change in the shape and structure of the dynamic cloud layer, which improves the computational efficiency by more than 10 times. Realistic simulation of the overall structural change in the position and shape of the clouds realizes the simulation of large-scale dynamic cloud images.
Infrared image target recognition method based on decision fusion of classifiers
Liao Huichuan, Zhao Haixia
2022, 51(8): 20210725. doi: 10.3788/IRLA20210725
[Abstract](58) [FullText HTML] (12) [PDF 1293KB](28)
The problem of infrared image target recognition based on classifier decision fusion was proposed. The sparse representation-based classification (SRC) and convolutional neural network (CNN) were used as the basic classifiers. For the test sample, it was first classified based on SRC, and the reliability of the decision was judged based on the output decision variables. When it was determined that the recognition result is reliable, the recognition process ended and the target category was output. On the contrary, some candidate categories with higher confidence were selected according to the results of SRC, and CNN was employed to confirm the classification result in the next stage. In addition, the CNN output result and SRC were subjected to linear weighted fusion processing, and the final target category decision was made according to the fusion result. The proposed method integrated the advantages of both SRC and CNN classifiers to comprehensively improve the performance of infrared target recognition. At the same time, this hierarchical decision fusion method avoided the two classification processes for all samples, and could ensure the overall efficiency of the recognition algorithm. The experiment was carried out using five types of infrared images of common vehicle targets in daily life, and the original sample conditions, noise sample conditions and occlusion sample conditions were set respectively. By comparing with some existing methods, the results reflect the effectiveness and reliability of the proposed method.
Infrared small target detection method based on the improved weighted enhanced local contrast measurement
Lu Xiaofeng, Bai Xiaofei, Li Sixun, Wang Xuan, Hei Xinhong
2022, 51(8): 20210914. doi: 10.3788/IRLA20210914
[Abstract](74) [FullText HTML] (11) [PDF 2411KB](33)
Infrared dim and small target detection is an important part of the infrared search and tracking system (IRST). Generally, in a complex background environment, infrared dim and small target detection often has the problem of a high false alarm rate and low detection rate. To solve this problem, an improved weighted enhanced local contrast measurement (IWELCM) detection framework is proposed. First, by combining the local contrast mechanism with the signal-to-clutter ratio (SCR) calculation, an enhanced local contrast measurement is proposed to enhance the SCR of the infrared image while enhancing the suspected small target region. Second, an improved weighting function is proposed to enhance the target and suppress the background by taking advantage of the characteristics of the target in infrared images and the significant difference between the target and the surrounding background. Finally, an adaptive threshold segmentation method is used to extract real targets. Experimental results on different scene datasets show that compared with the seven existing methods, the proposed method can effectively extract real dim targets from interference objects under complex backgrounds and has better detection performance.
Parallel multifeature extracting network for infrared image enhancement
Pang Zhongxiang, Liu Xie, Liu Guihua, Gong Yinjun, Zhou Han, Luo Hongwei
2022, 51(8): 20210957. doi: 10.3788/IRLA20210957
[Abstract](90) [FullText HTML] (23) [PDF 3585KB](39)
To solve the problems of fuzzy details and low contrast of low-quality infrared images, a parallel multifeature extraction network for infrared image enhancement is proposed, and a structural feature mapping network and a two-scale feature extraction network are designed. The structural feature mapping network is used to establish the global structural feature weight to maintain the spatial structure information of the original images. The two-scale feature extraction network using multiscale convolutional layers and the attention mechanism fused dilated convolutions is applied to enhance the attention on contextual information, improve the feature extraction capability for regions of interest, and simultaneously learn feature information of different scales, complete the exchange of information of the two scales, and then generate a target enhancement map to achieve adaptive enhancement of detailed texture of target areas. Experiments have proven that the proposed method can effectively improve contrast, avoid overenhancement, enrich image details and textures, and reduce artifacts and halos. Compared with typical traditional methods and deep learning methods, the PSNR and SSIM on the BSD200 dataset are increased by approximately 37.35%, 2.1% and 25.94%, 3.15%, and increased by approximately 30.62%, 1.04% and 24.83%, 2.08% on real infrared images. The proposed method also has good generalization performance on low-quality images with different contrast factors as well.
Radiation calibration and correction in infrared light field imaging
Wang Tengfei, Fu Yutian
2022, 51(7): 20210646. doi: 10.3788/IRLA20210646
[Abstract](105) [FullText HTML] (24) [PDF 2820KB](55)
To realize the application of light field imaging technology in the longwave infrared band, the radiation calibration and nonuniformity in infrared light field imaging were investigated. First, according to the principle of light field imaging and nonuniformity correction, a radiation calibration model for infrared light field imaging was proposed, and the relationship between response drift and nonuniformity was analysed. Next, a standard blackbody experiment was designed to record the image data within 30 hours after the two-point calibration, and the nonuniformity changes of light field data and light field imaging under the same conditions were compared. The experimental results show that within 10 minutes to 30 hours, the nonuniformity of light field data increases from 0.062% to 0.62%, while the nonuniformity of light field imaging increases from 0.024% to 0.27%. Therefore, the effect of response drift on the nonuniformity of infrared light field imaging is affected by the calculation of vignetting and refocusing of the microlens array. Refocusing can effectively suppress the increase in nonuniformity due to response drift.
Research on real-time absolute radiometric calibration technology of infrared cameras
Lv Yuan, Cong Mingyu, Zhao Yini, Niu Kaiqing, Lu Ziwei
2022, 51(7): 20220395. doi: 10.3788/IRLA20220395
[Abstract](105) [FullText HTML] (23) [PDF 2085KB](53)
Radiometric calibration technology is the key link to realize quantitative remote sensing. In recent years, with the maturity of infrared telemetry technology, onboard infrared radiation calibration has become an important development direction of space quantitative remote sensing technology. Based on the background of real-time absolute radiometric calibration of infrared cameras, this paper puts forward the semioptical path on-board absolute radiometric calibration and site absolute radiometric calibration based on multitemperature field. Combined with the experimental data, three schemes of onboard calibration, site calibration and cross calibration are used to verify the on-orbit absolute radiometric calibration experiment. The applicable scenarios of onboard calibration, site calibration and cross calibration are analysed. The results show that by combining the semi and all optical calibration data processing and conversion technology, using the site absolute radiation calibration method of the water surface field and land surface field, a suitable calibration site is selected, and typical ground object scenes are added to the land surface field to realize multitemperature field calibration. The radiometric calibration method proposed in this paper realizes real-time high-precision absolute radiometric calibration, and the calibration accuracy is better than 1.5 K.
Fictitious gas-based model for calculating radiation characteristics of gas
Cheng Wen, Sun Xiaolin, Ma Shan
2022, 51(7): 20220286. doi: 10.3788/IRLA20220286
[Abstract](69) [FullText HTML] (10) [PDF 1793KB](28)
The classical Malkmus statistical narrow-band model was extended with a fictitious gas method to improve the numerical accuracy of the infrared radiation signature of high-temperature gas in aeroengine exhaust systems. In this study, the accuracy of the extended model and the classical Malkmus statistical narrow-band model were evaluated. The results show that the numerical accuracy of the classical Malkmus statistical narrow-band model was improved significantly by the fictitious gas assumption, particularly for nonisothermal and nonhomogeneous gases. Compared with the line-by-line results, the root mean square error of the classical Malkmus statistical narrow-band model for the average band transmissivity of CO2-H2O-N2 mixture is 0.018, while the root mean square error of the fictitious gas-based Malkmus statistical narrow-band model is 0.012, which is reduced by 33.3% compared with the former.
Analytical calculation method of the maximum attack angle of an infrared guided air-to-ship missile
Luo Musheng, Yu Fengquan, Wang Junmin, Li Mansi
2022, 51(7): 20210558. doi: 10.3788/IRLA20210558
[Abstract](93) [FullText HTML] (17) [PDF 1434KB](36)
Aiming at the angle of attack, which is an important influencing factor of infrared guided air-to-ship missile path planning, constraint models of the attack angle were built, including the number of waypoints, distance between two adjacent waypoints, turning angle and pathway distance. An analytical calculation method of the maximum attack angle was proposed. Applying the principle of geometry, the maximum angle of attack calculation model was built, which could be used to solve the pathway with one waypoint, two waypoints and multiple points. Finally, the maximum attack angle under different conditions was simulated when the waypoint number, turning angle and missile range were changed separately. The results show that the maximum angle of attack would increase rapidly as the missile path waypoint increased; it would also increase as the turning angle decreased if the waypoint number was constant. However, the attack angle increased at the expense of the infrared guided air-to-ship missile range.
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