Infrared technology and application

Research of Au-doped LWIR HgCdTe detector
Song Linwei, Kong Jincheng, Zhao Peng, Jiang Jun, Li Xiongjun, Fang Dong, Yang Chaowei, Shu Chang
2023, 52(4): 20220655. doi: 10.3788/IRLA20220655
[Abstract](160) [FullText HTML] (34) [PDF 3534KB](73)
  Significance   Due to the high quantum efficiency and ultra-wide infrared wavelengths (from SWIR to VLWIR), Mercury cadmium telluride (Hg1xCdxTe, MCT) is regarded as the preferred material for high-performance infrared focal plane arrays (FPAs). Compared with p-on-n, n-on-p FPAs have the advantages of simple and reliable manufacturing process. However, in n-on-p FPAs, P-type material with intrinsic mercury vacancy is generally used as the absorption layer. The mercury vacancy belongs to the deep-level defect, which leads to the low carrier lifetime of the absorption layer and the difficulty in controlling the dark current of the device at a low level. Replacing Hg-vacancy with Au (gold) in P-type materials is meaningful to increase minority carrier lifetime, and reduce dark current, which is the most effective way to improve the overall performance of MCT LWIR n-on-p devices. In Kunming Institute of Physics (KIP), the Au-doped MCT devices have been investigated since 2010. After years of continuous research, the key technologies including Au-doped material growth, electrical parameters control, device manufacturing and so on have been successfully broken through, which promoted the fabrication of the high-performance Au-doped n-on-p devices. In this paper, the progress of extrinsic Au-doped MCT LWIR n-on-p technologies in Kunming Institute of Physics was reported comprehensively, which was expected to pave a way for mass production of high-performance LWIR n-on-p FPAs.  Progress   In Kunming Institute of Physics, Te-rich liquid phase epitaxy technology was used to prepare Au-doped LW material. The mercury vacancy concentration was tuned through the heat treatment process with mercury saturation, so as to achieve effective control of electrical parameters. Through the optimization of heat treatment process, the preparation of high-quality Au-doped MCT LW materials was realized, and the carrier concentration can be controlled within 1.0-4.0×1016 cm−3.  The dark current is a significant parameter that determines the performance of device. The substitution of Au atoms for mercury vacancies is efficient to reduce the deep-level defects in the MCT materials, increase the minority carrier lifetime of P-type materials, and reduce the dark current of devices. The high-performance MCT LWIR devices (10.5 μm@80 K) have been fabricated by Au-doping technology in Kunming Institute of Physics. Compared with the Hg- vacancy n-on-p device, R0A of the Au-doped LWIR n-on-p device increased from 31.3 Ω·cm2 to 363 Ω·cm2, which was close to the level of p-on-n devices (Rule07) and laid a foundation for the development of high-performance LWIR FPAs.  Based on the Au-doped technology, LWIR FPAs including 256×256 (30 μm pitch), 640×512 (25 μm pitch), 640×512 (15 μm pitch) and other specifications were fabricated at Kunming Institute of Physics. The performance of these devices was comparable to those reported abroad. The series development and further mass production of non-intrinsic Au-doped MCT LWIR FPAs have been realized. Furthermore, the researches involved high and low temperature storage, high and low temperature cycle (+70-−40 ℃) and long-term storage stability were carried out, and the results show that after 7 years of long-term storage, the performance of the devices have no obvious change.   Conclusions and Prospects  In this paper, the development progress of extrinsic Au-doped MCT materials and devices in Kunming Institute of Physics was reported. The stability of Au-doped HgCdTe materials, dark current control and other key technologies have been broken through up to now. The merit factor (R0A) has been improved from 31.3 Ω·cm2 to 363 Ω·cm2λcutoff=10.5 μm@80 K) for LWIR HgCdTe focal plane arrays by use of Au-doped technology. The dark current has been reduced by one order of magnitude compared with Hg-vacancy n-on-p devices. And the performance of n-on-p LWIR HgCdTe focal plane arrays has been greatly improved. The performance has not change by storage more than 7 years of the Au-doped HgCdTe device, which shown that the devices have better long-term stablity. Based on this, Kunming Institute of Physics has realized the series development of Au-doped LWIR HgCdTe with a format of 256×256 (30 μm pitch), 640×512 (25 μm pitch), 640×512 (15 μm pitch), and 1 024×768 (10 μm pitch), which has provided a foundation for the mass production of long wave HgCdTe focal plane arrays.
Uncertainty analysis of inter-calibration collocation based on FY-3E spaceborne infrared observations
Yang Tianhang, Zhang Chunming, Zuo Fenghua, Hu Yong, Gu Mingjian
2023, 52(4): 20220616. doi: 10.3788/IRLA20220616
[Abstract](76) [FullText HTML] (10) [PDF 1922KB](34)
  Objective   Spaceborne infrared hyperspectral sensors and multi-channel spectral sensors can continuously observe the earth for a long period of time, and have important applications in the fields of climate prediction, weather change, environmental monitoring, etc. The high-precision spectral calibration and radiation calibration of their observation data are crucial to the quantitative application of remote sensing. With the increase of operational time of satellite after being launched, the performance of the spaceborne sensors will change, which will lead to the deviation of observation data accuracy. Therefore, it is necessary to effectively improve the calibration accuracy and the data quality of the instrument through on-orbit inter-calibration. The samples of inter-calibration are generally collocated and filtered through the method of the on-orbit alternative calibration of the Global Space-based Inter-Calibration Sytem (GSICS), including spatial, temporal, observation geometry and spectral collocation through simultaneous nadir overpass (SNO) observations, and consequently achieve the goal of inter-calibration with the target sensor. The SNO observations can make two satellite sensors observe the earth from different heights at the similar time and place, which fully reduces the comparison uncertainty caused by different observation time and angle of satellites. This is a necessary prerequisite for the feasibility of inter-calibration, but these factors are also the main source of calibration uncertainty, and the uncertainty of collocating bias will have effects on the inter-calibration accuracy finally. Therefore, we analyze the uncertainty of the samples collocating processing in this paper, including spatial collocation, observation angle collocation and spectral response function collocation between sensors.  Methods  We establish the sifting process of inter-observation sample pairs above uniform clear-sky background scenes (Fig.1) of the infrared hyperspectral atmospheric sounder HIRAS-II and the low-light medium-resolution spectral imager MERSI-LL onboard the same platform of the FY-3E of China Fengyun-3 series sun-synchronous orbit meteorological satellite. Collocating MERSI-LL pixels within HIRAS-II nadir instantaneous field of view (IFOV) based on line-of-sight (LOS) vectors, HIRAS-II projects the FOV footprint from the satellite to the earth's surface at a fixed solid angle, and all coordinates are converted into Earth Centered Earth Fixed (ECEF) coordinate system after calculation. All MERSI-LL pixels in the coverage area of HIRAS-II FOV footprint can be determined by calculating the line-of-sight vector (Fig.3). The uncertainty of the samples collocation introduced by spatial, observation geometry and spectral collocating bias is separately analyzed by simulating IFOV shift, observation zenith angle deviation and spectral response function change, respectively.  Results and Discussions   The results of uncertainty analysis above each section of collocating process through cross observation of sensors on the same platform, radiation transmission model simulation and statistical analysis show that, in terms of spatial collocation, we evaluated the percentage deviation and standard deviation of radiance brightness temperature between the disturbed value and the standard value (Fig.5) by comparing the standard value of radiance brightness temperature in the target area with the disturbed value of radiance brightness temperature after simulating pixel offset, the spatial mis-collocation causes the changes of radiance brightness temperature above observed background scenes, the relative uncertainty is approximately 10% when the IFOV is shifted by half a pixel. In terms of geometric collocation, we evaluated the deviation and relative accuracy of the brightness temperature of the observed and simulated spectrum by comparing the brightness temperature sample of spectrum observed by HIRAS-II with the simulated spectral brightness temperature after changing the satellite zenith angle, it is found that the misalignment of observation geometry causes deviation of spectrum radiance brightness temperature, the uncertainty is less than 0.2% when the observed zenith angle is shifted by 20 degree (Fig.7). In terms of spectral collocation, the hyperspectral equivalent radiance can be obtained by simulating and calculating the HIRAS-II infrared hyperspectral radiance and channel spectral response function of MERSI-LL. The difference of the spectral response function causes bias of spectral equivalent radiance brightness temperature, the uncertainty of the absorption channel and window channle is approximately 2.5% and 0.4% respectively for expanding the response function, and the uncertainty is better than 0.3% overall for shrinking the response function, the uncertainty is relatively small for shifting response function, and it is better than 0.1% when shifting five times the wavelength interval (Fig.9).  Conclusions   In this study, we analyzed the uncertainty and its influence introduced by observation collocation in terms of spatial, observation geometry and spectral collocation, which are aimed at the spaceborne infrared hyperspectral sensors and multi-channel spectral sensors before inter-calibration. We used the pixel matching method above observation field based on the line-of-sight vector to separately analyze the uncertainty introduced by spatial, observation geometry and spectral collocating bias. The spatial mis-collocation caused by IFOV shift leads to the change of observation background radiance, the relative uncertainty is approximately 25%-30% when the IFOV is shifted by a pixel. In order to reduce the uncertainty introduced by pixel offset, the offset distance should be limited to half of the spatial resolution of the nadir instantaneous field of view. The misalignment of observation geometry caused by observation zenith angle difference leads to the bias of observation background radiance, and the bias is more obvious in vapor channel, the deviation of observation zenith angle should be constrained within 10 degree or more less. The deviation of hyperspectral equivalent radiance caused by the difference of spectral response function has an impact on the calibration accuracy, the effective bandwidth change of spectral response function will cause greater uncertainty relative to the central wavelength shift of spectral response function. This study provides a reference for setting reasonable threshold in the condition of sifting collocated samples before inter-calibration, and also provides support for improving accuracy of inter-comparison and calibration.
On-board calibration and verification of GF5B thermal infrared channel
Ma Xiuxiu, Wang Haiyan, Han Qijin, Zhang Xuewen, Zhao Hang, Xu Zhaopeng, Zeng Jian, Ma Lingling, Wang Ning
2023, 52(4): 20220644. doi: 10.3788/IRLA20220644
[Abstract](82) [FullText HTML] (12) [PDF 2247KB](29)
  Objective   Thermal infrared remote sensing has the ability of day and night detection and good environmental adaptability, which makes it have important applications in natural ecological environment monitoring, urban heat island effect monitoring, lake and reservoir water quality monitoring, etc. The application of thermal infrared remote sensing has gradually changed from qualitative to quantitative, and absolute radiometric calibration is the prerequisite for the quantification of remote sensing information. Among them, on-board blackbody calibration uses on-board blackbody as the calibration source, which is not limited by time, environment and other factors. It can produce corresponding calibration coefficients for each orbit data, improve the frequency of on-orbit absolute radiometric calibration. Based on the on-board 0-level blackbody calibration data of GF5B VIMI (Hyperspectral observation satellite, visible and infrared multispectral image), the absolute radiometric calibration research of satellite thermal infrared channel is carried out. In this way, reliable calibration results can be obtained to provide a method basis for the subsequent blackbody calibration of satellite thermal infrared remote sensing.  Methods   Based on the laboratory calibration before the launch of GF5B satellite, the on-board blackbody calibration data is used to establish the on-board absolute radiometric calibration model applicable to the GF5B thermal infrared channel. Firstly, relative radiometric correction is carried out for the high and low temperature blackbody image data transmitted from satellite; based on the blackbody image data after relative radiation correction, the average DN of each channel corresponding to the high and low temperature blackbody is obtained. At the same time, the high and low blackbody temperature is calculated based on the high and low temperature blackbody auxiliary data, and then the radiance value of the corresponding channel of the high and low temperature blackbody is calculated using the Planck function. Then, according to the actual response average DN of the high and low temperature blackbody image and the corresponding channel radiance, the inner blackbody absolute radiometric calibration coefficient is calculated. Finally, the internal and external blackbody calibration conversion coefficients are used to convert the internal calibration coefficients into the absolute radiometric calibration coefficients of the on-board blackbody (Fig.1). In addition, according to the error sources of the on-board calibration system, various indicators affecting the accuracy of the on-board calibration system are analyzed. The accuracy of on-board blackbody calibration is evaluated and verified by using the ground synchronous buoy measurement data.  Results and Discussions  The on-board blackbody calibration data of the 1 850th orbit on January 12, 2022 are selected to conduct the on-board blackbody absolute radiometric calibration, and its on-board absolute radiometric calibration coefficient (Tab.3) is obtained. Through the analysis of various indicators affecting the accuracy of the on-board radiometric calibration system, the results show that the total error of the on-board radiometric calibration of the camera is 1.268% (Tab.4), and the equivalent temperature is 299.1 K@300 K. Therefore, the absolute calibration accuracy of the on-board calibration system is 0.9 K. The verification results of satellite-ground synchronization show that the relative differences of radiance of B11 and B12 channels are 0.64% and 1.35% respectively. The brightness temperatures of B11 channel monitored by satellite and ground measurements are 273.78 K and 273.45 K respectively, with a difference of 0.33 K; the brightness temperatures of B12 channel monitored by satellite and ground measurements are 272.58 K and 273.35 K respectively (Tab.5), with a difference of 0.77 K, which shows that the brightness temperature difference is within 0.8 K. The satellite-ground data have a good consistency, which indicates that the thermal infrared channel of GF5B satellite has a high calibration accuracy on orbit, and the results are true and reliable.  Conclusions   The on-board blackbody calibration method based on GF5B thermal infrared channel has good accuracy and reliable calibration results, which can meet the needs of remote sensing data quantification application. It provides a method reference for real-time and accurate acquisition of thermal infrared channel calibration coefficient. The construction of the research method is based on GF5B on-board calibration blackbody, which has important reference value for the on-board blackbody calibration of other satellites.
Simulation of airborne dynamic dispersion characteristics and application of point-surface composite infrared decoy
Zhao Feiyu, Wang Liang, Guo Kai, Zhang Jingyuan, Pan Bochen, Guo Shuchao
2023, 52(4): 20220476. doi: 10.3788/IRLA20220476
[Abstract](78) [FullText HTML] (7) [PDF 5970KB](31)
  Objective   Point-surface composite infrared decoy is one of the advanced infrared jamming equipment used in aircraft platforms at home and abroad, which has a good capability against infrared guided missiles. For aircraft platforms, it is important to master the use strategy of point-surface composite infrared decoy. It determines the aircraft’s survivability during terminal defense. Currently, the use of infrared decoy lacks simulation analysis support, and there is a certain degree of blindness. With the improvement of couter-coutermeasure ability of infrared guided missiles, it brings higher requirements for the development and use of infrared decoy. Besides, there is a lack of simulation and research related to point-surface composite infrared decoy. So the airborne dynamic dispersion characteristics and application of point-surface composite infrared decoy is studied.  Methods   To obtain the dynamic walk characteristics of point-surface infrared decoy in the air, theoretical basis for its use is provided, and the effectiveness of point-surface infrared decoy is improved, dynamic and kinematic analysis of point source decoy and surface source decoy of point-surface infrared decoy (Fig.3) is performed, the simultaneous equations are solved, so the trajectory of point source decoy and dispersion of surface source decoy in the air were obtained. Then by changing the aircraft platform speed, the relative motion trend of the point source decoy and surface source decoy, and the influence law of the platform speed are obtained. Based on the simulation of airborne dynamic dispersion characteristics of point-surface infrared decoy, the use research is conducted, and the jamming characteristics and mechanism of the point-surface infrared decoy are described. Jamming characteristics mainly include radiation intensity value, rate of radiation intensity change and radiation area. The formation characteristics of point-surface infrared decoy in the field of view of infrared guided missiles are analyzed. And based on this, the mechanism research is carried out.  Results and Discussions   Through simulation analysis, airborne dynamic dispersion characteristics are acquired (Fig.6). It provides a good foundation for the use of point-surface composite infrared decoy. At the same time, the infrared radiation characteristics of point-surface composite infrared decoy are acquired (Fig.9). For infrared guidance seeker, it is sensitive for radiation intensity change rate (Fig.10) and radiation area (Fig.11) of infrared decoy. The jamming mechanism of the point-surface infrared decoy in the imaging phase (Fig.13) and the non-imaging phase (Fig.12) of the infrared guided missile is analyzed, which can provide reference for the formulation of decoy use strategy and improve the battlefield survivability of aircraft platforms.  Conclusions   In this study, starting from the basic physical laws, the dynamic dispersion characteristics of point surface composite infrared decoys in the air are studied, and the impact of platform speed on the dynamic dispersion of point-surface composite infrared decoys in the air is simulated. The results show that the faster the platform speed is, the smaller the relative separation speed of point-surface composite infrared decoy relative to area source decoys is, and the greater the diffusion speed of area source decoys is. The interference characteristics and mechanism of point-surface composite infrared decoy during use are analyzed. Its key characteristics such as radiation intensity value, radiation intensity change rate, and radiation area have the ability to interfere with infrared guided missiles. The interference mechanism of point-surface composite infrared decoy in the imaging and non-imaging stages of infrared imaging guided missiles is described, and the confrontation process is described based on simulation results. The research on the dynamic dispersion characteristics simulation and use of point-surface composite infrared decoy in the air conducted in this paper is mainly based on the characteristics of the decoy itself and the basic interference principles. The actual use strategy should be comprehensively studied and determined in combination with multiple factors such as missiles, aircraft targets, and maneuver strategies.
Quantitative analysis of the uncertainty of infrared radiation signature of rocket exhaust plume caused by incoming flow
Xiao Zhiru, Niu Qinglin, Wang Zhenhua, Dong Shikui
2023, 52(4): 20220621. doi: 10.3788/IRLA20220621
[Abstract](51) [FullText HTML] (3) [PDF 1897KB](20)
  Objective   The rocket exhaust plume is one of the key objects of the space-based infrared system (SBIRS) due to its strong infrared radiation characteristics. The infrared radiation signature of the plume is not only related to the motor prototype parameters but also to the flight parameters of the vehicle. In practical applications, the variation characteristics of infrared radiation signature of the rocket exhaust plume can be predicted through numerical methods based on the known motor and flight parameters. However, the flight parameters of non-cooperative targets are often difficult to obtain accurately, which means that there must be some deviation in predicting the infrared radiation signatures of the rocket exhaust plume by numerical methods. Therefore, it is necessary to study the influence of flight parameter disturbance on the infrared radiation of rocket exhaust plumes. For this purpose, the non-intrusive polynomial chaos (NIPC) method is used for the uncertainty quantification and sensitivity analysis of free stream parameters on the infrared radiation signatures of the rocket exhaust plume.  Methods   The Latin hypercube sampling (LHS) method is used to design the samples of frees tream parameters. The infrared radiation characteristics of the rocket exhaust plume are calculated based on the infrared signature analysis tool (IRSAT), and the corresponding infrared response values of the plume at each sample point are obtained. The regression analysis method is used to solve the polynomial chaotic expansion coefficient and the statistical characteristics of the plume infrared signatures, including the mean value, standard deviation and uncertainty. Based on the Sobol index, the NIPC method can be utilized to quantify the uncertainty and sensitivity of the infrared radiation signature, and analyze the impact of a single variable and multiple variables on the infrared radiation characteristics of the rocket exhaust plume.  Results and Discussions   The free stream velocity has a high sensitivity to spectral radiation intensity in most spectral bands except for 4.3 μm, and the corresponding Sobol index is above 0.5. The maximum sensitivity of free stream pressure occurs in the 4.3 μm band, and the peak of the Sobol index is close to 1.0. The Sobol index of angle of attack to spectral radiation intensity is about 0.4, and it shows high sensitivity in multiple bands. The influence of the ambient temperature on the radiation spectrum is negligible. The Sobol index of the in-band radiance shows that the free stream velocity is the most sensitive to the radiation intensity in most bands. The free stream pressure and the angle of attack are the second, and the free stream temperature is the smallest. The coupling effect of free stream velocity and ambient temperature has the most obvious contribution to the in-band radiance. The coupling effect of free stream velocity and pressure, and the coupling effect of temperature and angle of attack only affect some extremely narrow spectral bands. The coupling effect among other parameters can be almost ignored.  Conclusions  The low altitude under-expanded Atlas-IIA plume is taken as the research object, and the uncertainty quantification and sensitivity analysis of infrared radiation signatures of free stream velocity, temperature, pressure and angle of attack are carried out using NIPC method. The uncertainty of radiation intensity caused by the incoming flow has a high correlation with the spectral band. The standard deviation of the in-band radiance is positively correlated with the mean value, and the uncertainty of the radiance is opposite to the mean value of the radiation intensity. In most wavebands, the free stream velocity is the most sensitive to the radiation intensity, followed by the free stream pressure and angle of attack, and the ambient temperature is the least. The coupling effect of velocity and temperature have the most obvious contribution to the radiance. The coupling effect of velocity and pressure, and temperature and angle of attack only have an effect in some very narrow spectral bands. The ratio of angle of attack to the main Sobol index of the radiation intensity is between 15% and 23%. The main Sobol index of the inflow velocity accounts for nearly 80% except for the 4.3 μm band. The impact of inflow pressure in the 4.3 μm band is dominant. The coupling effect of each incoming flow parameter has little influence on the radiation intensity in each spectral band, which is less than 4%.
Research on circuit board fault diagnosis based on infrared temperature series
Hao Jianxin, Wang Li
2023, 52(4): 20220492. doi: 10.3788/IRLA20220492
[Abstract](67) [FullText HTML] (4) [PDF 3895KB](30)
  Objective   A rapid and accurate detection of the fault occurring to the airborne electronic system plays a crucial role in ensuring the safety of civil aircraft. However, due to the increase of circuit board size and component density in airborne electronic system, the traditional contact fault diagnosis method encounters various problems such as low accuracy, huge time cost and the demanding requirements on personnel competency. Therefore, this study aims to explore the solution to circuit board fault diagnosis based on non-contact infrared technology, which is essential for improving the accuracy of fault diagnosis for the airborne electronic system.   Methods   After the sequential thermal image of the circuit board is captured by using the infrared camera, the region of interest in the thermal image is processed as the infrared temperature series. Since the infrared temperature series of the circuit board contains various fault-related information, the accuracy of fault diagnosis can be improved by making full use of its local and global features. In this study, a fault diagnosis algorithm is proposed to achieve this purpose. Composed of the features extraction network (FEN) and the relationship learning network (RLN), it utilizes the local features of temperature series and the relationship between the features. Built on a residual structure with multi-scale dilated CNN, FEN plays the role of a local-feature extraction network to construct a multi-scale receptive field without increasing the number of training parameters and to learn the spatial features of temperature series of different ranges. Based on the embedded structure of two identical layers, attention mechanism and LSTM network, RLN is a network that can apply control on the transmission of temperature series to learn the importance of features and assign attention weights for mining the correlations between the features extracted from different positions. To develop a complete circuit board fault diagnosis algorithm, the parallel FEN and RLN networks are connected to the "Softmax" classifier.  Results and Discussions   The temperature series datasets representing 27 different fault categories are constructed based on the infrared thermal image of airborne power board (Tab.1, Tab.5). (1) By analyzing the temperature series datasets, it can be found that there are significant differences between the temperature curves of the chip under different fault conditions, and the temperature curves of non-faulty chips are also affected by faulty chips (Fig.5). (2) The experimental results show that the proposed algorithm achieves a better diagnostic performance than FCN, MFCN, LSTM and LSTM-FCN on the datasets of the temperature series testing on two self-built circuit boards. To be specific, its diagnostic accuracy reaches 91.15% and 96.27%, respectively (Fig.8) (Tab.5). (3) Given the identical hyperparameter setting, the increase in dimension of temperature sequence feature vector contributes to improving the diagnostic performance. That is to say, appropriate sample is one of the key influencing factors in improving the accuracy of fault diagnosis (Tab.5). (4) Ablation studies reveal that the performance of FEN in feature extraction capability can be improved by the proper setting of hyperparameters, which is conducive to enhancing the diagnostic accuracy of the algorithm (Tab.6). (5) The long Short-term Memory hybridized with Attention (LSTMwAtt) plays a role in improving the performance of the proposed algorithm in terms of relation extraction. By fully utilizing the intrinsic relationship between the characteristics of different locations of temperature series, the proposed algorithm is more likely to capture the differentiated data carried by similar faults (Tab.6).  Conclusions   In this study, a fault diagnosis algorithm intended for the airborne circuit board is proposed by using infrared temperature series. In this algorithm, the features extraction network is responsible for extracting local features and learning the spatial features of temperature series of different ranges, while the relationship learning network is proposed to discover the intrinsic relationships among the representations learned from infrared temperature series. According to the experimental results, the proposed diagnosis algorithm performs well on self-built testing datasets. However, it is worth noting that the small size of the self-built datasets reduces the accuracy of the algorithm when the proposed algorithm is applied to the new datasets. As the size of self-built datasets increases, it performs better in fault diagnosis. Hopefully, it would be applicable in circuit board fault systems to deal with the fault that occurs to the airborne electronic systems.
Optimal design and verification of thermal adaptive structure for infrared calibrator with large surface
Fei Zhihe, Xu Jun, Lan Shaofei, Zhou Xiaodong, Wang Xiaodong
2023, 52(3): 20220463. doi: 10.3788/IRLA20220463
[Abstract](93) [FullText HTML] (17) [PDF 1746KB](30)
  Objective   Infrared calibrators directly determine the detection accuracy of infrared devices as the reference standard for radiation measurement of infrared devices before the satellite launching. More precise infrared calibrators with large surface are required with the development of infrared optical satellites characterized by large aperture, large field of view and high precision, which means the structure of infrared calibrators must keep stable in high and low temperatures to guarantee the high temperature uniformity of the radiant surface, high precision of temperature control and high stability of the system. In the calibration test, the structure thermal mismatch easily occurs because the multilayered structure of infrared calibrators connected with bolts usually includes a variety of different materials and the deformations become unmatched during heating and cooling process for different thermal expansivity, which can reduce the calibration accuracy and increase security risks and test cost. As a result, optimal design and verification of thermal adaptive structure for the infrared calibrator with large surface, wide temperature range and multiple materials were carried out, to solve the problems caused by structure thermal mismatch, including the loose bolts, low cooling rate and bad thermal uniformity at the low temperatures, as well as the compression failure of heat insulating mattress made of glass reinforced plastic at the high temperatures.   Methods   From the two aspects of normal preload regulation and in-plane warping deformation control, the key materials were selected, the assembly parameters were adjusted and the structure parameters were optimized. Simulation analysis and tests were combined to explore the change rules of bolts preload on multilayered structure made of different materials when the temperature changed, at the same time verify the safety and stability of the structure. Finally, the key technical indexes of infrared calibrator were verified by means of heating and cooling tests.  Results and Discussions   The calculations based on the linear elastic theory indicated that the change of preload was controlled effectively by means of choosing Teflon as heat insulation material and stainless steel as bolt material (Tab.1), which provided a smaller relative deformation between bolts and connected members caused by the temperature change. The original preload was applied between 12 N·m to 20 N·m to avoid bolts looseness at −100 ℃ and deformation failure at 140 ℃ (Tab.2). Furthermore, the diameters of mounting holes were enlarged to be greater than 25 mm to reduce the in-plane warping deformation resulting from bolts shearing (Tab.3). The tightening torque test based on multilayered structure composed of different materials discovered the rules that the tightening torque got linear relation with the deformation in the certain range. The elastic deformation occurred at the low temperatures and on the other hand the plastic deformation was more likely to occur at the high temperatures. The axial stiffness of multilayered structure could be improved by repeating heating and cooling process (Fig.4). The simulation result of the whole system suggested that the proportion of bolts with safe and effective connections had reached more than 90% under the high and low temperatures (Tab.3). The stress of bolts at the upper and lower edges of the calibrator changed more significantly than that at other positions and therefore different assembly parameters could be set according to the bolt positions. The heating and cooling test of infrared calibrator showed that the structure was safe and stable with the temperature change, the cooling time was shortened from 30 h to 4 h (Fig.7), and the temperature deviation of the radiant surface at 193 K was improved from −0.8 K/+0.9 K to −0.3 K/+0.4 K.  Conclusions   The optimal design of thermal adaptive structure can significantly increase the cooling rate of infrared calibrator and improve the thermal uniformity of radiant surface at the low temperatures. The difficulties of loose bolts at the low temperatures and compression failure of heat insulating mattress at the high temperatures were overcome at the same time. This study solved the practical problems in the calibration test and the structural safety and stability after optimal design can meet the design requirements. The optimal design methods of thermal adaptive structure can be referred for the same type of products.
Analysis of distributed detection range changes caused by infrared system self-thermal radiation
Li Baoku, Liu Le, Xu Wei, Zeng Wenbin, Hu Haifei, Yan Feng, Cai Sheng
2023, 52(3): 20220417. doi: 10.3788/IRLA20220417
[Abstract](67) [FullText HTML] (6) [PDF 1773KB](32)
  Objective   Detection range is an important evaluation index of infrared system application. Stray radiation is the main factor limiting the detection distance of infrared system, and the irradiance generated by it shows uneven distribution on the focal plane. Currently, the focal plane of the detector is regarded as a whole or the central region is extracted, and the influence factors such as self-thermal radiation and background radiation are calculated on average. The detection distance is obtained by inputting target parameters, and the overall influence of self-thermal radiation on the focal plane is considered in the cold optical design of the system. When the target imaging is in different focal plane regions, the detection range calculated by the above method is not accurate enough, and the pertinence is not strong in cold optical design. To solve the above problems, a detection range calculation formula including the system noise term is established, and a distributed detection distance analysis method is proposed, which is verified by a transmitted infrared optical system.  Methods   Based on the self-thermal radiation and the classical detection range theory, this paper deduces the calculation formula of the detection range of the infrared system including the system noise term, and proposes an analysis method of the distributed detection range. Taking the transmitted optical system as an example, the sensitivity analysis of the influencing factors is carried out. By sub-regional data processing on the detector focal plane, the main influence surfaces corresponding to the detection range are obtained. On this basis, the change of the detection range before and after the low temperature treatment of the main affected surface (cooling from 293.15 K to 173.15 K) was analyzed (Fig.10, 11).  Results and Discussions   Based on the theory of self-thermal radiation and classical detection range theory, a calculation model of detection ability including its own thermal radiation noise is given, and a direct theoretical calculation relationship is established for the influence of the self-thermal radiation on detection ability. When the target imaging is in different focal plane regions, the detection range obtained through traditional calculation is not accurate enough and the pertinence is not strong in cold optical design, and the distributed detection range analysis method is proposed (Fig.1). Under the condition of only considering its self-thermal radiation, a simple partitioning principle is discussed (Fig.2). Taking the transmitted optical system as an example, the main influence surfaces in each area of the focal plane are obtained (Fig.9) through the statistical results of the influence weights of each component's own thermal radiation in different areas (Tab.3). The detection distance of the corresponding main influence region is significantly improved (Fig.10, 11), providing a new idea for the calculation of target detection range.  Conclusions   Based on the theory of self-thermal radiation and classical detection range theory, the detection range formula directly related to the noise item of infrared optical machine system is obtained, the analysis method of distributed detection distance is proposed, and the principle of focal plane partitioning under the influence of self-heat radiation is given, and a transmitted infrared optical system is analyzed with this method. Under the premise that only the influence of self-thermal radiation is considered and the target is an ideal point target, the variation trend of detection distance along with the irradiance of image plane is given. Then, the focal plane of detector is divided into regions to obtain the irradiance ratio of different regions. Through the radiation amount generated by the surface light source of different components in different focal plane areas, the influence weight of each component self-thermal radiation in different areas was calculated, and the main influence surface of each area was obtained. On this basis, lens 7 and lens 3 were respectively treated with low temperature (293.15 K cooling to 173.15 K), and the maximum increase of detection distance in the main affected areas was 17.03% and 43.32%, with obvious improvement. It can be seen through the example verification that the proposed distributed detection range analysis method can be used as the basis for the calculation of distributed detection range and the design of cold optical index of infrared system after determining the corresponding partition principle according to the analysis environment and analysis conditions.
Development of high precision CO2 detection system based on near infrared absorption spectroscopy
Li Hengkuan, Piao Heng, Wang Peng, Jiang Yankun, Li Zheng, Chen Chen, Qu Na, Bai Huifeng, Wang Biao, Li Meixuan
2023, 52(3): 20210828. doi: 10.3788/IRLA20210828
[Abstract](72) [FullText HTML] (5) [PDF 1469KB](31)
  Objective   Crustal movement will discharge CO2 and other gases to the surface, and the surface concentration of CO2 near the fault zone will be abnormal before the earthquake. High-precision measurement of CO2 gas near the seismic zone can provide important help for the analysis of earthquake precursors. At present, the main methods for measuring CO2 concentration include non-dispersive infrared analysis technology, electrochemical technology, chromatographic analysis technology, etc. However, the above methods generally have the disadvantages of being easily disturbed by its background gas, low accuracy, and unable to achieve real-time monitoring. Tunable diode laser absorption spectroscopy (TDLAS) technology has the advantages of not being disturbed by its background gas, high accuracy, and real-time monitoring. In recent years, it has become a research hotspot at home and abroad and has been widely used in the field of gas detection. In this paper, a high-precision CO2 detection system is developed by using tunable diode laser absorption spectroscopy technology.  Methods   In this paper, a high-precision CO2 detection system for seismic monitoring is established. The tunable diode laser absorption spectroscopy technology is adopted, and the wave number 4 978.202 cm−1 is selected as the absorption spectral line of the CO2 detection system (Fig.1). A multi-channel unit with an effective optical path of 40 m is adopted, and STM32 is used as the control equipment and data processing core equipment (Fig.2). For the detector noise and optical interference fringe noise in the system, Kalman-wavelet analysis algorithm is used to filter and improve the system.  Results and Discussions   The system uses Kalman-wavelet analysis method to eliminate the influence of detector noise and optical fringe interference. The experiment shows that the second harmonic signal to noise ratio of the system at 50 ppmv CO2 concentration is 2.06 times higher than that before filtering (Fig.3). Under different CO2 concentrations (50 ppmv, 300 ppmv, 1 000 ppmv, 4 000 ppmv, 8 000 ppmv), the system error is 2.57%-2.66% (Fig.4). When the system measures CO2 at 4 000 ppmv concentration, the detection precision reaches 20.9 ppmv (Fig.5). According to Allan variance analysis, the method detection limit (MDL) corresponding to the integration time of about 61s is 5.2 ppmv (Fig.6), which realizes the high-precision measurement of CO2 gas.  Conclusions   This paper develops a high-precision CO2 detection system for seismic monitoring. The system adjusts the current injected into the DFB laser to make its output central wavelength at 2 008 nm and serve as the detection light source of CO2. In order to improve the lower detection limit of CO2 gas concentration, the system uses a self-developed cylindrical mirror multi-pass cell with an effective optical path of 40 m. The multi-pass cell can work stably in the temperature range of 0-40 ℃ and the pressure range of 1.333-101.325 kPa to ensure the reliability of the system in the field measurement process. The system control TEC realizes the temperature control of the controlled object, and the control precision of the temperature control system in the laboratory can reach 0.01 ℃. The Kalman-wavelet analysis algorithm is used to filter the system noise, and the frequency of optical fringe interference in the frequency domain is similar to that of cosine wave in the time domain, so as to separate it and remove the optical fringe interference. The experimental results show that the accuracy, precision and the method detection limit of the system are improved after filtering. The system combined with this method can make the geochemical gas measurement have a broader application prospect and provide important help for the accurate analysis of earthquake precursors.
Research on atmospheric transmission calibration method of infrared target simulator
Zhang Xinyi, Chen Zhenlin
2023, 52(3): 20220378. doi: 10.3788/IRLA20220378
[Abstract](52) [FullText HTML] (4) [PDF 2672KB](29)
  Objective   The infrared radiometer is an important device for the calibration of the infrared target simulator and is used as a measurement transfer standard during inspections. The primary calibration parameter for the IR target simulator's radiant energy is irradiance, so the role of the IR radiometer is to measure and calibrate its outgoing irradiance. In infrared transmission, the process will be affected by the atmosphere, including two aspects: One is the infrared radiation by atmospheric molecules, aerosol particles scattered or absorbed by the attenuation, the general use of atmospheric transmittance to characterize the degree of atmospheric attenuation of infrared radiation; second is the atmosphere itself emitted by the atmospheric range of radiation will be superimposed on the target radiation. Atmospheric corrections must be made to improve calibration and measurement accuracy.  Methods   An atmospheric transmission calibration method for infrared target simulators is proposed based on a wide dynamic infrared radiometry method based on a constant standard source. In the calibration of the IR target simulator with a horizontal homogeneous atmospheric approach, a network model of atmospheric transmittance and atmospheric range radiation at different wavelengths, temperatures, and distances is developed using the data analysis capability of convolutional neural networks (Fig.2). Based on the encoder-decoder structure, the detector output voltage under three wavelengths is used as the input of the convolutional neural network, and the test data are normalized and input to the encoder in batches for learning and training, with the batch size set to 8 and the test distance input directly in the embedding layer, and the network is trained according to the training process (Fig.3) to obtain the test distance and atmospheric transmittance and atmospheric range, the model of radiation is given as the correspondence between them.  Results and Discussions   A wide dynamic infrared radiometry method based on a constant standard source was used for multiple experiments to obtain multiple detector output voltage values, which were trained using a network model (Fig.2) to obtain network output values of atmospheric transmittance and atmospheric range radiation at different distances (Fig.7). To verify the improvement of IR radiation measurement accuracy, radiation inversion is performed, and the results of radiation inversion under different methods (Fig.9) can be obtained, and the corresponding IR radiation measurement error graph (Fig.10) and specific values (Tab.2) are shown. The experimental results show that the convolutional neural network algorithm based on the encoder-decoder structure can better predict atmospheric transmittance and atmospheric path radiation, the infrared radiometric average error in three bands of the proposed method is 3.0783%, 3.8186%, 5.3452%, which is far lower than the traditional method, reduces the influence of atmospheric transmittance and atmospheric path radiation, reduces the measurement error of infrared radiation, and improves the calibration accuracy.  Conclusions   The atmospheric transmission correction algorithm is proposed for the problem of atmospheric transmission influence using the direct measurement method. Based on the wide dynamic infrared radiation measurement method with a constant standard source, a convolutional neural network algorithm based on an encoder-decoder structure is used to obtain the relationship between atmospheric transmittance, atmospheric range radiation and waveband and test distance, and atmospheric correction is performed for different wavebands and different test distances. Compared with the traditional method, there is no need to use MODTRAN software to calculate atmospheric transmittance, atmospheric range radiation and atmospheric parameters of the measurement experiment environment, which improves the problem of low distance resolution and accuracy of MODTRAN software under close measurement conditions and improves the accuracy of infrared radiation measurement.
Optimal driving method design of infrared cryocooler under high-order driving
Zhu Jinghao, Yang Baoyu, Zhang Jiakun, Wu Yinong
2023, 52(2): 20220369. doi: 10.3788/IRLA20220369
[Abstract](82) [FullText HTML] (22) [PDF 4164KB](41)
High order active vibration suppression technology has been gradually applied to the multi-order vibration of space infrared mechanical cryocooler to improve the working life of cryocooler and the working performance of infrared load. When the mechanical cryocooler is driven by high-order working frequency, it will produce serious harmonic distortion, which will affect the active suppression effect of high-order vibration. By analyzing the working mechanism of the driving circuit and the high-frequency characteristics of the load, the method of using the control freewheeling path to suppress the harmonic distortion in high-order driving is put forward, and the corresponding implementation method according to the required freewheeling path is also presented. For one of the freewheeling methods, simulation and experiments show that the scheme can effectively suppress the waveform distortion and reduce the high-order harmonic distortion by more than 75%.
Wall emissivity solved by bidirectional reflection distribution function combined with Bi-LSTM network
Fu Li, Fan Jinhao, Zhang Zhaoyi, Zhang Lei
2023, 52(2): 20220355. doi: 10.3788/IRLA20220355
[Abstract](77) [FullText HTML] (14) [PDF 3501KB](33)
Wall spectral emissivity solution is one of the key techniques for infrared stealth of aircraft. Firstly, the wall reflected light path and light source were designed, and the brightness sequence of wall reflected radiation was obtained by spectral radiometer. In order to eliminate the influence of external interference on the solving accuracy of spectral emissivity as much as possible, Bi-LSTM brightness regression network model was designed based on bidirectional LSTM network, and the test samples were trained and learned. The wall emissivity solution model based on BRDF and the luminance regression model based on Bi-LSTM network were used to solve the wall emissivity. The calculation results show that the relative error of the proposed wall emissivity solution method based on BRDF is 12.21%, which meets the requirements of engineering test.
Test research on far-infrared extinction performance of graphene
Li Huiying, Wang Xuanyu, Liu Zhilong, Sun Shubao, Dong Wenjie
2023, 52(2): 20220263. doi: 10.3788/IRLA20220263
[Abstract](86) [FullText HTML] (13) [PDF 1788KB](39)
In order to investigate the infrared extinction properties of graphene, graphene was prepared by redox method. The structure of graphene was also confirmed by scanning electron microscope images and X-ray diffraction mapping. The infrared extinction properties of graphene were tested using the smoke box test and potassium bromide compression method, and compared with those of graphite and carbon fibres under the same conditions. The results show that the infrared extinction performance of graphene in the far infrared band is excellent. For the 8-14 μm far infrared band, its average mass extinction coefficient is approximately 2.10 m2/g, which is 2.39 times of that of the the average mass extinction coefficient of graphite and 3.56 times that of carbon fiber under the same conditions, providing better infrared interference than conventional carbon material smoke screens. Potassium bromide press tests also show that graphene exhibits very good infrared extinction in both mid and far infrared bands, outperforming traditional carbon material smoke screens.
Research on the supporting structure of the cold platform of the large format infrared detector
Zhang Yang, Mo Defeng, Fan Cui, Shi Xinmin, Yu Jun, Gong Haimei, Li Xue
2023, 52(2): 20220445. doi: 10.3788/IRLA20220445
[Abstract](106) [FullText HTML] (17) [PDF 1809KB](59)
In order to meet the space application requirements of the large format Mosaic infrared detector, ultra-scale cold platform need to work at low temperatures, and the cold platform support structure requires high rigidity to meet the components' anti-vibration performance, and a high structure thermal resistance to reduce its conduction heat leakage. A symmetrical eight-bar structure is proposed as the cold platform support, which adopts a new type of zirconia ceramic material with high strength and low thermal conductivity. Based on the finite element software, the influence of the height of the support structure, the installation inclination angle, the aspect ratio and the material on the modal fundamental frequency of the module, the thermal resistance of the support structure and the maximum stress of the module under 30 g static load are analyzed. A set of parameters is used to design the actual test component, the thermal resistance of the support structure reaches 220 K/W, and the components are subjected to a 5-2 000 Hz sine frequency sweep test, a total root mean square of 9 g RMS, and random vibration in the three directions of XYZ and other mechanics. In the environmental test, the final component passes the experimental verification of space environment adaptability. The fundamental frequency of the component reaches 560 Hz, and the test results are in good agreement with the simulation results. The results show that the symmetrical eight-rod zirconia support structure solves the problem that the cold platform of the large format infrared detector requires both high mechanical properties and low heat leakage, and meets the needs of engineering applications.
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](393) [FullText HTML] (58) [PDF 2475KB](163)
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](218) [FullText HTML] (28) [PDF 5195KB](107)
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](105) [FullText HTML] (25) [PDF 6242KB](53)
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](169) [FullText HTML] (47) [PDF 2417KB](75)
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](303) [FullText HTML] (75) [PDF 1929KB](122)
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](173) [FullText HTML] (40) [PDF 2081KB](68)
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.
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