Abstract:As one of the mainstream development directions of future infrared detectors, large-format infrared detectors have developed very rapidly in recent years. They are mainly used in the fields such as astrophysics, earth science, and planetary science. They are also a major tool for earth′s weather and climate description and air pollution detection in the future. With the increase of array format and material size, the difficulty of making devices has become more and more difficult. The two most commonly used infrared detectors in the world—HgCdTe and InSb infrared detectors—are introduced. Based on some domestic and foreign literatures, the development of the large-area-array technology of these two infrared detectors is summarized, and the relevant products and technical levels of several leading infrared detector manufacturers in the global industry are highlighted. Finally, the main problems in the development of large-format infrared detectors are pointed out.

Abstract:With the development of infrared detector technology, extending the operating wavelength of the detector has become one of the important development directions. Because the operating wavelength of the detector varies with the x value, mercury cadmium telluride (HgCdTe) materials have been widely used. As the operating wavelength increases, dark current becomes a major factor limiting the development of infrared detectors. Taking a 12.5 μm HgCdTe long-wave infrared detector as an example, the effects of operating temperature and fixed charge on its dark current are studied by simulation, and different types of dark currents at 77 K and 60 K are analyzed. This research gives us a deeper understanding of the dark current of 12.5 μm detectors, and provides a direction for improving the preparation level of 12.5 μm detectors.

Abstract:The horizontal air convection and complex ground conditions lead to the uncertainty increasment of the calculation of atmospheric thermal radiation. The measurement of infrared radiation characteristics during the initial part of target launching is helpful for target recognition. Therefore, it is very important to study the atmospheric transmittance and thermal radiation in the horizontal direction to improve the accuracy of the infrared radiation characteristics measurement of the target. Based on the problems mentioned above, the "horizontal temperature profile" model of the same layer atmosphere is established referring to the vertical profile theory firstly. Then the formula of calculating the atmospheric transmittance and thermal radiation in the horizontal direction is deduced, and the experiment verification is carried out. Finally, the results of MODTRAN software calculation and experiment measurement of the atmospheric thermal radiation are compared. The results show that the accuracy of traditional software is 8.65% and the accuracy of the proposed calculation method is 4.91%. The experiment proves that the calculation method is correct in the horizontal direction. The validity of the calculation method is demonstrated by formula derivation and experimental verification. A new idea is provided for the calculation of the atmospheric transmittance and thermal radiation in the horizontal direction.

Abstract:Conventional Doppler signal recognition is mainly based on the amplitude of the Doppler signal. In the process of target recognition of sector beam detectors, this method has the problem of low recognition rate due to the narrowing of the Doppler time domain waveform. Based on the measured Doppler signal data, the time-frequency conversion analysis is carried out， and a signal recognition method based on combined judgment of frequency and amplitude is proposed without changing the existing beam shape. The experimental results show that the target can be identified accurately by the detector all the six times of the target entering the detection range, which provides reference value for UAV target recognition.

Abstract:Principal components analysis (PCA) is used to analyze the distribution characteristics of stripe noise in the observational data of the microwave temperature sounder (MWTS) on FY-3D satellite, and the modes in which stripe noise exists primarily are described. Based on the ensemble empirical mode decomposition (EEMD) method, the time coefficients corresponding to the mode in which the stripe noise exists are decomposed and filtered, and the stripe noise is suppressed by reconstructing the observed brightness temperatures. On the basis of qualitative verification of the stripe noise suppression effect, a method of comparing the observed brightness temperatures with the mode brightness temperatures is proposed to evaluate the data accuracy after stripe noise suppression quantitatively. The statistical results show that the standard deviation of observed brightness temperatures and mode brightness temperatures decreases by about 0.018 K after stripe noise suppression, which further improves the data accuracy of the MWTS .

Abstract:In order to monitor and identify chemical fires quickly, a flame spectrum test platform is established based on FTIR spectrometer. The flame spectrums of two nitrogenous chemicals (acrylonitrile and acetonitrile) and the anhydrous ethanol are detected and analyzed in the indoor sealing condition, and the spectral range is 600-8000 cm^-1. The results show that the order of molecular radiation intensity in the same combustion conditions is acrylonitrile, acetonitrile and anhydrous ethanol from large to small. This is because acrylonitrile and acetonitrile produces more H₂O molecules than the anhydrous ethanol when combusting, and a lot of carbon black is produced by the combustion of acrylonitrile. The flame spectrums of acrylonitrile, acetonitrile and absolute ethanol are substantially similar after denoising and smoothing, but there are unique differences of high-temperature nitrogenous gas at the wave numbers of 1650 cm^-1, 1830 cm^-1, 2857 cm^-1 and 3750 cm^-1. The experiment conclusion shows that the flame spectrum radiation detection of nitrogenous chemicals by using FTIR spectrometer can enhance the ability of rapid monitoring and identification of chemical fires in China.