Research On High Sensitivity Infrared Detection Technology For Space Point Targets

After entering the 21st century,with the rapid development of science and technology in the field of space remote sensing,especially the new infrared detectors,with the application of many new materials and the improvement of the production process,infrared detection technology is widely used in the military and people’s livelihood because of its large detection distance,good concealment,strong antiinterference ability,can work around the clock and high recognition of camouflaged targets.In the national defense security,infrared detection system is used in large-scale early warning and continuous tracking of unknown targets in the air,which greatly solves the problem of low detection rate of targets at night and continuous tracking of targets around the clock and plays an important role in the modern military field;in the field of people’s livelihood,infrared detection system is widely used in agricultural construction,hydrological observation,power line monitoring,urban construction and so on.Infrared detection system uses optical components to collect infrared radiation from the target itself and the surrounding environment,then focus the radiation signal to the infrared detector array,convert the optical signal to electrical signal,and then through the processing of information systems to get the final detection image.Thanks to the rapid development of materials science and preparation process,infrared detectors are constantly being developed and their performance is more superior than before.To improve the detection sensitivity of the infrared detection system,the following research work has been done in this paper on the radiation characteristics of the target and the surrounding environment in which it is located,the selection of the detection band,the design of the optical system,and infrared image processing:(1)In this paper,the infrared radiation characteristics of the target,including the skin infrared radiation and the tail flame infrared radiation,are firstly simulated and calculated using Planck’s formula.Because the trailing flame radiation occupies a major position in the target radiation,the influence of the trailing flame gas composition on its infrared radiation characteristics is focused on.For the influence of atmospheric transmission path on the target tail flame infrared radiation transmission,the atmospheric simulation software MODTRAN is used to simulate the atmospheric model at different altitudes,different detection distances,different detection angles(pitch angles),different latitudes and different seasons and atmospheric transmission in different weather to discuss the influence of atmospheric transmission path on the target infrared radiation characteristics under different detection scenarios.Finally,two bands,4.2μm～4.45μm and 5.8μm～7.3μm,are selected to reduce the influence of background radiation on the detection results.(2)Research is conducted on the method of acquiring information with high sensitivity for infrared detection systems.By studying the scheme of lowtemperature cooling and reflective structure to reduce the stray radiation inside the optical system,it is found that low-temperature cooling reduces the system’s own radiation,but for some extreme conditions,the cooling time is too long to meet the use requirements,while the reflective structure can reduce the stray radiation and improve the system sensitivity compared to the transmitting structure.At the same time,the use of multi-frame accumulation technique can also improve the sensitivity of the system.(3)Comparison and analysis of the characteristics of refractive,refractive,reflective three infrared optical system,in order to suppress internal stray radiation,improve energy utilization,determine the use of off-axis three-reverse optical structure;according to the mask,the radiation intensity of the tail flame simulation calculation results,optical parameter calculation,the use of Zemax design optical system,optimize the tolerance distribution to ensure that the system design transmission requirements.(4)To address the difficulty of detecting and identifying point targets in complex backgrounds,the acquired raw IR images are pre-processed with Butterworth highpass filtering and adaptive histogram equalization to highlight the surrounding features of the targets and form a strong contrast with the background;at the same time,the images are processed with multi-frame overlay technology,and the experimental results show that multi-frame overlay can improve the image signal-tonoise ratio by about 20%.