Research On Optical System For Multi-band Infrared Imaging

Infrared optical imaging system is widely used in infrared guidance,battlefield reconnaissance,ground survey,marine pollution detection and other fields.In the application of airborne reconnaissance,multi band infrared optical imaging system can obtain the information of multiple bands of target and environment.Compared with single band system,it is more conducive to target feature extraction and improve the recognition accuracy.Its structural form mostly adopts refraction or catadioptric structure.Because only a few infrared materials can pass through multiple infrared bands,and the transmittance in some bands is very low,it is difficult to realize multiple infrared band imaging.Total reflection structure can overcome the problem of limited material types and has the advantage of no chromatic aberration.It is very urgent to study the total reflection multi-band infrared optical imaging system applied to airborne reconnaissance.In this paper,the research of multi band optical imaging system is carried out,the generation principle of chromatic aberration and its influence on transmission and reflection optical elements are analyzed,and the appropriate initial structure of optical system is determined.Combined with the primary aberration theory and the design theory of reflective optical system,the parameters of the initial structure are analyzed and calculated.Zemax software is used to complete the optimization and image quality evaluation of off-axis three mirror optical system,and Monte Carlo analysis method is used to complete the analysis and allocation of system tolerance.Finally,a multi band airborne infrared optical imaging system is realized.Its focal length of the system is changed to 50.4mm and the full field of view is 12°× 10°,and the F number is 2.5,which meets the requirements of small and light weight.The system can realize imaging in three infrared bands: short wave,medium wave and long wave.Secondly,the external frame structure design of the whole machine and the supporting structure design of the first mirror,second mirror and third mirrors are completed by using Solidworks software.The external frame structure of the whole machine of the system is designed as a lightweight frame structure.The material of the mirror body is aluminum alloy6061,and the material of the mirror support structure and external frame structure is aluminum alloy 7075.The peripheral support is adopted to fix the mirror.Finally,the design of the external frame structure of the whole machine and the supporting structure of each mirror and the deformation analysis of the mirror are completed by using Solidworks software.The results of static stress and thermodynamic analysis show that the maximum self weight stress deformation of each mirror is less than its maximum yield stress.Within the temperature range of-30℃～+60℃,the maximum deformation displacement of each mirror shall not exceed 0.9um,which meets the surface accuracy requirements of the mirror.The maximum stress of the external frame structure is far less than the maximum yield stress it can bear,which meets the design requirements.