Optimization Of Optomechanical Structure Of Infrared Lens And Study Of Stray Light

With the development of infrared thermal imaging technology,the performance requirements of infrared lens use are becoming more and more stricter.Under the influence of different temperature environments,the optical components of large-diameter infrared lenses will undergo different thermal deformation and thermal stress,which will affect the imaging quality of the infrared system.At the same time,the large-caliber infrared lens needs to meet the requirements of light weight,high rigidity and adaptability in high and low temperature environments.Therefore,the optical lens structure optimization design of the infrared lens is performed,and the optical performance of the whole machine before and after optimization is analyzed,and then the optimized model base is used.Above,the stray light analysis and suppression structure design of the large-caliber infrared lens.In This master's thesis,the optomechanical structure design of the large-caliber infrared lens is firstly carried out,and then the thermal characteristics of the large-caliber infrared lens at different temperatures are analyzed by ANSYS finite element software.The wall thickness of the lens barrel is optimized by the finite element optimization design method.The objective function is the volume of the lens.The constraint variable is the thermal deformation of the lens and the distance change between the two lenses.Compared with the original lens,the optimized thermal deformation of the lens is reduced.Small and quality-reduced,high-low temperature environment,for the analysis of the optical performance of the model before and after the optimization,the thermal strain data of the lens is extracted,using the Zernike polynomial fitting program as the interface between finite element analysis and optical performance analysis,will optimize the two blocks before and after The numerical matrix of thermal deformation of the four surfaces of the lens is imported into the Zernike polynomial fitting program.The surface quality parameters of the lens before and after optimization,the mirror rigid body displacement,and the 37 Zernike coefficient values are calculated.Finally,the corresponding parameters are substituted into the CODEC optical analysis software.In the optical transfer function diagram and dot-column diagram of the optomechanical model before and after optimization,the optical performance before and after optimization is evaluated.The analysis results show that compared with the original lens,the lens surface parameters,rigid body displacement and Zernike coefficient of the lens surface are all decreased.In the low temperature environment,the MTF value of the optimized lens is nearly doubled.Reduced,system imaging performance improved,this optimization design improves the mechanical and optical performance of the system.Based on the optimized lens,the hood and the light blocking ring are designed to suppress the stray light from the outside.At the same time,the extinction thread is designed on the inner wall of the lens barrel to analyze the effect of the extinction threads of different densities and shapes on the stray light suppression.An optimal matte thread replaces the shading structure to suppress stray light.Finally,the high-low temperature test,stray light test and MTF test of the lens show that the imaging quality of the infrared lens will decrease compared with the normal temperature at high and low temperatures,and the image quality at the low temperature is the worst,and the density of the extinction thread is large.Infrared lens is more effective in eliminating stray light.The left-angled 75° right-angled triangular extinction thread lens has the best effect of suppressing stray light.The experimental results show that the simulation results are basically correct,It has important guiding significance for the optimization of infrared lens optomechanical structure and structural design for suppressing stray light.