Design And Optimization Of Large Aperture Laser Window Support Structure

With the further maturity of laser technology,laser transmitting system is developing towards larger aperture,higher power and more complex environment adaptability.The requirement of optical protection window is more and more important.Its optical protection window is used to isolate the internal and external space of the system,ensure the sealing of the channel in the system,prevent its internal photoelectric elements from being eroded by external salt spray particles,mold and so on,and protect the entire internal optical system.In this thesis,the optical protection window structure of large-aperture high-power laser launching system is studied,and its support structure is designed,analyzed and optimized to reduce the mirror deformation of the optical protection window mirror.The protective window can not only isolate the internal and external space of the system,but also ensure the cleanliness of the internal passage.At the same time,it can withstand the superimposed load of high and low temperature and gravity complex physical field to ensure the surface precision of the window mirror,and will not change the quality of the laser beam output by the system.By referring to the domestic and foreign information,to understand the research status of laser window and support structure design.The window mirror bases on this research is different from the conventional mirror,the two sides of the mirror body need to transmit laser,and the support structure should minimize the requirement of light blocking.This paper proposes for the first time the support method of combining the three-blade support structure with the base structure with a center through ring.The flexible structure of radial and axial support is designed and installed on the base.The radial support is designed as a flexible ring structure with grooves,and the axial support is designed as a structure of 2 axial flexible rings and 12 flexible joints equivalent to springs.Use UG modeling software to build a preliminary model of window components.After the initial modeling,Ansys Workbench software is used for finite element analysis and parameter optimization.By analyzing the mirror deformation under the condition of dead weight and superimposed ambient temperature,RMS value（root mean square value）is mainly used to evaluate the mirror shape of window.In addition,the modal analysis of the window mirror is carried out,and its dynamic stiffness is calculated by using the first four modal frequencies.When the preliminary structure design of the simulation results can not meet the requirements of the form,the further optimization analysis,sensitivity analysis,the first screening across the shape precision of target sensitive parameters optimized,eliminate not sensitive parameters,then the remaining variables generated sample points,iterate calculation,to the RMS value of the minimum and maximum equivalent stress value of the minimum as the optimization goal,optimization iteration,Finally,the optimal RMS of the mirror surface shape accuracy is 90.26 nm,which meets the technical requirements of RMS≤λ/5（λ=632.8nm）.And the natural frequency of the optimized window mirror and the supporting structure is higher than the technical requirement of 150 Hz.