Surface Analysis and Optimization of Large Aperture Mirror Supported by Elastic Expansion Sleeves

Abstract

In order to meet the stability of the support structure of arrayed large aperture mirror and improve the surface accuracy of the mirror, the elastic expansion sleeve is proposed as the back-support structure of the large aperture mirror. The feasibility of the support method is verified by theoretical analysis and experiment. The PV value of additional wavefront distortion is about 75.3nm<λ/5(λ=632.8nm) when the torque of single mandrel screw is 40N·cm, which meets the technical specifications. The change trend of the support-induced surface is compared between the finite element simulation and the measured results under different mandrel screw torque conditions. When the support torque is increased in equal increments, there is a linear positive correlation between the PV value of support-induced surface and the support torque. Based on the change trend of the support-induced surface, the optimization design scheme of the initial surface is proposed. And the simulation results show that the optimized induced distortion is smaller than that of the ideal surface (the compensation ratio is 7.68%), which reduces the additional wavefront distortion under the actual mounting support.