φ1650 mm口径反射镜的坦克链支撑研究

Research on Roller-chain Radial Support System for Φ1650 mm Aperture Mirror

φ1650mm口径反射镜是某套大口径精密光学元件检测装置中的定标校正模块,用于对检测光路中的缩焦透镜等光学部件进行定标.反射镜口径越大,由于自身重力引起的变形问题越严重,面型精度受到的影响也越大.对于φ1650mm口径反射镜,系统要求的技术指标是面型误差的均方根(Root Mean Square,RMS)小于1/70波长(波长为632.8 nm).针对这块光轴始终处于水平状态的大口径反射镜,提出了坦克链支撑方案,并与传统的钢带支撑做对比.对坦克链支撑方案进行有限元分析,逐步确定了坦克链节数和中心距,根据标准选取了型号C2162H的双节距大滚子坦克链.基于赫兹接触理论,对坦克链滚子与反射镜的边缘非线性接触进行了模型简化.经过Zernike多项式拟合后,RMS为2.58 nm,满足设计要求.坦克链支撑结构简单、成像质量好,同时降低了反射镜的倾覆风险,可靠性高.

TheΦ1650 mm large aperture mirror in the calibration and correction unit is used to calibrate the system errors for strict optical metrology.The larger the mirror aperture,the more serious the deformation caused by its own gravity,the accuracy of the mirror surface will also be more severely affected.According to the system requirement,RMS(Root Mean Square)of the mirror deformation has to be less than one seventieth of the wavelength.For the horizontal large aperture mirror,compared to the traditional steel belt support,the roller chain as radial support has many advantages.In this paper,finite element analysis is used to calculate the roller chain support system forΦ1650 mm aperture mirror,the number of pitches in contact and the center distance of the two roller chains is determined.According to the Standard Handbook of Chains,doublepitch and oversized roller chain(Chain C2162H)is chosen.The individual contact region for each roller is simplified as a small rectangular protrusion from a thin strap,while the contact patch size is predicted by the Hertzian contact analysis equations.After fitting with Zernike polynomial,RMS is 2.58 nm which meets the technical requirement.It is concluded that the roller-chain support system has an excellent supporting performance and can satisfy the engineering requirements.It has relatively simple structure and provides good quality of surface accuracy.Also,it reduces the risk of overturning and has high reliability.