结合环形抛光工艺,提出了新的球面抛光方法,以满足环形激光器、同步辐射加速器、光学振荡器等对大曲率半径球面反射镜球面误差的特殊要求.基于Preston抛光方程,分析了传统工艺在抛光过程中球面区域沿径向不同点的相对运动轨迹,建立了抛光过程材料去除模型.运用所建立的数学模型对大曲率半径球面反射镜传统抛光过程进行计算机仿真,揭示了传统抛光方法产生球面误差的两个原因,即工件无法始终处于抛光盘工作区域内以及工件自转与抛光盘转速不一致.由此提出增大抛光盘面积和驱动工件同步转动两条措施来降低球面误差.应用提出的新工艺加工了半径为6 000 mm的大曲率半径球面反射镜,测试显示其球面误差△R/R＜0.02,粗糙度小于0.25 nm,表面疵病达到0级,满足设计要求.%On the basis of continuous polishing, a new polishing process was developed to meet the special requirements of ring lasers, synchrotron radiation accelerators and optical oscillators for the sphere mirrors with a large radius of curvature. Based on the Preston hypothesis, a mathematical model of material removal was established by analysis on the relative velocity at the radial point of an optical sphere surface in the classic polishing process. Via computer simulation, it explored that the reasons of the nonuniformity in sphere mirrors were that the mirrors cannot stay in the polishing pan during the polishing process and the rotation rate of the polishing pan is asynchronous with the mirrors. Two improvements were enlarging the size of the polishing pan and synchronizing the mirror rotation with the polishing pan. With the proposed process, a spherical mirror with the radius of 6 000 mm was polished. Obtained results show that the nonuniformity AR/R in a sphere is less than 0. 02, the roughness is less than 0. 25 nm and the surface defect reaches a zero grade.
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