刀具对中误差对离轴抛物面镜慢刀伺服车削加工的影响

摘要

High efficiency fabrication of off-axis parabolic mirrors is a crucial technique in some optical systems, such as three-mirror-anastigmatic ( TMA) telescopes. Slow tool servo ( STS) diamond turning process can be used in the machining of off-axis aspheric mirrors. with large range of machining size and high machining precision. The form accuracy of off-axis parabolic machined with STS process can be better than micrometer, and surface roughness can achieve nanometric level. The work piece machined with STS process can be directly used in infrared optical systems, and after post-polishing can be used in some rigorous applications. In this paper STS diamond turning process that allows fabrication of off-axis parabolic mirrors on-axis was introduced, and the maximal values distribution rule of the figure error caused by tool centering error was theoretically studied. An off-axis parabolic mirror was fabricated and experimental machining data were discussed, which are consistant with theoretical and simulation results.%离轴抛物面镜单件高效加工是离轴三反消像散(TMA)结构光学系统的技术难点之一.单点金刚石慢刀伺服车削加工技术可用于离轴非球面加工,加工尺寸范围较大,加工精度较高.此工艺制造的离轴抛物面面型精度可达到亚微米级,粗糙度达到纳米级.因此,可直接用于红外光学应用,若经后续抛光则可用于空间望远镜等更高精度需求的场合.介绍了慢刀伺服车削加工离轴抛物面镜的在轴加工方法,理论推导了刀具对中误差所带来的面形误差的极值分布规律.仿真研究进一步揭示了工件中心区域面形误差的详细分布.实验数据与理论结果和仿真计算结果均吻合.