轻质碳化硅反射镜抛光过程镜面变形影响的研究

轻量化的碳化硅反射镜有自己独特的结构特点,加工中的变形与传统实体反射镜不同,对加工后的面形结果有独特的影响。对一直径为318mm的轻量化碳化硅反射镜进行了传统的研磨抛光,由于镜面变形对抛光结果带来了很大的影响,其面形误差的RMS值在0.048λ(λ=0.6328μma)左右就不再收敛。对抛光状态的镜体进行了有限元分析,探讨了减轻镜面变形对抛光结果影响的方法。采用计算机控制小磨头对该反射镜进行了确定性抛光,有效地降低了镜面形变的影响,使面形满足了精度的要求。

Research on the effect of optical facesheet deformation during polishing lightweight silicon carbide mirror

SiC lightweight mirrors are used for a large number of space telescopes.The primary characteristics silicon car- hide offers relative to other more traditional materials include high stiffness,high toughness,low thermal distortion and poten- tial cost and schedule advantages.A lightweight SiC mirror with an aperture of 318 mm is grinded and polished by the tradition- al method.The mirror deforms during polishing process.Therefore the surface RMS error reaches 0.062λ(λ=0.6328μm), it no longer converges.The mirror during the polishing process is analyzed by the finite element method,and some methods for reducing the mirror deformation are discussed.The mirror is polished by the computer control optical surfacing(CCOS)tech- nique.It effectively reduces the deformation during the polishing process,and satisfies requirements for the mirror surface error.