大口径SiC反射镜的焊接加工和测试

Fabrication and testing of brazed SiC space large aperture mirror

SiC是目前空间用大口径反射镜的首选材料,随着空间光学系统的发展,出现了1m以上空间用SiC反射镜的需求。对该反射镜采用焊接拼接然后再进行加工可以节约成本,降低风险。作为演示实验件,首先,对直径为600 mm的焊接SiC反射镜进行了焊接拼接,粗磨成型、精细研磨和粗抛光。然后,采用CCOS技术对反射镜进行了精抛光,并分析了加工过程中焊缝边缘优先去除的原因和抛光过程镜面变形对加工结果的影响。最后,反射镜面形收敛到RMS值1/20λ(λ=632.8 nm)。结果表明,所采用的焊接技术和加工工艺制造的反射镜可以满足空间反射镜的需要。

SiC is the preferential material for space large aperture mirror at present. With the development of space optical system, SiC mirror with the aperture larger than one meter is needed. It is not economical and safe to make the monolithic body directly. The SiC mirror brazed assembly with several segments can solve these problems. In this paper, a φ600 mm SiC plane mirror as demonstration welded with 3 radial segments was roughly grinded to the required figure, finely grinded and roughly polished at first, then the mirror was finely polished by the technology of CCOS, the RMS of the figure error was less than 1/20λ （λ =632.8 nm） finally. The problems of the preferential removal near braze joint and material remove rate influenced by deformation of mirror surface were solved. The results conclude that the brazed SiC mirror can meet the requirement of large aperture optical systems.