超轻超薄反射镜制造过程中的变形控制研究

针对超轻超薄反射镜(超薄镜)径厚比大,自身刚度小、单独加工难度大的问题,采用基底支撑方式对超薄镜进行加工.我们研究了在加工过程中粘接,温度、应力等因素所导致的超薄镜变形的控制手段并对变形控制效果提出了评判方法.通过195 mm口径超薄铣工艺实验对控制变形的工艺进行改进,用改进后的加工工艺进行了340 mm口径的超薄镜制造,得到了比较理想的面形,下盘后PV值5.74λ,RMS值1.02λ(λ=632.8 nm).这表明在超薄镜制造过程中变形控制的技术方案可行,工艺改进方向正确.同时,实验结果表明,超薄镜制造过程中的变形最终表现为镜面出现非重力因素引起的像散.

Controlling Distortion in the Process of Ultra-thin Mirror Manufacture

Because of the difficulty to fabricate the ultra-thin mirror individually, we proposed a base supporting method. Methods which were applied to control the distortion caused by adhesion, heat, and stress during ultra-thin mirror fabricating were researched, and means to estimate the effect was put forward. Technology of controlling mirror distortion was improved based on the experience on φ195 mm ultra-thin mirror manufacture. Then a φ340 mm ultra-thin mirror was fabricated by improved technics. When it was de-blocked from blocking body, the surface error of PV=5.74λ, RMS=1.02λ (λ=632.8 nm) caused by distortion is acceptable. Those experiments indicate that those technics can control distortion effectively and technical improvement is correct. Results of these experiments also indicate that the final error on ultra-thin mirror surface is astigmatism, which is not caused by gravity.