Wolter-Ⅰ型掠入射反射镜的加工

Fabrication of Wolter-Ⅰ grazing mirror

针对Wolter-Ⅰ型掠入射反射镜柱面内表面的特殊结构,研究了弹性球状小磨头以旋偏方式运动逐环带修正面形时的去除函数模型。分析了相关工艺参数,如磨头-工件旋转角速度比、旋偏角大小、磨头中心压强以及磨头和工件的趋近距离对去除函数的影响,通过实验获得了驻留时间和去除函数中心去除深度的关系。采取两步加工法控制研抛后的表面质量,分析表明:当磨头-工件角速度比为1.41时,反射镜的表面质量最好。介绍了计算机控制光学表面成形(CCOS)法加工Wolter-Ⅰ型掠入射反射镜的过程。选择微晶玻璃为反射镜的镜胚,在自行研制的研抛设备上,以不同粒径的氧化铈作为抛光液,对金刚砂砂轮粗磨后的工件进行抛光。通过改变磨头相对工件的压入深度,获得不同大小的磨头去除区域,实现了对上一个抛光周期后的残留误差的有效去除。最终获得的反射镜面形精度为PV:1.39μm,RMS:0.34μm,圆度均方根误差优于0.1μm。实验结果表明:提出的两步法旋偏加工方案可用于掠入射反射镜的加工。

For the special structure of cylindrical inner surface of a Wolter-Ⅰ grazing mirror,the removal function of an elastic ball tool with deflected rotation motion was researched,and the relations between the max removal depth of removal function,dwell time and other parameters obtained by experiments were demonstrated.By using a 2-step method for polishing,it shows that when the ratio of rotating angle velocity to tool-workpiece is 1.41,the surface quality is in the best state.Furthermore,the fabrication of Wolter-Ⅰ grazing mirror base on Computer Control Optical Surface（CCOS） was introduced.In the research,Zerodur glass was selected as mirror substrates and it was polished by CeO abrasive on a Digital Control（NC） platform developed by ourselves.By changing the distance between the tool and the workpiece,the removal functions in different contact areas were determined in the experiments,and the residual error from previous polishing process was corrected effectively.Using two kinds of measurement devices to outline the surface profile,it shows that the final surface figure of the mirror is 1.39 μm（PV）,0.34 μm（RMS） and the error of circularity is less than 0.1 μm（RMS）.These results demonstrate the feasibility of fabricating Wolter-Ⅰ grazing mirror with the 2-step deflected rotation method.