New technology to magnetorheological finishing aspheric cylindrical mirror
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摘要: 高精密的柱面镜光学元件,不但要求其具有极低的表面粗糙度、无表面/亚表面损伤和低的残余应力等,而且需要保证其柱面母线的平行度与垂直度。通过分析传统磨研抛技术和计算机控制的光学表面成型技术(CCOS) 2种技术对柱面镜加工后的表面粗糙度、面形精度和母线误差的影响,归纳2种加工方法的优缺点,针对现有加工方法存在的低效率、高粗糙度、表面/亚表面损伤等问题提出一种具有对称结构的非球柱面镜磁流变抛光新工艺,并通过时间参数实验验证了新工艺的可行性。该工艺降低了柱面镜的表面粗糙度,提高了面型精度,在抛光时间为40 min时,表面粗糙度Ra从1.84 μm降低至0.36 μm,局部面型精度RMS1从 1.91 μm降低到0.24 μm,母线截面面型精度RMS2从4.1 μm下降到0.68 μm。Abstract: Cylindrical mirror is a high-precision optical element, which requires not only very low surface roughness, no surface/subsurface damage and low residual stress, but also parallelism and verticality of cylindrical generatrix. By analyzing the influence of traditional grinding and polishing technology and computer controlled optical surfacing (CCOS) on surface roughness, surface profile accuracy and generatrix error of cylindrical mirror after machining, the advantages and disadvantages of two methods are summarized. Aiming at the low efficiency, high roughness and surface/subsurface damages of the existing machining methods,a new magnetorheological finishing process with symmetrical structure for aspheric cylindrical mirror is proposed, and the feasibility of the new process is verified by the experiment of time parameters. The surface roughness and profile accuracy of the cylindrical mirror are effectively reduced. At the polishing time of 40 min, the surface roughnessRadecreases from 1.84 to 0.36 μm, the local profile accuracyRMS1decreases from 1.91 to 0.24 μm, and the generatrix section profile accuracyRMS2decreases from 4.1 to 0.68 μm.
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Key words:
- cylindrical mirror /
- magnetorheological polishing /
- surface roughness /
- profile accuracy
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