熔石英光学元件亚表面损伤评价与磁流变抛光抑制方法

Evaluation and removal of subsurface damage in polished fused silica by magnetorheological finishing

针对研磨抛光处理后熔石英元件残余亚表面损伤不易检测和难以消除的特点,本文提出采用磁流变抛光柔性加工方法抑制亚表面损伤。通过采用磁流变抛光技术去除熔石英元件的不同深度表层材料,使其残余的亚表面损伤充分暴露。基于灰度熵值和功率谱密度分别对暗场检测获得的二值图像中缺陷数量以及磁流变处理前后空间频率的变化进行量化分析。研究表明,抛光后熔石英元件的亚表面缺陷数量随去除材料深度的增加呈现出先增加后逐步降低的趋势;缺陷分布的不均性则随去除深度增加呈上升趋势。实验结果说明磁流变抛光技术对微米级的亚表面缺陷有较好的抑制效果。

As it is difficult to detect and remove residual subsurface defects （SSD） of fused silica processed by grinding and polishing, using magnetorheologieal finishing （MRF） to remove different damaged layer to make SSD visible. Applying entropy for grey and power spectral density （PSD） to quantify SSD in dark field inspection and analyse how MRF influence information of spatial frequency. Study suggests the amount of defects increased and then decreased as depth beneath surface increasing. There is an increment trend in uniformity increase when polished depth in- creased. In addition, MRF can eliminate SSD and the length of them is mainly mierometre level.