为了提高光学元件的面形精度,精确拟合出离子束去除函数。以去除函数的方均根(RMS)为分析对象,分析不同叠加间距下离子束等量去除的去除量及波动量。根据理论及实验数据分析验证一维等量去除的可行性,得出最优叠加间距为σ。再以σ为叠加间距进行二维等量去除理论及实验分析,通过30 s熔石英二维等量去除实验,得出去除量为384.7 nm。结合抛光实验,对RMS值为138.5 nm的Φ100 mm口径的熔石英平面窗口玻璃进行面形修正,加工后RMS值为18 nm,面形收敛率达到7.82。

To improve the surface accuracy of the optical elements, the ion beam removal function was accurately fitted. Taking the root mean square (RMS) value of the removal function as the analysis object, the removal and fluctuation amount of the ion beam equivalent removal under different stacking spacings were analyzed. The feasibility of one-dimensional equivalent removal was verified on ground of theoretical and experimental data analysis, and the optimal stacking spacing was σ. With σ as the stacking spacing, the theoretical and experimental analyses of two-dimensional equivalent removal were carried out. Fused silica was used for 30 s two-dimensional equivalent removal experiments, and the removal value was 384.7 nm. The surface modification of fused silica plane window glass with the RMS of 138.5 nm (Φ100 mm) was carried out in combination with polishing experiment. The RMS was 18 nm after processing and the surface convergence rate reached 7.82.