Dai Yifan, Liao Wenlin, Zhou Lin, Chen Shanyong, Xie Xuhui
National University of Defense Technology, DeYa Road, Changsha, Hunan, China 410073.
Appl Opt. 2010 Dec 1;49(34):6630-6. doi: 10.1364/AO.49.006630.
In a deterministic figuring process, it is critical to guarantee high stability of the removal function as well as the accuracy of the dwell time solution, which directly influence the convergence of the figuring process. Hence, when figuring steep optics, the ion beam is required to keep a perpendicular incidence, and a five-axis figuring machine is typically utilized. In this paper, however, a method for high-precision figuring of high-slope optics is proposed with a linear three-axis machine, allowing for inclined beam incidence. First, the changing rule of the removal function and the normal removal rate with the incidence angle is analyzed according to the removal characteristics of ion beam figuring (IBF). Then, we propose to reduce the influence of varying removal function and projection distortion on the dwell time solution by means of figure error compensation. Consequently, the incident ion beam is allowed to keep parallel to the optical axis. Simulations and experiments are given to verify the removal analysis. Finally, a figuring experiment is conducted on a linear three-axis IBF machine, which proves the validity of the method for high-slope surfaces. It takes two iterations and about 9 min to successfully figure a fused silica sample, whose aperture is 21.3 mm and radius of curvature is 16 mm. The root-mean-square figure error of the convex surface is reduced from 13.13 to 5.86 nm.
在确定性加工过程中，确保去除函数的高稳定性以及驻留时间解的准确性至关重要，这直接影响加工过程的收敛性。因此，在加工陡峭光学元件时，要求离子束保持垂直入射，通常使用五轴加工机床。然而，本文提出了一种利用线性三轴机床对高斜率光学元件进行高精度加工的方法，允许离子束倾斜入射。首先，根据离子束加工（IBF）的去除特性，分析去除函数和法向去除率随入射角的变化规律。然后，我们提出通过图形误差补偿来减少变化的去除函数和投影畸变对驻留时间解的影响。因此，允许入射离子束与光轴保持平行。给出了仿真和实验来验证去除分析。最后，在一台线性三轴离子束加工机上进行了加工实验，证明了该方法对高斜率表面的有效性。成功加工一个孔径为21.3mm、曲率半径为16mm的熔融石英样品需要两次迭代，耗时约9分钟。凸面的均方根面形误差从13.13nm减小到5.86nm。
