Zhou Peng, Xue Changxi, Yang Chao, Liu Chang, Liu Xingguo
Appl Opt. 2020 Feb 20;59(6):1537-1544. doi: 10.1364/AO.376978.
Single point diamond turning is a commonly used method for manufacturing harmonic diffractive optical elements (HDOEs). Diffraction efficiency of HDOEs is sensitive to surface-relief profile errors, and a half-round tool can reduce the profile error obviously. Furthermore, the diamond tools also create surface roughness errors. The two errors will produce shadowing and scattering effects. In this paper, the two kinds of errors, especially the surface roughness, are described accurately. A mathematical model is proposed to reveal the relationship among diffraction efficiency, cutting tool radius, feed rate, microstructure zone period widths, and the refractive index of the substrate material and balance the influence of shadowing and scattering effects. The simulation results show that the model can guide the acquisition of high-precision surface topography and high diffraction efficiency, which improves the imaging quality of the optical system.
单点金刚石车削是制造谐波衍射光学元件（HDOE）的常用方法。HDOE的衍射效率对表面轮廓误差很敏感，而半圆刀具可以明显降低轮廓误差。此外，金刚石刀具还会产生表面粗糙度误差。这两种误差会产生阴影和散射效应。本文准确描述了这两种误差，特别是表面粗糙度。提出了一个数学模型来揭示衍射效率、切削刀具半径、进给速度、微结构区周期宽度以及基底材料折射率之间的关系，并平衡阴影和散射效应的影响。仿真结果表明，该模型可以指导获取高精度表面形貌和高衍射效率，从而提高光学系统的成像质量。
