Gao Xiang, Xue Changxi, Chao Yang, Liu Yue
Appl Opt. 2021 Jan 1;60(1):162-171. doi: 10.1364/AO.411706.
Single-point diamond turning is a high-efficiency, low-cost method for manufacturing harmonic diffractive optical elements (HDOEs). Generally, in order to ensure high diffraction efficiency of HDOEs, a half-round tool is used to reduce surface-relief profile errors and a super small feed rate is selected to control surface roughness when hard-brittle materials are turning. However, this method is no longer suitable for soft-brittle materials, which have a strict requirement for the range of the feed rate. It limits the types of materials available for HDOEs. Therefore, according to the range of the feed rate and the cutting depth for soft-brittle materials, an optimized turning model is proposed in this paper. It overcomes the high surface roughness caused by the half-round tool; meanwhile, the advantage of the half-round tool is kept in terms of surface-relief profile errors. On this basis, a mathematical model is proposed to reveal the relationship among diffraction efficiency, period widths, tool radius, and feed rate with different soft-brittle optical materials. As a typical soft-brittle material, barium fluoride () was selected to be the material for manufacturing HDOEs. By using the optimized model, the turning experiment of HDOEs was completed, and then the HDOEs with =2.75 were obtained. The optimized model is verified to be effective and further provides theory guidance and engineering application in the optical manufactory field of soft-brittle materials for HDOEs. The range of application materials for HDOEs is enriched, and the freedom of advanced optical design is broadened.
单点金刚石车削是制造谐波衍射光学元件（HDOEs）的一种高效、低成本的方法。一般来说，为了确保HDOEs的高衍射效率，在硬脆材料车削时，使用半圆刀具来减少表面轮廓误差，并选择超小进给率来控制表面粗糙度。然而，这种方法不再适用于对进给率范围有严格要求的软脆材料。它限制了可用于HDOEs的材料类型。因此，根据软脆材料的进给率范围和切削深度，本文提出了一种优化的车削模型。它克服了半圆刀具导致的高表面粗糙度；同时，在表面轮廓误差方面保留了半圆刀具的优势。在此基础上，提出了一个数学模型来揭示不同软脆光学材料的衍射效率、周期宽度、刀具半径和进给率之间的关系。作为一种典型的软脆材料，氟化钡（）被选为制造HDOEs的材料。通过使用优化模型，完成了HDOEs的车削实验，然后获得了=2.75的HDOEs。验证了优化模型的有效性，并进一步为软脆材料在HDOEs光学制造领域提供了理论指导和工程应用。丰富了HDOEs的应用材料范围，拓宽了先进光学设计的自由度。
