Frank Samson, Seiler Michael, Bliedtner Jens
Appl Opt. 2021 Mar 10;60(8):2118-2126.
Subsurface damage (SSD) induced during conventional manufacturing of optics contributes mainly to a reduction in the performance and quality of optics. In this paper, we propose the application of full-field optical coherence tomography (FF-OCT) as a high-resolution and nondestructive method for evaluation of SSD in optical substrates. Both ground and polished surfaces can be successfully imaged, providing a path to control SSD throughout the entire optics manufacturing process chain. Full tomograms are acquired for qualitative and quantitative analyses of both surface and SSD. The main requirements for the detection of SSD are addressed. Data processing allows the removal of low-intensity image errors and the automatic evaluation of SSD depths. OCT scans are carried out on destructively referenced glass samples and compared to existing predictive models, validating the obtained results. Finally, intensity projection methods and depth maps are applied to characterize crack morphologies. The experiments highlight differences in crack characteristics between optical glasses SF6 and HPFS7980 and illustrate that wet etching can enhance three-dimensional imaging of SSD with FF-OCT.
光学元件传统制造过程中产生的亚表面损伤（SSD）主要会导致光学元件的性能和质量下降。在本文中，我们提出将全场光学相干断层扫描（FF-OCT）作为一种高分辨率、无损的方法来评估光学基底中的亚表面损伤。无论是研磨表面还是抛光表面都能成功成像，这为在整个光学元件制造工艺链中控制亚表面损伤提供了途径。获取完整的断层图像用于对表面和亚表面损伤进行定性和定量分析。阐述了检测亚表面损伤的主要要求。数据处理可以去除低强度图像误差并自动评估亚表面损伤深度。对经过破坏性参考的玻璃样品进行光学相干断层扫描（OCT）并与现有的预测模型进行比较，验证所得结果。最后，应用强度投影方法和深度图来表征裂纹形态。实验突出了光学玻璃SF6和HPFS7980之间裂纹特征的差异，并表明湿法蚀刻可以增强利用FF-OCT对亚表面损伤进行的三维成像。
