Wu Xiupin, Gao Wanrong, He Yong
Appl Opt. 2016 Jan 20;55(3):A32-42. doi: 10.1364/AO.55.000A32.
In this work, a new method for imaging subsurface damage (SSD) is proposed, which is, to the best of our knowledge, the first application of the in-line digital holographic microscopy (IDHM) to the reconstruction of the subsurface damage in glass. By combination of the in-line arrangement and an objective lens to image the hologram on the CCD surface, the method is characterized by its high resolution in both the lateral and depth directions. Then the three-dimensional reconstruction of the microcracks within the glass was realized by numerically focusing en-face images at different depths, and the sizes of SSD along the transversal and depth directions were estimated. Based on the experimental results, the cracks can be divided into two categories: one is that the cracks begin from the surface of optical elements, the other is totally within the components. To indicate the propagation or development trajectory of the cracks and predict the magnitude of the laser-induced damage threshold, the relative intensity distributions of the light scattered by the cracks compared with the ones without cracks were also reconstructed. In this case all the required parameters for evaluating SSD are obtained with our IDHM system, so that the SSD produced in the manufacturing process can be reduced or removed more easily to optimize the performance of the optical component and extend its lifetime. These results provide the guidance for the optical system design of precision measurements.
在这项工作中，提出了一种用于成像亚表面损伤（SSD）的新方法，据我们所知，这是在线数字全息显微镜（IDHM）首次应用于玻璃亚表面损伤的重建。通过将在线配置与物镜相结合以在CCD表面上对全息图进行成像，该方法的特点是在横向和深度方向上都具有高分辨率。然后，通过对不同深度的正面图像进行数值聚焦，实现了玻璃内部微裂纹的三维重建，并估计了沿横向和深度方向的SSD尺寸。基于实验结果，裂纹可分为两类：一类是从光学元件表面开始的裂纹，另一类完全在元件内部。为了指示裂纹的扩展或发展轨迹并预测激光诱导损伤阈值的大小，还重建了有裂纹与无裂纹情况下光散射的相对强度分布。在这种情况下，利用我们的IDHM系统获得了评估SSD所需的所有参数，从而可以更轻松地减少或消除制造过程中产生的SSD，以优化光学元件的性能并延长其使用寿命。这些结果为精密测量的光学系统设计提供了指导。
