Li Mengmeng, Zhang Hongchao, Lu Jian, Shen Zhong-Hua
Opt Lett. 2022 Aug 1;47(15):3736-3739. doi: 10.1364/OL.461125.
The traditional optical detection method has a limitation in detecting closed cracks in optical elements. In this Letter, a novel, to the best of our knowledge, method has been developed for the detection of closed cracks in transparent samples. Firstly, behaviors of closed cracks under ultrasonic waves loading are demonstrated through the finite-element method (FEM). Simulation results show that the crack can be opened by the laser ultrasonic shear wave (S-wave). Then, a Mach-Zehnder interferometer system is experimentally established to detect closed cracks under ultrasonic waves loading in the sample. It is demonstrated that closed cracks which cannot be detected by interferometry become visible in interferogram images under ultrasonic waves loading. The width of the opened crack can also be quantitatively estimated. Thus the method would be a promising approach to detect initially closed cracks in optical elements.
传统的光学检测方法在检测光学元件中的闭合裂纹时存在局限性。在本信函中，据我们所知，已开发出一种用于检测透明样品中闭合裂纹的新方法。首先，通过有限元方法（FEM）展示了闭合裂纹在超声波加载下的行为。模拟结果表明，裂纹可通过激光超声剪切波（S波）打开。然后，通过实验建立了马赫-曾德尔干涉仪系统，以检测样品在超声波加载下的闭合裂纹。结果表明，在干涉测量中无法检测到的闭合裂纹在超声波加载下的干涉图中变得可见。还可以定量估计打开的裂纹宽度。因此，该方法将是检测光学元件中初始闭合裂纹的一种有前途的方法。
