Wang Qinghua, Ri Shien, Xia Peng
Appl Opt. 2021 Feb 20;60(6):1637-1645. doi: 10.1364/AO.416742.
A scanning-based second-order moiré method is proposed for high-accuracy deformation measurement in a large field of view (FOV) by analyzing the phase distribution of a single-shot scanning moiré fringe image using a spatial phase-shifting technique. In this method, the grating pitch can be as small as around one pixel in the scanning moiré image to ensure a wide FOV, while high-precision phase measurement is achievable. The strain measurement accuracy has been verified from simulations at different grating pitches, applied strains, and noise levels. The simulation results show that the closer the grating pitch is to the scanning pitch, the smaller the strain measurement error, and the recommended pitch ratio is 0.9∼1.1. Furthermore, the feasibility of this method has been verified from a tensile experiment on an aluminum specimen under a laser scanning microscope with scanning moiré images recorded. The microscale strains of aluminum measured at different tensile loads agree well with the strain gauge results. As an integration of the scanning and sampling moiré methods, this method has the advantages of a large FOV, high accuracy, strong noise immunity, and visualization of magnified deformation. Compared with the traditional phase-shifting scanning moiré method, this method only needs to record a single scanning moiré image and is suitable for dynamic deformation analysis.
提出了一种基于扫描的二阶莫尔条纹方法，通过使用空间相移技术分析单次扫描莫尔条纹图像的相位分布，在大视场（FOV）中进行高精度变形测量。在该方法中，扫描莫尔条纹图像中的光栅间距可小至约一个像素，以确保宽视场，同时可实现高精度的相位测量。通过在不同光栅间距、施加应变和噪声水平下的模拟验证了应变测量精度。模拟结果表明，光栅间距越接近扫描间距，应变测量误差越小，推荐的间距比为0.9∼1.1。此外，通过在激光扫描显微镜下对铝试样进行拉伸实验并记录扫描莫尔条纹图像，验证了该方法的可行性。在不同拉伸载荷下测量的铝的微观应变与应变片结果吻合良好。作为扫描和采样莫尔条纹方法的集成，该方法具有视场大、精度高、抗噪声能力强以及放大变形可视化的优点。与传统的相移扫描莫尔条纹方法相比，该方法只需要记录一幅扫描莫尔条纹图像，适用于动态变形分析。
