Chen ChangFu, Mao FengShan, Yu JiaYong
Appl Opt. 2021 Feb 10;60(5):1232-1240. doi: 10.1364/AO.413778.
Sampling moiré method (SMM) is a highly accurate vision-based deformation measurement method, whose measurement error is minimized when an integer that is closest to the grating pitch is selected as the sampling pitch. We propose a subpixel SMM by applying subpixel interpolation operation before the downsampling in traditional SMM; the sampling pitch was selected as a noninteger nearest to the grating pitch in the subpixel resolution image. Meanwhile, the average filter method was used to eliminate the symmetric error cause by interpolation. As a result, the period of moiré fringe was enlarged greatly, and the measurement accuracy was also increased. To investigate the efficiency of the subpixel SMM, a computer simulation was applied to analyze the accuracy of the subpixel SMM. Then a simple tensile experiment was conducted to validate the efficiency of this method, and the result of the subpixel SMM accorded well with the fiber Bragg grating. In summary, the proposed novel subpixel SMM is capable of being used for high accuracy in-plane deformation measuring.
采样莫尔条纹法（SMM）是一种高精度的基于视觉的变形测量方法，当选择最接近光栅间距的整数作为采样间距时，其测量误差最小。我们通过在传统SMM的下采样之前应用亚像素插值操作来提出一种亚像素SMM；在亚像素分辨率图像中，采样间距被选择为最接近光栅间距的非整数。同时，使用平均滤波方法来消除由插值引起的对称误差。结果，莫尔条纹的周期大大增大，测量精度也得到提高。为了研究亚像素SMM的效率，应用计算机模拟来分析亚像素SMM的精度。然后进行了一个简单的拉伸实验来验证该方法的效率，亚像素SMM的结果与光纤布拉格光栅吻合良好。总之，所提出的新型亚像素SMM能够用于高精度的面内变形测量。
