基于模板匹配的莫尔条纹倾角计算

Calibration method for angular measurement of Moiré patterns based on template matching

提出了一种基于模板匹配的亚像素处理方法,可以精确计算出在大口径长焦距测量过程中出现的莫尔条纹的角度。基于泰伯效应和莫尔条纹干涉的长焦距测量方法是一种高精度的焦距测量方法。理论分析表明:这种测量方法的精度很大程度上依赖于莫尔条纹角度的精度。之前是通过迭代算法在亚像素域中寻找莫尔条纹频谱的最大值点来计算莫尔条纹的角度。然而实验过程中得到的莫尔条纹往往会出现不同程度的弯曲和畸形,这会大大影响这种方法的测量精度。从改进测算角度算法这个角度出发,针对傅里叶变换后的频谱图,基于模板匹配的思想,对各种莫尔条纹进行二维正态分布拟合,找出频谱点精确坐标,从而精确测量莫尔条纹角度。理论分析和软件仿真表明:这种方法具有高精度、高稳定等优点,能有效提高长焦距的测量精度。

A high-accuracy calibration method for angular measurement of deformed and curved Moire patterns, based on template matching algorithm, was presented. It was feasible and accurate method, based on Talbot interferometry and Moire deflectometry, to measure long focal-length lenses. Theoretical analysis indicated that the precision of this method was mainly influenced by the angle of Moire patterns. However, it was difficult to obtain high-accuracy angle of Moire patterns, since the Moire patterns derived from experiment were constantly deformed or curved. A method based on template matching algorithm, was demontrated to calibrate deformed and curved Moire patterns, thus their angle can be calculated fast and accurately in sub-pixel domain. Numerical analysis and simulation prove that the method mentioned above demonstrates high precision and stability, and experiment results show that the accuracy of the long focal lengths measurement is improved obviously.