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长焦距测量的Talbot-Moiré法是研究热点,目前很多方法虽然都是基于Talbot现象和Moiré技术,但基本原理和实验方案各不相同,因此焦距计算公式也不相同。基于透镜位相变换作用,利用Talbot效应和Moiré条纹,通过图像处理的方法获得条纹的斜率变化,根据焦距与莫尔条纹斜率之间的关系求得透镜焦距。由于长焦透镜的焦距相对于被测透镜厚度大得多,完全可以看作是薄透镜对光束的变换,可用薄透镜对球面波的变换作用来近似表示其对高斯光束的变换。因此,该方法测量长焦透镜焦距对于高斯光束与非高斯光束焦距测量结果无差别,均适用。最后全面分析了该测量方法的误差及精度极限。在影响测量精度的各个误差因素中,光栅节距误差对焦距测量的影响最为显著。
The Talbot-Moiré method of long focal length measurement is a hot research topic. Although many methods are based on the Talbot phenomenon and the Moiré technique at present, the fundamental principle and experiment scheme are different, so the focal length calculation formula is not the same. Based on the phase transformation of the lens, the slope of the stripe is obtained by using the Talbot effect and the moiré fringe, and the focal length of the lens is obtained according to the relationship between the focal length and the slope of the moiré fringe. Since the focal length of the telephoto lens is much larger than the thickness of the lens under test, it can be completely considered as the transformation of the thin beam to the light beam. The conversion of the spherical wave by the thin lens can be used to approximate the transformation of the Gaussian beam. Therefore, the method of measuring the focal length of the telephoto lens does not discriminate between the Gaussian beam and the non-Gaussian beam focal length measurement results, are applicable. Finally, a comprehensive analysis of the measurement error and accuracy limit. Among the error factors that affect the measurement accuracy, the influence of the grating pitch error on the focal length measurement is the most significant.