莫尔轮廓术是实现物体三维面形测量的主要方法之一，它基于莫尔条纹产生和分析技术。莫尔条纹产生方法主要有阴影法、投影法和数字合成法三种。对于数字合成法，目前通常采用低通滤波提取莫尔条纹，低频区域含有许多无用频率成分，会降低所提取的莫尔条纹的质量。通过分析参考条纹图像和变形条纹图像经相乘、相加、相减运算结果图像的频谱，比较不同滤波处理方法对提取莫尔条纹的影响，提出一种采用带通滤波提取莫尔条纹的新方法。与低通滤波相比，带通滤波可以产生衬比度更高的强度分布为标准余弦分布的莫尔条纹；此外，相加和相减运算产生的莫尔条纹之间相位相差p，明暗反转。计算机模拟和实际实验均验证了上述分析结论的正确性和该方法的有效性与可行性。

Moire topography, a generation and analysis technique of moire fringes, is one of the techniques usually applied to three-dimensiond (3D) object shape measurement. Three kinds of methods, shadow moire, projection moire and digital moire, are mainly used to generate moire fringes. At present, low- pass filtering is used for extracting the moire fringes, since the low-frequency region contains lots of unwanted frequency components, the extracted moire fringes are not satisfactory and need to be improved. After theoretical analysis, a new method for extracting moire fringes, the band-pass filtering method, is proposed. This method can be used to extract moire fringes generated by multiplication, addition or subtraction of the reference fringes and deformed fringes by digital image processing. Compared with the traditional low-pass filtering method, the contrast of moire fringes with bandpass filtering is higher, and the intensity distribution is standard cosine. Besides, there is a phase shift of π between the moire fringes produced by addition and subtraction operation, so their bright and dark fringes are justly reversed. The correctness and validity of the proposed method and analysis have been verified by computer simulations and experiments.