Yu Q, Andresen K, Osten W, Jueptner W
Appl Opt. 1996 Jul 10;35(20):3783-90. doi: 10.1364/AO.35.003783.
Noise reduction is one of the most exciting problems in automatic fringe processing. We propose a two-dimensional (2-D) envelope transform for normalization of fringe patterns, coupled with spin filtering, to construct so-called noise-free normalized fringe patterns. The 2-D envelope transform uses correct fringe intensity envelopes for normalization of fringe patterns, i.e., for making the fringe background and amplitude constant over the whole field. Spin filtering is applied to fringe patterns for removal of random noise taking into account fringe flow. With spin filtering and the 2-D envelope transform, a noise-free normalized fringe pattern is constructed for postprocessing. Based on this improved fringe pattern, two local pixel transforms for strain extraction from a single moiré pattern are developed, in which the digital pure secondary moiré method is improved and the strain-field image method with division is developed.
降噪是自动条纹处理中最令人兴奋的问题之一。我们提出一种二维（2-D）包络变换用于条纹图案归一化，并结合自旋滤波，以构建所谓的无噪声归一化条纹图案。二维包络变换使用正确的条纹强度包络对条纹图案进行归一化，即使条纹背景和幅度在整个视场中保持恒定。自旋滤波应用于条纹图案，以去除考虑条纹流动的随机噪声。通过自旋滤波和二维包络变换，构建出无噪声归一化条纹图案用于后续处理。基于这种改进的条纹图案，开发了两种从单个莫尔条纹图案中提取应变的局部像素变换方法，其中改进了数字纯二次莫尔法，并开发了带除法的应变场图像法。
