Canabal H, Quiroga J A, Bernabeu E
Appl Opt. 1998 Sep 1;37(25):5894-901. doi: 10.1364/ao.37.005894.
An algorithm for accurately extracting the local fringe direction is presented. The algorithm estimates, in the neighborhood of n x n points, the direction of the gradient that points normal to the local fringe direction. The performance of four different derivative kernels is also compared. Since this method is sensitive to noise and variations in background and amplitude, a preprocessing step is used to limit these error sources. The method has been applied to the moiré deflectogram of a spherical and a progressive addition ophthalmic lens, resulting in a map of the refractive power of these lenses. The results are compared with the data obtained with a commercial focimeter. This technique is useful for analyzing the fringe patterns where the fringe direction is variable and must be obtained locally.
提出了一种精确提取局部条纹方向的算法。该算法在n×n个点的邻域内估计垂直于局部条纹方向的梯度方向。还比较了四种不同导数核的性能。由于该方法对噪声、背景和幅度变化敏感，因此使用预处理步骤来限制这些误差源。该方法已应用于球面和渐进多焦点眼镜片的莫尔偏折图，得到了这些镜片的屈光力图。将结果与用商业焦度计获得的数据进行比较。该技术对于分析条纹方向可变且必须局部获取的条纹图案很有用。
