傅里叶变换轮廓术中滤波窗方位选择研究

在傅里叶变换轮廓术频域滤波过程中通常采用不对称的汉宁窗滤波窗来提取基频信号,当投影呈二维变化的光栅条纹时,采用的滤波窗长短轴方向和载频方向不吻合,会导致被测物体的部分高频信息丢失,从而影响相位展开的难易程度和系统测量的精度。分析比较物体高度的分布与频谱的关系,通过旋转滤波窗使其短轴方向与载频方向一致,可以保留物体的高频信息,降低相位展开的复杂度,提高测量的精确度。计算机模拟和实物实验结果表明滤波窗旋转滤波可以避免相位展开在物体高度突变处的出错,有效地提高测量精度。

Research on Filter Orientation Selection in Fourier Transform Profilometry

In the spectrum filtering process of FTP, an asymmetric hanning filter is usually used to extract the fundamental component. When a fringe pattern with one-dimensional frequency carrier is projected, the direction of filters major axis and minor axis is not consistent with the direction of carrier frequency, and some high frequency information of the tested object will be lost, which will affect phase unwrapping and measuring accuracy. By analyzing the relationship between the shape of an measured object and its corresponding Fourier spectrum, this paper draws a conclusion that some high frequency information of the tested object can be kept when the employed filter is rotated to make the direction of its minor axis consistent with that of the carrier frequency. The results of computer simulation and actual experiment show that this proposed filter orientation selection can successfully reduce the failure probability of phase unwrapping on the discontinuous area of the tested object and effectively increase the measuring accuracy of the system.