傅里叶变换轮廓术中带通滤波器窗口参数的自动选取方法

频域带通滤波器是傅里叶变换轮廓术(FTP)中的一个重要环节。考虑到FTP系统光学结构和相关参数的变化，本文提出了一种FTP轮廓术中带通滤波器窗口参数的自动选取方法。该方法只利用一帧变形条纹图，对变形条纹图像的傅里叶频谱进行数值微分，粗略找到基频中心的初始位置；然后，利用图像直方图和阈值分割技术处理傅里叶频谱，获取带通滤波器的中心频率和带宽，实现频域滤波的自动化处理。该方法能自动适应FTP系统光学结构和相关参数的变化，使傅里叶变换轮廓术发挥其动态测量的优势，在三维光学测量工程应用中有较大实用价值。计算机模拟实验和实测结果均验证了本文方法的有效性。 

Automatic Selection Method for Parameters of Bandpass Filter in Fourier Transformation Profilometry

The digital bandpass filter in frequency domain plays a key role in Fourier transformation profilometry (FTP). Considering the variations of optical geometry and relevant parameters in FTP, an automatic selection method for parameters of bandpass filter in FTP is presented in this paper. In the proposed method, with only one frame of deformed fringe pattern, numerical differentiation is applied to the Fourier frequency spectrum of the deformed fringe pattern in FTP, in order to find roughly the initial center position of base frequency; next, image histogram and threshold segmentation techniques are used to process the Fourier frequency spectrum to automatically and accurately obtain the center frequency and bandwidth of the bandpass filter, so to realize the automatic processing of frequency filtering. The proposed method can automatically adapt to the variations of optical geometry and relevant parameters in FTP, can make the FTP produce its advantage in dynamic measure, and it will find wide application in engineering. Computer simulation and experimental results with real data show the validity of the proposed method.