利用灰度图减小Fourier变换轮廓术的频谱混叠

Eliminate frequency spectrum alias employing a gray image in FTP

本文利用常常被人们忽略的灰度图中包含的频谱信息来减小零频分量对基频分量的影响。先记录一帧被测物体灰度图 ,然后投影正弦条纹到被测物体表面 ,记录变形条纹图。在对变形条纹图进行处理以前 ,先从变形条纹图中通过灰度图消除非均匀反射率对变形条纹的影响 ,得到均匀的变形条纹分布。文中给出的理论分析和实验结果可以证明 :该方法可以限制零频分量的扩展 ,提高FTP测量范围和精度 ,且测量系统简单 。

Now we propose a novel method,in which a gray image captured by CCD camera is used to prevent the zero frequency component of deformed fringe pattern from extending to fundamental component in Fourrier transform profilometry.In our method,we first record a gray image and a deformed fringe pattern of the same object,then calculate their quotient,after that,equal intensity distribution fringe pattern can be obtained.Finally,by calculating the Fourier transform of result fringe,filtering out fundamental frequency and calculating its inverse Fourier transform,we can obtain retrieved shape.Theoretical analysis and experiments have verified that this method can limit the zero frequency component to overlap fundamental component,make FTP have an extended measurement range and improved measurement precision.Further more the experimental setup is very simple because of no phase-shift device.