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19 June 2002 Realization of aliasing reduction in FTP using microscanning
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We use the micro-scanning technique to eliminate the frequency aliasing caused by sub-sampling in Fourier trans-form profilometry (FTP). It has been discussed that in FTP correct 3-D surface shape retrieval can be obtained only when the slope of the height variation of the measured object is limited within maximum measurement range. If this condition is not satisfied, it is im-possible to obtain correct retrieval because of shadows existed in the fringe pattern. In a crossed-optical-axes system for FTP, a smaller included angle between axis of the projection and the detection system is set to avoid the frequency alias caused by shadows. But the smaller the included angle is, the lower the phase sensitivity in FTP. That is, a small phase error can cause a large height distribution error. In order to eliminate this kind of error, we should project a dense grating image onto an object to reduce equivalent wavelength of fringe. At the same time, we need a high resolution CCD to record the fringe pattern to satisfy the sampling theory. When there is not suitable high resolution CCD, the sub-sampled fringe is obtained. In this paper, we discuss how to combine a cor-rect fringe from sub-sampling fringe patterns using micro-scanning technique in FTP in theory. Computer simulations experiments have proved our analysis.
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Wenjing Chen, Xianyu Su, Yiping Cao, and Liqun Xiang "Realization of aliasing reduction in FTP using microscanning", Proc. SPIE 4778, Interferometry XI: Applications, (19 June 2002);

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