PROBLEM TO BE SOLVED: To analyze a pattern so that even when a pattern image data expressed in the orthogonal coordinate system shows a closed pattern shape, an open pattern shape can be obtained by transforming the data into a coordinate system different therefrom, the low-frequency signal components and a carrier frequency components can be separated by Fourier transformation and hence a good shape of an object under observation can be obtained.;SOLUTION: For analyzing the surface shape of an object to be observed, using Fourier transformation for a closed interference fringe pattern image data, the original image data expressed in the orthogonal coordinate system is once transformed into an interference fringe pattern image data expressed in the polar coordinate system, this transformed data is subject to Fourier transformation and returned to the orthogonal coordinate system by the inverse polar coordinate transformation, thus analyzing the surface shape of the object to be observed, and hence the low-frequency signal components can be separated surely from a signal, having the low frequency signal components mixed with the carrier frequency component in the Fourier spectrum.;COPYRIGHT: (C)2001,JPO
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