Optical EngineeringWavelet-aided spatial carrier fringe pattern analysis for 3-D shape measurement
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The latest time-frequency tool, wavelet analysis, is presented to extract the phase information φ(x,y) from a single spatial carrier fringe pattern. First, the fringe pattern is generated and projected onto an object. The spatial carrier fringe pattern, carrying the 3-D shape of the object, is then captured using a CCD camera. Afterward, the spatial carrier fringe pattern is modulated by two high-frequency waves, which makes the spectrum of the carried phase relatively lower among the spectra of two modulated patterns. Following this, the spectrum of the object is separated into the approximation subband using a wavelet transform. The phase map of the 3-D shape of the object is then extracted from the mixed spectra by reconstructing only the approximation of their wavelet transforms. Finally, the 3-D shape of the object can be calculated from the phase map.