A COMPARISON OF PHASE-SHIFTING AND FOURIER METHODS IN THE ANALYSIS OFDISCONTINUOUS FRINGE PATTERNS

Phase Shifting Interferometry is a highly accurate data acquisition te chnique that efficiently utilizes several frames of information for ea ch measurement. In this work, the advantages of phase shifting have be en applied to a conventional moire interferometer, yielding a system c apable of recording phase shifted fringe patterns for both in-plane di splacement components. Using this method, the phase of a wavefront of interest can be determined at each detector location, so that the reso lution of the phase measurements is limited primarily by the detector discrimination and geometry. Unlike traditional Fourier fringe analysi s, the noise rejection of phase shift processing algorithms does not d egrade image fidelity in the presence of edges and discontinuities. A general discussion of both the phase shifting technique and the Fourie r fringe analysis method is included to provide insight into the probl ems of processing discontinuous fringe patterns.