Optical EngineeringDirect quadratic polynomial fitting for fringe peak detection of white light scanning interferograms
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We present a new computational method of white light scanning interferometry for 3-D surface mapping. This method accomplishes the task of detecting the true peak of the interference fringe in two steps. The first step is global search locating the envelope peak by fitting sampled intensity data directly to a symmetric quadratic polynomial. The second step is fine-tuning to precisely determine the fringe peak by compensating for the phase shift on reflection using the absolute fringe order identified by the envelope peak obtained in the first step. This two-step method offers an efficient means of computation to provide a good measuring accuracy with high noise immunity owing to its inherent reliance on least squares principles.