The problem of recovering a wavefront or surface deviation from a fringe pattern image is investigated. The data sets generated in sampling a fringe pattern are considered in the frequency domain and errors that arise in analyzing the pattern are given an aliasing interpretation. Uniform sampling is shown to be superior to other sampling schemes. A variety of techniques for locating fringe centers are reviewed and three synchronous convolution methods are demonstrated that do not require the location of fringe centers. For the latter, direct phase measurements are obtained from fringe pattern photographs over a uniform grid with an accuracy comparable to temporal heterodyne interferometry. Two microprocessor-based video systems are described in which the traditional and synchronous convolution methods were implemented.
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