FRINGE-PATTERN ANALYSIS USING A SPATIAL PHASE-STEPPING METHOD WITH AUTOMATIC PHASE UNWRAPPING

This paper presents a new method of fringe-pattern analysis by spatial phase stepping (sps). The sps method combines the computational simplicity of phase stepping with the single-image analysis capability of the Fourier transform method, The technique works by subdividing a linearized fringe pattern into three component images, from which the phase is calculated by a three-phase step algorithm, A computer simulation has been undertaken to demonstrate the theory and to enable an analysis of systematic errors. In addition, an experimental transonic flow field is solved by sps and a comparison is made with results derived using the Fourier transform method, The experiment also demonstrates the use of the minimum spanning tree phase-unwrapping strategy to create a continuous map of the whole transonic flow field.