Extraction of phase field from a single contoured correlation fringe pattern of ESPI

Abstract

Speckle fringe patterns of ESPI are full of high-level speckle noise and normally are processed by phase shifting methods that require multi speckle fringe patterns. We propose a novel method to generate a speckle-noise-free fringe pattern from a single speckle fringe pattern and to extract the phase field from the new pattern. With the new method, the correlation between two speckle patterns is performed only within contour windows instead of rectangular windows and this contoured correlation results in a smooth, normalized fringe pattern without speckle noise. The new ESPI fringe patterns are speckle-noise-free and of comparable quality to that of moiré and hologram, which is unimaginable with traditional ESPI methods. In addition to the smoothness, the resultant fringe pattern is normalized automatically so that the full phase field can be extracted from this single fringe pattern by the single-image phase-shifting method.