Generation of speckle fringe patterns by curved-surface window correlation method

Subtraction method is usually adopted to generate the speckle fringe patterns in electronic speckle pattern of interferometry (ESPI), but it would result in high-level speckle noise inevitably. Another method is the direct correlation technique with rectangular windows, which could suppress the high contrast speckle noise and produce some new large size speckles with low contrast. This paper proposes a new method in which correlation is practiced in curved-surface window so as to reduce the affection of non-correlation elements, thus, smoother speckle fringe patterns are generated. Finally, we extend the method to the phase shifting techniques and provide experimental results and conclusion.