Modulo-2pi phase determination from individual ESPI images

► A practical algorithm suitable for use with moving surfaces is presented that determines modulo 2pi ESPI phase changes. ► It requires only a single subsequent ESPI image after acquisition of a conventional set of reference images. ► The method uses an efficient correlation procedure that is comparable in speed to conventional calculation methods. ► Practical measurements confirm the effectiveness of the method and of additional features to improve image quality.