Fringe sharpening is required to obtain a higher accuracy of measurement. Nonlinear recording and consequently filtering at the higher-order halos for image formation give sharpened fringes in the image. Furthermore, if the apertures during recording are properly arranged, cross-frequency orders appear, which when used for filtering provide moiré fringes of higher contrast due to intercoupling.
© 1984 Optical Society of America
R. K. Mohanty, C. Joenathan, and R. S. Sirohi, "Fringe sharpening and information coupling in speckle shear interferometry," Appl. Opt. 23, 4596-4600 (1984)