Fringe sharpening occurs in the higher diffraction orders of nonlinear two-exposure holographic interferograms. The fringe functions in these various orders are modified by diffraction. At the Talbot distance the fringes replicate those near the plate, and a variety of fringe patterns can be obtained at different propagation distances.
© 1976 Optical Society of America
D. Dameron and C. M. Vest, "Fringe sharpening and diffraction in nonlinear two-exposure holographic interferometry," J. Opt. Soc. Am. 66, 1418-1421 (1976)