The difference in the information obtained by the single-aperture and the double-aperture methods in speckle shearing interferometry is discussed. It is shown theoretically and experimentally that the use of a single aperture is essential for obtaining the proper value of the deflection slope of an object: the single-aperture method enables us to obtain the proper slope distribution regardless of the direction of displacement. With the double-aperture method, however, proper distribution can be obtained only for displacement in a particular direction, and this introduces an error into the slope measurement.
© 1985 Optical Society of America
Yoshihisa Iwahashi, Koichi Iwata, and Ryo Nagata, "Influence of in-plane displacement in single-aperture and double-aperture speckle shearing interferometry," Appl. Opt. 24, 2189-2192 (1985)