ABSTRACT
This chapter describes a novel dual hologram shearing interference technique and corresponding interferometer. Optical interferometry has been used as a diagnostic tool in fluid dynamic research for longer than 40 years. Suggested optical principles of the design effectively facilitate a high mechanical stability of the optical scheme in comparison with any reference beam holographic interferometer’s scheme. A horizontal finite-width-fringe interferometric pattern and its spatial frequency could be produced and controlled by a dual hologram holder as follows. It should be emphasized that the spatial frequency of the grating should be small enough so that the spatial frequency of the output Mach–Zehnder hologram does not exceed the resolving power of photographic film. After being adjusted by the holder to form an infinite-width-fringe interferogram, signal and comparison holograms should be rotated at a certain angle with respect to each other in order to obtain a series of finite-width-fringe interferograms with horizontal fringes.
