Moire-holograms contain a parallel-line grating recorded during the exposure process of the model grid under three-dimensional deformation. Utilizing the diffraction of a white light beam striking the holoplate, frozen moire patterns can be observed, under proper angles, directly by reflection. With a Fourier transform optical system, the reconstruction is achieved by means of a white source, filtering one among the chromatic wavefronts at the first diffracted order. If the wavefronts of two complementary colors are allowed to pass through the filter, direct derivatives of displacement fringes will appear on the planes where the images are slightly shifted, before or after overlapping. By a grounded glass the image plane is determined where the differentiation fringes exibit the neatest pattern, which may be recorded on a photographic film.
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