Optical EngineeringThree-dimensional imaging of objects focused on a selectogram surface
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Selectogram characteristics are analyzed. The term selectogram stands for the structure obtained by recording the interference pattern of the radiation of an object and that of an extended reference source of light on an inclined photographic plate. Unlike a hologram, the selectogram reproduces 3-D images of objects by selecting definite components out of the radiation of an extended source whose phase distribution is not correlated with that of the reference source used at the recording stage. A case for which the image of the object being recorded is focused near the surface of the selectogram is described. It is shown that in this case, the angular size of an element determining the resolving power of the image reconstructed by the selectogram is equal to the double-angular width of a horizontal slit that filters the radiation of the object. The general structure of the radiation reconstructed by the selectogram is considered. It is shown that apart from the main image being observed through an output filtering slit, the selectogram reconstructs the multiplicity of distorted images of the object, which can be observed through horizontal stripes parallel to the filtering slit. It is pointed out that the total diffraction efficiency of all images reconstructed by the selectogram does not differ from that of a hologram. At the same time, the diffraction efficiency of the main image being observed through the output filtering slit is essentially decreased because of the presence of additional images. Ways to increase the diffraction efficiency of the selectogram are studied. Experimental data that prove these regularities are presented. Possible development of this method is discussed.