Formation of an image in a coherent synthesized-aperture system

An investigation was made of a coherent optical imaging system in which aperture synthesis was performed by additional optical elements (diffraction gratings). Sinusoidal gratings with a period of 150 μ. and a depth of modulation 4 π at the wavelength 630 nm were selected on the basis of an analysis of the instrumental function of this system. A twelvefold reduction in the size of the minimum resolvable element (from 200 to 17 μ) was achieved for a relative aperture of the objective 1:90. It was demonstrated experimentally that the requirements in respect of the alignment of the whole system, including diffraction gratings, were no more stringent than the requirements in respect of the alignment of the conventional optical systems and were governed by the objectives used.