A superresolving optical system with a spatial resolution exceeding the classical limit is described. The gain in spatial bandwidth is obtained by reduction of the usable object field. The superresolving system is essentially a conventional system modified by the insertion of two masks (line or crossed gratings) into conjugate planes of object and image space. Its spread and transfer functions for coherent and incoherent illumination are derived theoretically. The experiments with different extended objects clearly show the expected increase of the spatial bandwidth; the experimental point images agree with the theoretical predictions.
A. BACHL and W. LUKOSZ, "Experiments on Superresolution Imaging of a Reduced Object Field," J. Opt. Soc. Am. 57, 163-164 (1967)