Some superresolving pupils, featuring a central maximum narrower than Airy’s core and a first secondary maximum of a few percent, have been computed, following Frieden’s formula and his criterion of maximum superresolution for circular symmetry. A superresolution factor of about 28% may be achieved without much sacrifice of illumination. Other pupils have been investigated where the SF reaches 35%. The behavior of the sidelobes in the point impulse image is examined. The corresponding encircled energy and point impulse response are given.
G. R. Boyer, "Pupil filters for moderate superresolution," Appl. Opt. 15, 3089-3093 (1976)