Two-point resolution of a microscope: effect of nonuniform and nonsymmetric illumination using a semitransparent pi-phase annular aperture.

This paper presents a theoretical study of the effects of partial coherence (via the effect of condenser aperture) on the resolution of two pinholes by a semitransparent and pi-phase annular aperture microscope. The illumination used is nonuniform and nonsymmetric. The response of the resolution has been studied in three discrete planes of illumination. It has been seen that by making the central region of the pi-phase annular aperture completely transparent, best resolution is obtained in the plane of illumination ø = pi/2. The oscillatory behavior of the limiting resolution has also been displayed graphically.