Resolution of a microscope: improvement using a centrally obstructed condenser aperture and a semitransparent II-phase annular aperture objective system.

This paper presents a study of the effects of annular sources of illumination on the resolution of two pinholes of equal brightness by a semitransparent and II-phase annular aperture microscope. It has been shown that by using a centrally obstructed illuminating condenser and a semitransparent and II-phase annular aperture microscope objective the resolution of a microscope can be considerably improved. The effect of condenser blocking provides the lower values of the degree of coherence (less than zero), favoring an increase in the degree of resolution; whereas the semitransparent and II-phase annular aperture objective still lowers this limiting resolution without much loss of light by the central region of the objective. The best resolution is obtained when the central region is completely transparent. It has also been observed that the limiting separation exhibits an oscillatory behavior around the value corresponding to incoherent illumination in the particular case concerned.