Spatial coherence using a cascaded black and quadratic annulus for the 2nd objective aperture in a confocal scanning laser microscope

In this article, we considered two models of apertures in the confocal laser microscope. The 1st model has cascaded black and quadratic (B/Q) annuli for the aperture corresponding to the 2nd objective in the confocal microscope. The 2nd model has a concentric black and white (B/W) annulus. For practical reasons, we replaced a detector of finite size instead of the coherent point detector in the confocal imaging systems. Hence, we computed the spatial coherence factor for both cases using the confocal laser microscope. In addition, we obtained an empirical formula that represents the coherence factor in the confocal laser microscope. We compared our results on spatial coherence with the previous results obtained in the case of circular and quadratic apertures.