Optimization of axial resolution in a confocal microscope with D-shaped apertures

We show theoretically that the axial resolution is improved when two centrosymmetric D-shaped apertures are combined in a confocal microscope with a finite-sized pinhole. The optimum width of a divider that separates the D-shaped apertures to give the maximum axial resolution for a given pinhole size is investigated, and the magnitude of the signal level is explored.