Spatial coherence using an aperture of two different distributions for the 2nd objective in a confocal scanning laser microscope

Abstract

We considered a model of aperture modulation. It has two equal zones of different distributions for the aperture corresponding to the 2nd objective in the confocal microscope. The zone from the center has a quadratic distribution, and the outer zone has a constant distribution. We computed the point spread function (PSF) corresponding to the model and extracted the resolution information from the cut-off of the diffraction pattern. We compared the PSF results with previous results for uniform circular and quadratic apertures. For practical reasons, the coherent point detector in confocal imaging systems is replaced by a detector of finite size. Then, we computed the spatial coherence factor for the described model using MATLAB code. We compared our results on spatial coherence with previous results obtained for circular and quadratic apertures using MATLAB. We have a direct relationship between the PSF and the SCF in conventional and confocal microscopes. In addition, we deduced the spatial resolution from either the cut-off spatial frequency in the PSF or the square root of the product of the derivative of the SCF and 1/r^2.