Enlargement of source size and improvement of resolution in fluorescent confocal microscope

Since the larger source size causes the worse optical resolution in a fluorescent confocal optical scanning microscope, a two-zone (annular) phase-only filter is employed to modify the phase information of each annular zone of the enlarged coherent source. The three-dimensional optical transfer function (3D OTF) of the above optical system is derived. The calculated results of the 3D OTF show that the source size is enlarged and the optical resolution is improved.