Calculation of three-dimensional optical transfer function for a confocal scanning fluorescent microscope

A confocal scanning fluorescent microscope is suitable for 3-dimensional (3-D) imaging. The 3-D optical transfer functions (OTF’s) for such a microscope are calculated to show their dependence on the wavelength of the fluorescence. These calculations reveal that when the wavelength of the fluorescence is equivalent to that of the excitation light, the 3-D OTF has no missing-cone region. However, as the wavelength becomes longer, the 3-D OTF approaches that of an incoherent conventional microscope at the wavelength of the excitation light.