Effects of defocus and primary spherical aberration on three-dimensional coherent transfer functions in confocal microscopes

For both reflection- and transmission-mode confocal scanning microscope systems, three-dimensional coherent transfer functions are investigated by considering the effects of defocus and primary spherical aberration. We numerically calculate the three-dimensional coherent transfer functions for various amounts of aberration and show that three-dimensional confocal imaging is strongly degraded if the amount of aberration is larger than a quarter wavelength. The compensation of the primary spherical aberration by introducing defocus is also discussed.