OPTICAL TRANSFER-FUNCTION ANALYSIS FOR 2-PHOTON 4PI CONFOCAL FLUORESCENCE MICROSCOPY

The imaging behaviour in a two-photon 4Pi confocal fluorescence microscope is analysed in terms of the optical transfer function. For comparison, the optical transfer function for two-photon non-4Pi confocal fluorescence imaging is also given. It is shown that the optical transfer function for two-photon 4Pi confocal fluorescence imaging is significantly enhanced at high axial spatial frequencies, thus providing a physical explanation of axial super-resolution obtained in this system.