The point spread function of optical microscopes imaging through stratified media.

We propose a model for imaging point objects through a dielectric interface or stratified media. The model is applicable to conventional and confocal fluorescence microscopy, with single- or multiphoton excitation. An analytical solution is obtained in the form of readily computable functions. When large mismatches occur in the refractive indices of the media of the objective lens and specimen the illumination and detection point spread functions differ significantly, showing that currently used imaging models may fail to correctly predict imaging properties of optical microscopes.