Aberration correction for confocal imaging in refractive‐index‐mismatched media

A major limitation to the use of confocal microscopes to image thick biological tissue lies in the dramatic reduction in both signal level and resolution when focusing deep into a refractive‐index‐mismatched specimen. This limitation may be overcome by measuring the wavefront aberration and pre‐shaping the input beam so as to cancel the effects of aberration. We consider the images of planar and point objects in brightfield, single‐photon fluorescence and two‐photon fluorescence imaging. In all cases, the specimens are imaged using an oil‐immersion objective through various thicknesses of water.