Adaptive optics for multiphoton microscopy

Specimen-induced aberrations are frequently encountered in high resolution microscopy, particularly when high numerical aperture lenses are used to image deep into biological specimens. These aberrations distort the focal spot causing a reduction in resolution and, often more importantly, reduced signal level and contrast. This is particularly problematic in multiphoton microscopy, where the non-linear nature of the signal generation process means that the signal level is strongly affected by changes in the focal spot intensity. We have developed an adaptive two-photon fluorescence microscope to correct for these aberrations. Unlike a conventional adaptive optics system, the microscope does not include a wavefront sensor but uses an efficient sensorless optimisation scheme to obtain optimum aberration correction.