An optical imaging system comprises at least one deformable mirror (34) and an adjustment and control arrangement (36, 38) which is coupled to the mirror and is adapted to displace the image-side focal point (52) of the imaging system in the beam propagation direction by deformation of the mirror, particularly in accordance with a predetermined focal point displacement profile. The optical imaging system is preferably employed in a device for femtosecond laser surgery of the human eye, for example for corneal lenticle extraction.