Axial superresolution with ultrahigh aperture lenses.

We explore the current limits of the axial resolution of optical sectioning microscopy using a single lens, by combining the resolving power of novel 1.45 numerical aperture oil immersion lenses with superresolving binary aperture filters. We quantify the axial resolution brought about by the increase in semiaperture angle to max á =72.8 degrees and demonstrate an absolute gain in axial resolution through binary pupil filters. Implemented in a confocalized two-photon excitation microscope, the combination of both effectively improves the axial resolution to 330 nm full-width-half-maximum, which is by 34% over that of a standard 1.4 NA system.