Abstract

Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique to image deep biological living tissue [1]. Given that TPEF is mostly generated by ballistic (unscattered) light, this technique provides high resolution images even within scattering media. Recently, we have shown that the rejection of out-of-focus TPEF background in scattering tissue can be significantly enhanced with a differential aberration technique [2,3]. This technique is based on an intermittent introduction of extraneous aberrations to control the phase profile of the near-infrared femtosecond laser beam in the back aperture of the focusing objective. The subtraction of an aberrated image from a standard image then leads to enhanced background rejection.

© 2009 Optical Society of America