Real time two-photon absorption microscopy using multi point excitation

In this communication we present the development of a real time two- photon absorption microscope, based on parallel excitation with many loci. This pattern of loci is created by a two-dimensional microlens array. The fluorescence is detected by direct, non descanned detection on a CCD camera. Due to the parallel nature of both excitation and detection it is possible to speed up image acquisition significantly. This makes the instrument especially suitable for studying living specimens and/or real time processes. The optical design of the instrument is discussed and an imaging example is given. We specifically address the relation between the axial sectioning capability and the distance between the illumination loci at the sample.