Conversion of the Nikon C1 confocal laser-scanning head for multiphoton excitation on an upright microscope

Most commercial laser-scanning imaging systems used for confocal fluorescence microscopy can be readily adapted for use with two-photon fluorescence excitation. We report here on the details of the conversion of the Nikon C1 (product released November 2001) with two channels of nondescanned detection of two-photon-excited fluorescence. One of the goals of the design was to utilize off-the-shelf components as much as possible to minimize the use of custom machining and electronics assembly. We also give some initial characterization of the imaging properties of the system.