Laser-scanning confocal and 2-photon laser sources are used in biophysical research to quantify fluorescence in optical sections of biological preparations. Current commercial systems suffer from two major technical limitations: (i) simultaneous acquisition of multiple channels of analog data cannot be easily stored and accessed as one data file, (ii) images acquired in line scan mode cannot be recorded indefinitely, the limit is usually set by a maximum file size (e.g. 30 000 lines). To overcome these limitations a fast integrator circuit was developed that used pixel clock and laser scan signals in conjunction with the photomultiplier (PMT) output from a confocal microscope (BioRad Radiance 2000). The current circuit can integrate the PMT signal over cycle periods as short as 1 ms. Using the accompanying sweep timing signal, these data can be acquired by a separate A/D converter (National Instruments PCI-MIO-16E1) to recreate the x-y or line scan image on separated data acquisition software. Software written by one of the authors (J.D.) can acquire PMT signals and associated analog signals (e.g. current and voltage) display the signals and stream the data to hard disk. The data file can be stored as binary or 16-bit tif format. This configuration allows continuous acquisition of image data and associated high bandwidth analog data with a file size that is only limited by the capacity of the computer hard disk. Programs for off-line examination and data extraction are also available. A commercial version of the integrator unit with higher specifications and additional features is currently under trial (M.T. & J.G.).

The BioRad Radiance 2000 confocal microscope is part of the facilities of the Biophotonics Centre, University of Strathclyde funded by Scottish Higher Education Funding Council, Joint Infrastructure Fund and The Wellcome Trust.