MULTIPLEXED SINGLE-PHOTON COUNTING .1. A TIME-CORRELATED FLUORESCENCELIFETIME CAMERA

We report the operation of a new type of fluorescence lifetime imaging camera based on the time-correlated single-photon counting (TCSPC) te chnique. To the best of our knowledge the application-specific integra ted circuit (ASIC) used in the camera is the first ASIC designed for t he field of fluorescence. The ASIC also forms the basis for the first read-out system for single-photon timing array detectors and is capabl e of multiplexing and routing counts from up to sixteen detection chan nels, while preserving their timing characteristics with picosecond re solution. In conjunction with an array detector such as a multianode M CP-PM this ASIC allows multiple fluorescence decays to be routinely an d simultaneously acquired using a single set of TCSPC timing electroni cs. To demonstrate one practical application of this technology, we ha ve observed for the first time the spatial distribution of fluorescenc e lifetime contours through a strongly self-absorbing sample, and the effects observed demonstrate how differences in optical geometry can c ontribute to the lack of consistency between results obtained in diffe rent laboratories. (C) 1996 American Institute of Physics.