Multiplexed single-photon counting. I. A time-correlated fluorescence lifetime camera

We report the operation of a new type of fluorescence lifetime imaging camera based on the time-correlated single-photon counting (TCSPC) technique. To the best of our knowledge the application-specific integrated circuit (ASIC) used in the camera is the first ASIC designed for the field of fluorescence. The ASIC also forms the basis for the first read-out system for single-photon timing array detectors and is capable of multiplexing and routing counts from up to sixteen detection channels, while preserving their timing characteristics with picosecond resolution. In conjunction with an array detector such as a multianode MCP-PM this ASIC allows multiple fluorescence decays to be routinely and simultaneously acquired using a single set of TCSPC timing electronics. To demonstrate one practical application of this technology, we have observed for the first time the spatial distribution of fluorescence lifetime contours through a strongly self-absorbing sample, and the effects observed demonstrate how differences in optical geometry can contribute to the lack of consistency between results obtained in different laboratories.