Video-rate fluorescence lifetime imaging camera with CMOS single-photon avalanche diode arrays and high-speed imaging algorithm

A high-speed and hardware-only algorithm using a center of mass method (CMM) has been proposed for single-detector fluorescence lifetime sensing applications [J. Biomedical Opt. 15, 2010]. This algorithm is now implemented on a field programmable gate array (FPGA) to provide fast lifetime estimates from a 3232 low dark count 0.13m CMOS single-photon avalanche diode (SPAD) plus time-to-digital converter (TDC) array. A simple look-up table (LUT) is included to enhance the lifetime resolvability range and photon economics, making it comparable to the commonly used least-square method (LSM) and maximum-likelihood estimation (MLE) based software. To demonstrate its performance, a widefield microscope was adapted to accommodate the SPAD array and image different test samples. Fluorescence lifetime imaging microscopy (FLIM) on fluorescent beads in Rhodamine 6G at a frame rate of 50fps is also shown.