Hardware implementation and calibration of background noise for an integration-based fluorescence lifetime sensing algorithm.

A new integration based fluorescence lifetime imaging microscopy (FLIM) called IEM has been proposed to implement lifetime extraction [J. Opt. Soc. Am. A25, 1190 (2008)]. A real-time hardware implementation of the IEM FLIM algorithm suitable for single photon avalanche diode arrays in nanometer-scale CMOS technology is now proposed. The problems of reduced pixel readout bandwidth and background noise are studied and a calibration method suitable for FPGA implementation is introduced. In particular, the relationship between signal-to-noise ratio and background noise is considered based on statistics theory and compared with a rapid lifetime determination method and maximum-likelihood estimator with-without background correction. The results are also compared with Monte Carlo simulations giving good agreement. The performance of the proposed methods has been tested on monoexponential decay experimental data. The high flexibility, wide range, and hardware friendliness make IEM the best candidate for system-on-chip integration to our knowledge.