UC Irvine

A system and method is provided for improved fluorescence lifetime measurement. A high frequency digital heterodyning technique is described in which photon counting mode detectors are sampled at a rate slightly slower than a digitally pulsed excitation signal. A digital mixer produces a difference frequency which contains the same information than the high frequency signal. This lower frequency is still suitable for fluorescence lifetime measurements in microscopy. The digital algorithm provides phases and modulations of detected photons binning them into phase steps and time windows. The digital heterodynig algorithm was implemented in a very low cost FPGA (Field Programmable Gate Array).