At count rates approaching the reciprocal dead time of the TCSPC electronics the photon number in the pixels of a FLIM image becomes a nonlinear function of the intensity. The images are therefore losing contrast in bright regions, whereas the decay data in the individual pixels remain correct. To improve the image quality at high count rates we have implemented a counter in parallel with the TCSPC timing electronics. The counter delivers pixel photon numbers with virtually no counting loss. A new ‘Lifetime/Intensity’ mode of bh’s SPCM software builds up FLIM images by using pixel intensities from the parallel counter and pixel decay data from the timing electronics. These images show substantially improved contrast at high count rates. The mode is available for the SPC-160 and the new SPC-180N TCSPC/FLIM modules.
Keywords: FLIM, TCSPC, Intensity Scale, Image Contrast