Parametric investigations for frequency-domain lifetime psp technique (FLIM)

The effects of measurement parameters on frequency-domain fluorescence lifetime imaging (FLIM) with a new CMOS camera sensor (pco.flim) were investigated. The phase and demodulation indices were calculated from acquired images, and a function for the pressure is constructed. Pressure calibration tests performed with changing measurement parameters illustrate that increasing excitation modulation frequency significantly increases the pressure sensitivity but has a negative effect on a signal-to-noise ratio. The excitation modulation amplitude and its offset should be as high as possible for the reduction of the shot-noise influence. The pressure error calculated from the normalized phase index was the smallest at the modulation frequency of 20 kHz, while that from normalized demodulation index decreased as the modulation frequency increased. An impinging jet test has been conducted and the applicability of FLIM-PSP technique was investigated. Pressure distribution obtained from the test at the modulation frequencies of 20 kHz and 80 kHz were successfully compared to the pressure tap measurements. Considering the pressure error evaluation, the best results using the phase and demodulation indices were obtained at the modulation frequencies of 20 kHz and 80 kHz, respectively.