Investigation of frequency-domain lifetime PSP technique using a Fluorescence Lifetime Imaging (FLIM) camera

Frequency-domain fluorescence lifetime imaging (FLIM) is applied for acquiring pressure sensitive paint (PSP) images by using a pco.flim camera, which has an in-pixel dual tap control CMOS image sensor. In this FLIM technique, an excitation light is modulated sinusoidally, and modulation depth and phase angle, which depend on lifetime or pressure, are estimated from four gated images. In the calibration test, the influences of modulated excitation light, exposure time and modulation frequency are shown. The pressure sensitivity of phase angle has similar sensitivity to that in the standard lifetime method (gated intensity ratio). As the first step of application, a low speed wind tunnel test was performed. The pressure distribution caused by the vortex on a delta wing is visualized successfully by this technique