Intensity-Based Measurement Systems
The photodetector output V responding to the luminescent emission, Eq. (4.22), is re-written as
The parameters Пс and nf are Пс = (n/4)GAl[F2(1 + Mop )2 ]- and Пf = K1K2, which are related to the imaging system (camera) performance and filter parameters, respectively. The quantum yield Ф( p, T) is described by Ф( p, T) = kr /(kr + knr + kqS0O2p), where kr is the radiative rate constant, knr is the radiationless deactivation rate constant, kq is the quenching rate constant, p is air pressure, S is the solubility of oxygen, and фO2 is the volume fraction of
oxygen in air. In PSP applications, the intensity-ratio method is commonly used to eliminate the effects of spatial variations in illumination, paint thickness, and molecule concentration. Without any model deformation, air pressure p is related to a ratio between the wind-off and wind-on outputs by the Stern-Volmer relation
V f p
= A(T) + B(T)^— . (4.25)
The essential elements of a measurement system for PSP and TSP include illumination sources, optical filters, photodetectors and data acquisition/processing units. In terms of the detectors and illumination sources used, measurement systems can be generally categorized into CCD camera system and laser scanning system with a single-sensor detector. Since each system has advantages over the other, researchers can choose one most suitable to meet the requirements for their specific experiments.