Correction of self-illumination and spectral-leakage effects in luminescent-paint measurements

An analytical model is presented that accounts for the effects of self-illumination of a diffusely reflecting test article in luminescent-paint measurements. Contributions from multiple reflections of excitation and emission light are summed to infinite order in closed form. Also included are the effects of spectral leakage resulting from an imperfectly filtered source and imperfectly rejected reflected excitation light. It is shown that the conventional method of determining flow variables from the ratio of flow-on and flow-off signals is adversely affected by self-illumination and spectral leakage. An explicit solution is derived for the associated inversion problem. Sample calculations are presented.