Minimizing the angle of incidence errors in intensity ratio phosphor thermometry

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Abstract Intensity ratio-based phosphor thermometry is a promising technique for instantaneous temperature measurement of fast-moving objects. However, its accuracy is limited by the blueshift effects of interference filters induced by angle of incidence (AOI) variations. This is especially problematic for phosphors with significant temperature-dependent emission band shifts. To address this issue, we propose the following two-step method: Firstly, a simulation procedure is developed to evaluate measurement errors induced by AOI variations under different filter sets using the BaMgAl10O17:Eu2+ (BAM:Eu) phosphor. Simulation results are carefully analyzed, and a filter set is selected which results in low AOI errors and high temperature sensitivity. Secondly, an experimental temperature-AOI calibration method is developed by fitting the intensity ratio distribution under different AOIs and temperatures using a bivariate quadratic function. Finally, the intensity ratio-based phosphor thermometry method with the selected filter set and the temperature-AOI calibration is validated via surface temperature measurements on a heated disk. AOI-induced errors up to 25 K and 12 K are effectively removed under stationary and rotating conditions, respectively.