Investigation for Simultaneous Measurement of Pressure and Temperature Using Frequency-Domain Lifetime Imaging Technique

Abstract

There are two methods for measuring pressure using conventional pressure-sensitive paints (PSP). The first one is the intensity method using constant excitation light. The second one is the lifetime method using pulsed light. The pressure distribution on body surface is obtained by measuring the emission intensity and the lifetime depending on the pressure, respectively. If the temperature distribution changes due to heat generated by an excitation light and a flow, or heat from an external element such as a motor, it is necessary for high-accuracy pressure measurement to correct the temperature in the both methods. Therefore the temperature data is additionally acquired by a temperature sensor. In this study, frequency–domain lifetime imaging technique (FLIM-PSP) is investigated using sinusoidaly modulated light. The emission intensity is also modulated with same frequency of the light. But the modulated emission wave has the phase angle, the modulation amplitude and average intensity depend on the pressure and the temperature. That is, since FLIM-PSP technique has plural variables, it is investigated that simultaneous measurement of temperature and pressure is possible. It is shown that the phase angle and the modulation depth, which represents a ratio of the modulation amplitude to the averaging intensity, depend on pressure and temperature in a calibration test, as shown in the figure. It is shown that FLIM-PSP technique has possibility of a simultaneous pressure and temperature measurement based on the different sensitivity to pressure and temperature in the phase angle and the modulation depth.