Measurement of Surface Temperature Using a Laser-Induced Fluorescence Thermal Imaging System

Abstract

This paper describes a novel, non-intrusive thermal imaging system based on the fluorescence properties of an europium-doped lanthanum oxysulfide (Eu+3:La2O2S) thermographic phosphor. In this system the phosphor coating on a test surface is excited by a pulsed Nd:YAG laser. The resulting fluorescent emission of the temperature-sensitive 512 nm transition, along with that of the relatively temperature independent 620 nm transition, is acquired using an image-intensified charged coupled device (ICCD) camera. The ratio of the 512- and 620-nm emissions, integrated over a set gating period, is then correlated with temperature. Quality data obtained from a calibration procedure have demonstrated that the present approach can be more advantageous than many existing thermal imaging techniques. The system has been specifically designed to provide two-dimensional temperature measurements with high accuracy and exceptional spatial resolution. Because of the extremely short fluorescent lifetimes of various thermographic phosphors (∼μs), applicability of the technique to fast-moving or rotating surfaces is very promising.