Surface temperature-field imaging with laser-induced thermographic phosphorescence

A technique to remotely image temperature distributions of heated metallic surfaces is extended to higher temperatures. It uses a Dy'S:YAG thermographic phosphor (TP) bonded to the surface and excited by radiation at 355 nm. Digital images of the emission from two excited states were recorded and divided by each other to correct by normalization for illumination and coating nonuniformities. Results show that the TP can survive heating and cooling cycles to 1400 K and that emitting states achieve thermodynamic equilibrium before radiating. Temperatures in the range of 300-1300 K were determined by normalization of pairs of emission images with a single calibration constant. Uncertainties of +/-7-13% at a spatial resolution of 20 mu m and +/-0.7-4% at a resolution of 500 mu m were achieved. (C) 2000 Optical Society of America.