[ASME]

INTRODUCTION

Laser Induced Fluorescence (LIF) is based on the use of a light source to excite a fluorescence substance (fluorophore or fluorescent dye) that subsequently emits light. The fluorescence substance is used as a tracer to determine characteristics of interest. LIF has gained popularity as a general purpose visualization tool for numerous 1-D, 2-D, and 3-D applications. It, however, has seen limited use as a quantitative tool. The reason for this stems primarily from the difficulty in separating variations in excitation illumination and vignetting effects from tracer emission. Presented herein is a two-dye ratiometric technique that allows measurement of temperature and film thickness while minimizing variations in excitation illumination and non-uniformities in optical imaging.