Determination of temperature in glass with a fluorescence method

We have developed a method for measurement of temperature in glass products with the following features: (1) non-contacting, (2) real time, and (3) through-thickness. The method is based on fluorescence emission. Many glass products include Fe2O3 as an additive in various amounts. Ferric (Fe3+) and ferrous (Fe2+) ions absorb light in the ultraviolet and infrared parts of the spectrum. Absorption of light by iron ions in glass results in a predictable fluorescence emission. The emission in turn depends on the glass temperature, and this dependence is the basis for our method of measuring temperature. We have measured the fluorescence emission lifetimes in several commercial automotive glass samples over a temperature range from 25°C to 550°C (about 300–825 K). Imaging the fluorescence emission from glass samples onto a segmented photomultiplier tube provided spatially resolved measurements. A simple model that relates the temperature to the fluorescence lifetime has been developed.