Simultaneous Measure of Thickness and Temperature of an Infrared Semi-Transparent Layer

A novel thermographic techniques is proposed to measure simultaneously the thickness and the temperature of a layer that is semi-transparent to infrared radiations. The layer may be a thin solid or liquid film, like in the presented experiments, but the technique can be also used with minor modifications to a suspension of particles or droplets or a solution of different fluids. The technique can be applied when the measured layer reaches a minimum thickness such to be detected by an infrared sensor, like a camera, but it is not too thick to become totally opaque in the sensor wavelength range. These limits depend on the fluid investigated, on the precision of the measured temperatures, and on the accepted accuracy of the results. In the present work, we illustrate the working principles of the technique developed in a real situation, and present preliminary results on a new application.