Applying Dynamic Thermography for Observation of Water Level in Column-Shaped Opaque Beverage Containers

Abstract

Beverages are generally preserved in various opaque containers, and some type of liquid measure is an important aspect of quality control. In this paper, a method for observation of the level of water in opaque beverage containers is described. In this method, rapid heating of the surface of the beverage containers by a light flash was followed by thermographic observation of the dynamic changes in surface temperature. The proposed observation method was used with a globe-type reflector to observe the liquid level clearly and does not require blackbody paint to enhance the flash energy of the containers. The method exploits the differences in the dynamic heat transfer between the portion containing air and the portion filled with water. We carried out verification experiments on containers made of several different materials and found that the temperature in the portion filled with water was lower compared with that in the portion containing air. The surface temperature of the container becomes more uniform when the globe-type reflector is used. Here, we outline the theoretical basis for the detection of the liquid level in opaque containers, and we discuss possible applications of this observation method.