Remote Recognition of Materials Using the Laser Photothermal Radiometry

Abstract

The issues related to the possibility of recognizing opaque materials of remote objects using the pulsed laser photothermal radiometry with long-term pulsed exposure are considered. Theoretical calculations of the range of recognition of materials with laser activation of their surface are given. The calculation results indicate a significant influence of thermal parameters on the recognition range. It has been experimentally shown that there is a decrease in the range by about an order of magnitude if the material of the search object has a large thermal inertia (metals), compared with a material with a small thermal inertia (polycarbonate, rubber), which provides a sufficient probability for their difference. At the same time, the condition of strong surface absorption must be fulfilled at the wavelength of the laser radiation. For synthetic polymer products, CO₂ laser satisfies these considerations to the greatest extent. The influence of wind load on the temperature of the laser spot on the object is one of the key ones in the proposed method. The paper suggests a way to minimize this influence and even eliminate it almost completely. Issues related to the possibility of increasing the recognition range are discussed.