Thermal wave interferometry (TWI) for materials characterization is based on detecting the surface temperature variations caused by a modulated heat source at the material surface, and consequently deducing the internal structure from the observed thermal energy propagation properties. The usefulness of the methodology has been accepted for a large variety of measurement problems, including thermal diffusivity determination of materials, coatings thermal properties and thicknesses, detection of laminations, detection of bulk defects, etc. A typical TWI system is shown in Figure 1. The sruface is illuminated with square-wave modulated uniform laser light and the thermal response is observed radiometrically with an IR-detector. Measurements of the relative amplitude of the surface and the phase difference between the excitation and the surface temperature variation are obtained.
展开▼
