Heat-flow thermography is a non-destructive testing method and is based on the fact that all objects emit infrared radiation which is characteristic for the respective surface temperature. This can be detected using special cameras and presented as an image of the surface temperature.
In its most important variant, the object being examined is subjected to a thermal impulse (active thermography). The diffusion rate of the resulting heat front, which penetrates into the object, depends on the thermal conductivity, the specific heat capacity and the density of the material below the surface. Patterns therefore form in the surface temperature which enable conclusions to be drawn concerning the condition of the measurement object below the surface.
In this way, defects can be detected which lie below the surface and which are not externally visible. The procedure provides images, is fast and can be relatively easily automated. Fields of application are primarily the detection of bonding and adhesion defects, delamination, blisters and cavities, as well as the detection of foreign bodies, for example in food items.