Thermal imaging cameras detect electromagnetic radiation from the infrared range (between ~5–15 µm). The intensity of this radiation is dependent on the material of the emitting body. Each material has a specific emissivity which can be either determined from tables or by a specific measurement method.
The opto-electronic sensor inside a thermal camera is measuring the emitted infrared radiation and transforming it into temperature values. The temperature variations are then transferred into colour variations which enable the user to see temperature differences in a picture or video. Warm objects stand out against cooler backgrounds and become visible against the environment – at day and at night.

The most important feature of thermal imaging is the ability to measure temperatures contact-free. Moving objects can be analysed as well as objects that are difficult to access. Thermal imaging is non-destructive and able to cover big areas without problems.