Theoretical basics of thermography

Any object with a temperature above absolute zero (0 Kelvin = -273.15 °C) emits infrared radiation (IR radiation). However, the human eye cannot perceive this because it is virtually blind in this wavelength range. Not so with the thermal imaging camera. Their core, the infrared detector, is sensitive to IR radiation. Based on the intensity of the IR radiation, it determines the temperature of the object surface and makes it visible to the human eye using a thermal image. This process is called thermography.

To make the IR radiation visible, the detector detects it, converts it into electrical signals and gives each signal a specific color, which is then shown on the thermal imaging camera's display. Basically, thermal imaging cameras translate wavelengths from the infrared spectrum into wavelengths (colors) that humans can perceive.

Contrary to a relatively common misunderstanding, you cannot use a thermal imaging camera to look into objects, but rather only make their surface temperature visible.