Thermographic inspection refers to the nondestructive testing of parts, through the imaging of the thermal patterns at the object's surface. Thermal imaging is an example of infrared imaging science.
Thermographic cameras usually detect radiation in the long-infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nanometers) and produce images of that radiation, called thermograms.
Since infrared radiation is emitted by all objects with a temperature above absolute zero, thermography makes it possible to see one's environment with or without visible illumination.
The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature.