What is Infrared?

Infrared radiation is also known as heat radiation.  Specialized detectors can passively detect signals in the infrared wavelengths.  Night Vision Goggles (NVGs) detect signals in the Near Infrared range (0.75 to 1.4 micrometers) and are also known as "image enhancement systems" as they can amplify very low amounts of existing light.  Security cameras with night vision capability use LEDs that emit infrared radiation in these wavelengths to provide better views of what the camera is looking at. 

Thermal imaging systems, such as those in use by the military and fire departments, are used to track body heat.  Forward-looking Infrared (FLIR) cameras use this type of infrared technology, as it does not need a source such as the sun, infrared illuminator, or moon.  Thermal imaging systems operate in the Far Infrared spectrum, which have wavelengths of 8 to 15 micrometers.