Infrared, known as I/R, is a form of light, which is almost invisible to the human eye. I/R is used with nightvision or other equipment, which is I/R sensitive. Almost all nightvision units are equipped with built in I/R. I/R is used in total darkness, or when there is too little light for the lightamplifier in the nightvision unit to work with, such as caves and warehouses etc.

In such a situation, the I/R is activated, and the nightvision unit now has a lightsource to amplify. You are now able to see as if you where in daylight, even if you are in total darkness.