Night-vision devices are commonly used among military forces.
Night-vision devices help individuals see in the dark through an optical instrument. Humans have limited night vision compared to many animals because the human eye has no tapetum lucidum -- a layer of tissue within or behind the retina that reflects light through the retina to increase light. Many night-vision devices rely on image intensifiers or thermal imaging as their main source of technology to generate images even in complete darkness.
History
Night-vision devices were first used during World War II. The German military used "Generation 0" night-vision devices as early as 1939. The "Vampir" man-portable systems were paired with Sturmgewehr 44 infantry rifles. Sniper scopes incorporating M1 and M3 infrared light detectors were used in WWII and the Korean War. As the technology evolved through several generations, so did the devices' performance, while their price came down.
Function
The objective lens gathers ambient light, either moonlight, starlight, or infrared light, before the light enters an image intensifier tube (IIT). Light is made of photons, which transform into electrons as they come in contact with the photocathode within the IIT. The electrons are then combined with a phosphorus screen that changes the electrons back into a visible light that can be seen by the human eye. The image that the human sees is a green-hued re-creation of the amplified scene.
Warning
The objectives lens of a night-vision device should never be exposed to daylight. Aiming the active unit at bright lights, such as fires, headlamps, or lights, can damage the image intensifier tube.
Tags: image intensifier, image intensifier tube, infrared light, intensifier tube, night-vision devices, Night-vision devices
