Night vision goggles
From Free net encyclopedia
(Difference between revisions)
Current revision
Image:Nightvision.jpg Night vision goggles (NVG) are a type of optical instrument that allows one to see in the dark. They are most often used by the military.
There are three common types of night vision goggles:
- Passive night vision goggles— these pick up any light in the given area and amplify it several thousand times using an image intensifier. This works by the photoelectric effect. As a photon collides with a detector plate, the metal ejects several electrons that are then amplified into a cascade of electrons that light up a phosphor screen. Often a dim star in the sky is enough to illuminate an entire field. This type is commonly used for war reporting, tinting the picture green. The color green is chosen because the human eye is most sensitive and able to discern the most shades in green.
- Active night vision goggles— these project infrared light (the same type used by a remote control), and produce an image from the light reflected back. These goggles may require an image enhancer to amplify the light. This feature is commonly found on home video cameras, as it suits most consumer's needs for seeing in the dark. Pointing a television remote control at this type of system produces a glaringly bright image.
- Heat-sensing or infrared goggles— these show anything that emits normal heat radiation in the given area.
There are currently goggles that combine both of these technologies to create images that are almost as clear as day. In addition to goggles, night vision technology is also used in rifle scopes, security cameras, binoculars, etc.
[edit]
See also
he:אמצעי לראיית לילה pl:Noktowizor ru:Прибор ночного видения sv:Nattkikare