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Night vision video devices use electronics and chemistry to produce images in low lighting conditions. The devices can be packaged as, or built into, produces such as goggles, binoculars, and weapon sights. There are a wide range of technologies, with similarly wide ranging prices.
Night vision video works through a tube set-up that somewhat resembles a telescope. What light is available at night time passes through a lens at the front into a photocathode tube. This changes the photons, which make up the light, into electrons. These electrons are then electrically and chemically amplified and then beamed onto a green phosphorus tube. This turns them back into visible photons. As the process reduces the light to a single color, green is used, as it is the easiest color for the human eye to detect contrast.
Different types of video devices are generally classified into four generations, with generation 0 being the original and now obsolete World War II devices, and the later generations usually costing more. First generation devices have notable limitations, such as a high-pitched noise when in use, some blurring around the edge of the image, and a glow that persists for some time after the device is switched off.
Second generation night vision video devices use an additional component, known as a micro-channel plate, to further amplify the electrons. This increases the brightness and sharpness of the image. There are a range of second generation devices available, with the more sophisticated ones used by law enforcement officials.
Third generation night vision video devices make two further changes. The photocathode tube is made of gallium arsenide, which allows a clearer resolution. A special film helps extend the life of the tube, in some cases doubling its expected lifespan. Third generation devices are usually considered military standard and, although available to consumers, have a high price tag.
Fourth generation night vision video devices have an automated power supply system that allows the photocathode to instantly react to changes in light conditions. There are also other technical improvements that improve image quality, and extend the distance over which the devices work. Such devices often cost in the region of $5,000.
People may need to check the legal situation in their jurisdiction regarding night vision video devices. Generally, there are no restrictions in the United States. Some European countries restrict either the possession of some devices, or their use in certain situations, usually involving mounting the equipment on firearms.