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Digital night vision devices, like other passive optical night vision technologies, allow a viewer to perceive images in near-total darkness. They amplify low levels of ambient light to create a usable image, as opposed to other night vision devices such as thermal imagers and forward-looking infrared (FLIR), which rely on infrared light for illumination. Scopes, binoculars, monocles and cameras are made with digital night vision technology, and there is a large selection available to consumers.
Night vision devices have been used primarily by military forces and have been designed with military applications in mind. The earliest night vision devices, introduced during World War II, were infrared scopes requiring the use of infrared lights that could could give away the user's position. In Vietnam, United States forces used the first passive night vision scopes that required no additional light source. Innovations since then have created generations of optical devices with improved light amplification, image quality and noise reduction. Digital night vision devices do not match the quality of the latest night vision sensors but are cheaper to produce, making good quality light amplification available at a fraction of the cost.
Standard optical night vision devices amplify light projected through a photocathode and intensifier tube, then project the amplified image onto a phosphor screen in front of the eyepiece. In a digital night vision device, light is instead processed in a charged coupling device before projecting onto a liquid crystal display (LCD). Because the glow from the LCD can expose the viewer’s position, many of these devices are fitted with eyepieces instead of screens.
While the latest generation of optical night vision devices do offer superior image quality and can create usable images in lower light, digital devices do have some advantages. First among these is cost; the price of the latest optical models is prohibitive for most consumers and even many law enforcement agencies, but digital devices cost less than first-generation models. Like their optical cousins, digital devices do not work in total darkness, but most are equipped with small infrared lights that provide some illumination.
Many digital devices come with multiple display settings, allowing the viewer to see the image in green, red or gray. Green provides the sharpest quality, red maintains the viewer’s night vision, and gray creates the least display light. Digital devices also have the further advantage of versatility, because unlike optical devices, digital night vision devices such as scopes and binoculars can be used normally in daylight without risking damage to the item.