Night vision is the ability to see in low light conditions. Whether bybiological or technological means, night vision is made possible by acombination of two approaches: sufficient spectral range, and sufficientintensity range. Humans have poor night vision compared to manyanimals, in part because the human eye lacks a tapetum lucidum. Contents [hide]1 Types of ranges o 1.1 Spectral range o 1.2 Intensity range2 Biological night vision3 Night vision technologies4 Night vision goggles5 Active infrared6 Laser range gated imaging7 Thermal vision8 Image intensifier9 Night vision devices10 Automotive night vision11 See also12 Patents13 References14 External linksTypes of rangesSpectral rangeNight-useful spectral range techniques can sense radiation that isinvisible to a human observer. Human vision is confined to a smallportion of the electromagnetic spectrum called visible light. Enhancedspectral range allows the viewer to take advantage of non-visiblesources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals can see using much moreof the infrared and/or ultraviolet spectrum than humans.
Intensity rangeSufficient intensity range is simply the ability to see with very smallquantities of light.Many animals have better night vision than humans do, the result of oneor more differences in the morphology and anatomy of their eyes. Theseinclude having a larger eyeball, a larger lens, a largeroptical aperture (the pupils may expand to the physical limit of theeyelids), more rods than cones (or rods exclusively) in the retina, anda tapetum lucidum.Enhanced intensity range is achieved via technological means throughthe use of an image intensifier, gain multiplication CCD, or other verylow-noise and high-sensitivity array of photodetectors.Biological night visionFor more details on this topic, see Adaptation (eye).In biological night vision, molecules of rhodopsin in the rods ofthe eye undergo a change in shape as they absorb light. Rhodopsin isthe chemical that allows night-vision, and is extremely sensitive to light.Exposed to a spectrum of light, the pigment immediately bleaches, and ittakes about 30 minutes to regenerate fully, but most ofthe adaptation occurs within the first five or ten minutes in the dark.Rhodopsin in the human rods is less sensitive to the longerred wavelengths of light, so traditionally many people use red light tohelp preserve night vision as it only slowly depletes the eyes rhodopsinstores in the rods and instead is viewed by the cones. Howeverthe USsubmarine force ceased using red lighting for night adaptationafter studies found little significant advantage of using low level red overlow level white lighting.Many animals have a tissue layer called the tapetum lucidum in the backof the eye that reflects light back through the retina, increasing theamount of light available for it to capture. This is found inmany nocturnal animals and some deep sea animals, and is the causeof eyeshine. Humans lack a tapetum lucidum.
Nocturnal mammals have rods with unique properties that makeenhanced night vision possible. The nuclear pattern of their rodschanges shortly after birth to become inverted. In contrast tocontemporary rods, inverted rods have heterochromatin in the center oftheir nuclei andeuchromatin and other transcription factors along theborder. In addition, the outer nuclear layer (ONL) in nocturnal mammalsis thick due to the millions of rods present to process the lower lightintensities of a few photons. Rather than being scattered, the light ispassed to each nucleus individually. In fact, an animals ability to see inlow light levels may be similar to what humans see when using first- orperhaps second-generation image intensifiers.Night vision technologiesFilm about the development of military night vision technologyNight vision technologies can be broadly divided into three maincategories:Image intensification Image intensification technologies work on the principle of magnifying the amount of received photons from various natural sources such as starlight or moonlight. Examples of such technologies include night glasses and low light cameras. Active illumination Active illumination technologies work on the principle of coupling imaging intensification technology with an active source of illumination in the near infrared (NIR) or shortwave infrared (SWIR) band. Examples of such technologies include low light cameras. Thermal imaging
Thermal imaging technologies work by detecting the temperature difference between the background and the foreground objects.Some organisms are able to sense a crude thermal image by means of special organs that function as bolometers. This allowsthermal infrared sensing in snakes, which functions by detection of therm HOW NIGHT VISION WORKS
GENERAL OVERVIEW:Click on the image to your right to watch the new "How Night Vision WorksVideo producted by ITT Industries. Night Vision technology consists of twomajor types: image intensification (light amplification) and thermalimaging (infrared).Most consumer night vision products are light amplifying devices. Lightamplification is less expensive than thermal, however, higher-end andmore effective night vision tubes can become more expensive. Lightamplification technology takes the small amount of light, such as moonlight or starlight, that is inthe surrounding area, and converts the light energy (scientists call it photons), into electricalenergy (electrons). These electrons pass through a thin disk thats about the size of a quarter andcontains over 10 million channels. As the electrons travel through and strike the walls of thechannels, thousands more electrons are released. These multiplied electrons then bounce off of aphosphor screen which converts the electrons back into photons and lets you see an impressivenighttime view even when its really dark.All image intensified night vision products on the market today have onething in common: they produce a green output image. Like the one yoursee to your right - >>. But thats where the similarities end.In the night vision world there are generations that reflect the level oftechnology used. The higher the generation, the more sophisticated thenight vision technology.Generation 0 - The earliest (1950s) night vision products were based on image coversion,rather than intensification. They required a source of invisible infrared (IR) light mounted on ornear the device to illuminate the target area.Generation 1 - The "starlight scopes" of the 1960s (Vietnam Era) have three image intensifiertubes connected in a series. These systems are larger and heavier than Gen 2 and Gen 3. TheGen 1 image is clear at the center but may be distorted around the edges. (Low-cost Gen 1imports are often mislabeGeneration 2 - The microchannel plate (MCP) electron multiplierprompted Gen 2 development in the 1970s. The "gain" provided by the MCP eliminated the needfor back-to-back tubes - thereby improving size and image quality. The MCP enableddevelopment of hand held and helmet mounted goggles.Generation 3 - Two major advancements characterized development of Gen 3 in the late 1970sand early 1980s: the gallium arsenide (GaAs) photocathode and the ion-barrier film on the MCP.The GaAs photocathode enabled detection of objects at greater distances under much darkerconditions. The ion-barrier film increased the operational life of the tube from 2000 hours (Gen 2)
to 10,000 (Gen 3), as demonstrated by actual testing and not extrapolation.Generation 4 - Myth vs. FactSome say that generation (Gen) 4 is the most advanced night vision you can buy. This is not thecase. To dispel this myth, lets start with the basics. There are four Generations of night vision;however, they are Gen 0-3, not Gen 1-4. Historically, the U.S. Army has defined each Generationof night vision. In the late 90s the Army did define Gen 4 as the removal of the ion barrier filmcreating a "filmless" tube. This new advancement was to reduce halos while increasing sensitivity,signal-to-noise ratio (SNR) and resolution, for overall improved performance. While performancewas improved, the lack of an ion barrier in Gen 4 tubes led to high failure rates, ultimatelyleading the U.S. Army to recant the existence of Gen 4 definition. Recognizing the high failurerates of Gen 4 tubes, ITT chose to improve upon the existing Gen 3 technology and create a"thin-filmed" tube. By keeping the protective ion barrier, but greatly reducing its thickness, ITTwas able to maintain the reliability of Gen 3 while—at the same time—delivering on the Armysperformance requirements intended for Gen 4. This innovation resulted in the production of theGen 3 thin-filmed tube, which is now the highest performing Gen 3 tube available. Not long after,the gated power supply was added and the PINNACLE® tube was born. The Generation 3PINNACLE® tube is the most advanced night vision manufactured to date.led as a higher generation.