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Snippet from Wikipedia: Night vision

Night vision is the ability to see in low-light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range. Humans have poor night vision compared to many animals, in part because the human eye lacks a tapetum lucidum.

http://www.opticsplanet.com/reviews/reviews-bushnell-night-vision-2x24-night-watch-260224.html

ATN MARS4x-3 3rd Generation Night Vision Rifle Scope 4x 74mm Illuminated Red Mil-Dot Reticle with Integral Weaver-Style Mount Matte

$3,088.71

Product Information

The ATN MARS Night Vision Rifle Scope represents the absolute latest in the world of night vision equipment. Similar to all ATN scopes the, ATN MARS features only the purest grades of heavy glass and computer-aided optical designs to create multi-element, high-speed, multi-coated lenses for ultra-fast light transmission and resolution beyond current military standards. 

Technical Information: ATN MARS Night Vision Rifle Scope Generation: 3 Visual Magnification: 4x Objective lens(mm): 74 Power Supply: 1 CR123A Length: 9-3/10“ Weight: 2.9 lbs

A night vision device works by taking existing light, whether infra-red, moonlight or starlight, and changing it into visible light. This visible light is amplified to the point where it may be viewed in the device's eyepiece. The process, where the existing light (made up of photons) moves through a photocathode tube, changes to electrons that are electro-chemically amplified and then driven against a phosphorus screen to return them to visible light, gives the final image a green hue. Night vision devices are referred to by what “Generation” they are. Each generation has a different type of intensifier tube.

1st Generation amplifies light several thousand times. The image will generally be sharp in the center and slightly blurry around the edges, allowing wildlife observation or for general security use. A 1st generation will hum when on, it may continue to glow for some time after it is turned off, but is the least expensive type of night vision device. Recognition of a deer on a cloudy night is possible at 75 yards using a 1st generation unit.

2nd Generation has an extra process because a micro-channel plate is directly behind the photocathode tube and amplifies the light many times more than a 1st generation. The image is sharper and brighter. Recognition of a deer on a cloudy night is possible at 100 yards using a 2nd generation unit.

CGT IIT Generation type of Image Intensifier tubes are engineered for significantly enhanced performance over current 2nd generation IITs. The CGT IIT is a Multi-Alkali compact 18mm format MCP Image Intensifier. Highlights of the CGT specifications are typical SNR of 16-22 and resolution of 45-54 lp/mm. CGT IITs are sensitive in a wide spectral band and thus provide good contrast in all scene circumstances.

HPT IIT Generation tubes are an upgrade of the CGT Generation tube. They are a Multi-Alkali compact 18mm format MCP Image Intensifier. The HPT tube increases sensitivity, resolution, Signal-to-Noise Ratio (SNR), and the Modulation Transfer Function (MTF). These improvements produce an exceptional image clarity and brightness. Most HPT specifications typically are equivalent to standard 3rd generation. Highlights of the HPT specifications are the typical SNR of 22 and resolution of 64 lp/mm.

3rd Generation has a chemical added to the photocathode and a film is added to increase tube life. These changes give excellent low light performance. Recognition of a deer on a cloudy night is possible at 150 yards using a 3rd generation unit.

4th Generation does not use the film in the 3rd generation but uses a radically different way in which power is supplied to the unit. Image resolution is increased and there is a significant decrease in interference from bright light sources. Range is increased. The US Military does not use the 4th generation designation. These devices are referred to as “Filmless & Gated”. Recognition of a deer on a cloudy night is possible at 200 yards using a 4th generation unit.

http://www.midwayusa.com/product/259625/atn-mars4x-3-3rd-generation-night-vision-rifle-scope-4x-74mm-illuminated-red-mil-dot-reticle-with-integral-weaver-style-mount-matte

soldiers pictured during the 2003 Iraq War seen through an image intensifier]]

Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range. Humans have poor night vision compared to many animals, in part because the human eye lacks a tapetum lucidum.<ref>

</ref>

Types of ranges

Spectral range

Night-useful spectral range techniques can sense radiation that is invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals can see using much more of the infrared and/or ultraviolet spectrum than humans.

Intensity range

Sufficient intensity range is simply the ability to see with very small quantities of light.<ref>

</ref>

Many animals have better night vision than humans do, the result of one or more differences in the morphology and anatomy of their eyes. These include having a larger eyeball, a larger lens, a larger optical aperture (the pupils may expand to the physical limit of the eyelids), more rods than cones (or rods exclusively) in the retina, and a tapetum lucidum.

Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors.

Biological night vision

In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is less sensitive to the longer red wavelengths of light, so traditionally many people use red light to help preserve night vision as it only slowly depletes the eye's rhodopsin stores in the rods and instead is viewed by the cones. However the US submarine force ceased using red lighting for night adaptation after studies found little significant advantage of using low level red over low level white lighting.<ref>

}}</ref> <ref>

}}</ref> Many animals have a tissue layer called the tapetum lucidum in the back of the eye that reflects light back through the retina, increasing the amount of light available for it to capture. This is found in many nocturnal animals and some deep sea animals, and is the cause of eyeshine. Humans lack a tapetum lucidum.

Nocturnal mammals have rods with unique properties that make enhanced night vision possible. The nuclear pattern of their rods changes shortly after birth to become inverted. In contrast to contemporary rods, inverted rods have heterochromatin in the center of their nuclei and euchromatin and other transcription factors along the border. In addition, the outer nuclear layer (ONL) in nocturnal mammals is thick due to the millions of rods present to process the lower light intensities of a few photons. Rather than being scattered, the light is passed to each nucleus individually.<ref>

</ref> In fact, an animal's ability to see in low light levels may be similar to what humans see when using first- or perhaps second-generation image intensifiers.

Night vision technologies

File:Night vision.ogv

Night vision technologies can be broadly divided into three main categories: ;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 allows thermal infrared sensing in snakes, which functions by detection of thermal radiation.

Night vision goggles

Night glasses are single or binocular with a large diameter objective. Large lenses can gather and concentrate light, thus intensifying light with purely optical means and enabling the user to see better in the dark than with the naked eye alone. Often night glasses also have a fairly large exit pupil of 7&nbsp;mm or more to let all gathered light into the user's eye. However, many people cannot take advantage of this because of the limited dilation of the human pupil. To overcome this, soldiers were sometimes issued atropine eye drops to dilate pupils.

Before the introduction of image intensifiers, night glasses were the only method of night vision, and thus were widely utilized, especially at sea. Second World War era night glasses usually had a lens diameter of 56&nbsp;mm or more with magnification of seven or eight. Major drawbacks of night glasses are their large size and weight.

Active infrared

Active infrared night-vision combines infrared illumination of spectral range 700–1,000&nbsp;nm (just below the visible spectrum of the human eye) with CCD cameras sensitive to this light. The resulting scene, which is apparently dark to a human observer, appears as a monochrome image on a normal display device.<ref>CCTV Information</ref>

Because active infrared night-vision systems can incorporate illuminators that produce high levels of infrared light, the resulting images are typically higher resolution than other night-vision technologies.<ref>

</ref><ref>Extreme CCTV Surveillance Systems</ref> Active infrared night vision is now commonly found in commercial, residential and government security applications, where it enables effective night time imaging under low-light conditions. However, since active infrared light can be detected by night-vision goggles, there can be a risk of giving away position in tactical military operations.

Laser range gated imaging

Laser range gated imaging is another form of active night vision which utilizes a high powered pulsed light source for illumination and imaging. Range gating is a technique which controls the laser pulses in conjunction with the shutter speed of the camera's detectors.<ref>

</ref> Gated imaging technology can be divided into single shot, where the detector captures the image from a single light pulse, and multi-shot, where the detector integrates the light pulses from multiple shots to form an image.

One of the key advantages of this technique is the ability to perform target recognition as opposed to detection with thermal imaging.

Thermal vision

Thermal imaging cameras are excellent tools for night vision. They detect thermal radiation and do not need a source of illumination. They produce an image in the darkest of nights and can see through light fog, rain and smoke. Thermal imaging cameras make small temperature differences visible. Thermal imaging cameras are widely used to complement new or existing security networks, and for night vision on aircraft, where they are commonly referred to as “FLIR” (for “forward-looking infrared”.)

Image intensifier

The image intensifier is a vacuum-tube based device that converts invisible light from an image to visible light so that a dimly lit scene can be viewed by a camera or the naked eye. While many believe the light is “amplified,” it is not. When light strikes a charged photocathode plate, electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the light that strikes the photocathode, and is on a frequency that the human eye can see. This is much like a CRT television, but instead of color guns the photocathode does the emitting.

The image is said to become “intensified” because the output visible light is brighter than the incoming IR light, and this effect directly relates to the difference in passive and active night vision goggles. Currently, the most popular image intensifier is the drop-in ANVIS module, though many other models and sizes are available at the market.

Night vision devices

A night vision device (NVD) is a device comprising an image intensifier tube in a rigid casing, commonly used by military forces. Lately, night vision technology has become more widely available for civilian use. For example, enhanced vision systems (EVS) have become available for aircraft to help pilots with situational awareness and avoid accidents. These systems are included in the latest avionics packages from manufacturers such as Cirrus and Cessna.

A specific type of NVD, the night vision goggle (NVG) is a night vision device with dual eyepieces. The device can utilize either one intensifier tube with the same image sent to both eyes, or a separate image intensifier tube for each eye. Night vision goggle combined with magnification lenses constitutes night vision binoculars. Other types include monocular night vision devices with only one eyepiece which may be mounted to firearms as night sights. NVG and EVS technologies are becoming more popular products for helicopter operations to improve safety. The NTSB is considering EVS as recommended equipment for safety features.

Automotive night vision

An automotive night vision system is a night vision system used to improve a vehicle driver's perception and seeing distance in darkness or poor weather. Such systems typically use infrared cameras, sometimes combined with active illumination techniques, to collect information that is then displayed to the driver. Such systems are currently offered as optional equipment on certain premium vehicles.

See also

Patents

References

<!– Please do not add links here that do not conform to the guidance at EL else they will be removed without discussion.–>

Infrared imaging Eye


soldiers pictured during the 2003 Iraq War seen through an image intensifier]]

Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range. Humans have poor night vision compared to many animals, in part because the human eye lacks a tapetum lucidum.<ref>

</ref>

Types of ranges

Spectral range

Night-useful spectral range techniques can sense radiation that is invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals can see using much more of the infrared and/or ultraviolet spectrum than humans.

Intensity range

Sufficient intensity range is simply the ability to see with very small quantities of light.<ref>

</ref>

Many animals have better night vision than humans do, the result of one or more differences in the morphology and anatomy of their eyes. These include having a larger eyeball, a larger lens, a larger optical aperture (the pupils may expand to the physical limit of the eyelids), more rods than cones (or rods exclusively) in the retina, and a tapetum lucidum.

Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors.

Biological night vision

In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is less sensitive to the longer red wavelengths of light, so traditionally many people use red light to help preserve night vision as it only slowly depletes the eye's rhodopsin stores in the rods and instead is viewed by the cones. However the US submarine force ceased using red lighting for night adaptation after studies found little significant advantage of using low level red over low level white lighting.<ref>

}}</ref> <ref>

}}</ref> Many animals have a tissue layer called the tapetum lucidum in the back of the eye that reflects light back through the retina, increasing the amount of light available for it to capture. This is found in many nocturnal animals and some deep sea animals, and is the cause of eyeshine. Humans lack a tapetum lucidum.

Nocturnal mammals have rods with unique properties that make enhanced night vision possible. The nuclear pattern of their rods changes shortly after birth to become inverted. In contrast to contemporary rods, inverted rods have heterochromatin in the center of their nuclei and euchromatin and other transcription factors along the border. In addition, the outer nuclear layer (ONL) in nocturnal mammals is thick due to the millions of rods present to process the lower light intensities of a few photons. Rather than being scattered, the light is passed to each nucleus individually.<ref>

</ref> In fact, an animal's ability to see in low light levels may be similar to what humans see when using first- or perhaps second-generation image intensifiers.

Night vision technologies

File:Night vision.ogv

Night vision technologies can be broadly divided into three main categories: ;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 allows thermal infrared sensing in snakes, which functions by detection of thermal radiation.

Night vision goggles

Night glasses are single or binocular with a large diameter objective. Large lenses can gather and concentrate light, thus intensifying light with purely optical means and enabling the user to see better in the dark than with the naked eye alone. Often night glasses also have a fairly large exit pupil of 7&nbsp;mm or more to let all gathered light into the user's eye. However, many people cannot take advantage of this because of the limited dilation of the human pupil. To overcome this, soldiers were sometimes issued atropine eye drops to dilate pupils.

Before the introduction of image intensifiers, night glasses were the only method of night vision, and thus were widely utilized, especially at sea. Second World War era night glasses usually had a lens diameter of 56&nbsp;mm or more with magnification of seven or eight. Major drawbacks of night glasses are their large size and weight.

Active infrared

Active infrared night-vision combines infrared illumination of spectral range 700–1,000&nbsp;nm (just below the visible spectrum of the human eye) with CCD cameras sensitive to this light. The resulting scene, which is apparently dark to a human observer, appears as a monochrome image on a normal display device.<ref>CCTV Information</ref>

Because active infrared night-vision systems can incorporate illuminators that produce high levels of infrared light, the resulting images are typically higher resolution than other night-vision technologies.<ref>

</ref><ref>Extreme CCTV Surveillance Systems</ref> Active infrared night vision is now commonly found in commercial, residential and government security applications, where it enables effective night time imaging under low-light conditions. However, since active infrared light can be detected by night-vision goggles, there can be a risk of giving away position in tactical military operations.

Laser range gated imaging

Laser range gated imaging is another form of active night vision which utilizes a high powered pulsed light source for illumination and imaging. Range gating is a technique which controls the laser pulses in conjunction with the shutter speed of the camera's detectors.<ref>

</ref> Gated imaging technology can be divided into single shot, where the detector captures the image from a single light pulse, and multi-shot, where the detector integrates the light pulses from multiple shots to form an image.

One of the key advantages of this technique is the ability to perform target recognition as opposed to detection with thermal imaging.

Thermal vision

Thermal imaging cameras are excellent tools for night vision. They detect thermal radiation and do not need a source of illumination. They produce an image in the darkest of nights and can see through light fog, rain and smoke. Thermal imaging cameras make small temperature differences visible. Thermal imaging cameras are widely used to complement new or existing security networks, and for night vision on aircraft, where they are commonly referred to as “FLIR” (for “forward-looking infrared”.)

Image intensifier

The image intensifier is a vacuum-tube based device that converts invisible light from an image to visible light so that a dimly lit scene can be viewed by a camera or the naked eye. While many believe the light is “amplified,” it is not. When light strikes a charged photocathode plate, electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the light that strikes the photocathode, and is on a frequency that the human eye can see. This is much like a CRT television, but instead of color guns the photocathode does the emitting.

The image is said to become “intensified” because the output visible light is brighter than the incoming IR light, and this effect directly relates to the difference in passive and active night vision goggles. Currently, the most popular image intensifier is the drop-in ANVIS module, though many other models and sizes are available at the market.

Night vision devices

A night vision device (NVD) is a device comprising an image intensifier tube in a rigid casing, commonly used by military forces. Lately, night vision technology has become more widely available for civilian use. For example, enhanced vision systems (EVS) have become available for aircraft to help pilots with situational awareness and avoid accidents. These systems are included in the latest avionics packages from manufacturers such as Cirrus and Cessna.

A specific type of NVD, the night vision goggle (NVG) is a night vision device with dual eyepieces. The device can utilize either one intensifier tube with the same image sent to both eyes, or a separate image intensifier tube for each eye. Night vision goggle combined with magnification lenses constitutes night vision binoculars. Other types include monocular night vision devices with only one eyepiece which may be mounted to firearms as night sights. NVG and EVS technologies are becoming more popular products for helicopter operations to improve safety. The NTSB is considering EVS as recommended equipment for safety features.

Automotive night vision

An automotive night vision system is a night vision system used to improve a vehicle driver's perception and seeing distance in darkness or poor weather. Such systems typically use infrared cameras, sometimes combined with active illumination techniques, to collect information that is then displayed to the driver. Such systems are currently offered as optional equipment on certain premium vehicles.

See also

Patents

References

External links

<!– Please do not add links here that do not conform to the guidance at EL else they will be removed without discussion.–>

Infrared imaging Eye

night_vision.txt · Last modified: 2020/08/11 09:48 (external edit)