Night vision device

A U.S. Army aviator uses a pair of helmet-mounted AN/AVS-6 vision goggles. The effect on the natural night vision of the eye is evident
A standard telescopic sight augmented with a night vision device in front. Note that in addition to the image intensifier the NVD gathers much more light via its much larger aperture
A 1PN51-2 night vision reticle with markings for range estimation

A Night Vision Device (NVD) is an optoelectronic device that allows images to be produced in levels of light approaching total darkness. The image may be a conversion to visible light of both visible light and near-infrared, while by convention detection of thermal infrared is denoted thermal imaging. The image produced is typically monochrome, e.g. shades of green. NVDs are most often used by the military and law enforcement agencies, but are available to civilian users. The term usually refers to a complete unit, including an image intensifier tube, a protective and generally water-resistant housing, and some type of mounting system. Many NVDs also include optical components such as a sacrificial lens,[1] or telescopic lenses or mirrors. An NVD may have an IR illuminator, making it an active as opposed to passive night vision device.

Night vision devices were first used in World War II, and came into wide use during the Vietnam War.[2][3] The technology has evolved greatly since their introduction, leading to several "generations" of night vision equipment with performance increasing and price decreasing. Consequently, they are available for a wide range of applications, e.g. for gunners, drivers and aviators. Another term is "night optical/observation device" or NOD.

The USA

Generations

The classification below was initially introduced by the US manufacturers through the US government. Other manufacturers do not abide by it.

Generation 0

The first practical commercial night vision device offered on the market was developed by Dr. Vladimir K. Zworykin working for the Radio Corporation of America[4] and was intended for civilian use. At that time infra-red was commonly called black light, a term later restricted to ultraviolet. It was not a success due to its size and cost.[5]

The first military night vision devices were introduced by the German army as early as 1939. The first devices were being developed by AEG starting in 1935. In mid-1943, first tests with infrared night-vision (Nacht Jager) devices and telescopic rangefinders mounted on Panther started. Two different arrangements / solutions were created and used on Panther tanks. Solution A - Sperber FG 1250 (Sparrow Hawk), with range up to 600m, was made up of one 30 cm infrared searchlight and image converter operated by the commander. This was matched by an earlier experimental Russian version dubbed the PAU-2 and was field tested in 1942. From late 1944 to March 1945, some Panzerkampfwagen V Panther Ausf G (and other variants) mounted with FG 1250, were successfully tested. By the end of World War II, the German Reich had equipped approximately 50 (or 63) Panther tanks, which saw combat on both the Eastern and Western Fronts. The "Vampir" man-portable system for infantrymen was being used with Sturmgewehr 44 assault rifles.[6] Parallel development of night vision systems occurred in the USA. The M1 and M3 infrared night sighting devices, also known as the "sniperscope" or "snooperscope", were introduced by the US Army in World War II,[7] and also used in the Korean War, to assist snipers.[2] They were active devices, using a large infrared light source to illuminate targets. Their image intensifier tubes function using an anode and an S-1 photocathode, made primarily of silver, caesium, and oxygen and an electrostatic inversion with electron acceleration were used to achieve gain.[8]

Examples

Generation 1 (GEN I)

An M16A1 rifle fitted with the AN/PVS-2 Starlight scope.

First generation passive devices, introduced during the Vietnam War, were an adaptation of earlier active GEN 0 technology, and rely on ambient light instead of an infrared light source. Using an S-20 photocathode, their image intensifiers produce a light amplification of around 1,000×,[9] but are quite bulky and require moonlight to function properly.

Examples:

Generation 2 (GEN II)

A cut-open and depotted AN/PVS-5 showing the components of a night vision device. This device was manufactured in 2nd Generation (5A to 5C) and 3rd Generation (5D)

Second generation devices feature an improved image-intensifier tube utilizing micro-channel plate (MCP)[10] with an S-25 photocathode,[8] resulting in a much brighter image, especially around the edges of the lens. This leads to increased illumination in low ambient light environments, such as moonless nights. Light amplification is around 20,000×.[9] Also improved were image resolution and reliability.

Examples:

Later advancements in GEN II technology brought the tactical characteristics of "GEN II+" devices (equipped with better optics, SUPERGEN tubes, improved resolution and better signal-to-noise ratios)[14][15] into the range of GEN III devices, which has complicated comparisons.

Generation 3 (GEN III)

An early development version of the AN/PVS-7 goggle.

Third generation night vision systems maintain the MCP from Gen II, but now use a photocathode made with gallium arsenide, which further improves image resolution. In addition, the MCP is coated with an ion barrier film for increased tube life. However, the ion barrier causes fewer electrons to pass through, diminishing the improvement expected from the Gallium arsenide photocathode. Because of the ion barrier, the "halo" effect around bright spots or light sources is larger too. The light amplification is also improved to around 30,000–50,000×.[9] Power consumption is higher than GEN II tubes.

Examples:

Generation 3+ (GEN III OMNI IV - VII)

"Diagram of an image intensifier."
Gereration II, III, and IV devices use a microchannel plate for amplification. Photons from a dimly lit source enter the objective lens (on the left) and strike the photocathode (gray plate). The photocathode (which is negatively biased) releases electrons which are accelerated to the higher-voltage microchannel plate (red). Each electron causes multiple electrons to be released from the microchannel plate. The electrons are drawn to the higher-voltage phosphor screen (green). Electrons that strike the phosphor screen cause the phosphor to produce photons of light viewable through the eyepiece lenses.

U.S. Army Night Vision and Electronic Sensors Directorate (NVESD) is part of the governing body that dictates the name of the generation of night vision technologies. Although the recent increased performance associated with the GEN-III OMNI-VI - VII components is impressive, the U.S. Army has not yet authorized the use of the name GEN-IV for these components.

GEN-III OMNI-V - VII devices can differ from standard Generation 3 in one or both of two important ways. First, an automatic gated power supply system regulates the photocathode voltage, allowing the NVD to instantaneously adapt to changing light conditions.[19] The second is a removed or greatly thinned ion barrier, which decreases the number of electrons that are usually rejected by the Standard GEN III MCP, hence resulting in less image noise and the ability to operate with a luminous sensitivity at 2,850 K of only 700, compared to operating with a luminous sensitivity of at least 1,800 for GEN III image intensifiers.[20] The disadvantage to a thin or removed ion barrier is the overall decrease in tube life from a theoretical 20,000 hrs mean time to failure (MTTF) for Gen III type, to 15,000 hrs MTTF for GEN IV type. However, this is largely negated by the low number of image intensifier tubes that reach 15,000 hrs of operation before replacement.

While the consumer market classifies this type of system as Generation 4, the United States military describes these systems as Generation 3 Autogated tubes (GEN-III OMNI-VII). Moreover, as autogating power supplies can now be added to any previous generation of night vision, "autogating" capability does not automatically class the devices as a GEN-III OMNI-VII. Any postnominals appearing after a Generation type (i.e., Gen II +, Gen III +) do not change the generation type of the device, but instead indicates an advancement(s) over the original specification's requirements.[21]

Examples:

Auto-gating

The ATG function was designed to improve the BSP feature to be faster and to keep the best resolution and contrast at all times. It is particularly suitable for Aviator’s Night Vision goggles, operations in urban areas or for special operations. ATG is a unique feature that operates constantly, electronically reducing the “duty cycle” of the photocathode voltage by very rapidly switching the voltage on and off. This maintains the optimum performance of the I² tube, continuously revealing mission critical details, safeguarding the I² tube from additional damage and protecting the user from temporary blindness.

The benefits of ATG can easily be seen not only during day-night-day transitions, but also under dynamic lighting conditions when rapidly changing from low light to high light conditions (above 1 lx), such as sudden illumination of dark room. A typical advantage of ATG is best felt when using a weapon sight which experiences a flame burst during shooting (see figures below showing pictures taken at the impact zone of a dropped bomb). ATG would reduce the temporary blindness that a standard BSP tube would introduce, allowing them to continuously maintain “eyes on target”.

ATG provides added safety for pilots when flying at low altitudes, and especially during takeoffs and landings. Pilots operating with night vision goggles are constantly subjected to dynamic light conditions when artificial light sources, such as from cities, interfere with their navigation by producing large halos that obstruct their field of view.

Figure of Merit

In the late 1990s, innovations in photocathode technology significantly increased the signal-to-noise ratio, with newly developed tubes starting to surpass the performance of Gen 3 tubes.

By 2001, the United States federal government concluded that a tube’s “Generation” was not a determinant factor of a tube’s global performance, making the term “Generation” irrelevant in determining the performance of an Image Intensifier Tube, and therefore eliminated the term as a basis of export regulations.

Though image intensification technology employed by different manufacturers varies, from the tactical point of view a night vision system is an optical device that enables vision at low light. The US government itself has recognized the fact that technology itself makes little difference as long as an operator can see clearly at night. Consequently, the United States bases export regulations not on the generations, but on a calculated factor called figure of merit (FOM). The method of FOM calculation and its implications for export are briefly described in a National Defense University document called “The NATO Response Force”[23] authored by Jeffrey P. Bialos, the Executive Director of the Transatlantic Security and Industry Program at the Johns Hopkins University and Stuart L. Koehl, a Fellow at the Center for Transatlantic Relations of the same university.

… beginning in 2001, the U.S. implemented a new figure of merit (FOM) system for determining the release of night vision technology. FOM is an abstract measure of image tube performance, derived from the number of line pairs per millimeter multiplied by the tube's signal-to-noise ratio.

US-made tubes with a FOM greater than 1,400 are not exportable outside the US; however, the Defense Technology Security Administration (DTSA) can waive that policy on a case-by-case basis.

Other technologies

A U.S. airman tests panoramic night vision goggles in March 2006.

The United States Air Force experimented with panoramic night vision goggles (PNVGs) which double the user's field of view to around 95 degrees by using four 16 mm image intensifier tubes, rather than the more standard two 18 mm tubes. They are in service with A-10 Thunderbolt II, MC-130 Combat Talon and AC-130U Spooky aircrew.[24]

The AN/PSQ-20, manufactured by ITT (also known as the Enhanced Night Vision Goggle, ENVG), seeks to combine thermal imaging with image intensification, as does the Northrop Grumman Fused Multispectral Weapon Sight.[25][26]

A new technology is being introduced to the consumer market currently. It was first shown at the 2012 Shot Show in Las Vegas, NV by Armasight.[27] This technology called Ceramic Optical Ruggedized Engine (CORE) produces a higher performance Gen 1 tubes. The main difference between CORE tubes and standard Gen 1 tubes is introduction of a ceramic plate instead of a glass one. This plate is produced of specially formulated ceramic and metal alloys. Edge distortion is improved, photo sensitivity is increased and the resolution can get as high as 60 lp/mm. CORE is still considered Gen 1 as it does not utilize a micro channel plate.[28]

Scientists at the University of Michigan have developed a contact lens that can act as night vision device. The lens has a thin strip of graphene between layers of glass that reacts to photons to make dark images look brighter. Current prototypes only absorb 2.3 percent of light, so the percentage of light pickup has to rise before the lens can be viable. The graphene technology can be expanded into other uses like car windshields to increase night driving abilities. The U.S. Army is interested in the technology to potentially replace night vision goggles.[29]

The Soviet Union and Russia

Active night vision scope NSP-2 mounted on a AKML
NSPU (1PN34) 3.5x night vision scope mounted on a AKS-74U
1PN93-2 night vision scope mounted on a RPG-7D3

The Soviet Union and after it the Russian Federation has developed a range of night vision devices. Models used after 1960 by the Russian/Soviet Army are designated 1PNxx (Russian: 1ПНxx) where 1PN is the GRAU index of night vision devices. The PN stands for Nochnoy Pritsel (Russian: Ночной прицел) meaning night sight and the xx is the model number. Different models introduced around the same time use the same type of batteries and mechanism for mounting on the weapon. The multi-weapon models have replaceable elevation scales, with one scale for the ballistic arc of each supported weapon. The weapons supported include the AK-family, sniper rifles, light machine guns and hand-held grenade launchers. The latest Russian Federation designed and manufactured Generation 3 IIT (FOM ≤ 2300) are equal to, or have better performance characteristics, than current US military issue IIT systems.

The Russian army has also contracted the development of and fielded a series of so-called counter-sniper night sights. The counter-sniper night sight is an active system that uses laser pulses from a laser diode to detect reflections from the focal elements of enemy optical systems and estimate their range. The vendor claims that this system is unparalleled:[35]

Legality

Certain countries (e.g. Hungary and other European Union members) regulate possession and or use of night-vision devices. German law forbids such devices if their purpose is to be mounted on firearms.[36]

Belgian firearms legislation forbids any nightvision devices if they can be mounted on a firearm, even if not mounted they are considered illegal. [37]

In the Netherlands, although being a full member of the European Union, the possession of night vision devices is not regulated, nor is it forbidden to use them mounted on firearms. The usage of night vision equipment for nighttime hunting (weapon mounted) is only allowed with a special permit in certain areas (the Veluwe) for hunting wild boar.

In Iceland, the use of night-vision devices for hunting is prohibited, while there are no restrictions on the devices themselves.

New Zealand rescue helicopter services use several sets of 3rd-generation night vision goggles imported from the USA, and the country is required to restrict access to the equipment to comply with the strict regulations regarding their export.[38] There are no prohibitions on the ownership or use of night vision equipment for shooting non-indigenous game animals, such as rabbits, hares, deer, pigs, tahr, chamois, goats, wallabies, etc.

In the U.S., a 2010-2011 summary of State hunting regulations for the use of night-vision equipment in hunting[39] listed 13 States in which the equipment is prohibited, 17 States with various restrictions (e.g. only for certain non-game species, and/or in a certain date range), and 20 States without restrictions. It did not summarize the regulations for thermal-imaging equipment.

In California, it is a misdemeanor to possess a device "designed for or adaptable to use on a firearm which, through the use of a projected infrared light source and electronic telescope, enables the operator thereof to visually determine and locate the presence of objects during the nighttime".[40] This essentially covers scopes using Gen0 technology, but not the subsequent generations. There was an effort in 1995[41] to further expand restrictions to forbid night vision devices that did not incorporate a light source, but it did not become law.

In Minnesota, as of 2014, "A person may not possess night vision or thermal imaging equipment while taking wild animals or while having in possession [an uncased and loaded weapon] that could be used to take wild animals."[42] There is an exception for law-enforcement and military use. The night-vision prohibition was enacted in 2007, and the thermal-imaging prohibition was added in 2014. Two bills were introduced in the Minnesota Legislature in 2016, proposing to allow night-vision and thermal-imaging equipment for, respectively, 1) "predator" or 2) "unprotected wild animal" hunting.[43]

See also

References

  1. ↑ Sacrificial Lenses are mounted on the front or away from face lens on NVDs. Meant for protecting original lens from damage by environmental hazards.
  2. 1 2 Jeff Tyson. "How Night Vision Works". HowStuffWorks. Retrieved 2011-03-01.
  3. ↑ Night Vision & Electronic Sensors Directorate - Fort Belvoir, VA
  4. ↑ Pennsylvania State University Zworykin, Vladimir biographical sketch
  5. ↑ "Black-Light Telescope Sees In The Dark" Popular Science Monthly March 1936
  6. ↑ Achtung Panzer! - German Infrared Night-Vision Devices!
  7. ↑ "Bull's-eyes in the Night." Popular Science, July 1946, p. 73.
  8. 1 2 "Image Intensification Tube Technology and Evolution". GlobalSecurity.org. Retrieved 2011-03-01.
  9. 1 2 3 Night Vision Goggles (NVG)
  10. ↑ Night Vision Equipment by Pulsar FAQ
  11. ↑ AN/PVS-4 Individual Weapon Night Sight
  12. ↑ AN/PVS-5 Night Vision Goggles
  13. ↑ http://www.ieimil.com/SimpleProducts/ViewSimpleProductsProductDetails.aspx?ProductID=81&CategoryID=9&Style=../css/style05.css
  14. 1 2 Night Vision Area - PHOTONIS
  15. ↑ http://www.ieimil.com/SimpleProducts/ViewSimpleProductsProductDetails.aspx?ProductID=128&CategoryID=9&Style=../css/style05.css
  16. ↑ AN/PVS-7 Night Vision Goggle
  17. ↑ AN/PVS-14, MONOCULAR NIGHT VISION DEVICE (MNVD)
  18. ↑ CNVS-4949, Binocular Color Night Vision Device
  19. ↑ \\Baksan\Shared Docs\For Candace\New Folder\LET.tif
  20. ↑ www.nivitech.com / Nightvision Technology / Principles of Nightvision Devices
  21. ↑ How night vision works - image intensifier technology by ATN
  22. ↑ AN/PVS-22 Universal Night Sight
  23. ↑ Jeffrey P. Bialos; Stuart L. Koehl (September 2005). "The NATO Response Force" (PDF). National Defense University. Retrieved 2011-03-01.
  24. ↑ FOUR-EYES: Air Force Spec Ops Get Panoramic Night Vision
  25. ↑ Defense Tech: Army Optic Combines Heat, Light for Better Sight
  26. ↑ Northrop Grumman Delivers First Fused Multispectral Weapon Sight to U.S. Army
  27. ↑ "About Armasight brand". Retrieved 2015-12-29.
  28. ↑ "Night Vision Generations".
  29. ↑ Scientists Develop Night Vision Contact Lens - Defensetech.org, 28 March 2014
  30. ↑ БИНОКЛЬ НОЧНОЙ 1ПН50 ТЕХНИЧЕСКОЕ ОПИСАНИЕ И ИНСТРУКЦИЯ ПО ЭКСПЛУАТАЦИИ [NIGHT BINOCULARS 1PN50 TECHNICAL DESCRIPTION AND OPERATING INSTRUCTIONS] (in Russian). 55 pages.
  31. ↑ ИЗДЕЛИЕ 1ПН51 ТЕХНИЧЕСКОЕ ОПИСАНИЕ И ИНСТРУКЦИЯ ПО ЭКСПЛУАТАЦИИ [PRODUCT 1PN51 TECHNICAL DESCRIPTION AND OPERATING INSTRUCTIONS] (in Russian). January 1992. 48 pages.
  32. ↑ ИЗДЕЛИЕ 1ПН51-2 ТЕХНИЧЕСКОЕ ОПИСАНИЕ И ИНСТРУКЦИЯ ПО ЭКСПЛУАТАЦИИ [PRODUCT 1PN51-2 TECHNICAL DESCRIPTION AND OPERATING INSTRUCTIONS] (in Russian). September 1991. 52 pages.
  33. ↑ ИЗДЕЛИЕ 1ПН58 ТЕХНИЧЕСКОЕ ОПИСАНИЕ И ИНСТРУКЦИЯ ПО ЭКСПЛУАТАЦИИ [PRODUCT 1PN58 TECHNICAL DESCRIPTION AND OPERATING INSTRUCTIONS] (in Russian). February 1991. 53 pages.
  34. 1 2 "1PN110 and 1PN113 Night Vision Sights". gunsru.ru. Retrieved 2014-11-26.
  35. ↑ "Anti-Sniper Special Purpose Night Vision Sights". gunsru.ru. Retrieved 2015-03-15.
  36. ↑ Section 19 5a of the German Bundesjagdgesetz (BJagdG) states: "It is forbidden to use artificial light sources, mirrors, devices to illuminate or light targets, or night vision devices with image converters or electronic amplification intended for guns." These aids are not banned for observation purposes but for catching or killing game.
  37. ↑ http://www.wapenunie.be/node/21
  38. ↑ "Seeing in the Dark", Vector, magazine of the Civil Aviation Authority of New Zealand, January/February 2008, pages 10–11
  39. ↑ "A 50 State guide - is night vision legal to use for hunting in my State?". High Tech Red Neck. 2010.
  40. ↑ http://www.leginfo.ca.gov/cgi-bin/waisgate?WAISdocID=24717320313+1+0+0&WAISaction=retrieve Penal Code section 468
  41. ↑ http://info.sen.ca.gov/pub/95-96/bill/asm/ab_1051-1100/ab_1059_cfa_950417_155505_asm_comm.html AB 1059
  42. ↑ "MN Statutes Section 97B.086". MN Revisor of Statutes. State of MN. Retrieved 31 March 2016.
  43. ↑ Orrick, Dave (2016-03-29). "Would night vision make coyote hunting safer? Divisions arise.". Pioneer Press.

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