A night-vision device (NVD), also known as a night optical/observation device (NOD) or night-vision goggle (NVG), is an optoelectronic device that allows visualization of images in low levels of light, improving the user's night vision .
101-583: The AN/PSQ-20 Enhanced Night Vision Goggle ( ENVG ) is a third-generation passive monocular night vision device developed for the United States Armed Forces by ITT Exelis . It fuses image-intensifying and thermal-imaging technologies, enabling vision in conditions with very little light. The two methods can be used simultaneously or individually. The ENVG was selected by the US Army 's Program Executive Office Soldier (PEO Soldier) as
202-414: A core surrounded by a cladding layer, both of which are made of dielectric materials. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The boundary between the core and cladding may either be abrupt, in step-index fiber , or gradual, in graded-index fiber . Light can be fed into optical fibers using lasers or LEDs . Fiber
303-483: A micro-channel plate (MCP) with an S-25 photocathode . This produced a much brighter image, especially around the edges of the lens. This led to increased clarity in low ambient-light environments, such as moonless nights . Light amplification was around 20,000 . Image resolution and reliability improved. Examples: Later advances brought GEN II+ devices (equipped with better optics, SUPERGEN tubes, improved resolution and better signal-to-noise ratios ), though
404-411: A wavelength shifter collect scintillation light in physics experiments . Fiber-optic sights for handguns, rifles, and shotguns use pieces of optical fiber to improve the visibility of markings on the sight. An optical fiber is a cylindrical dielectric waveguide ( nonconducting waveguide) that transmits light along its axis through the process of total internal reflection. The fiber consists of
505-426: A 16,000-kilometer distance, means that there is a minimum delay of 80 milliseconds (about 1 12 {\displaystyle {\tfrac {1}{12}}} of a second) between when one caller speaks and the other hears. When light traveling in an optically dense medium hits a boundary at a steep angle of incidence (larger than the critical angle for the boundary), the light is completely reflected. This
606-443: A 97° FoV. Examples: Foveated night vision (F-NVG) uses specialized WFoV optics to increase the field of view through an intensifier tube. The fovea refers to the part of the retina which is responsible for central vision. These devices have users look "straight through" the tubes so light passing through the center of the tube falls on the foveal retina, as is the case with traditional binocular NVGs. The increased FoV comes at
707-567: A binocular apparatus called 'Design E'. This was bulky, needing an external power pack generating 7,000 volts, but saw limited use with amphibious vehicles of 79th Armoured Division in the 1945 crossing of the Rhine. Between May and June 1943, 43rd (Wessex) Infantry Division trialled man-portable night vision sets, and the British later experimented with mounting the devices to Mark III and Mark II(S) Sten submachine guns. However, by January 1945
808-423: A cladding made of pure silica, with an index of 1.444 at 1500 nm, and a core of doped silica with an index around 1.4475. The larger the index of refraction, the slower light travels in that medium. From this information, a simple rule of thumb is that a signal using optical fiber for communication will travel at around 200,000 kilometers per second. Thus a phone call carried by fiber between Sydney and New York,
909-451: A digital audio optical connection. This allows the streaming of audio over light, using the S/PDIF protocol over an optical TOSLINK connection. Fibers have many uses in remote sensing . In some applications, the fiber itself is the sensor (the fibers channel optical light to a processing device that analyzes changes in the light's characteristics). In other cases, fiber is used to connect
1010-783: A former radio-guided missile. At that time, infrared was commonly called black light , a term later restricted to ultraviolet . Zworykin's invention was not a success due to its large size and high cost. First-generation passive devices developed by the US Army in the 1960s were introduced during the Vietnam War . They were an adaptation of earlier active technology and relied on ambient light instead of using an extra infrared light source. Using an S-20 photocathode , their image intensifiers amplified light around 1,000 -fold, but they were quite bulky and required moonlight to function properly. Examples: 1970s second-generation devices featured an improved image-intensifier tube using
1111-522: A lasting impact on structures . It is based on the principle of measuring analog attenuation. In spectroscopy , optical fiber bundles transmit light from a spectrometer to a substance that cannot be placed inside the spectrometer itself, in order to analyze its composition. A spectrometer analyzes substances by bouncing light off and through them. By using fibers, a spectrometer can be used to study objects remotely. An optical fiber doped with certain rare-earth elements such as erbium can be used as
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#17327811095291212-438: A limited field of view (FoV); the commonly used AN/PVS-14 has a FoV of 40, less than the 95° monocular horizontal FoV and humans' 190° binocular horizontal FoV. This forces users to turn their heads to compensate. This is particularly evident when flying, driving, or CQB , which involves split second decisions. These limitations led many SF/SOF operators to prefer white light rather than night vision when conducting CQB. As
1313-429: A lower cost. At the higher end, SiOnyx has produced digital color NVGs. The "Opsin" of 2022 has a form factor and helmet weight similar to an AN/PVS-14 , but requires a separate battery pack. It offers a shorter battery life and lower sensitivity. It can however tolerate bright light and process a wider range of wavelengths. Ceramic Optical Ruggedized Engine (CORE) produces higher-performance Gen 1 tubes by replacing
1414-423: A network in an office building (see fiber to the office ), fiber-optic cabling can save space in cable ducts. This is because a single fiber can carry much more data than electrical cables such as standard category 5 cable , which typically runs at 100 Mbit/s or 1 Gbit/s speeds. Fibers are often also used for short-distance connections between devices. For example, most high-definition televisions offer
1515-714: A processor on the back of the helmet that wirelessly communicates with the weapon-mounted FWS-I; because of the systems' short range and low power, jamming the wireless connection is not a concern. Connecting with the ENVG-III also expands the field of vision from a scope's 18-26 degrees to the goggle's 40 degrees. By seeing what the scope sees through the goggles, soldiers during close-quarters combat (CQC) can point their weapons out of defilade positions like over walls and around corners and fire accurately without exposing their head or torso to enemy fire. The US Army first experimented with aiming and shooting weapons behind cover during
1616-608: A range of up to 600 m, had a 30 cm infrared searchlight and an image converter operated by the tank commander. From late 1944 to March 1945 the German military conducted successful tests of FG 1250 sets mounted on Panther Ausf. G tanks (and other variants). During the war, approximately 50 (or 63) Panthers were equipped with the FG 1250 and saw combat on both the Eastern and Western Fronts . The "Vampir" man-portable system for infantry
1717-491: A resonance superstructure to orient more of the electric field parallel, so that it can be absorbed. Although cryogenic cooling between 77 K and 85 K is required, QWID technology may be appropriate for continuous surveillance viewing due to its claimed low cost and uniformity in materials. Materials from the II–VI compounds , such as HgCdTe , are used for high-performance infrared light-sensing cameras. An alternative within
1818-410: A resonant non-local lithium niobate metasurface with a pump beam. The metasurface boosts the photons' energy, pushing them into the visible spectrum without converting them to electrons. Cooling is not required. Visible and infrared light appear in a single image. Traditionally, night-vision systems capture side-by-side views from each spectrum, so they can't produce identical images. Its frequency range
1919-402: A result, much time and effort has gone into research to develop a wider FoV solution. Panoramic night vision goggles (PNVG) increase FoV by increasing the number of sensor tubes. This solution adds size, weight, power requirements, and complexity. An example is GPNVG-18 (Ground Peripheral Night Vision Goggle). These goggles, and the aviation AN/AVS-10 PNVG from which they were derived, offer
2020-474: A sensor to a measurement system. Optical fibers can be used as sensors to measure strain , temperature , pressure , and other quantities by modifying a fiber so that the property being measured modulates the intensity , phase , polarization , wavelength , or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest since only a simple source and detector are required. A particularly useful feature of such fiber optic sensors
2121-713: A steady illumination level in the user's view that improves the ability to keep "eyes on target" in spite of temporary light flashes. These functions are especially useful for pilots, soldiers in urban environments , and special operations forces who may be exposed to rapidly changing light levels. OMNI, or OMNIBUS, refers to a series of contracts through which the US Army purchased GEN III night vision devices. This started with OMNI I, which procured AN/PVS-7A and AN/PVS-7B devices, then continued with OMNI II (1990), OMNI III (1992), OMNI IV (1996), OMNI V (1998), OMNI VI (2002), OMNI VII (2005), OMNI VIII, and OMNI IX. However, OMNI
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#17327811095292222-605: A supporting device for the Future Force Warrior program in 2004, and is intended to replace the older AN/PVS-7 and AN/PVS-14 systems. Although more expensive and heavier than previous models, US Special Forces began using the goggles in 2008 and the US Army's 10th Mountain Division began fielding the AN/PSQ-20 in 2009. Improvements to the goggles have been attempted to make them lighter, as well as enabling
2323-649: A target without a clear line-of-sight path. Many microscopes use fiber-optic light sources to provide intense illumination of samples being studied. Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope , which is used to view objects through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures. Industrial endoscopes (see fiberscope or borescope ) are used for inspecting anything hard to reach, such as jet engine interiors. In some buildings, optical fibers route sunlight from
2424-524: A transparent cladding. Later that same year, Harold Hopkins and Narinder Singh Kapany at Imperial College in London succeeded in making image-transmitting bundles with over 10,000 fibers, and subsequently achieved image transmission through a 75 cm long bundle which combined several thousand fibers. The first practical fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz , C. Wilbur Peters, and Lawrence E. Curtiss, researchers at
2525-563: A unit cost of US$ 18,000 and with a weight of almost 2 pounds (0.91 kg), the AN/PSQ-20 is more expensive and heavier than the devices it is intended to replace. In 2019, the Army plans to begin fielding the Family of Weapon Sights-Individual (FWS-I), an optic that can be mounted on various weapons like the M4 carbine , M16A4 rifle , M249 SAW , M136 AT4 , and M141 Bunker Defeat Munition . The FWS-I
2626-703: Is 1550-nm infrared to visible 550-nm light. Fiber optic An optical fiber , or optical fibre , is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications , where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss and are immune to electromagnetic interference . Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in
2727-468: Is a mechanical splice , where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors . The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics . The term was coined by Indian-American physicist Narinder Singh Kapany . Daniel Colladon and Jacques Babinet first demonstrated
2828-453: Is a way of measuring the speed of light in a material. Light travels fastest in a vacuum , such as in outer space. The speed of light in vacuum is about 300,000 kilometers (186,000 miles) per second. The refractive index of a medium is calculated by dividing the speed of light in vacuum by the speed of light in that medium. The refractive index of vacuum is therefore 1, by definition. A typical single-mode fiber used for telecommunications has
2929-411: Is bent towards the perpendicular ... When the ray passes from water to air it is bent from the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be totally reflected at the surface... The angle which marks the limit where total reflection begins is called the limiting angle of
3030-412: Is called multi-mode fiber , from the electromagnetic analysis (see below). In a step-index multi-mode fiber, rays of light are guided along the fiber core by total internal reflection. Rays that meet the core-cladding boundary at an angle (measured relative to a line normal to the boundary) greater than the critical angle for this boundary, are completely reflected. The critical angle is determined by
3131-418: Is called total internal reflection . This effect is used in optical fibers to confine light in the core. Most modern optical fiber is weakly guiding , meaning that the difference in refractive index between the core and the cladding is very small (typically less than 1%). Light travels through the fiber core, bouncing back and forth off the boundary between the core and cladding. Because the light must strike
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3232-507: Is designed for use in the near infrared . Multi-mode fiber, by comparison, is manufactured with core diameters as small as 50 micrometers and as large as hundreds of micrometers. Some special-purpose optical fiber is constructed with a non-cylindrical core or cladding layer, usually with an elliptical or rectangular cross-section. These include polarization-maintaining fiber used in fiber optic sensors and fiber designed to suppress whispering gallery mode propagation. Photonic-crystal fiber
3333-491: Is designed to work with the ENVG-III by transmitting data from the scope to the goggles, so the soldier can aim the weapon without needing to raise it to their eye. Both systems were brought together under the Rapid Target Acquisition (RTA) capability that combined two separate programs of record with separate devices together to make them interoperable. The goggles are connected through fiber optic wires to
3434-565: Is far less than in electrical copper cables, leading to long-haul fiber connections with repeater distances of 70–150 kilometers (43–93 mi). Two teams, led by David N. Payne of the University of Southampton and Emmanuel Desurvire at Bell Labs , developed the erbium-doped fiber amplifier , which reduced the cost of long-distance fiber systems by reducing or eliminating optical-electrical-optical repeaters, in 1986 and 1987 respectively. The emerging field of photonic crystals led to
3535-564: Is immune to electrical interference as there is no cross-talk between signals in different cables and no pickup of environmental noise. Information traveling inside the optical fiber is even immune to electromagnetic pulses generated by nuclear devices. Fiber cables do not conduct electricity, which makes fiber useful for protecting communications equipment in high voltage environments such as power generation facilities or applications prone to lightning strikes. The electrical isolation also prevents problems with ground loops . Because there
3636-418: Is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the fiber cores, and the coupling of these aligned cores. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together. Another common technique
3737-611: Is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide . Fibers that support many propagation paths or transverse modes are called multi-mode fibers , while those that support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,050 meters (3,440 ft). Being able to join optical fibers with low loss
3838-520: Is known as I ( image intensification ). By comparison, viewing of infrared thermal radiation is referred to as thermal imaging and operates in a different section of the infrared spectrum. A night vision device usually consists of an image intensifier tube, a protective housing, and an optional mounting system. Many NVDs also include a protective sacrificial lens, mounted over the front/ objective lens to prevent damage by environmental hazards, while some incorporate telescopic lenses . An NVD image
3939-405: Is made with a regular pattern of index variation (often in the form of cylindrical holes that run along the length of the fiber). Such fiber uses diffraction effects instead of or in addition to total internal reflection, to confine light to the fiber's core. The properties of the fiber can be tailored to a wide variety of applications. Attenuation in fiber optics, also known as transmission loss,
4040-412: Is monitored and analyzed for disturbances. This return signal is digitally processed to detect disturbances and trip an alarm if an intrusion has occurred. Optical fibers are widely used as components of optical chemical sensors and optical biosensors . Optical fiber can be used to transmit power using a photovoltaic cell to convert the light into electricity. While this method of power transmission
4141-439: Is no electricity in optical cables that could potentially generate sparks, they can be used in environments where explosive fumes are present. Wiretapping (in this case, fiber tapping ) is more difficult compared to electrical connections. Fiber cables are not targeted for metal theft . In contrast, copper cable systems use large amounts of copper and have been targeted since the 2000s commodities boom . The refractive index
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4242-417: Is not a specification. The performance of a particular device generally depends upon the tube which is used. For example, a GEN III OMNI III MX-10160A/AVS-6 tube performs similarly to a GEN III OMNI VII MX-10160A/AVS-6 tube, even though the former was manufactured in ~1992 and the latter ~2005. One particular technology, PINNACLE is a proprietary thin-film microchannel plate technology created by ITT that
4343-478: Is not as efficient as conventional ones, it is especially useful in situations where it is desirable not to have a metallic conductor as in the case of use near MRI machines, which produce strong magnetic fields. Other examples are for powering electronics in high-powered antenna elements and measurement devices used in high-voltage transmission equipment. Optical fibers are used as light guides in medical and other applications where bright light needs to be shone on
4444-502: Is not enough for practical use. The Sensor and Electron Devices Directorate (SEDD) of the US Army Research Laboratory developed quantum-well infrared detector (QWID). This technology's epitaxial layers use a gallium arsenide (GaAs) or aluminum gallium arsenide system (AlGaAs). It is particularly sensitive to that are mid-length infrared waves. The Corrugated QWIP (CQWIP) broadens detection capacity by using
4545-512: Is part of PEO Soldier, has been working on making the AN/PSQ-20 more rugged by using tougher housing material. Efforts have also been made to make the device lighter, as well as to produce and transmit digital images of the view provided. As a result, a prototype named Digital Enhanced Night Vision Goggle or ENVG (D) was provided to the US Army for evaluation in June 2009, which enables digitally fused images to be exported and imported. As of July 2015,
4646-484: Is roughly the same size as the AN/PVS-14 with similar controls, and is powered by four AA type batteries allowing continuous combined use of II and IR for 7.5 hours. The device can be used for a further 7.5 hours in image intensifier mode. Classified as a third-generation passive night vision device, the AN/PSQ-20 can provide vision through thermal imaging even in situations where there isn't enough ambient light for
4747-418: Is that they can, if required, provide distributed sensing over distances of up to one meter. Distributed acoustic sensing is one example of this. In contrast, highly localized measurements can be provided by integrating miniaturized sensing elements with the tip of the fiber. These can be implemented by various micro- and nanofabrication technologies, such that they do not exceed the microscopic boundary of
4848-422: Is the numerical aperture (NA) of the fiber. Fiber with a larger NA requires less precision to splice and work with than fiber with a smaller NA. The size of this acceptance cone is a function of the refractive index difference between the fiber's core and cladding. Single-mode fiber has a small NA. Fiber with large core diameter (greater than 10 micrometers) may be analyzed by geometrical optics . Such fiber
4949-474: Is the measurement of temperature inside jet engines by using a fiber to transmit radiation into a pyrometer outside the engine. Extrinsic sensors can be used in the same way to measure the internal temperature of electrical transformers , where the extreme electromagnetic fields present make other measurement techniques impossible. Extrinsic sensors measure vibration, rotation, displacement, velocity, acceleration, torque, and torsion. A solid-state version of
5050-428: Is the reduction in the intensity of the light signal as it travels through the transmission medium. Attenuation coefficients in fiber optics are usually expressed in units of dB/km. The medium is usually a fiber of silica glass that confines the incident light beam within. Attenuation is an important factor limiting the transmission of a digital signal across large distances. Thus, much research has gone into both limiting
5151-407: Is to use an I² device over one eye and a thermal device over the other eye, relying on the human visual system to provide a binocular combined view . Out of Band (OOB) refers to night vision technologies that operate outside the 500-900 nm NIR (near infrared) frequency range. This is possible with dedicated image intensifier tubes or with clip-on devices. Night vision devices typically have
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#17327811095295252-484: Is typical in deployed systems. Through the use of wavelength-division multiplexing (WDM), each fiber can carry many independent channels, each using a different wavelength of light. The net data rate (data rate without overhead bytes) per fiber is the per-channel data rate reduced by the forward error correction (FEC) overhead, multiplied by the number of channels (usually up to 80 in commercial dense WDM systems as of 2008 ). For short-distance applications, such as
5353-437: Is typically monochrome green, as green was considered to be the easiest color to see for prolonged periods in the dark. Night vision devices may be passive, relying solely on ambient light, or may be active, using an IR (infrared) illuminator. Night vision devices may be handheld or attach to helmets . When used with firearms, an IR laser sight is often mounted to the weapon. The laser sight produces an infrared beam that
5454-402: Is used as a medium for telecommunication and computer networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because infrared light propagates through the fiber with much lower attenuation compared to electricity in electrical cables. This allows long distances to be spanned with few repeaters . 10 or 40 Gbit/s
5555-931: Is visible only through an NVD and aids with aiming. Some night vision devices are made to be mounted to firearms. These can be used in conjunction with weapon sights or standalone; some thermal weapon sights have been designed to provide similar capabilities. These devices were first used for night combat in World War II and came into wide use during the Vietnam War . The technology has evolved since then, involving "generations" of night-vision equipment with performance increases and price reductions. Consequently, though they are commonly used by military and law enforcement agencies, night vision devices are available to civilian users for applications including aviation, driving, and demining . In 1929 Hungarian physicist Kálmán Tihanyi invented an infrared-sensitive electronic television camera for anti-aircraft defense in
5656-522: The III–V family of compounds from InAsSb , a III–V compound, which is common in opto-electronics in items such as DVDs and phones. A graded layer with increased atomic spacing and an intermediate layer of the GaAs substrate trap any potential defects. Metasurface -based upconversion technology provides a night-vision film that weighs less than a gram and can be placed across ordinary glasses. Photons pass through
5757-605: The Land Warrior program, but it relied on connecting wires between the helmet-mounted display and weapon-mounted thermal sight that could get caught, and early sights were too heavy and bulky. The AN/PSQ-20 ENVG was first issued to the US Army in April 2008. The 10th Mountain Division received about 300 units in February 2009, making it the first non-special forces unit to use the device. PM Soldier Sensors and Lasers, which
5858-471: The University of Michigan , in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. Kapany coined the term fiber optics after writing a 1960 article in Scientific American that introduced the topic to a wide audience. He subsequently wrote
5959-405: The gain medium of a fiber laser or optical amplifier . Rare-earth-doped optical fibers can be used to provide signal amplification by splicing a short section of doped fiber into a regular (undoped) optical fiber line. The doped fiber is optically pumped with a second laser wavelength that is coupled into the line in addition to the signal wave. Both wavelengths of light are transmitted through
6060-601: The British had only made seven infra-red receiver sets. Although some were sent to India and Australia for trials before the end of 1945, by the Korean War and Malayan Emergency the British were using night vision equipment supplied by the United States. Early examples include: After World War II, Vladimir K. Zworykin developed the first practical commercial night-vision device at Radio Corporation of America , intended for civilian use. Zworykin's idea came from
6161-583: The PAU-2 was field-tested in 1942. In 1938 the British Admiralty assumed responsibility for British military infra-red research. They worked first with Philips until the fall of the Netherlands , then with Philips' UK subsidiary Radio Transmission Equipment Ltd., and finally with EMI , who in early 1941 provided compact, lightweight image converter tubes. By July 1942 the British had produced
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#17327811095296262-642: The UK. Night vision technology prior to the end of World War II was later described as Generation 0. Night-vision devices were introduced in the German Army as early as 1939 and were used in World War II . AEG started developing its first devices in 1935. In mid-1943, the German Army began testing infrared night-vision devices and telescopic rangefinders mounted on Panther tanks . Two arrangements were constructed. The Sperber FG 1250 ("Sparrow Hawk"), with
6363-462: The US Army had bought about 9,000 ENVG-I and 16,000 ENVG-II units. Beginning in FY 2017, the ENVG-III is expected to begin fielding, with a total of 41,000 to be produced by BAE Systems and DRS Technologies . Like previous versions, the ENVG-III allows soldiers to choose between night vision, thermal, hybrid, and a hybrid where thermal images show up with an outline, but extends the thermal capacity out to
6464-411: The amount of voltage supplied to the microchannel plate (rather than the photocathode) in response to ambient light. Together, BSP and ABC (alongside autogating) serves to prevent temporary blindness for the user and prevent damage to the tube when the night vision device is exposed to sudden bright sources of light, like a muzzle flash or artificial lighting. These modulation systems also help maintain
6565-564: The attenuation in fibers available at the time was caused by impurities that could be removed, rather than by fundamental physical effects such as scattering. They correctly and systematically theorized the light-loss properties for optical fiber and pointed out the right material to use for such fibers— silica glass with high purity. This discovery earned Kao the Nobel Prize in Physics in 2009. The crucial attenuation limit of 20 dB/km
6666-416: The boundary with an angle greater than the critical angle, only light that enters the fiber within a certain range of angles can travel down the fiber without leaking out. This range of angles is called the acceptance cone of the fiber. There is a maximum angle from the fiber axis at which light may enter the fiber so that it will propagate, or travel, in the core of the fiber. The sine of this maximum angle
6767-402: The cameras had to be supervised by someone with an appropriate security clearance. Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables (STC) were the first to promote the idea that the attenuation in optical fibers could be reduced below 20 decibels per kilometer (dB/km), making fibers a practical communication medium, in 1965. They proposed that
6868-416: The case of a fiberscope . Specially designed fibers are also used for a variety of other applications, such as fiber optic sensors and fiber lasers . Glass optical fibers are typically made by drawing , while plastic fibers can be made either by drawing or by extrusion . Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction . Light
6969-407: The core-cladding boundary. The resulting curved paths reduce multi-path dispersion because high-angle rays pass more through the lower-index periphery of the core, rather than the high-index center. The index profile is chosen to minimize the difference in axial propagation speeds of the various rays in the fiber. This ideal index profile is very close to a parabolic relationship between the index and
7070-442: The development in 1991 of photonic-crystal fiber , which guides light by diffraction from a periodic structure, rather than by total internal reflection. The first photonic crystal fibers became commercially available in 2000. Photonic crystal fibers can carry higher power than conventional fibers and their wavelength-dependent properties can be manipulated to improve performance. These fibers can have hollow cores. Optical fiber
7171-404: The devices in a particular OMNI classification. Any postnominals appearing after a generation type (i.e., Gen II+, Gen III+) indicate improvement(s) over the original specification's requirements. Examples: Figure of merit (FoM) is a quantitative measure of a NVD's effectiveness and clarity. It is calculated using the number of line pairs per millimeter that a user can detect multiplied by
7272-467: The difference in the index of refraction between the core and cladding materials. Rays that meet the boundary at a low angle are refracted from the core into the cladding where they terminate. The critical angle determines the acceptance angle of the fiber, often reported as a numerical aperture . A high numerical aperture allows light to propagate down the fiber in rays both close to the axis and at various angles, allowing efficient coupling of light into
7373-445: The distance from the axis. Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic waveguide structure, according to Maxwell's equations as reduced to the electromagnetic wave equation . As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along
7474-621: The doped fiber, which transfers energy from the second pump wavelength to the signal wave. The process that causes the amplification is stimulated emission . Optical fiber is also widely exploited as a nonlinear medium. The glass medium supports a host of nonlinear optical interactions, and the long interaction lengths possible in fiber facilitate a variety of phenomena, which are harnessed for applications and fundamental investigation. Conversely, fiber nonlinearity can have deleterious effects on optical signals, and measures are often required to minimize such unwanted effects. Optical fibers doped with
7575-650: The entire 40-degree field of view rather than just a circle in the middle, and has a sleeker design for the device and battery pack, improved resolution, is lighter at less than 2 pounds (0.91 kg), and is designed to work with the FWS-I. Plans are to equip 24 ENVGs per platoon , with each costing an estimated US$ 10,000, cheaper than previous versions due to competition and improved technology. Night-vision device#Generation 3 (GEN III) The device enhances ambient visible light and converts near-infrared light into visible light which can then be seen by humans; this
7676-611: The fact that the technology itself makes little difference, as long as an operator can see clearly at night. Consequently, the United States bases export regulations directly on the figure of merit. ITAR regulations specify that US-made tubes with a FOM greater than 1400 are not exportable; however, the Defense Technology Security Administration (DTSA) can waive that policy on a case-by-case basis. Fusion night vision combines I² ( image intensification ) with thermal imaging , which functions in
7777-424: The fiber tip, allowing for such applications as insertion into blood vessels via hypodermic needle. Extrinsic fiber optic sensors use an optical fiber cable , normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor—or an electronic sensor connected to an optical transmitter. A major benefit of extrinsic sensors is their ability to reach otherwise inaccessible places. An example
7878-404: The fiber. Fiber supporting only one mode is called single-mode . The waveguide analysis shows that the light energy in the fiber is not completely confined in the core. Instead, especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave . The most common type of single-mode fiber has a core diameter of 8–10 micrometers and
7979-438: The fiber. However, this high numerical aperture increases the amount of dispersion as rays at different angles have different path lengths and therefore take different amounts of time to traverse the fiber. In graded-index fiber, the index of refraction in the core decreases continuously between the axis and the cladding. This causes light rays to bend smoothly as they approach the cladding, rather than reflecting abruptly from
8080-493: The first book about the new field. The first working fiber-optic data transmission system was demonstrated by German physicist Manfred Börner at Telefunken Research Labs in Ulm in 1965, followed by the first patent application for this technology in 1966. In 1968, NASA used fiber optics in the television cameras that were sent to the moon. At the time, the use in the cameras was classified confidential , and employees handling
8181-477: The fovea. Examples: Some night vision devices, including several of the ENVG ( AN/PSQ-20 ) models, are "digital". Introduced in the late 2000s, these allow transmission of the image, at the cost of increased size, weight, power usage. High-sensitivity digital camera technology enables NVGs that combine a camera and a display instead of an image intensifier . These devices can offer Gen-1-equivalent quality at
8282-502: The glass plate with a ceramic plate. This plate is produced from specially formulated ceramic and metal alloys. Edge distortion is improved, photo sensitivity is increased, and the resolution can be as high as 60 lp /mm. CORE is still considered Gen 1, as it does not utilize a microchannel plate. A night-vision contact lens prototype places a thin strip of graphene between layers of glass that reacts to photons to brighten dark images. Prototypes absorb only 2.3% of light, which
8383-510: The guiding of light by refraction, the principle that makes fiber optics possible, in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London , 12 years later. Tyndall also wrote about the property of total internal reflection in an introductory book about the nature of light in 1870: When the light passes from air into water, the refracted ray
8484-469: The gyroscope, using the interference of light, has been developed. The fiber optic gyroscope (FOG) has no moving parts and exploits the Sagnac effect to detect mechanical rotation. Common uses for fiber optic sensors include advanced intrusion detection security systems . The light is transmitted along a fiber optic sensor cable placed on a fence, pipeline, or communication cabling, and the returned signal
8585-497: The human eye and peak voltage supplied to the night vision device is maintained. This reduces the " duty cycle " (ie. the amount of time that the tube has power running through it) which increases the device's lifespan. Autogating also enhances the Bright-Source Protection (BSP), which reduces the voltage supplied to the photocathode in response to ambient light levels. Automatic Brightness Control (ABC) modulates
8686-457: The image intensifier's signal-to-noise (SNR) ratio. In the late 1990s, innovations in photocathode technology significantly increased the SNR, with new tubes surpassing Gen 3 performance. By 2001, the United States federal government concluded that a tube's generation was not a determinant performance factor, obsoleting the term as a basis of export regulations. The US government has recognized
8787-526: The image intensifiers, thus eliminating the need for infra-red illumination (active night vision). It can also see through battlefield obscurants such as smoke and fog. The combined technologies allow better target identification and recognition, thereby improving the soldier's mobility and situational awareness. The center of gravity of the device is close to the face of the wearer, making the helmet-mounted use more comfortable, as well as increasing stability. Aiming lasers can also be integrated with it. However, at
8888-414: The ion barrier allowed fewer electrons to pass through. The ion barrier increased the "halo" effect around bright spots or light sources. Light amplification (and power consumption) with these devices improved to around 30,000 – 50,000 . Examples: Autogating (ATG) rapidly switches the power supply's voltage to the photocathode on and off. These switches are rapid enough that they are not detectable to
8989-557: The label is not formally recognized by the NVESD. Third-generation night-vision systems, developed in the late 1980s, maintained the MCP from Gen II, but used a gallium arsenide photocathode, with improved resolution. GA photocathodes are primarily manufactured by L3Harris Technologies and Elbit Systems of America and imaged light from 500-900 nm . In addition, the MCP was coated with an ion barrier film to increase tube life. However,
9090-698: The medium (MWIR 3-5 μm ) and/or long (LWIR 8-14 μm) wavelength range. Initial models appeared in the 2000s. Dedicated fusion devices and clip-on imagers that add a thermal overlay to standard I² night vision devices are available. Fusion combines excellent navigation and fine details (I²), with easy heat signature detection (imaging). Fusion modes include night vision with thermal overlay, night vision only, thermal only, and others such as outline (which outlines objects that have thermal signatures) or "decamouflage", which highlights all objects that are of near-human temperature. Fusion devices are heavier and more power hungry than I²-only devices. One alternative
9191-413: The medium. For water this angle is 48°27′, for flint glass it is 38°41′, while for a diamond it is 23°42′. In the late 19th century, a team of Viennese doctors guided light through bent glass rods to illuminate body cavities. Practical applications such as close internal illumination during dentistry followed, early in the twentieth century. Image transmission through tubes was demonstrated independently by
9292-412: The price of image quality and edge distortions . Examples: Diverging image tube (DIT) night vision increases FoV by angle the tubes slightly outward. This increases peripheral FoV but causes distortion and reduced image quality. With DIT, users are no longer looking through the center of the tubes (which provides the clearest images) and light passing through the center of the tubes no longer falls on
9393-416: The radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. In the 1930s, Heinrich Lamm showed that one could transmit images through a bundle of unclad optical fibers and used it for internal medical examinations, but his work was largely forgotten. In 1953, Dutch scientist Bram van Heel first demonstrated image transmission through bundles of optical fibers with
9494-431: The roof to other parts of the building (see nonimaging optics ). Optical-fiber lamps are used for illumination in decorative applications, including signs , art , toys and artificial Christmas trees . Optical fiber is an intrinsic part of the light-transmitting concrete building product LiTraCon . Optical fiber can also be used in structural health monitoring . This type of sensor can detect stresses that may have
9595-568: The speed of manufacture to over 50 meters per second, making optical fiber cables cheaper than traditional copper ones. These innovations ushered in the era of optical fiber telecommunication. The Italian research center CSELT worked with Corning to develop practical optical fiber cables, resulting in the first metropolitan fiber optic cable being deployed in Turin in 1977. CSELT also developed an early technique for splicing optical fibers, called Springroove. Attenuation in modern optical cables
9696-450: The transmission of digital images to and from the battlefield. In August 2003, PEO Soldier, the acquisition agency of the US Army, started evaluating designs from ITT Industries and Northrop Grumman for an advanced night vision device that could support the planned Future Force Warrior program. Of the two competing designs, the ITT design which was developed in association with Raytheon ,
9797-447: The view of replacing the existing AN/PVS-7 and AN/PVS-14 . The AN/PSQ-20 Enhanced Night Vision Goggle combines image intensifier (I or II) and infra-red (IR, also called thermal imaging ) technologies, and is the first night vision device to do so. Before this "fusing", these two technologies could only be used separately. The AN/PSQ-20 allows both methods to be used together or individually, and can be helmet-mounted or hand held. It
9898-526: Was chosen for development in July 2004 with an initial order for 75 systems. Development testing of the ENVG with the US Army, designated AN/PSQ-20, began by mid-2006, and was completed in March 2007. Operational testing started in June 2007, with low-rate initial production of the device beginning around the same time. ITT were given a five-year contract in April 2005 with a potential value of US$ 560 million, with
9999-675: Was first achieved in 1970 by researchers Robert D. Maurer , Donald Keck , Peter C. Schultz , and Frank Zimar working for American glass maker Corning Glass Works . They demonstrated a fiber with 17 dB/km attenuation by doping silica glass with titanium . A few years later they produced a fiber with only 4 dB/km attenuation using germanium dioxide as the core dopant. In 1981, General Electric produced fused quartz ingots that could be drawn into strands 25 miles (40 km) long. Initially, high-quality optical fibers could only be manufactured at 2 meters per second. Chemical engineer Thomas Mensah joined Corning in 1983 and increased
10100-578: Was included in the OMNI VII contract. The thin-film improves performance. GEN III OMNI V–IX devices developed in the 2000s and onward can differ from earlier devices in important ways: The consumer market sometimes classifies such systems as Generation 4, and the United States military describes these systems as Generation 3 autogated tubes (GEN III OMNI V-IX). Moreover, as autogating power supplies can be added to any previous generation of night-vision devices, autogating capability does not automatically put
10201-706: Was used with StG 44 assault rifles. Parallel development occurred in the US. The M1 and M3 infrared night-sighting devices, also known as the "sniperscope" or "snooperscope", saw limited service with the US Army in World War II and in the Korean War , to assist snipers . These were active devices, using an infrared light source to illuminate targets. Their image-intensifier tubes used an anode and an S-1 photocathode , made primarily of silver , cesium , and oxygen , and electrostatic inversion with electron acceleration produced gain. An experimental Soviet device called
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