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105-442: Aviation HMD designs serve these purposes: HMD systems, combined with High Off- Boresight (HOBS) weapons, allow aircrew to attack and destroy nearly any target seen by the pilot. These systems allow targets to be designated with minimal aircraft maneuvering, minimizing the time spent in the threat environment, and allowing greater lethality, survivability, and pilot situational awareness . In 1962, Hughes Aircraft Company revealed

210-402: A beam of light from the eye could instantaneously light up the stars every time someone blinked. Euclid stated the principle of shortest trajectory of light, and considered multiple reflections on flat and spherical mirrors. Ptolemy , in his treatise Optics , held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and

315-430: A broad band, or extremely low reflectivity at a single wavelength. Constructive interference in thin films can create a strong reflection of light in a range of wavelengths, which can be narrow or broad depending on the design of the coating. These films are used to make dielectric mirrors , interference filters , heat reflectors , and filters for colour separation in colour television cameras. This interference effect

420-619: A changing index of refraction; this principle allows for lenses and the focusing of light. The simplest case of refraction occurs when there is an interface between a uniform medium with index of refraction n 1 and another medium with index of refraction n 2 . In such situations, Snell's Law describes the resulting deflection of the light ray: n 1 sin ⁡ θ 1 = n 2 sin ⁡ θ 2 {\displaystyle n_{1}\sin \theta _{1}=n_{2}\sin \theta _{2}} where θ 1 and θ 2 are

525-428: A collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in

630-432: A combination of sensors such as inertial and optical to improve tracking accuracy, update rate, and latency. Hybrid inertial tracking systems employ a sensitive Inertial Measurement Unit (IMU) and an optical sensor to provide reference to the aircraft. MEMS based IMUs benefit from high update rates such as 1,000 Hz but suffer from precession and drift over time, so they cannot be used alone. In this class of tracker,

735-399: A converging lens has positive focal length, while a diverging lens has negative focal length. Smaller focal length indicates that the lens has a stronger converging or diverging effect. The focal length of a simple lens in air is given by the lensmaker's equation . Ray tracing can be used to show how images are formed by a lens. For a thin lens in air, the location of the image is given by

840-537: A crash program to counter the technology. As a result, the MiG-29 was fielded in 1985 with an HMD and a high off-boresight weapon ( R-73 ), giving them an advantage in close maneuvering engagements. Several nations responded with programs to counter the MiG-29/HMD/R-73 (and later Su-27 ) combination once its effectiveness was known, principally through access to former East German MiG-29s that were operated by

945-625: A design that is 95% common to all platforms. Unlike the DASH, which is integrated into the helmet itself, JHMCS assemblies attach to modified HGU-55/P, HGU-56/P or HGU-68/P helmets. JHMCS employs a newer, faster digital processing package, but retains the same type of electromagnetic position sensing as the DASH. The CRT package is more capable, but remains limited to monochrome presentation of cursive symbology. JHMCS provides support for raster scanned imagery to display FLIR/ IRST pictures for night operations and provides collimated symbology and imagery to

1050-443: A gun barrel. Alternatively, the device could be designed to accommodate a range of circumstances and still be sufficiently accurate. Optical Optics is the branch of physics that studies the behaviour and properties of light , including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible , ultraviolet , and infrared light. Light

1155-489: A novel optical system featuring a light-guide optical element (LOE) which provides a compact color collimated image to the pilot. The display can be positioned by each pilot, thereby eliminating the need for precise helmet position on the user's head or special helmet fitting. Software correction accommodates the display position, providing an accurate image to the pilot and allowing the Scorpion HMCS to be installed onto

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1260-406: A pilot's existing helmet. A visor can be deployed in front of the display providing protection during ejection. The visor can be clear, glare, high contrast, gradient, or laser protective. For night operations, an NVG mount can be installed in place of the visor during flight. Once installed, NVGs can be placed in front of the display, thus allowing the pilot to view both the display symbols as well as

1365-477: A single scalar quantity to represent the electric field of the light wave, rather than using a vector model with orthogonal electric and magnetic vectors. The Huygens–Fresnel equation is one such model. This was derived empirically by Fresnel in 1815, based on Huygens' hypothesis that each point on a wavefront generates a secondary spherical wavefront, which Fresnel combined with the principle of superposition of waves. The Kirchhoff diffraction equation , which

1470-522: A single point on the image, while chromatic aberration occurs because the index of refraction of the lens varies with the wavelength of the light. In physical optics, light is considered to propagate as waves. This model predicts phenomena such as interference and diffraction, which are not explained by geometric optics. The speed of light waves in air is approximately 3.0×10  m/s (exactly 299,792,458 m/s in vacuum ). The wavelength of visible light waves varies between 400 and 700 nm, but

1575-437: A spectrum. The discovery of this phenomenon when passing light through a prism is famously attributed to Isaac Newton. Some media have an index of refraction which varies gradually with position and, therefore, light rays in the medium are curved. This effect is responsible for mirages seen on hot days: a change in index of refraction air with height causes light rays to bend, creating the appearance of specular reflections in

1680-718: A target located behind the wing-line of the ‘shooter' aircraft, was demonstrated by a Royal Australian Air Force (RAAF) F/A-18 using JHMCS. Elbit designed system is used by Qatar and India on Rafale F3R Gentex / Raytheon introduced the Scorpion® Head/Helmet-Mounted Display System to the military aviation market in 2008. In 2010, Scorpion was the winner of the USAF/ANG/AFRes Helmet Mounted Integrated Targeting (HMIT) program. The Gentex helmet mounted display and motion tracking division

1785-465: A thickness of one-fourth the wavelength of incident light. The reflected wave from the top of the film and the reflected wave from the film/material interface are then exactly 180° out of phase, causing destructive interference. The waves are only exactly out of phase for one wavelength, which would typically be chosen to be near the centre of the visible spectrum, around 550 nm. More complex designs using multiple layers can achieve low reflectivity over

1890-719: Is a derivative of the DASH III and the Kaiser Agile Eye HMDs, and was developed by Vision Systems International (VSI), a joint venture company formed by Rockwell Collins and Elbit (Kaiser Electronics is now owned by Rockwell Collins). Boeing integrated the system into the F/A-18 and began low-rate initial production delivery in fiscal year 2002. JHMCS is employed in the F/A-18 A++/C/D/E/F, F-15C/D/E/S/K/SG/SA/QA/EX, and F-16 Block 40/50/50+/60/70 with

1995-421: Is a method of visually pre-aligning a firearm barrel 's bore axis with the target, in order to more easily zero the gunsight ( optical or iron sights ). The process is usually performed on a rifle , and can be accomplished either with the naked eye, or with a specialized device called a boresighter . Optical boresighting, also referred to as "eyeball boresighting", as the name suggests, involves using

2100-427: Is a simple paraxial physical optics model for the propagation of coherent radiation such as laser beams. This technique partially accounts for diffraction, allowing accurate calculations of the rate at which a laser beam expands with distance, and the minimum size to which the beam can be focused. Gaussian beam propagation thus bridges the gap between geometric and physical optics. In the absence of nonlinear effects,

2205-491: Is a type of electromagnetic radiation , and other forms of electromagnetic radiation such as X-rays , microwaves , and radio waves exhibit similar properties. Most optical phenomena can be accounted for by using the classical electromagnetic description of light, however complete electromagnetic descriptions of light are often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics , treats light as

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2310-411: Is a wave-like property not predicted by Newton's corpuscle theory. This work led to a theory of diffraction for light and opened an entire area of study in physical optics. Wave optics was successfully unified with electromagnetic theory by James Clerk Maxwell in the 1860s. The next development in optical theory came in 1899 when Max Planck correctly modelled blackbody radiation by assuming that

2415-486: Is considered to travel in straight lines, while in physical optics, light is considered as an electromagnetic wave. Geometrical optics can be viewed as an approximation of physical optics that applies when the wavelength of the light used is much smaller than the size of the optical elements in the system being modelled. Geometrical optics , or ray optics , describes the propagation of light in terms of "rays" which travel in straight lines, and whose paths are governed by

2520-544: Is deployed on IDF F-15, and F-16 aircraft. Additionally, it has been certified on the F/A-18 and F-5 . The DASH III has been exported and integrated into various legacy aircraft, including the MiG-21 . It also forms the baseline technology for the US JHMCS. The DASH GEN III is a wholly embedded design, where the complete optical and position sensing coil package is built within the helmet (either USAF standard HGU-55/P or

2625-491: Is derived using Maxwell's equations, puts the Huygens-Fresnel equation on a firmer physical foundation. Examples of the application of Huygens–Fresnel principle can be found in the articles on diffraction and Fraunhofer diffraction . More rigorous models, involving the modelling of both electric and magnetic fields of the light wave, are required when dealing with materials whose electric and magnetic properties affect

2730-593: Is designed for day, night and brownout flight environments. Jedeye has a 70 x 40 degree FOV and 2250x1200 pixels resolution. Sweden's JAS 39C/D Gripen fighter utilizes the Cobra HMD. The helmet is a further development and refinement of the Striker helmet developed for the Eurofighter by BAE Systems. The refinement is done by BAE in partnership with Denel Cumulus. Boresight (firearm) Boresighting

2835-556: Is designed to provide the pilot with a wholly unobstructed field of view. TopNight, a Topsight derivative, is designed specifically for adverse weather and night air to ground operations, employing more complex optics to project infrared imagery overlaid with symbology. The most recent version the Topsight has been designated TopOwl-F, and is qualified on the Mirage-2000-5 Mk2 and Mig-29K. The Eurofighter Typhoon utilizes

2940-433: Is relevant to and studied in many related disciplines including astronomy , various engineering fields, photography , and medicine (particularly ophthalmology and optometry , in which it is called physiological optics). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors , lenses , telescopes , microscopes , lasers , and fibre optics . Optics began with

3045-415: Is shaped like a cartridge , and when inserted into the chamber projects a laser beam through the barrel onto the target. The user then adjusts the iron sights or scope reticle to align the point of aim with the projected laser dot. Another more commonly used type of laser boresighter is attached to the muzzle of the barrel, either inserted straight into the bore ("arbor" type) or held in alignment with

3150-409: Is to the lens, the further the image is from the lens. With diverging lenses, incoming parallel rays diverge after going through the lens, in such a way that they seem to have originated at a spot one focal length in front of the lens. This is the lens's front focal point. Rays from an object at a finite distance are associated with a virtual image that is closer to the lens than the focal point, and on

3255-660: The Electrocular , a compact CRT , head-mounted monocular display that reflected a TV signal onto a transparent eyepiece. One of the first aircraft with simple HMD devices appeared for experimental purpose in the mid-1960s to aid in targeting heat seeking missiles . The US Navy 's Visual Target Acquisition System (VTAS), made by Honeywell Corporation that was flown in early 1970s in F-4J and 1974–78 ACEVAL/AIMVAL on U.S. F-14 and F-15 fighters. VTAS received praise for its effectiveness in targeting off-boresight missiles, but

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3360-595: The Persian mathematician Ibn Sahl wrote the treatise "On burning mirrors and lenses", correctly describing a law of refraction equivalent to Snell's law. He used this law to compute optimum shapes for lenses and curved mirrors . In the early 11th century, Alhazen (Ibn al-Haytham) wrote the Book of Optics ( Kitab al-manazir ) in which he explored reflection and refraction and proposed a new system for explaining vision and light based on observation and experiment. He rejected

3465-618: The T-129 Turkish Attack Helicopter. The French thrust vectoring Matra MICA (missile) for its Dassault Rafale and late-model Mirage 2000 fighters was accompanied by the Topsight HMD by Sextant Avionique. TopSight provides a 20 degree FoV for the pilot's right eye, and cursive symbology generated from target and aircraft parameters. Electromagnetic position sensing is employed. The Topsight helmet uses an integral embedded design, and its contoured shape

3570-570: The U.S. Army fielded the AH-64 Apache and with it the Integrated Helmet and Display Sighting System (IHADSS), a new helmet concept in which the role of the helmet was expanded to provide a visually coupled interface between the aviator and the aircraft. The Honeywell M142 IHADSS is fitted with a 40°-by-30° field of view, video-with-symbology monocular display. IR emitters allow a slewable thermographic camera sensor, mounted on

3675-427: The muzzle end of the barrel via a bore-diameter arbor and projects a grid pattern onto the sight picture. Using this method, the normal sight (which is fixed to the receiver) and the collimator (which is fixed to the barrel) can be sighted to match. Most collimators have grid patterns for rechecking the zero after the barrel is sighted. A more modern method of boresighting is to use a laser pointer to illuminate

3780-456: The parity reversal of mirrors in Timaeus . Some hundred years later, Euclid (4th–3rd century BC) wrote a treatise entitled Optics where he linked vision to geometry , creating geometrical optics . He based his work on Plato's emission theory wherein he described the mathematical rules of perspective and described the effects of refraction qualitatively, although he questioned that

3885-523: The retina as the actual organ that recorded images, finally being able to scientifically quantify the effects of different types of lenses that spectacle makers had been observing over the previous 300 years. After the invention of the telescope, Kepler set out the theoretical basis on how they worked and described an improved version, known as the Keplerian telescope , using two convex lenses to produce higher magnification. Optical theory progressed in

3990-466: The surface normal , a line perpendicular to the surface at the point where the ray hits. The incident and reflected rays and the normal lie in a single plane, and the angle between the reflected ray and the surface normal is the same as that between the incident ray and the normal. This is known as the Law of Reflection . For flat mirrors , the law of reflection implies that images of objects are upright and

4095-529: The "emission theory" of Ptolemaic optics with its rays being emitted by the eye, and instead put forward the idea that light reflected in all directions in straight lines from all points of the objects being viewed and then entered the eye, although he was unable to correctly explain how the eye captured the rays. Alhazen's work was largely ignored in the Arabic world but it was anonymously translated into Latin around 1200 A.D. and further summarised and expanded on by

4200-465: The 19th century led to the discovery that light waves were in fact electromagnetic radiation. Some phenomena depend on light having both wave-like and particle-like properties . Explanation of these effects requires quantum mechanics . When considering light's particle-like properties, the light is modelled as a collection of particles called " photons ". Quantum optics deals with the application of quantum mechanics to optical systems. Optical science

4305-491: The Helmet-Mounted Symbology System (HMSS) developed by BAE Systems and Pilkington Optronics . Named the Striker and later version Striker II, it is capable of displaying both raster imagery and cursive symbology, with provisions for embedded NVGs . As with the DASH helmet, the system employs integrated position sensing to ensure that symbols representing outside-world entities move in line with

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4410-548: The Huygens–Fresnel principle states that every point of a wavefront is associated with the production of a new disturbance, it is possible for a wavefront to interfere with itself constructively or destructively at different locations producing bright and dark fringes in regular and predictable patterns. Interferometry is the science of measuring these patterns, usually as a means of making precise determinations of distances or angular resolutions . The Michelson interferometer

4515-473: The Israeli standard HGU-22/P) using a spherical visor to provide a collimated image to the pilot. A quick-disconnect wire powers the display and carries video drive signals to the helmet's cathode-ray tube (CRT). DASH is closely integrated with the aircraft's weapon system, via a MIL-STD-1553 B bus. Latest model DASH IV is currently integrated on India's HAL Tejas . After the U.S. withdrawal from ASRAAM ,

4620-546: The MiG-29 and Su-27 a significantly improved close combat capability. The Elbit Systems DASH III was the first modern Western HMD to achieve operational service. Development of the DASH began during the mid-1980s, when the IAF issued a requirement for F-15 and F-16 aircraft. The first design entered production around 1986, and the current GEN III helmet entered production during the early to mid-1990s. The current production variant

4725-882: The NVG image simultaneously. Scorpion is also used by Tactical Air Support Inc. on F-5AT, by French Air Force for Rafale F4, by the Spanish Air Force on EF-18s, the AC-130W Stinger II Gunship, the F-22 Raptor , and Belgian Air Force F-16AM/BM and U.S. Air National Guard F-16C. Aselsan of Turkey is working to develop a similar system to the French TopOwl Helmet, called the AVCI Helmet Integrated Cueing System. The system will also be utilized into

4830-523: The Polish monk Witelo making it a standard text on optics in Europe for the next 400 years. In the 13th century in medieval Europe, English bishop Robert Grosseteste wrote on a wide range of scientific topics, and discussed light from four different perspectives: an epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, and a theology of light, basing it on

4935-659: The South African Air Force (SAAF) used a locally developed helmet-mounted sight integrated with the Armscor V3A heat seeking missile. This enables the pilot to make off-bore attacks, without having to maneuver to the optimum firing position. After the South African system had been proven in combat, playing a role in downing Soviet aircraft over Angola, it is popularly claimed the Soviets embarked on

5040-588: The U.S. did not pursue fielding it except for integration into late-model Navy F-4 Phantoms equipped with the AIM-9 Sidewinder from 1969. HMDs were also introduced in helicopters during this time – examples include the Boeing AH-64 Apache with the Integrated Helmet and Display Sighting System (IHADSiSy) demonstrated in 1985. At the same time (1975) the Mirage 3CZ and Mirage F1AZ of

5145-599: The U.S. pursued and fielded JHMCS in conjunction with the Raytheon AIM-9X , in November 2003 with the 12th and 19th Fighter Squadrons at Elmendorf AFB , Alaska. The Navy conducted RDT&E on the F/A-18 C as lead platform for JHMCS, but fielded it first on the F/A-18 Super Hornet E and F aircraft in 2003. The USAF is also integrating JHMCS into its F-15E , F-15C , and F-16C aircraft. JHMCS

5250-484: The amplitude of the wave, which for light is associated with a brightening of the waveform in that location. Alternatively, if the two waves of the same wavelength and frequency are out of phase, then the wave crests will align with wave troughs and vice versa. This results in destructive interference and a decrease in the amplitude of the wave, which for light is associated with a dimming of the waveform at that location. See below for an illustration of this effect. Since

5355-435: The angles between the normal (to the interface) and the incident and refracted waves, respectively. The index of refraction of a medium is related to the speed, v , of light in that medium by n = c / v , {\displaystyle n=c/v,} where c is the speed of light in vacuum . Snell's Law can be used to predict the deflection of light rays as they pass through linear media as long as

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5460-440: The barrel and the sights on the top of the rifle, while doing this you can visually align the bore axis with the sights on a desired target. For bolt actions rifles the process is the same aside from the ability to remove different receivers, but the bolt can still be removed to view through the barrel. Once you are able to align the bore axis and the sights on the firearm you should then be able to at least get shots on or close to

5565-406: The barrel via a magnet , and projects a laser beam onto the target. Again, the user aligns the sights to the laser dot on the target. No matter which method of boresighting is used, the result is to align the sights to the spot where the barrel is pointing at a particular distance. Because of variations in the projectile trajectory and other factors, the boresighted rifle will always shoot below

5670-455: The base defining the visual field. The rays were sensitive, and conveyed information back to the observer's intellect about the distance and orientation of surfaces. He summarized much of Euclid and went on to describe a way to measure the angle of refraction , though he failed to notice the empirical relationship between it and the angle of incidence. Plutarch (1st–2nd century AD) described multiple reflections on spherical mirrors and discussed

5775-419: The boresighted spot and is only meant to approximate the actual points of impact, namely getting the shots "on paper " (landing in proximity to the point of aim). Live ammunition will need to be fired to further fine-tune the sighting process. Accuracy is the measure of how well the sighted object is represented. It can be measured from a specific decision-making circumstance, like the orientation of notches of

5880-576: The creation of magnified and reduced images, both real and imaginary, including the case of chirality of the images. During the Middle Ages , Greek ideas about optics were resurrected and extended by writers in the Muslim world . One of the earliest of these was Al-Kindi ( c.  801 –873) who wrote on the merits of Aristotelian and Euclidean ideas of optics, favouring the emission theory since it could better quantify optical phenomena. In 984,

5985-518: The development of lenses by the ancient Egyptians and Mesopotamians . The earliest known lenses, made from polished crystal , often quartz , date from as early as 2000 BC from Crete (Archaeological Museum of Heraclion, Greece). Lenses from Rhodes date around 700 BC, as do Assyrian lenses such as the Nimrud lens . The ancient Romans and Greeks filled glass spheres with water to make lenses. These practical developments were followed by

6090-602: The development of theories of light and vision by ancient Greek and Indian philosophers, and the development of geometrical optics in the Greco-Roman world . The word optics comes from the ancient Greek word ὀπτική , optikē ' appearance, look ' . Greek philosophy on optics broke down into two opposing theories on how vision worked, the intromission theory and the emission theory . The intromission approach saw vision as coming from objects casting off copies of themselves (called eidola) that were captured by

6195-449: The distance (as if on the surface of a pool of water). Optical materials with varying indexes of refraction are called gradient-index (GRIN) materials. Such materials are used to make gradient-index optics . For light rays travelling from a material with a high index of refraction to a material with a low index of refraction, Snell's law predicts that there is no θ 2 when θ 1 is large. In this case, no transmission occurs; all

6300-420: The distant point of aim, rather than using visual inspection. This method is preferable because it has less parallax , allows more movement in the gun as the projected laser beam will stay true to the bore axis, and does not require removing the bolt. As laser technology has become more affordable and portable, laser boresighters have become popular for sighting in riflescopes . One type of laser boresighter

6405-461: The distinction of being the first HMD introduced and deployed that can display full-color conformal symbology. It is used along with the aircraft mission system to cue the aircraft targeting pods, gimbaled sensors, and high off-boresight missiles. Scorpion provides an "eyes out" capability: even when objects may be obscured from view, Scorpion can provide visual graphic cues to the near-field display. Unlike most HMDs which require custom helmets, Scorpion

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6510-403: The early 17th century, Johannes Kepler expanded on geometric optics in his writings, covering lenses, reflection by flat and curved mirrors, the principles of pinhole cameras , inverse-square law governing the intensity of light, and the optical explanations of astronomical phenomena such as lunar and solar eclipses and astronomical parallax . He was also able to correctly deduce the role of

6615-426: The exchange of energy between light and matter only occurred in discrete amounts he called quanta . In 1905, Albert Einstein published the theory of the photoelectric effect that firmly established the quantization of light itself. In 1913, Niels Bohr showed that atoms could only emit discrete amounts of energy, thus explaining the discrete lines seen in emission and absorption spectra . The understanding of

6720-406: The eye. With many propagators including Democritus , Epicurus , Aristotle and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only speculation lacking any experimental foundation. Plato first articulated the emission theory , the idea that visual perception is accomplished by rays emitted by the eyes. He also commented on

6825-474: The focus to be smeared out in space. In particular, spherical mirrors exhibit spherical aberration . Curved mirrors can form images with a magnification greater than or less than one, and the magnification can be negative, indicating that the image is inverted. An upright image formed by reflection in a mirror is always virtual, while an inverted image is real and can be projected onto a screen. Refraction occurs when light travels through an area of space that has

6930-411: The gloss of surfaces such as mirrors, which reflect light in a simple, predictable way. This allows for the production of reflected images that can be associated with an actual ( real ) or extrapolated ( virtual ) location in space. Diffuse reflection describes non-glossy materials, such as paper or rock. The reflections from these surfaces can only be described statistically, with the exact distribution of

7035-440: The helmet) placed in an alternating field (generated in the flightdeck) to produce alternating electrical voltages based on the movement of the helmet in multiple axes. This technique requires precise magnetic mapping of the flightdeck to account for ferrous and conductive materials in the seat, flightdeck sills and canopy to reduce angular errors in the measurement. Acoustic sensing designs use ultrasonic sensors to monitor

7140-416: The incident rays came. This is called retroreflection . Mirrors with curved surfaces can be modelled by ray tracing and using the law of reflection at each point on the surface. For mirrors with parabolic surfaces , parallel rays incident on the mirror produce reflected rays that converge at a common focus . Other curved surfaces may also focus light, but with aberrations due to the diverging shape causing

7245-418: The indexes of refraction and the geometry of the media are known. For example, the propagation of light through a prism results in the light ray being deflected depending on the shape and orientation of the prism. In most materials, the index of refraction varies with the frequency of the light, known as dispersion . Taking this into account, Snell's Law can be used to predict how a prism will disperse light into

7350-436: The interaction between light and matter that followed from these developments not only formed the basis of quantum optics but also was crucial for the development of quantum mechanics as a whole. The ultimate culmination, the theory of quantum electrodynamics , explains all optics and electromagnetic processes in general as the result of the exchange of real and virtual photons. Quantum optics gained practical importance with

7455-426: The interaction of light with the material. For instance, the behaviour of a light wave interacting with a metal surface is quite different from what happens when it interacts with a dielectric material. A vector model must also be used to model polarised light. Numerical modeling techniques such as the finite element method , the boundary element method and the transmission-line matrix method can be used to model

7560-491: The inventions of the maser in 1953 and of the laser in 1960. Following the work of Paul Dirac in quantum field theory , George Sudarshan , Roy J. Glauber , and Leonard Mandel applied quantum theory to the electromagnetic field in the 1950s and 1960s to gain a more detailed understanding of photodetection and the statistics of light. Classical optics is divided into two main branches: geometrical (or ray) optics and physical (or wave) optics. In geometrical optics, light

7665-685: The late 1990s and early 2000s. The first civilian use of HMD on aircraft was the Elbit SkyLens HMD on ATR 72/42 airplane. While conceptually simple, implementation of aircraft HMDs is quite complex. There are many variables: HMD designs must sense the orientation (elevation, azimuth and roll) and in some cases the position (x, y, and z) of the pilot's head relative to the airframe with sufficient precision even under high " g ", vibration, and during rapid head movement. Five basic methods are used in current HMD technology – inertial, optical, electromagnetic, sonic, and hybrid. Hybrid trackers use

7770-504: The laws of reflection and refraction at interfaces between different media. These laws were discovered empirically as far back as 984 AD and have been used in the design of optical components and instruments from then until the present day. They can be summarised as follows: When a ray of light hits the boundary between two transparent materials, it is divided into a reflected and a refracted ray. The laws of reflection and refraction can be derived from Fermat's principle which states that

7875-422: The light is reflected. This phenomenon is called total internal reflection and allows for fibre optics technology. As light travels down an optical fibre, it undergoes total internal reflection allowing for essentially no light to be lost over the length of the cable. A device that produces converging or diverging light rays due to refraction is known as a lens . Lenses are characterized by their focal length :

7980-446: The mid-17th century with treatises written by philosopher René Descartes , which explained a variety of optical phenomena including reflection and refraction by assuming that light was emitted by objects which produced it. This differed substantively from the ancient Greek emission theory. In the late 1660s and early 1670s, Isaac Newton expanded Descartes's ideas into a corpuscle theory of light , famously determining that white light

8085-408: The naked eye and the bore axis of a firearm to dial in the sights of a firearm. Based on the type of firearm the procedure for optical bore sighting will vary. For AR style rifles the upper receiver can be dropped from the lower receiver and the bolt carrier group (BCG) can be removed exposing a clear line of sight through the barrel. With the upper receiver fixed in place you can then co-witness through

8190-661: The nose of the aircraft, to be slaved to the aviator's head movements. The display also enables Nap-of-the-earth night navigation. IHADSS is also used on the Italian Agusta A129 Mangusta . The Russian designed Shchel-3UM HMD design from 1981, has been fitted to the ZSh-5 series helmet (and later ZSh-7 helmets), and has been used on the MiG-29 and Su-27 in conjunction with the R-73 missile ( NATO reporting name : AA-11 Archer). The HMD/Archer combination gave

8295-405: The object and image distances are positive if the object and image are on opposite sides of the lens. Incoming parallel rays are focused by a converging lens onto a spot one focal length from the lens, on the far side of the lens. This is called the rear focal point of the lens. Rays from an object at a finite distance are focused further from the lens than the focal distance; the closer the object

8400-560: The optical sensor is used to constrain IMU drift. As a result, hybrid inertial/optical trackers feature low latency and high accuracy. The Thales Scorpion® HMCS and HMIT HMDs utilize a tracker made by InterSense called the Hybrid Optical-based Inertial Tracker (HObIT). Optical systems employ infrared emitters on the helmet (or flightdeck ) infrared detectors in the flightdeck (or helmet), to measure

8505-676: The path taken between two points by a ray of light is the path that can be traversed in the least time. Geometric optics is often simplified by making the paraxial approximation , or "small angle approximation". The mathematical behaviour then becomes linear, allowing optical components and systems to be described by simple matrices. This leads to the techniques of Gaussian optics and paraxial ray tracing , which are used to find basic properties of optical systems, such as approximate image and object positions and magnifications . Reflections can be divided into two types: specular reflection and diffuse reflection . Specular reflection describes

8610-630: The pilot video with imagery in day or night conditions. Consequently, the F-35 is the first tactical fighter jet in 50 years to fly without a HUD. A BAE Systems helmet was considered when HMDS development was experiencing significant problems, but these issues were eventually worked out. The Helmet-Mounted Display System was fully operational and ready for delivery in July 2014. Jedeye is a new system recently introduced by Elbit Systems especially to meet Apache and other rotary wing platform requirements. The system

8715-630: The pilot's head movements. Vision Systems International (VSI; the Elbit Systems / Rockwell Collins joint venture) along with Helmet Integrated Systems, Ltd. developed the Helmet-Mounted Display System (HMDS) for the F-35 Joint Strike Fighter aircraft. In addition to standard HMD capabilities offered by other systems, HMDS fully utilizes the advanced avionics architecture of the F-35 and provides

8820-412: The pilot's head position while being updated by computer software in multiple axes. Typical operating frequencies are in the 50 to 100  kHz range and can be made to carry audio sound information directly to the pilot's ears via subcarrier modulation of the ultrasonic sensing signals. Older HMDs typically employ a compact CRT embedded in the helmet, and suitable optics to display symbology on to

8925-541: The pilot's head position. The main limitations are restricted fields of regard and sensitivity to sunlight or other heat sources. The MiG-29/AA-11 Archer system uses this technology. The Cobra HMD as used on both the Eurofighter Typhoon and the JAS39 Gripen both employ the optical helmet tracker developed by Denel Optronics (now part of Zeiss Optronics). Electromagnetic sensing designs use coils (in

9030-547: The pilot's visor or reticle, focused at infinity . Modern HMDs have dispensed with the CRT in favor of micro-displays such as liquid crystal on silicon (LCOS) or liquid crystal display (LCD) along with an LED illuminator to generate the displayed image. Advanced HMDs can also project FLIR or night vision imagery. A recent improvement is the capability to display color symbols and video. Systems are presented in rough chronological order of initial operating capability . In 1985,

9135-540: The pilot. The integration of the night-vision goggles with the JHMCS was a key requirement of the program. When combined with the AIM-9X, an advanced short-range dogfight weapon that employs a Focal Plane Array seeker and a thrust vectoring tail control package, JHMCS allows effective target designation up to 80 degrees either side of the aircraft's nose. In March 2009, a successful 'Lock on After Launch' firing of an ASRAAM at

9240-511: The propagation of light in systems which cannot be solved analytically. Such models are computationally demanding and are normally only used to solve small-scale problems that require accuracy beyond that which can be achieved with analytical solutions. All of the results from geometrical optics can be recovered using the techniques of Fourier optics which apply many of the same mathematical and analytical techniques used in acoustic engineering and signal processing . Gaussian beam propagation

9345-423: The reflected light depending on the microscopic structure of the material. Many diffuse reflectors are described or can be approximated by Lambert's cosine law , which describes surfaces that have equal luminance when viewed from any angle. Glossy surfaces can give both specular and diffuse reflection. In specular reflection, the direction of the reflected ray is determined by the angle the incident ray makes with

9450-464: The rudimentary optical theory of the day (theory which for the most part could not even adequately explain how spectacles worked). This practical development, mastery, and experimentation with lenses led directly to the invention of the compound optical microscope around 1595, and the refracting telescope in 1608, both of which appeared in the spectacle making centres in the Netherlands. In

9555-415: The same distance behind the mirror as the objects are in front of the mirror. The image size is the same as the object size. The law also implies that mirror images are parity inverted, which we perceive as a left-right inversion. Images formed from reflection in two (or any even number of) mirrors are not parity inverted. Corner reflectors produce reflected rays that travel back in the direction from which

9660-407: The same side of the lens as the object. The closer the object is to the lens, the closer the virtual image is to the lens. As with mirrors, upright images produced by a single lens are virtual, while inverted images are real. Lenses suffer from aberrations that distort images. Monochromatic aberrations occur because the geometry of the lens does not perfectly direct rays from each object point to

9765-405: The simple equation 1 S 1 + 1 S 2 = 1 f , {\displaystyle {\frac {1}{S_{1}}}+{\frac {1}{S_{2}}}={\frac {1}{f}},} where S 1 is the distance from the object to the lens, θ 2 is the distance from the lens to the image, and f is the focal length of the lens. In the sign convention used here,

9870-444: The superposition principle can be used to predict the shape of interacting waveforms through the simple addition of the disturbances. This interaction of waves to produce a resulting pattern is generally termed "interference" and can result in a variety of outcomes. If two waves of the same wavelength and frequency are in phase , both the wave crests and wave troughs align. This results in constructive interference and an increase in

9975-422: The target. With the rifle reassembled you should be able to put shots down range and make more fine-tuned adjustments. A drawback of using the naked eye to boresight is that it can be difficult due to the tunnel vision and lack of brightness, especially with longer-barreled guns. A more advanced method of boresighting uses a collimator boresighter, an optical attachment similar to a scope sight, which fits onto

10080-440: The term "light" is also often applied to infrared (0.7–300 μm) and ultraviolet radiation (10–400 nm). The wave model can be used to make predictions about how an optical system will behave without requiring an explanation of what is "waving" in what medium. Until the middle of the 19th century, most physicists believed in an "ethereal" medium in which the light disturbance propagated. The existence of electromagnetic waves

10185-722: The unified German Air Force. One successful HMD was the Israeli Air Force Elbit DASH series, fielded in conjunction with the Python 4 , in the early 1990s. The U.S., UK, and Germany pursued a HMD combined with ASRAAM systems. Technical difficulties led to the U.S. abandoning ASRAAM, instead funding development of the AIM-9X and the Joint Helmet-Mounted Cueing System in 1990. American and European fighter HMDs became widely used in

10290-641: The works of Aristotle and Platonism. Grosseteste's most famous disciple, Roger Bacon , wrote works citing a wide range of recently translated optical and philosophical works, including those of Alhazen, Aristotle, Avicenna , Averroes , Euclid, al-Kindi, Ptolemy, Tideus, and Constantine the African . Bacon was able to use parts of glass spheres as magnifying glasses to demonstrate that light reflects from objects rather than being released from them. The first wearable eyeglasses were invented in Italy around 1286. This

10395-400: Was a famous instrument which used interference effects to accurately measure the speed of light. The appearance of thin films and coatings is directly affected by interference effects. Antireflective coatings use destructive interference to reduce the reflectivity of the surfaces they coat, and can be used to minimise glare and unwanted reflections. The simplest case is a single layer with

10500-447: Was a mix of colours that can be separated into its component parts with a prism . In 1690, Christiaan Huygens proposed a wave theory for light based on suggestions that had been made by Robert Hooke in 1664. Hooke himself publicly criticised Newton's theories of light and the feud between the two lasted until Hooke's death. In 1704, Newton published Opticks and, at the time, partly because of his success in other areas of physics, he

10605-423: Was designed to be installed on a standard issue HGU-55/P and HGU-68/P helmets and is fully compatible with standard issue U.S. Pilot Flight Equipment without special fitting. It is also fully compatible with standard unmodified AN/AVS-9 Night Vision Goggles (NVG) and Panoramic Night Vision Goggles (PNVG). Pilots, using Scorpion, can view both the night vision image and the symbols on the display. Scorpion uses

10710-403: Was generally considered to be the victor in the debate over the nature of light. Newtonian optics was generally accepted until the early 19th century when Thomas Young and Augustin-Jean Fresnel conducted experiments on the interference of light that firmly established light's wave nature. Young's famous double slit experiment showed that light followed the superposition principle , which

10815-467: Was predicted in 1865 by Maxwell's equations . These waves propagate at the speed of light and have varying electric and magnetic fields which are orthogonal to one another, and also to the direction of propagation of the waves. Light waves are now generally treated as electromagnetic waves except when quantum mechanical effects have to be considered. Many simplified approximations are available for analysing and designing optical systems. Most of these use

10920-453: Was subsequently acquired by Thales in 2012. The HMIT system was qualified and deployed on both A-10 and F-16 platforms in 2012. Starting in 2018, the installed base of HMIT systems went through a helmet tracker upgrade. The original AC magnetic tracking sensor was replaced by an inertial-optical hybrid tracker called Hybrid Optical based Inertial Tracker (HObIT). The HObIT was developed by InterSense and tested by Thales in 2014. Scorpion has

11025-463: Was the start of the optical industry of grinding and polishing lenses for these "spectacles", first in Venice and Florence in the thirteenth century, and later in the spectacle making centres in both the Netherlands and Germany. Spectacle makers created improved types of lenses for the correction of vision based more on empirical knowledge gained from observing the effects of the lenses rather than using

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