A gyro gunsight is a modification of the non-magnifying reflector sight in which target lead and bullet drop are calculated automatically. The first examples were developed in Britain just before the Second World War for use during aerial combat, more advanced models were common on Allied aircraft by the end of the war; the amount of lead required to hit a target is a function of the rate of turn of the attacking aircraft and the range to the target. The former is measured using a gyroscope in the sight, while the is estimated by the pilot by moving a dial or pointer so that a reticle in the sight matches the wingspan of the target. Post-war models added a small radar to automate the range measurement. Gyro sights contained more than one reticle to assist in proper aiming: a fixed one just a dot, signifying the direction the guns are pointing, a moving one showing the corrected aiming point, a ring to match to a target plane's known wingspan. A advanced model, the K-14 found in the North American P-51 Mustang, had separate projectors and displays for air and ground attacks.
In 1936 Royal Aircraft Establishment scientist Leslie Bennet Craigie Cunningham suggested using a gyroscope's resistance to rotation to modify the aiming point in a gun sight to compensate for deflection caused by a turning aircraft. This arrangement meant the information presented to the pilot was of his own aircraft, the deflection/lead calculated was based on his own bank-level, rate of turn, airspeed etc; the assumption was that the flight path was following the flight path of the target aircraft, as in a dogfight, therefore the input data was close enough. After tests with two experimental gyro gunsights which had begun in 1939, the first production gyro gunsight was the British Mark I Gyro Sight, developed at Farnborough in 1941. To save time in development the sight was based on the existing type G prismatic sight a telescopic gun sight folded into a shorter length by a series of prisms. Prototypes were tested in a Supermarine Spitfire and the turret of a Boulton Paul Defiant in the early part of that year.
With the successful conclusion of these tests the sight was put into production by Ferranti, the first limited-production versions being available by the spring of 1941, with the sights being first used operationally against Luftwaffe raids on Britain in July the same year. The Mark I sight had a number of drawbacks, including a limited field of view, erratic behaviour of the reticle, requiring the pilot/gunner to put their eye up against an eyepiece during violent manoeuvres. Production of the Mark I was postponed and work started on an improved sight. Changes involved incorporating the gyro adjusted reticle into a more standard reflector sight system, a non magnifying optical sight, around since 1918. Reflector sights consisting of a 45 degree angle glass beam splitter that sat in front of the pilot and projected an illuminated image of an aiming reticle that appeared to sit out in front of the pilot's field of view at infinity and was aligned with the plane's guns; the sight sat some distance away from the pilot making it safer to use and didn't impair the pilots field of view.
The optical nature of the reflector sight meant it was possible to feed other information into field of view. In the reflector sight version, range was measured by comparing the wingspan of the target seen through the sight to a pre-set number; the pre-set number was selected via a large dial on the front of the sight, the range was measured by turning another dial on the aircraft's throttle. This new sight became the Mark II Gyro Sight, first tested in late 1943 with production examples becoming available in the same year. Ferranti built a new factory in the Crewe Toll area of Scotland to build the sights; this factory would go on to be the center for Ferranti's long history in radar development. The Mark II was subsequently produced in the US by Sperry as the K-14 and Mk18; the K-14 included two projector systems for the reflector sight, one with gyro correction for attacking aircraft, a second for attacking ground targets. It was otherwise similar to the British models, although the dial for adjusting the target size was moved to the left side of the sight instead of the front.
The area were the Mark II had the dial was replaced by a moving scale that indicated the current range to the target, along with a large pad that stopped the pilot from smacking their head on it in the case of a rapid stop. The radar-aimed AGLT Village Inn tail turret incorporated a Mark II Gyro Sight and this turret was fitted to some Lancaster bombers towards the end of World War II. Although since 1935 the relevant German companies offered the Reich Air Ministry a new type of gyro-stabilized sight, the well-proven REVI remained in service for combat aircraft; the gyro-stabilized sights received an additional designation of EZ, such as EZ/REVI-6a. The development of the EZ 40 gyro sight began in 1935 at the Carl Zeiss and Askania companies, but was of low priority. Not until the beginning of 1942, when a US P-47 Thunderbolt fighter equipped with a gyro-stabilised sight was captured, did the RLM speed up research. In the summer of 1941, the EZ 40, for which both the Carl Zeiss and Askania companies were submitting their developments, was rejected.
Tested in a Bf 109 F, Askania's EZ 40 produced 50 to 100% higher hit probability compared to the standard sight, the REVI C12c. In the summer of 1943 an example of the EZ 41 developed by the Zeiss company was tested, bu
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 describes the behaviour of visible and infrared light; because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays and radio waves exhibit similar properties. Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however difficult to apply in practice. Practical optics is done using simplified models; the most common of these, geometric optics, treats light as 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; the ray-based model of light was developed first, followed by the wave model of light.
Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation. Some phenomena depend on the fact that light has both 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 is relevant to and studied in many related disciplines including astronomy, various engineering fields and medicine. Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, telescopes, microscopes and fibre optics. Optics began with the development of lenses by Mesopotamians; the earliest known lenses, made from polished crystal quartz, date from as early as 700 BC for Assyrian lenses such as the Layard/Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses.
These practical developments were followed by the development of theories of light and vision by ancient Greek and Indian philosophers, the development of geometrical optics in the Greco-Roman world. The word optics comes from the ancient Greek word ὀπτική, meaning "appearance, look". Greek philosophy on optics broke down into two opposing theories on how vision worked, the "intromission theory" and the "emission theory"; the intro-mission approach saw vision as coming from objects casting off copies of themselves that were captured by the eye. With many propagators including Democritus, Epicurus and their followers, this theory seems to have some contact with modern theories of what vision 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 commented on the parity reversal of mirrors in Timaeus. Some hundred years Euclid 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 a beam of light from the eye could instantaneously light up the stars every time someone blinked. Ptolemy, in his treatise Optics, held an extramission-intromission theory of vision: the rays from the eye formed a cone, the vertex being within the eye, the base defining the visual field; the rays were sensitive, conveyed information back to the observer's intellect about the distance and orientation of surfaces. He summarised 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. 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 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, the Persian mathematician Ibn Sahl wrote the treatise "On burning mirrors and lenses" describing a law of refraction equivalent to Snell's law. He used this law to compute optimum shapes for curved mirrors. In the early 11th century, Alhazen wrote the Book of Optics in which he explored reflection and refraction and proposed a new system for explaining vision and light based on observation and experiment, he rejected the "emission theory" of Ptolemaic optics with its rays being emitted by the eye, instead put forward the idea that light reflected in all directions in straight lines from all points of the objects being viewed and entered the eye, although he was unable to explain how the eye captured the rays. Alhazen's work was ignored in the Arabic world but it was anonymously translated into Latin around 1200 A. D. and further summarised and expanded on by 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, discussed light from four different perspectives: an epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, a theology of light, basing it on the works Aristotle and Platonism.
Grosseteste's most famous disciple, Roger Bacon, wrote w
A circumferentor, or surveyor's compass, is an instrument used in surveying to measure horizontal angles. It was superseded by the theodolite in the early 19th century. A circumferentor consists of a circular brass box containing a magnetic needle, which moves over a brass circle, or compass divided into 360 degrees; the needle is protected by a glass covering. A pair of sights is located on the North-South axis of the compass. Circumferentors were mounted on tripods and rotated on ball-and-socket joints. Circumferentors were made throughout Europe, including in England, France and Holland. By the early 19th century, Europeans preferred theodolites to circumferentors. However, the circumferentor remained in common use in mines and in wooded or uncleared areas, such as in America. To measure an angle with a circumferentor, such as angle EKG, place the instrument at K, with the fleur-de-lis in the card towards you. Direct the sights, until through them you see E. Turn the instrument around, with the fleur-de-lis still towards you, direct the sights to G.
Subtract the lesser number, 182, from the greater, 296°. If the remainder is more than 180 degrees, it must be subtracted from 360 degrees. To take the plot of a field, park, etc. with a circumferentor, consider region ABCDEFGHK in Figure 2, an area to be surveyed. Placing the instrument at A, the fleur-de-lis towards you, direct the sights to B. Placing the instrument at B, direct the sights as before to C. Move the instrument to C. In the same manner, proceed to D, E, F, G, H, lastly to K; this will result in a table of the following form: From this table, the field is to be plotted, or protracted. Alternative plotting method: An alternative way to plot the area in Figure 2 is to use several angles and only a few measurements and calculate their positions; this could be done by starting at the center point in Figure 2, not labeled, but which will be referred to as "Center." Assume each point can be seen from each other point. From the "center" point and record the angle to each point using the sights as described above.
Move to, measure the distance to, one of the other points referenced, such as point B. At point B, measure the angles to all the other points. Move to an additional point such as point F. Again, measure the distance from the center to the point chosen. At that point and record the angles to each of the other points as was done at point B. Chose a scale that will allow the plot to fit on your paper and plot the angles and distances; the advantage of this method over the first one above is that there are fewer distance measurements and any errors in angles or distances will not be cumulative. The second method can be used when it is not possible to measure some of the distances, for example, if there is a water barrier between two of the points. If there are any inaccuracies in the measurements, they will be revealed in the plot because the points plotted from various angles will not coincide. Additional considerations include the number of times the circumferentor must be aligned. With the first method, the instrument must be set up at each point with a compass.
With the second method, the initial set up is at "center." After that, for example at point B, the instrument can be set up by aligning the sight with the reciprocal of the angle between "center" and B. Thus, any local change in the magnetic field that would affect the compass would be nullified. A double prism is a device to measure right angles, consisting of two five sided prisms stacked on top of each other and a plumb-bob, it is used to stake for example on a construction site. Graphometer Alidade This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed.. "article name needed". Cyclopædia, or an Universal Dictionary of Arts and Sciences. James and John Knapton, et al. "Circumferentor". Oxford English Dictionary. Oxford University Press. 2nd edition. 1989
The diopter is an aperture sight component used to assist the aiming of devices firearms and crossbows. It is found in particular as a rear sight element on rifles. To obtain a usable sighting line the diopter has to have a complementing front sight element. Diopter and globe sighting lines are used in ISSF match rifle shooting events; the diopter is in principle a height and sideways adjustable occluder with a small hole, is placed close in front of the shooter's aiming eye. Through this small hole the shooter can view the intended target; the typical occluder used in target shooting diopters is a disc of about 2.5 cm in diameter with a small hole in the middle. The small diopter viewing opening ensures the shooter's eye is precisely and centered behind the diopter sight; the diopter sight is easy to use and allows for accurate aiming, because a relative long sighting line can be used. A long sighting line helps to reduce eventual angle errors and will, in case the sight has an incremental adjustment mechanism, adjust in smaller increments when compared to a further identical shorter sighting line.
The "diopter sight effect" is achieved when looking through an aperture opening of 1.2 millimeters or less, happens due to an optical phenomenon resulting in the light passing through being parallelized similar to how a collimated lens would. Because of this optical effect the front sight will appear more steady though the shooter moves the head in a way such that the sighting eye moves sideways relative to the rear sight; the depth of field is increased so that both the sights and shooting target will appear sharp at the same time which further simplifies the aiming process. A rear sight with a larger aperture than 1.2 mm is not a diopter sight, but nonetheless is still referred to as such. With larger aperture sights the shooter must make a conscious effort to center the eye in the rear sight for precise aiming. A true diopter sight however has the advantage that the shooter does not have to concentrate on eye and rear sight alignment for precision aiming, therefore the sighting process is reduced to only aligning the front sight to the target.
Aperture sights require being placed close to the aiming eye, while open sights have to be placed at least 30 cm away from the eye to in order to appear sharp. Typical modern target shooting diopters offer windage and elevation correction in increments of 2 to 4 mm at 100 m; some ISSF shooting events require this precision level for sight adjustment since the score of the top competitors last shots series is expressed in 0.1s of scoring ring points. High end target shooting diopters accept accessories like rubber eye shields, adjustable diopter aperture and optical filter systems for the aiming eye and semi-transparent occluders for the non-aiming eye to ensure optimal sighting conditions for match shooters; the complementing front sight element may be a simple bead or post for service arms, but is for target shooting more a globe type sight, which consists of a hollow cylinder with a threaded cap, which allows interchangeable differently shaped front sight elements to be used. Most common are posts of varying widths and heights or rings or holes of varying diameter — these can be chosen by the shooter for the best fit to the target being used.
Tinted transparent plastic insert elements may be used, with a hole in the middle. High end target front sight tunnels also accept accessories like adjustable aperture and optical systems to ensure optimal sighting conditions for match shooters; some high end target sight line manufacturers offer front sights with integrated aperture mechanisms. The use of round rear and front sighting elements for aiming at round targets, like used in ISSF match shooting, takes advantage of the natural ability of the eye and brain to align concentric circles. For optimal aiming and comfort the shooter should focus the aiming eye on the front sighting element. To avoid eye fatigue and improve balance the non-aiming eye should be kept open; the non-aiming eye can be blocked from seeing distractions by mounting a semi-transparent occluder to the diopter. For maximum precision, there should still be a significant area of white visible around the bullseye and between the front and rear sight ring. Since the best key to determining center is the amount of light passing through the apertures, a narrow, dim ring of light can be more difficult to work with than a larger, brighter ring.
The precise sizes of the employed components are quite subjective, depend on both shooter preference and ambient lighting, why target rifles come with replaceable front sight inserts, adjustable aperture mechanisms. Head Position, Diopter Interval and Lint by Heinz Reinkemeier, UIT Journal at www.issf-sports.org
A computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of called programs; these programs enable computers to perform an wide range of tasks. A "complete" computer including the hardware, the operating system, peripheral equipment required and used for "full" operation can be referred to as a computer system; this term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster. Computers are used as control systems for a wide variety of industrial and consumer devices; this includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer-aided design, general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers and it connects hundreds of millions of other computers and their users.
Early computers were only conceived as calculating devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations. Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century; the first digital electronic calculating machines were developed during World War II. The speed and versatility of computers have been increasing ever since then. Conventionally, a modern computer consists of at least one processing element a central processing unit, some form of memory; the processing element carries out arithmetic and logical operations, a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices, output devices, input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.
According to the Oxford English Dictionary, the first known use of the word "computer" was in 1613 in a book called The Yong Mans Gleanings by English writer Richard Braithwait: "I haue read the truest computer of Times, the best Arithmetician that euer breathed, he reduceth thy dayes into a short number." This usage of the term referred to a human computer, a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century. During the latter part of this period women were hired as computers because they could be paid less than their male counterparts. By 1943, most human computers were women. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations; the Online Etymology Dictionary gives the first attested use of "computer" in the 1640s, meaning "one who calculates". The Online Etymology Dictionary states that the use of the term to mean "'calculating machine' is from 1897."
The Online Etymology Dictionary indicates that the "modern use" of the term, to mean "programmable digital electronic computer" dates from "1945 under this name. Devices have been used to aid computation for thousands of years using one-to-one correspondence with fingers; the earliest counting device was a form of tally stick. Record keeping aids throughout the Fertile Crescent included calculi which represented counts of items livestock or grains, sealed in hollow unbaked clay containers; the use of counting rods is one example. The abacus was used for arithmetic tasks; the Roman abacus was developed from devices used in Babylonia as early as 2400 BC. Since many other forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, markers moved around on it according to certain rules, as an aid to calculating sums of money; the Antikythera mechanism is believed to be the earliest mechanical analog "computer", according to Derek J. de Solla Price.
It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, has been dated to c. 100 BC. Devices of a level of complexity comparable to that of the Antikythera mechanism would not reappear until a thousand years later. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use; the planisphere was a star chart invented by Abū Rayhān al-Bīrūnī in the early 11th century. The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BC and is attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was an analog computer capable of working out several different kinds of problems in spherical astronomy. An astrolabe incorporating a mechanical calendar computer and gear-wheels was invented by Abi Bakr of Isfahan, Persia in 1235. Abū Rayhān al-Bīrūnī invented the first mechanical geared lunisolar calendar astrolabe, an early fixed-wired knowledge processing machine with a gear train and gear-wheels, c. 1000 AD.
The sector, a calculating instrument used for solving problems in proportion, trigonometry and division, for various functions, such as squares and cube roots, was developed in
A reticle, or reticule known as a graticule, is a pattern of fine lines or markings built into the eyepiece of a sighting device, such as a telescopic sight in a telescope, a microscope, or the screen of an oscilloscope, to provide measurement references during visual examination. Today, engraved lines or embedded fibers may be replaced by a computer-generated image superimposed on a screen or eyepiece. Both terms may be used to describe any set of lines used for optical measurement, but in modern use reticle is most used for gunsights and such, while graticule is more used for the oscilloscope display, microscope slides, similar roles. There are many variations of reticles. Crosshairs are most represented as intersecting lines in the shape of a cross, "+", though many variations exist, including dots, circles, chevrons, or a combination of these. Most associated with telescopic sights for aiming firearms, crosshairs are common in optical instruments used for astronomy and surveying, are popular in graphical user interfaces as a precision pointer.
The reticle is said to have been invented by Robert Hooke, dates to the 17th century. Another candidate as inventor is the amateur astronomer William Gascoigne. Telescopic sights for firearms just called scopes, are the device most associated with crosshairs. Motion pictures and the media use a view through crosshairs as a dramatic device, which has given crosshairs wide cultural exposure. While the traditional thin crossing lines are the original and still the most familiar cross-hair shape, they are best suited for precision aiming at high contrast targets, as the thin lines are lost in complex backgrounds, such as those encountered while hunting. Thicker bars are much easier to discern against a complex background, but lack the precision of thin bars; the most popular types of cross-hair in modern scopes are variants on the duplex cross-hair, with bars that are thick on the perimeter and thin out in the middle. The thick bars allow the eye to locate the center of the reticle, the thin lines in the center allow for precision aiming.
The thin bars in a duplex reticle may be designed to be used as a measure. Called a 30/30 reticle, the thin bars on such a reticle span 30 minutes of arc, equal to 30 inches at 100 yards; this enables an experienced shooter to deduce, on the basis of the known size of an object in view, the range within an acceptable error limit. Crosshairs were constructed out of hair or spiderweb, these materials being sufficiently thin and strong. Many modern scopes use wire crosshairs, which can be flattened to various degrees to change the width; these wires are silver in color, but appear black when backlit by the image passing through the scope's optics. Wire reticles are by nature simple, as they require lines that pass all the way across the reticle, the shapes are limited to the variations in thickness allowed by flattening the wire; the advantage of wire crosshairs is that they are tough and durable, provide no obstruction to light passing through the scope. The first suggestion for etched glass reticles was made by Philippe de La Hire in 1700.
His method was based on engraving the lines on a glass plate with a diamond point. Many modern crosshairs are etched onto a thin plate of glass, which allows a far greater latitude in shapes. Etched glass reticles can have floating elements. A potential disadvantage of glass reticles is that they are less durable than wire crosshairs, the surface of the glass reflects some light lessening transmission through the scope, although this light loss is near zero if the glass is multicoated. Reticles may be illuminated, either by a plastic or fiber optic light pipe collecting ambient light or, in low light conditions, by a battery powered LED; some sights use the radioactive decay of tritium for illumination that can work for 11 years without using a battery, used in the British SUSAT sight for the SA80 assault rifle and in the American ACOG. Red is the most common color used, as it is the least destructive to the shooter's night vision, but some products use green or yellow illumination, either as a single colour or changeable via user selection.
A graticule is another term for reticle encountered in British and British military technical manuals, came into common use during World War One. The reticle may be located at rear focal plane of the telescopic sight. On fixed power telescopic sights there is no significant difference, but on variable power telescopic sights the front plane reticle remains at a constant size compared to the target, while rear plane reticles remain a constant size to the user as the target image grows and shrinks. Front focal plane reticles are more durable, but most American users prefer that the reticle remains constant as the image changes size, so nearly all modern American variable power telescopic sights are rear focal plane designs. American and European hig
Thermal weapon sight
A thermographic weapon sight, thermal imagery scope or thermal weapon sight is a sighting device combining a compact thermographic camera and an aiming reticle. They can be mounted on a variety of small arms as well as some heavier weapons; as with regular ultraviolet sensors, thermal weapon sights can operate in total darkness. The thermal scope can be quite useful in places with snow as the extreme difference in temperatures between the snow and any source of heat creates a high visual contrast between the two; this makes it easy to locate any source of heat against its low-temperature background. Thermal weapon sights are used by hunters to aid in the detection of game, such as feral hogs, coyotes, or rodents such as rats; the sight's ability to see unaided in complete darkness allows the hunter to be undetected and aware of potential prey, facilitating a quick and precise takedown. The new generation of thermal weapon have sharing features and are compatible with video-sharing websites including Youtube.
The whole shooting adventure is recorded by the thermal imaging device and forwarded by a mobile phone application. The file is transferred by a wifi network and the video clips can be copied directly into a video-sharing website or videos can be stored in the SD card as well and can subsequently be viewed on a personal computer or television; the new generation thermal weapon by companies including Flir and Pulsar, where as the previous generation were used by the military and hunters. Night vision Thermography Thermographic camera