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Asight orsighting device is anydevice used to assist in precisevisual alignment (i.e.aiming) of weapons,surveying instruments, aircraft equipment,[1][2] optical illumination equipment or larger optical instruments with the intended target. Sights can be a simple set or system of physical markers that serve as visual references for directly aligning the user'sline of sight with the target (such asiron sights onfirearms),[3] oroptical instruments that provide an optically enhanced—oftenmagnified—target image aligned in the samefocus with anaiming point (e.g.telescopic,reflector andholographic sights). There are also sights that actively project an illuminated point of aim (a.k.a. "hot spot") onto the target itself so it can be observed by anyone with a direct view, such aslaser sights andinfrared illuminators on somenight vision devices,[citation needed] as well asaugmented or evenvirtual reality-enableddigital cameras ("smart scopes") with softwarealgorithms that producedigitally enhanced target images.
At its simplest, a sight typically has two components, front and rear aiming pieces that have to be lined up. Sights such as this can be found on many types of devices including weapons,surveying and measuring instruments, and navigational tools.
On weapons, these sights are usually formed by rugged metal parts, giving them the name "iron sights",[4] as distinct from optical or computing sights.[5] On many types of weapons they are built-in and may be fixed, adjustable, or marked forelevation,windage, target speed, etc.[3] They are also classified in forms of notch (open sight) or aperture (closed sight). These types of sights can require considerable experience and skill, as the user has to hold proper eye position and simultaneously focus on the rear sight, the front sight, and a target, all at different distances, and align all threeplanes of focus.[6]
Optical sights useoptics that give the user an enhanced image with an aligned aiming point or pattern (also called areticle)superimposed onto the target image, preferably at the samefocal plane.
Atelescopic sight is arefracting telescope equipped with some form ofreferencing pattern (reticle) mounted in an optically appropriate position in the optical system to give an accurate aiming point. Telescopic sights are used on a wide range of devices includingguns,surveying equipment, and even as sights on larger telescopes (called afinderscope).
Another type of optical sight is thereflector (or "reflex") sight, a generally non-magnifying optical device that allows the user to look through a glass element and see a reflection of an illuminated aiming point or some other image superimposed on thefield of view.[7] These sights have been around for over 100 years and have been used on all types of weapons and devices.
Reflector sights were first used as a weapon sight in German aircraft towards the end ofWorld War I. Over the years they became more sophisticated, adding lead computing gyroscopes and electronics (theWorld War IIGyro gunsight)[8] radar range finding and other flight information in the 1950s and 1960s, eventually becoming the modernhead-up display.
There are many types of sighting devices. They can be fixed, mechanical, optical,computational, or a mixture of all of these attributes.
