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A reflector sight or reflex sight is an optical
sight Visual perception is the ability to interpret the surrounding Biophysical environment, environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the ...
that allows the user to look through a partially reflecting glass element and see an illuminated projection of an aiming point or some other image superimposed on the field of view. These sights work on the simple optical principle that anything at the focus of a lens or curved mirror (such as an illuminated reticle) will appear to be sitting in front of the viewer at infinity. Reflector sights employ some sort of "reflector" to allow the viewer to see the infinity image and the field of view at the same time, either by bouncing the image created by lens off a slanted glass plate, or by using a mostly clear curved glass reflector that images the reticle while the viewer looks through the reflector. Since the reticle is at infinity it stays in alignment with the device to which the sight is attached regardless of the viewer's eye position, removing most of the
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
and other sighting errors found in simple sighting devices. Since their invention in 1900, reflector sights have come to be used as gun
sight Visual perception is the ability to interpret the surrounding Biophysical environment, environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the ...
s on various weapons. They were used on
fighter aircraft Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
, in a limited capacity in
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, widely used in
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, and still used as the base component in many types of modern head-up displays. They have been used in other types of (usually large) weapons as well, such as
anti-aircraft gun Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
sights, anti-tank gun sights, and any other role where the operator had to engage fast moving targets over a wide field of view, and the sight itself could be supplied with sufficient electrical power to function. There was some limited use of the sight on small arms after World War II, but the sight came into widespread use during the late 1970s with the invention of the red dot sight. This sight uses a red
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LED) as its illumination source, making a durable, dependable sight with an extremely long illumination run time. Reflector sights are also used in civilian applications such as sights on surveying equipment,
optical telescope An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electro ...
pointing aids, and camera
viewfinder In photography, a viewfinder is what the photographer looks through to compose, and, in many cases, to focus the picture. Most viewfinders are separate, and suffer parallax, while the single-lens reflex camera lets the viewfinder use the main ...
s.


Design

Reflector sights work by using a lens or an image-forming curved mirror with a luminous or reflective overlay image or reticle at its focus, creating an optical collimator that produces a virtual image of that reticle. The image is reflected off some form of angled
beam splitter A beam splitter or ''beamsplitter'' is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding wide ...
or the partially silvered collimating curved mirror itself so that the observer (looking through the beam splitter or mirror) will see the image at the focus of the collimating optics superimposed in the sight's field of view in focus at ranges up to
infinity Infinity is that which is boundless, endless, or larger than any natural number. It is often denoted by the infinity symbol . Since the time of the ancient Greeks, the philosophical nature of infinity was the subject of many discussions amo ...
. Since the optical collimator produces a reticle image made up of
collimated light A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A perfectly collimated light beam, with no divergence, would not disperse with distance. However, diffraction pr ...
, light that is nearly parallel, the light making up that image is theoretically perfectly parallel with the axis of the device or
gun barrel A gun barrel is a crucial part of gun-type weapons such as small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure ...
it is aligned with, i.e. with no
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
at infinity. The collimated reticle image can also be seen at any eye position in the cylindrical volume of collimated light created by the sight behind the optical window. But this also means, for targets closer than infinity, sighting towards the edge of the optical window can make the reticle move in relation to the target since the observer is sighting down a parallel light bundle at the edge. Eye movement perpendicular to the device's
optical axis An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens, microscope or telescopic sight. The optical axis is an imaginary line that defines the path along which light propagat ...
will make the reticle image move in exact relationship to eye position in the cylindrical column of light created by the collimating optics.American rifleman: Volume 93, National Rifle Association of America - THE REFLECTOR SIGHT By JOHN B. BUTLER, page 31 A common type (used in applications such as aircraft gun sights) uses a collimating lens and a beam splitter. This type tends to be bulky since it requires at least two optical components, the lens and the beam splitter/glass plate. The reticle collimation optics are situated at 90° to the optical path making lighting difficult, usually needing additional electric illumination, condensing lenses, etc. A more compact type replaces the lens/beam splitter configuration with a half silvered or
dichroic In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are abs ...
curved collimating mirror set at an angle that performs both tasks of focusing and combining the image of an offset reticle. This type is most often seen as the
red dot The Red Dot Design Award is a German international design prize awarded by Red Dot GmbH & Co. KG. There are prize categories for product design, brands and communication design, and design concept. Since 1955, designers and producers can apply ...
type used on small arms. It is also possible to place the reticle between the viewer and the curved mirror at the mirror's focus. The reticle itself is too close to the eye to be in focus but the curved mirror presents the viewer with an image of the reticle at infinity. This type was invented by Dutch
optical engineer Optical engineering is the field of science and engineering encompassing the physical phenomena and technologies associated with the generation, transmission, manipulation, detection, and utilization of light. Optical engineers use optics to solve ...
Lieuwe Van Albada in 1932, originally as a camera viewfinder, and was also used as a gunsight on World War II bazookas: the US M9 and M9A1 "Bazooka" featured the D7161556 folding "''Reflecting Sight Assembly''". The viewing portion of a reflector sight does not use any
refractive In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...
optical elements, it is simply a projected reticle bounced off a beam splitter or curved mirror right into the users eye. This gives it the defining characteristics of not needing considerable experience and skill to use, as opposed to simple mechanical sights such as
iron sights Iron sights are a system of physical alignment markers (usually made of metallic material) used as a sighting device to assist the accurate aiming of ranged weapons (such as a firearm, airgun, crossbow or even compound bow), or less commonly ...
. A reflector sight also does not have the field of view and eye relief problems of sights based on
optical telescope An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electro ...
s: depending on design constraints their field of view is the user's naked eye field of view, and their non-focusing collimated nature means they don't have the optical telescopes constraint of eye relief. Reflector sights can be combined with telescopes, usually by placing the telescope directly behind the sight so it can view the projected reticle creating a telescopic sight, but this re-introduces the problems of narrow field of view and limited eye relief. The primary drawback of reflector sight is that they need some way to illuminate the reticle to function. Reticles illuminated by ambient light are hard to use in low light situations, and sights with electrical illumination stop functioning altogether if that system fails.


History

The idea of a reflector sight originated in 1900 with Irish optical designer and telescope maker Howard Grubb in patent No.12108. Grubb conceived of his "''Gun Sight for large and small Ordnance''" as a better alternative to the difficult to use iron sight while avoiding the
telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate po ...
's limited field of view, greater apparent target speed, parallax errors, and the danger of keeping the eye against an eye stop. In the 1901 the ''Scientific Transactions of the Royal Dublin Society'' he described his invention as: It was noted soon after its invention that the sight could be a good alternative to iron sights and also had uses in surveying and measuring equipment. The reflector sight was first used on German fighter aircraft in 1918British Aircraft Armament Vol.2: Guns and Gunsights", by R Wallace Clarke, page 134 and widely adopted on all kinds of fighter and bomber aircraft in the 1930s. By World War II the reflector sight was being used on many types of weapons besides aircraft, including anti-aircraft guns, naval guns, anti-tank weapons, and many other weapons where the user needed the simplicity and quick target acquisition nature of the sight. Through its development in the 1930s and into World War II the sight was also being referred to in some applications by the abbreviation "''reflex sight''".


Weapon sights

Reflector sights were invented as an improved gun-sight and since their invention they have been adapted to many types of weapons. When used with different types of guns, reflector sights are considered an improvement over simple
iron sights Iron sights are a system of physical alignment markers (usually made of metallic material) used as a sighting device to assist the accurate aiming of ranged weapons (such as a firearm, airgun, crossbow or even compound bow), or less commonly ...
(sights composed of two spaced metal aiming points that have to be aligned). Iron sights take considerable experience and skill in the user who has to hold a proper eye position and focus exclusively on the front sight, keeping it centered on the (unfocused) rear sight, while keeping the whole centered on a target at different distances, requiring alignment of all three ''planes of focus'' to achieve a hit. The reflector sight's single, parallax-free virtual image, in focus with the target, removes this aiming problem, helping poor, average, and expert shooters alike. Since the collimated image produced by the sight is only truly parallax free at infinity, the sight has an error circle equal to the diameter of the collimating optics for any target at a finite distance. Depending on the eye position behind the sight and the closeness of the target this induces some aiming error. For larger targets at a distance (given the non-magnifying, quick target acquisitions nature of the sight) this aiming error is considered trivial. On small arms aimed at close targets this is compensated for by keeping the reticle in the middle of the optical window (sighting down its
optical axis An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens, microscope or telescopic sight. The optical axis is an imaginary line that defines the path along which light propagat ...
). Some manufacturers of small arms sights also make models with the optical collimator set at a finite distance. This gives the sight
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
due to eye movement the size of the optical window at close range which diminishes to a minimal size at the set distance (somewhere around a desired target range of 25-50 yards). Compared to standard telescopic sights, a reflector sight can be held at any distance from the eye (does not require a designed eye relief), and at almost any angle, without distorting the image of the target or reticle. They are often used with both eyes open (the brain will tend to automatically superimpose the illuminated reticle image coming from the dominant eye onto the other eye's unobstructed view), giving the shooter normal
depth perception Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth perception happens primarily due to stereopsis an ...
and full field of view. Since Reflector sights are not dependent on eye relief, they can theoretically be placed in any mechanically-convenient mounting position on a weapon.


Aircraft

The earliest record of the reflector sight being used with fighter aircraft was in 1918. The optical firm of ''Optische Anstalt Oigee'' of Berlin, working from the Grubb patents, developed two versions what came to be known as the Oigee Reflector Sight. Both used a 45 degree angle glass beam splitter and electrical illumination and were used to aim the plane's machine guns. One version was used in operational trials on the biplane
Albatros D.Va The Albatros D.V is a fighter aircraft built by the Albatros Flugzeugwerke and used by the ''Luftstreitkräfte'' (Imperial German Air Service) during World War I. The D.V was the final development of the Albatros D.I family and the last Albatros ...
and triplane
Fokker Dr.1 The Fokker Dr.I (''Dreidecker'', "triplane" in German), often known simply as the Fokker Triplane, was a World War I fighter aircraft built by Fokker-Flugzeugwerke. The Dr.I saw widespread service in the spring of 1918. It became famous as the ...
fighters. There was some interest in this sight after World War I but reflector sights in general were not widely adopted for fighter and bomber aircraft until the 1930s, first by the French, then by most other major airforces. These sights were not only used for aiming fighter aircraft, they were used with aircraft defensive guns and in bombsights. Reflector sights as aircraft gun-sights have many advantages. The pilot/gunner need not position their head to align the sight line precisely as they did in two-point mechanical sights, head position is only limited to that determined by the optics in the collimator, mostly by the diameter of the collimator lens. The sight does not interfere with the overall view, particularly when the collimator light is turned off. Both eyes may be used simultaneously for sighting. The optical nature of the reflector sight meant it was possible to feed other information into field of view, such as modifications of the aiming point due to
deflection Deflection or deflexion may refer to: Board games * Deflection (chess), a tactic that forces an opposing chess piece to leave a square * Khet (game), formerly ''Deflexion'', an Egyptian-themed chess-like game using lasers Mechanics * Deflection ...
determined by input from a gyroscope.Lon O. Nordeen, ''Air warfare in the missile age'', page 265 1939 saw the development by the British of the first of these
gyro gunsight A gyro gunsight (G.G.S.) is a modification of the non-magnifying reflector sight in which target lead (the amount of aim-off in front of a moving target) and bullet drop are calculated automatically. The first examples were developed in Britain ...
s, reflector sights adjusted by gyroscope for the aircraft's speed and rate of turn, enabling the display of a lead-adjusted sighting reticle that lagged the actual "boresight" of the weapon(s), allowing the boresight to lead the target in a turn by the proper amount for an effective strike As reflector sight designs advanced after World War II, giving the pilot more and more information, they eventually evolved into the head-up display (HUD). The illuminated reticle was eventually replaced by a video screen at the focus of the collimating optics that not only gave a sighting point and information from a lead-finding computer and radar, but also various aircraft indicators (such as an artificial horizon, compass, altitude and airspeed indicators), facilitating the visual tracking of targets or the transition from instrument to visual methods during landings.


Firearms

The idea of attaching a reflector sight to a firearm has been around since its invention in 1900. Soon after World War II models appeared for rifles and shotguns including the Nydar shotgun sight (1945), which used a curved semi-reflective mirror to reflect an ambient lit reticle, and the Giese electric gunsight (1947), which had a battery-powered illuminated reticle. Later types included the Qwik-Point (1970) and the Thompson Insta-Sight. Both were beam-splitter type reflector sights that used ambient light: illuminating a green crosshair in the Insta-Sight, and a red plastic rod "
light pipe Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
" that produced a red aiming spot reticle in the Qwik-Point. The mid- to late 1970s saw the introduction of what are usually referred to as red dot sights, a type that gives the user a simple bright red dot as an aiming point. The typical configuration for this sight is a compact curved mirror reflector design with a red
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LED) at its focus. Using an LED as a reticle is an innovation that greatly improves the reliability and general usefulness of the sight: there is no need for other optical elements to focus light behind a reticle; the mirror can use a
dichroic In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are abs ...
coating to reflect just the red spectrum, passing through most other light; and the LED itself is solid state and consumes very little power, allowing battery-powered sights to run for hundreds and even tens of thousands of hours. Reflector sights for military firearms (usually referred to as reflex sights) took a long time to be adopted. The US House Committee on Armed Services noted as far back as 1975 on the suitability of the use of reflex sight for the
M16 rifle The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-roun ...
, but the US military did not widely introduce reflector sights until the early 2000s with the Aimpoint CompM2 red dot sight, designated the "M68 Close Combat Optic".


Reticle types

Many reticle illumination and pattern options are available. Common light sources used in firearm reflector sights include
battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...
powered lights, fiber optic light collectors, and even tritium capsules. Some sights are specifically designed to be visible when viewed through night vision devices. The color of a sight reticle is often red or amber for visibility against most backgrounds. Some sights use a
chevron Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * ''Eulithis testata'', a moth * Chevron (geology), a fold in rock lay ...
or triangular pattern instead, to aid precision aiming and range estimation, and still others provide selectable patterns. Sights that use dot reticles are almost invariably measured in minutes of arc, sometimes called "minutes of angle" or "moa". Moa is a convenient measure for shooters using Imperial or US customary units, since 1 moa subtends approximately at a distance of , which makes moa a convenient unit to use in
ballistics Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially ranged weapon munitions such as bullets, unguided bombs, rockets or the like; the science or art of designing and a ...
calculations. A 5 moa (1.5 milliradian) dot is small enough not to obscure most targets, and large enough to quickly acquire a proper "sight picture". For many types of
action shooting Practical shooting, also known as dynamic shooting or action shooting, is a set of shooting sports where the competitors try to unite the three principles of precision, power, and speed, by using a firearm of a certain minimum power factor to score ...
, a larger dot has traditionally been preferred; 7, 10, 15 or even 20 moa (2, 3, 4.5 or 6 mil) have been used; often these will be combined with horizontal and/or vertical lines to provide a level reference. Most sights have either active or passive adjustments for the reticle brightness, which help the shooter adapt to different lighting conditions. A very dim reticle will help prevent loss of
night vision Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vi ...
in low-light conditions, while a brighter reticle will display more clearly in full sunlight.


Configurations

Modern optical reflector sights designed for firearms and other uses fall into two housing-configurations: "tubed" and "open". * ''Tube sights'' look similar to standard
telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate po ...
s, with a cylindrical tube containing the optics. Many tube sights offer the option of interchangeable filters (such as polarizing or haze-reducing filters), glare-reducing sunshades, and conveniently protective "flip-up" lens covers. * ''Open sights'' (also known as "mini reflex sights" and "mini red dots") take advantage of the fact that the reflector sight's only optical element, the optical window, doesn't need any housing at all. This configuration consists of a base with just the necessary reflective surface for collimating the reticle mounted on it. Due to their diminished profile, open sights do not usually accommodate filters and other accessory options typically supported by tube designs.


Other uses

Reflector sights have been used over the years in nautical navigation devices and surveying equipment. Albada type sights were used on early large format
camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...
s, "Point and shoot" type cameras, and on simple disposable cameras. These sights are also used on astronomical
telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...
s as finderscopes, to help aim the telescope at the desired object. There are many commercial models, the first of which was the Telrad, invented by amateur astronomer Steve Kufeld in the late 1970s. Others are now available from companies such as Apogee, Celestron, Photon, Rigel, and
Televue Tele Vue Optics is a Chester, New York-based astronomical optics company known primarily for its premium brand of speciality eyepieces and apochromatic refractor telescopes. Founded in 1977 by Al Nagler, an optical engineer from The Bronx who desi ...
. Reflector sights are also used in the entertainment industry in productions such as live
theater Theatre or theater is a collaborative form of performing art that uses live performers, usually actor, actors or actresses, to present the experience of a real or imagined event before a live audience in a specific place, often a stage. The p ...
on "Follow Spot" spotlights. Sights such as Telrad's adapted for use and the purpose built Spot Dot allow the
spotlight operator The spotlight operator or followspot operator is a theatrical technician who operates a specialized stage lighting instrument known as a followspot. A followspot is any lighting instrument manually controlled by an operator during a performance. ...
to aim the light without turning it on.


Similar types

*
Collimator sight A collimator sight is a type of optical sight that allows the user looking into it to see an illuminated aiming point aligned with the device the sight is attached to, regardless of eye position (with little parallax). They are also referred to as ...
s (also called collimating or "occluded eye gunsight" (OEG)) are simply the optical collimator focusing a reticle without any optical window. The viewer cannot see through them and only sees an image of the reticle. They are used either with both eyes open while one looks into the sight, with one eye open and moving the head to alternately see the sight and then at the target, or using one eye to partially see the sight and target at the same time. The reticle is illuminated by an electric, radioluminescent or passive ambient light source. The ''Armson OEG'' and the Normark Corp. ''Singlepoint'' are two examples of commercially available ambient lit collimator sights. These sights have the advantage of requiring less illumination for the reticle for the same level of usability, due to the high contrast black background behind the reticle. For this reason occluded eye gunsights were more practical for use on small arms before low power consumption illumination sources such as LEDs became commonplace. *
Holographic weapon sight A holographic weapon sight or holographic diffraction sight is a non- magnifying gunsight that allows the user to look through a glass optical window and see a holographic reticle image superimposed at a distance on the field of view. The hologram ...
s are similar in layout to reflector sights but do not use a projected reticle system. Instead, a representative reticle is recorded in
three-dimensional space Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position (geometry), position of an element (i.e., Point (m ...
onto holographic film at the time of manufacture. This image is part of the optical viewing window. The recorded hologram is illuminated by a collimated
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
built into the sight. The sight can be adjusted for range and windage by simply tilting or pivoting the optical window.


See also

*
Fire-control system A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a ...
*
Collimator sight A collimator sight is a type of optical sight that allows the user looking into it to see an illuminated aiming point aligned with the device the sight is attached to, regardless of eye position (with little parallax). They are also referred to as ...
*
Holographic weapon sight A holographic weapon sight or holographic diffraction sight is a non- magnifying gunsight that allows the user to look through a glass optical window and see a holographic reticle image superimposed at a distance on the field of view. The hologram ...
* Red dot sight *
Red dot magnifier A red dot magnifier is an optical telescope that can be paired with a non-magnifying optical sight on a weapon to create a telescopic sight. They work with the parallel collimated reticle image produced by certain non-magnifying sights so, con ...
* Prism sight, a type of
telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate po ...
*
Laser sight A laser sight is a device attached or integral to a firearm to aid target acquisition. Unlike optical and iron sights where the user looks through the device to aim at the target, laser sights project a beam onto the target, providing a visual re ...
* Glossary of firearms terminology


References


Further reading

* * * *


External links

* * *
Article on the WWII Maxon M45 machine gun mount with section on the Navy Mark 9 reflector sight

May-June, 2007 CBS Interactive Business Network article: Seeing red: illuminated reticle sights
{{good article Firearm sights Optical devices