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 Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, i ...

reticle A reticle, or reticule also known as a graticule, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the screen of an oscilloscop ...

image superimposed at a distance on the

field of view The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. Human ...

. The

hologram Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, i ...

of the reticle is built into the window and is illuminated by a

laser diode The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...

History

The first-generation holographic sight was introduced by

EOTech EOTECH is an American company that designs, manufactures, and markets electro-optic and night vision products and systems. The company is headquartered in Plymouth, Michigan. They produce holographic weapon sights for small arms that have bee ...

—then an ERIM subsidiary—at the 1996 SHOT Show,Jane's international defence review: IDR.: Volume 34, page 76 under the

trade name A trade name, trading name, or business name, is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is a "fictitious" business name. Registering the fictitious name w ...

HoloSight by Bushnell (with whom the company was partnered with at the time), initially aiming for the civilian

sport shooting Sport pertains to any form of Competition, competitive physical activity or game that aims to use, maintain, or improve physical ability and Skill, skills while providing enjoyment to participants and, in some cases, entertainment to specta ...

and

hunting Hunting is the human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products ( fur/ hide, bone/tusks, horn/antler, ...

market. It won the Optic of the Year Award from the Shooting Industry Academy of Excellence. EOTech was the only company that manufactured holographic sights until early 2017 (possibly January 2017), when

Vortex In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in ...

introduced the Razor AMG UH-1 into the market as a competing product.

Design

Holographic weapon sights use a laser transmission hologram of a reticle image that 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 of an element (i.e., point). This is the informa ...

onto

film at the time of manufacture. This image is part of the optical viewing window. The recorded hologram is illuminated by the

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 ...

of a

built into the sight. The sight can be adjusted for range and

windage Windage is a term used in aerodynamics, firearms ballistics, and automobiles. Usage Aerodynamics Windage is a force created on an object by friction when there is relative movement between air and the object. Windage loss is the reduction in ...

by simply tilting or pivoting the holographic grating. To compensate for any change in the laser wavelength due to temperature, the sight employs a holography grating that disperses the laser light by an equal amount but in the opposite direction as the hologram forming the aiming reticle. The optical window in a holographic weapon sight looks like a piece of clear glass with an illuminated reticle in the middle. The aiming reticle can be an infinitely small dot whose perceived size is given by the acuity of the eye. For someone with

20/20 vision Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...

, it is about 1 minute of arc (0.3

mrad The Barrett MRAD (Multi-role Adaptive Design) is a bolt-action sniper rifle designed by Barrett to meet the requirements of the SOCOM PSR. The MRAD is based on the Barrett 98B and includes a number of modifications and improvements. The Barret ...

). Holographic sights can be paired with " red dot magnifiers" to better engage farther targets.

Parallax error

Like the

reflector sight A reflector sight or reflex sight is an optical sight 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 sig ...

, the holographic sight is not " parallax free", having an aim-point that can move with eye position. This can be compensated for by having a holographic image that is set at a finite distance with parallax due to eye movement being the size of the optical window at close range and diminishing to zero at the set distance (usually around the target range of 100 yards).

Compared to reflector sights

Light transmission

Since the reticle is a transmission hologram, illuminated by a laser shining through hologram presenting a reconstructed image, there is no need for the sight "window" to be partially blocked by a semi-

silvered Silvering is the chemical process of coating a non-conductive substrate such as glass with a reflective substance, to produce a mirror. While the metal is often silver, the term is used for the application of any reflective metal. Process Mos ...

or dielectric

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 ...

coating needed to reflect an image such as in standard

reflex sight A reflector sight or reflex sight is an optical sight 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 sig ...

s. Holographic sights therefore have the potential for better light transmission than reflector sights.

Manufacturing costs

Holographic sights are considerably more expensive than

red dot sight A red dot sight is a common classification for a type of non- magnifying reflector (or reflex) sight for firearms, and other devices that require aiming, that gives the user a point of aim in the form of an illuminated red dot. A standard desig ...

s, due to their complexity as well as there being only two manufacturers of holographic sights.

Size

Holographic sights are generally bulkier than reflex sights and require a rifle to mount, while red dot sights have been made small enough to fit handguns.

Battery life

Holographic sights have shorter battery life when compared to reflex sights that use

LEDs 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 ...

, such as

s. The

in a holographic sight uses more power and has more complex driving electronics than a standard LED of an equivalent brightness, reducing the amount of time a holographic sight can run on a single set of batteries compared to a red dot sight (around 600 hours for typical holographic sights, compared to sometimes up to tens of thousands of hours for red dot sights). For example, the Vortex Razor AMG UH-1 holographic sight has been quoted as having an expected battery life of 1,000 to 1,500 hours (1½ to 2 months) on medium setting,Vortex Razor AMG UH-1 , Holographic Greatness , SOFREP
/ref> while the Aimpoint CompM5s red dot sight has an expected battery life of around 8000 to hours (1 to 5 years) depending on setting.Aimpoint - CompM5s
/ref>

References

External links

Red Dot Sights / Reflex Sights & Holosights Explained -Electronic Sights; A look at why they exist, how they work, and how you use them.
{{Firearms Firearm sights Optical devices