Holographic weapon sight
Encyclopedia
A holographic weapon sight or holographic diffraction sight is a non-magnifying
gun sight
that allows the user to look through a glass optical window and see a reticle image superimposed at a distance on the field of view
. The hologram of the reticle is built into the window and is illuminated by a laser diode
.
Holographic weapon sights use a laser transmission hologram of a reticle image that is recorded in three-dimensional space
onto holographic
film at the time of manufacture. This image is part of the optical viewing window. The recorded hologram is illuminated by the collimated light
of a laser diode
built into the sight. The sight can be adjusted for range and windage
by simply tilting or pivoting the optical window. 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. Like the reflector sight
, 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 size of the optical window at close range and diminishing to zero at the set distance (usually around a desired target range of 100 yards).
Since the hologram is illuminated by a laser there is no need for the sight "window" to be partially blocked by a semi-silvered or dielectric dichroic
coating found in standard reflex sights. 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, it is about 1 MoA
.
One drawback of a holographic sight is shorter battery life when compared to reflex sights that use LEDs, such as red dot sight
s. The laser diode
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.
Magnification
Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification"...
gun sight
Sight (device)
A sight is a device used to assist aligning or aim weapons, surveying instruments, or other items by eye. Sights can be a simple set or system of markers that have to be aligned together as well as aligned with the target...
that allows the user to look through a glass optical window and see a reticle image superimposed at a distance on the field of view
Field of view
The field of view is the extent of the observable world that is seen at any given moment....
. The hologram of the reticle is built into the window and is illuminated by a laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
.
Description
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...
onto holographic
Holography
Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that when an imaging system is placed in the reconstructed beam, an image of the object will be seen even when the object is no longer present...
film at the time of manufacture. This image is part of the optical viewing window. The recorded hologram is illuminated by the collimated light
Collimated light
Collimated light is light whose rays are parallel, and therefore will spread slowly as it propagates. The word is related to "collinear" and implies light that does not disperse with distance , or that will disperse minimally...
of a laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
built into the sight. The sight can be adjusted for range and windage
Windage
Windage is a force created on an object by friction when there is relative movement between air and the object.There are two causes of windage:# the object is moving and being slowed by resistance from the air...
by simply tilting or pivoting the optical window. 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. Like the reflector sight
Reflector sight
A reflector or reflex sight is a generally non-magnifying optical device 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...
, 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
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. The term is derived from the Greek παράλλαξις , meaning "alteration"...
due to eye movement being size of the optical window at close range and diminishing to zero at the set distance (usually around a desired target range of 100 yards).
Since the hologram is illuminated by a laser there is no need for the sight "window" to be partially blocked by a semi-silvered or dielectric dichroic
Dichroic filter
A dichroic filter, thin-film filter, or interference filter is a very accurate color filter used to selectively pass light of a small range of colors while reflecting other colors. By comparison, dichroic mirrors and dichroic reflectors tend to be characterized by the color of light that they...
coating found in standard reflex sights. 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, it is about 1 MoA
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
.
One drawback of a holographic sight is shorter battery life when compared to reflex sights that use LEDs, such as red dot sight
Red dot sight
A red dot sight is a common classification for a type of non-magnifying reflector sight for firearms that gives the user an aimpoint in the form of an illuminated red dot...
s. The laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
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.
See also
- Fire-control systemFire-control systemA fire-control system is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a weapon system in hitting its target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more...
- Iron sightIron sightIron sights are a system of shaped alignment markers used as a sighting device to assist in the aiming of a device such as a firearm, crossbow, or telescope, and exclude the use of optics as in telescopic sights or reflector sights...
- Glossary of firearms terminologyGlossary of firearms terminology-A:*accurize, accurizing: The process of altering a stock firearm to improve its accuracy.*action: The physical mechanism that manipulates cartridges and/or seals the breech. The term is also used to describe the method in which cartridges are loaded, locked, and extracted from the mechanism....
- Glossary of military abbreviationsGlossary of military abbreviationsList of terms, acronyms, information, related to modern armour, artillery, infantry, weapons, and related military subject matter.- A :* AA anti-aircraft* AAA anti-aircraft artillery "Triple A"* AAAV Advanced Amphibious Assault Vehicle...
- Reflector sightReflector sightA reflector or reflex sight is a generally non-magnifying optical device 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...