The first-generation holographic sight was introduced by EOTech—then an ERIM subsidiary—at the 1996 SHOT Show, under the trade name HoloSight by Bushnell, initially aiming for the civilian sport shooting and hunting 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, when Vortex introduced the Razor AMG UH-1 into the market as a competing product.
Overview
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 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. 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 the size of the optical window at close range and diminishing to zero at the set distance. 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 or dielectric dichroic coating needed to reflect an image 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 minute of arc. Holographic sights are generally superior to red dot sights for most applications. However, holographic sights also have numerous drawbacks. Holographic sights are considerably more expensive than red dot sights, due to the increased sophistication as well as there being only two manufacturers. Holographic sights are also bulkier and require a rifle to mount, while red dot sights have been made small enough to fit handguns. Holographic sights have shorter battery life when compared to reflex sights that use LEDs, such as red dot sights. 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.
