EOTech



EOTech designs, manufactures, and markets electro-optic products and systems. The company is headquartered in Ann Arbor, Michigan. They produce holographic weapon sights for small arms that have been adopted by various military and law enforcement agencies as close quarters battle firearm sights.

They also have roots in the Environmental Research Institute of Michigan (ERIM), a non-profit R&D institute. Of the many inventions by ERIM researchers, some were in the fields of synthetic aperture radar, laser holography, and aircraft head-up displays.

Products
As of 2012, EOTech primarily manufactures holographic weapon sights. EOTech was the first company to create these types of sights, having solved the problem of wavelength instability exhibited by laser diodes. They developed achromatic holographic optics that compensate for any change in the emission wavelength of the laser diode with temperature. The sights are designed to be mounted on small arms via a MIL-STD-1913 Picatinny or Weaver rail, and powered by either AA, N or CR123 size batteries for up to 1,100 hours of runtime. Sights display either a 65 MoA ring with a 1 MoA dot in the center, a single 1 MoA dot, a vertical series of dots for bullet drop compensation in certain calibers, or, in the case of their less-lethal sights, a flared vase-like sight to assist in the aiming of bean-bag or rubber ball rounds commonly used in riot control. Bushnell marketed the non-military versions under the brand name "Holosight". The EOTech 553 is in U.S. military service under the designation SU-231/PEQ and M553 in the commercial market. A specialty sight for the grenade launcher has also been accepted by the U.S. military and is given the designation SU-253/PEQ.

An archery sight was discontinued in November 2004, in line with the company's desire to concentrate on military and law-enforcement products.

Technology
Unlike reflector sights, the holographic weapon sight does not use a reflected reticle system. Instead a representative reticle is recorded in three-dimensional space onto holographic film that is part of the optical viewing window. Like the reflector sight, the holographic sight's reticle uses collimated light and therefore has an aim-point that can move with eye position. This is compensated for by having a holographic image that is set at a finite distance, in this case around 100 yards. The sight's parallax due to eye movement is the size of the optical window at close range and diminishes to zero at the set distance. Since a laser is used as the light source, 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.

To compensate for any change in the laser wavelength, the EOTech 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 result is a reticle that is stable with the change in temperature.

One requirement of holographic projection is a laser. Lasers use more power and more complex driving electronics than an LED of an equivalent brightness, reducing the amount of time a holographic sight can run on a single set of batteries.