Holog. gunsights were first demonstrated in the mid 1970s by researchers at the Environmental Research Institute of Michigan (ERIM) under contracts with the Air Force and the Army.The sights utilized He-Ne gas lasers and were designed for use with large weapons systems.With the advent of low cost visible laser diode, ERIM formed a new company, EOTech, to develop, manufacture and market a holog. gun sight for small arms.A hologram is used to reconstruct the image of a reticle pattern that appears at the target plane.Unlike red-dot sights, virtually any reticle pattern, 2-dimensional or 3-dimensional, can be formed.The design challenges include an opto-mech. package that is compact, light weight and low cost which can withstand recoils up to 4,000 Gs and provide fine elevation/windage pointing adjustments, and optics that are aberration-free and stable over a wide temperature range.Manufacturing challenges include the mass production of high quality holog. optics at low cost and the precision alignment of the very low f/number optics.