Collimator sights as weapon sights are considered to be very simple, rugged and low cost devices. They have been used on mortars and field guns since World War I. There have had more modern incarnations such as the Armson Occluded Eye Gunsight (OEG) and the Normark Corp. Singlepoint. These both used a light gathering rod in a protective clear dome collecting ambient light to illuminate a 'dot' style reticle.