Aimpoint did not make the original red dots.
Armson OEG occulated red dot gun sights were used by US Army special forces during the Son Tay prison raid in Vietnam, in 1972.
An Armson simply projects a red dot onto a black background. When you use it with both eyes open the circuitry in your brain causes the dot to "appear" on your target as the scope itself turns into an almost transparent blur.
All reflex sights are intended and designed to be used this way. Hence, for unmagnified shooting, the actual glass itself exists simply to reflect the dot into your focal plane. It has no other purpose. You could spray paint the objective lens black and it would still work every bit as well.