A lamp for producing a collimated light beam includes at least one light source disposed on a casing, a retaining plate having at least one opening for accommodating an optical assembly. The optical assembly includes an upper portion having a convex shaped lens, a bottom portion having an upper wall configured as a concave shaped lens and having an aperture. The optical assembly further includes an inverted dome shaped shell defined by lateral walls and a refractive wall and a domed portion having the convex shaped lens extending outwardly from the lamp.