US Patent 7234265 Internal red dot sight

An internal red dot sight includes an objective lens formed of a convex lens, a planar eye lens set in a tilt angle relative to the objective lens and facing the concave surface of the objective lens, and a light emitting device set in between the planar eye lens and the objective lens and controlled to emit a point light source onto the eye lens for enabling the eye lens to reflect the point light source and to further produce a virtual point light source on the focal point of the objective lens for viewing by the user.