An object is placed in front of a converging lens at a distance equal to twice the focal length `f_(1)` of the lens. On the other side of the lens is a concave mirror of focal length `f_(2)` separated from the lens is a concave mirror of focal length `f_(2)` separated from the lens by a distance `2(f_(1)+f_(2))`. Light from the object passes rightward through the lens, reflects from the mirror, passes leftward throught the lens, and forms a final image of the object.