US Patent 7558005 Compact lens system

A compact lens system that includes a first lens that is a meniscus lens with positive refractive power and having aspheric surfaces on both sides, and a convex surface on a surface facing an object; a second lens formed of a biconcave lens having aspheric surfaces on both sides; a third lens having aspheric surfaces on both sides and having positive refractive power; and a fourth lens formed of a biconcave lens having aspheric surfaces on both sides and an inflection point on an upper aspheric surface. The first through fourth lenses are arranged sequentially from the object, and an aperture diaphragm is disposed on the object side of the first lens.