US Patent 7813057 Optical lens system for taking image

An optical lens system for taking image comprises: a first lens element with positive refractive power, an Abbe Number of the first lens element being V1, and it satisfying the relation: 50<V1<60; a second lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a third lens element having a convex object-side surface and a concave image-side surface, at least one of the object-side and the image-side surfaces of the third lens element being aspheric; a fourth lens element having at least one aspheric surface; and an aperture stop being located in front of the second lens element.