Patent ID: 7365920

Claim:
An four-piece lens assembly, in order from the object side, consisting of: an aperture, a first lens, a second lens, a third lens, a fourth lens, a flat parallel glass and an image plane; wherein the first lens is a double convex positive lens; the second lens is a double concave negative lens or a plano-concave lens, and an object side surface of the second lens contacts an image side surface of the first lens; the third lens is a convex-concave positive lens whose convex surface facing the image side and has at least an aspherical refractive surface; and the fourth lens is a convex-concave positive lens whose convex surface facing the object side and has at least an aspherical refractive surface; a total focal length of the lens assembly is f, and a radius of curvature of an image side surface of the fourth lens is R 42 , then they satisfy the relation of: 2.0<f/R 42 <3.7.