Patent ID: 8520321

Claim:
An imaging lens comprising: an aperture stop; a first lens configured to have positive refractive power; a second lens configured to have negative refractive power, surfaces of the second lens near an optical axis having a bi-concave shape; a third lens configured to have positive refractive power, an object-side surface of the third lens near the optical axis being concave toward an object side; and a fourth lens configured to have negative refractive power, an object-side surface of the fourth lens near the optical axis being convex toward the object side, wherein the aperture stop, the first lens, the second lens, the third lens, and the fourth lens are sequentially disposed from the object side toward an image side, both surfaces of the first lens, both surfaces of the second lens, both surfaces of the third lens, and both surfaces of the fourth lens are formed as aspheric surfaces, and condition expression (1), condition expression (2), and condition expression (3) are satisfied: −1.09≦ f 2/ f≦− 0.81 (1) −1.62≦ f 2/ f 1≦−1.42 (2) 0.65≦ f 3/ f≦ 0.97 (3) in which f1: focal length of the first lens f2: focal length of the second lens f3: focal length of the third lens f: focal length of a lens whole system.