Patent ID: 8416510

Claim:
An imaging lens comprising: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having positive refractive power; and a fourth lens group, arranged in this order from an object side to an image plane side, wherein said first lens group has refractive power stronger than that of the second lens group, the third lens group, or the fourth lens group, and includes a first lens having a concave surface facing the image plane side, said second lens group includes a second lens having a meniscus lens shape with a concave surface facing the object side, said fourth lens group includes a third lens having positive refractive power and a fourth lens having negative refractive power, and said imaging lens is arranged to satisfy the following expression when the imaging lens as a whole lens system has a focal length f, and the first lens group, the second lens group, and the third lens group have a composite focal length Fa: 0.3 <f/Fa< 1.0.