Patent attributes
An imaging lens includes a first lens group; a second lens group; and a third lens group, arranged in this order from an object side to an image plane side. The first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens. The second lens group includes a fourth lens and a fifth lens. The third lens group includes a sixth lens and a seventh lens having negative refractive power. The fourth lens has a concave surface facing the object side near an optical axis thereof. The seventh lens has an image plane-side surface formed in an aspheric shape having at least one inflexion point. The fifth lens is disposed away from the sixth lens by a specific distance on an optical axis thereof. The first to third lenses have specific Abbe's numbers.
