Patent ID: 7508601
Filing Date: 2009-03-24
Classification: G02B

Abstract:
1. An imaging lens comprising, in order from an object side to an image-plane side: a first lens with a positive refractive power having a biconvex shape; an aperture stop having a predetermined aperture diameter; a second lens with a positive refractive power having a concave surface on the object side, at least one of the object-side surface and an image-plane-side surface of the second lens being aspherical; a third lens with a negative refractive power having a concave surface on the object side and an aspherical surface with an inflection point in an effective-diameter area on the image-plane side; and wherein the following conditional expression is satisfied: 0.95<TL/f<1.4 where TL is a distance from an object-side surface of the first lens to an image plane, the distance including an air conversion distance for an area between the third lens and the image plane, and f is a focal length of the lens system.