Patent ID: 9116329
Filing Date: 2015-08-25
Classification: G02B

Abstract:
1. An imaging lens with a fixed focal length which forms an image of an object on a solid-state image sensor, in which lenses are arranged in order from an object side to an image side, comprising: a first lens group with positive refractive power; a second lens group with positive refractive power; and a third lens group with negative refractive power, wherein the first lens group includes a first lens with positive refractive power having a convex object-side surface and a second lens with negative refractive power having a concave image-side surface near an optical axis which are arranged in order from the object side; wherein the second lens group includes a third lens and a fourth lens each having at least one aspheric surface which are arranged in order from the object side; wherein the third lens group includes a fifth lens with negative refractive power having a concave object-side surface near the optical axis, a sixth lens with positive refractive power having a convex image-side surface near the optical axis, and a seventh lens with negative refractive power having a concave image-side surface near the optical axis which are arranged in order from the object side; and wherein the lenses are not joined to each other and the image-side surface of the seventh lens has an aspheric surface whose shape changes from concave to convex as a distance from the optical axis increases, and conditional expressions (10) and (11) given below are satisfied: where f: focal length of the overall imaging lens system, f12: composite focal length of the first lens group, f34: composite focal length of the second lens group, and f567: composite focal length of the third lens group.