Patent attributes
An imaging lens in which a positive (refractive power) first lens group, positive second lens group, and negative third lens group are arranged in order from the object side to the image side. The first lens group includes a positive first lens having a convex object-side surface and a negative second lens having a concave image-side surface near the optical axis. The second lens group includes third and fourth lenses each having at least one aspheric surface. The third lens group includes a negative fifth lens having a concave object-side surface near the axis, a positive sixth lens having a convex image-side surface near the axis, and a negative seventh lens having a concave image-side surface near the axis. The lenses are not joined to each other and the seventh lens has an aspheric image-side surface whose shape changes from concave to convex as the distance from the axis increases.
