Lens system for modifying spherical aberration

摘要

A lens system for modifying the spherical aberration of optical apparatus comprises three groups of lens elements arrayed in order along an optical axis of the apparatus: a first lens group has a negative optical power; a second lens group has substantially zero optical power and is bent to have a substantial amount of spherical aberration; and a third lens group has a positive optical power. The relative spacing between the second lens group and the first and third lens groups is variable to modify the spherical aberration introduced into the optical apparatus.