The spherical aberration problem with the spherical cat's eye can be solved in various ways, one being a spherically symmetrical index gradient within the sphere, such as in the Luneburg lens design. Practically, this can be approximated by a concentric sphere system.
The spherical aberration problem with the spherical cat's eye can be solved in various ways, one being a spherically symmetrical inde,x gradient within .the sphere such as in the Luneburg lens design Practically, this can be approximated by a concent.ric sphere system