Optical design with Wood lenses 1: infinite conjugate systems.

Spherical aberration in a flat-surfaced radial gradient-index lens (a Wood lens) with a parabolic-index profile can be corrected by altering the profile to include higher-order terms. However, this results in a large amount of third-order coma. An alternative method of aberration correction similar to that used in the catadioptric Schmidt system is presented. A Wood lens with a parabolic-index profile is used to provide all or most of the optical power. Coma is corrected by stop shifting, and spherical aberration is corrected by placing a powerless Wood lens corrector plate at the stop.