Apochromat

Chromatic aberration of a single lens causes different wavelengths of light to have differing focal lengths.

An apochromat, or apochromatic lens (apo), is a photographic or other lens that has better correction of chromatic and spherical aberration than the much more common achromat lenses.

The prefix apo- comes from the Greek preposition ἀπό-, meaning free from or away from.