What Does Aplanatic Mean?

An aplanatic lens is a lens that is free of both spherical and coma aberrations. Aplanatic lenses can be made by combining two or three lens elements. A single-element aplanatic lens is an aspheric lens whose surfaces are surfaces of revolution of a cartesian oval.

What is meant by aplanatic?

: free from or corrected for spherical aberration an aplanatic lens.

What is an Aplanatic lens used for?

Aplanatic optics are designed to eliminate both spherical aberration and coma, two major aberrations (image defects) found in telescopes. The end result is sharper images across a much wider field of view than in other designs.