aplanat

noun

1. A lens that has been corrected for spherical aberration and coma in order to produce a rectilinear image.

   “For comparison, an aplanat of a focus catalogued at 16 inches, actually found by experiment to have a focus of 16 11-16 inches, was used.”

   “2009, Gérard René Lemaitre, Astronomical Optics and Elasticity Theory, Springer, Astronomy and Astrophysics Library, Corrected 3rd printing, page 11, […] which is totally false since he established the algebraic conditions for thin-lens achromatic aplanats;”

   “Some infra-red detectors are sold already embedded in a plastic aplanat.”