The elimination of distortion and coma in an image is met when
M = n sin u/n′ sin u′ or nh sin u = n′h′ sin u′
where
M is the lateral magnification,
n and
n′ the refractive indices of the media in the object and image space,
u and
u′ are the angular apertures on the object and image sides, and
h and
h′ the sizes of the object and image, respectively.
Syn. Abbé's condition.
See angular aperture;
coma;
correction;
distortion.