Aplanatic focus
Related to Aplanatic focus: aplanatic points, coma aberration
| (Opt.) | the point or focus from which rays diverging pass the lens without spherical aberration. In certain forms of lenses there are two such foci; and it is by taking advantage of this fact that the best aplanatic object glasses of microscopes are constructed. |
| (Opt.) | See under Aplanatic. |