1. a compound lens system that forms an image free from chromatic aberration
The Collaborative International Dictionary of English v.0.48:
Achromatic \Ach`ro*mat"ic\, a. [Gr. 'achrw`matos colorless; 'a
priv. + chrw^ma, chrw`matos, color: cf. F. achromatique.]
1. (Opt.) Free from color; transmitting light without
decomposing it into its primary colors.
2. (Biol.) Uncolored; not absorbing color from a fluid; --
said of tissue.
Achromatic lens (Opt.), a lens composed usually of two
separate lenses, a convex and concave, of substances
having different refractive and dispersive powers, as
crown and flint glass, with the curvatures so adjusted
that the chromatic aberration produced by the one is
corrected by other, and light emerges from the compound
Achromatic prism. See Prism.
Achromatic telescope, or microscope, one in which the
chromatic aberration is corrected, usually by means of a
compound or achromatic object glass, and which gives
images free from extraneous color.
WordNet (r) 3.0 (2006):
n 1: a compound lens system that forms an image free from