1) Corrected 
• (a.) Free from chromatic and spherical aberration; -- said esp. of a lens in which rays of three or more colors are brought to the same focus, the degree of achromatism thus obtained being more complete than where two rays only are thus focused, as in the ordinary achromatic objective.
A lens or optical system virtually free of chromatic aberration, which for practical purposes means that light of at least three different wavelengths is brought to focus at the same point. The best apochromatic lenses use fluorite crystal and may correct three wavelengths with only two optical elem...
(ap″o-kro-mat´ik) free from chromatic aberration.
Ap`o·chro·mat'ic adjective [ Prefix apo- + chromatic .] (Optics) Free from chromatic and spherical aberration; -- said esp. of a lens in which rays of three or more colors are brought to the same focus, the degree of achromatism thus obtained being more complete than where two ray...
The inability to bring light of all colours to the same plane of focus is known as chromatic aberration. Light refraction is a function of wavelength, and as such each colour is normally brought to as lightly different plane of focus. By using complex lens designs, special glass materials and coating, designer can bring the colours within a much na...
[adj] - (optics) corrected for both chromatic and spherical aberration
adjective corrected for both chromatic and spherical aberration; `an apochromatic lens`
corrected for spherical aberration at two wavelengths or colors and for chromatic aberration at three wavelengths.