Apochromatic lens: Compound lens corrected for chromatic aberration, i.e. the three primary colours , red, green and blue are corrected. Also called Apochromat.
However,in the processing of multispectral and hyperspectral,the usage of this technology has been restricted because of the unconsidering the chromatic aberration.
So don't get nervous when you reread this quote and see inimitable contrivance or adjusting the focus, or correction of spherical and chromatic aberration.