Also known as achromatic.  A lens consisting of two or more elements, usually of crown and flint glass,  that  has been corrected for chromatic aberration with respect to two selected wavelengths.FACIMTON provides the achromatic lenses consisting of two element. These lenses have considerably reduced not only  chromatic  aberration  but  also  spherical aberration and coma aberration. These are designed with respect three wavelength 480nm, 546.1nm and 643.8nm. Best used to replace singlet where performance must be improved.