Apochromatic objectives

From Biology-Online Dictionary | Biology-Online Dictionary

apochromatic objective

(Science: microscopy) a lens system whose secondary chromatic aberrations have been substantially reduced.

It is designed to provide the same focal length for three wavelengths and freedom from spherical aberration for two wavelengths of light. The magnification can still vary with wavelength in which case a compensating eyepieces used to cancel the coloured fringes.