The importance of induced aberrations in the correction of secondary color

Abstract

Much publicity has been given to the art and science of choosing glass types for the reduction of secondary color, particularly for systems (such as achromats) in which all the elements are in contact. Although it has long been recognized that airspaces between elements can influence chromatic aberration and can even be used to reduce or correct secondary color, comparatively, little emphasis has been placed on this in the published literature. This tutorial is intended to call attention to the induced component of secondary color and suggests methods for improving color correction.