November 2004
Intermediate to advanced
631 pages
16h 42m
English
A mirror element has several advantages over a refracting element. It is completely achromatic, having neither axial nor lateral color, nor chromatic variation of the aberrations (e.g., spherochromatism). A mirror can be used in any spectral region for which a reflecting coating is available (and the wide range of available coatings make this a very broad region), whereas a refractor may be quite severely limited by the transmission characteristics of its materials. Yet a third advantage is the fact that the aberrations of a spherical mirror are inherently smaller than those of a comparable spherical-surfaced lens. For example, the spherical aberration of a ...