Aberration coefficients and surfaces of best focus

Abstract

An explicit parametric equation (with field variable as parameter) is derived for the surface of best focus of an optical system In terms of the aberration coefficients of the system and its working aperture. In this context, an image is focused by minimizing the radius of gyration of the corresponding spot diagram, or equivalently by maximizing the low-frequency response. Examples are given; surfaces of best focus predicted on the basis of the derived expressions are compared with those obtained from ray tracing and the possible sources of observed discrepancies in these are discussed.