Optical MTF and aberration predictions with the Helmholtz-Lagrange invariant

Abstract

The paper presents a method for a rough estimation of the aberrations and of the MTF of an optical system by means of the Helmholtz-Lagrange invariant. The method allows for a rough understanding of an optical design and can find application in those cases where approximated performance predictions are needed, for example, before running complex and time-consuming analyses. The simple approach presented here is a rough approximation and should always be followed by the usual tolerance analyses.