Focusing and the optical transfer function in a rotationally symmetric optical system

Two criteria of focusing in a rotationally symmetric optical system, the focal-amplification ratio and the encircled-energy factor, are expressed by the integrals of the optical transfer function, thus providing a simple relation between these two types of characteristics. The approximation of the optical transfer function of diffractive lenses is made possible on the basis of this relation, as is an estimation of the effect of certain apodizers on the image quality.