On aberrations of eikonal in planar lens antennas

A formula for the eikonal distribution over the surface of a cylindrical dielectric lens with an error on the fourth-order of the displacement of the source from the focus is found. The accuracy of this formula and the first three terms of its expansion in this parameter for describing the eikonal and its aberrations are analyzed. A method for finding the parameters of the optical aplanatic lens (with minimum aberrations) is proposed. An approximate equation of the focal curve is derived.