Analysis and synthesis of axial field patterns of focused apertures

It is shown that the axial field pattern of an aperture focused in the Fresnel region can be synthesized in the same manner as the angular pattern of an aperture in the Fraunhofer region. The aperture distribution which achieves a specified axial pattern is related to the aperture distribution of the specified pattern in the far field through a simple variable transformation. Therefore all analysis and synthesis techniques for far-field patterns can be applied to Fresnel region axial patterns of focused apertures.