Seamless transition to geometrical optics concepts in a fully physical optics framework

It is a well understood fact, that geometrical optics constitutes a subset of physical optics. However, this theoretical understanding has not materialized in practical concepts and most optics software products. In practical work of optical engineers and most optics textbooks, physical optics and geometrical optics are discussed without delving into the strong connection of both disciplines. We present a way to formulate physical optics propagation in homogeneous media which enables a seamless transition to the subset of geometrical optics in theory and practice. The resulting algorithm applies solely mathematical quantities to decide about a seamless inclusion of diffraction in an otherwise fully physical optics model.