The description of the light propagation in or between planar diffractive optical elements is done with the angular spec-trum method. That means, the confinement to the paraxial approximation is removed. In addition it is not necessary to make a difference between Fraunhofer and Fresnel diffraction as usually done by the solution of the of the Rayleigh Sommerfeld formula. The diffraction properties of slits of varying width are analysed first. The transitional phenomena between Fresnel and Fraunhofer diffraction will be discussed from the view point of metrology. The transition phenomena is characterised as a problem of reduced resolution or low pass filtering in free space propagation. The light distributions produced by a plane screens, including slits, line and space structures or phase varying structures are investigated in detail.