Perturbation theory - a unified approach to describe diffractive optical elements

The conceptual advantage of Kirchhoffs approximation1 for the description of optical elements and systems is the intensive use of the Fourier transformation2. Its simple mathematical relations can be used to predict spatially distributed light signals in any plane of an optical system. An analysis in terms of Fourier optics and, more specific, the paraxial approximation is even appropriate if more rigorous calculations are required to achieve a desired accuracy for the design of the system.