Diffraction of electromagnetic wave by screen of arbitrary shape

An analysis is made of the problem of diffraction of a plane homogeneous electromagnetic wave by a screen with arbitrary boundaries. Calculations are done in the Kirchoff approximation for the case of normal incidence of the wave on the screen for the field in the Fraunhofer zone. A formula is derived for the average intensity of the diffracted radiation that is valid for arbitrary deviations of the screen outline from circular shape. The proposed formula can also be used to solve the inverse problem of synthesizing optical and radio devices that provide an assigned distribution of average intensity.