Study of Optical Diffraction Images at Microwave Frequencies*

Abstract

Experimental investigations of the intensity distribution in the region of the focus of microwave lenses are described. The circularly symmetric lenses, made from polystyrene plastic, were illuminated by a linearly polarized beam of radiation of 1.25-cm wavelength. Most of the measurements are presented in the form of intensity contours in planes both containing the principal ray and lying perpendicular to it. Images formed by nearly perfect optical systems and by systems suffering from various third-order monochromatic aberrations were examined. In most cases the results are compared with calculations made from the scalar-diffraction theory of optical systems. In general, good agreement between theory and experiment is found.Some preliminary measurements of the phase variations of the electromagnetic field in the vicinity of the focus are given and the results discussed.