The influence of aberrations and aperture inclinations on the phase and intensity structure in the image region of a lens

Microwave-optical image formation by a lens focusing system is studied in the presence of aberrations. The theoretical approach is based on diffraction and aberration theories and a modified diffraction integral is presented, showing that previously unreported effects describable as additional primary order aberrations exist due to aperture inclination. Direct relationships are shown to exist between the geometry of Airy dark rings and the type and amount of aberration present, thus providing a means for determining the aberrations present in a physical system. The practical part of the study compares numerical evaluations of the modified diffraction integral with experimental measurements. Results presented are for the case of a solid dielectric microwave lens operated at 3.2-cm wavelength. Detailed maps of phase and intensity contours are given, showing the three-dimensional structure of the image region.