Geometric theory of Fresnel diffraction patterns - Part V. Elliptic obstacles and apertures
Photographs of the Fresnel diffraction patterns of elliptic apertures and obstacles are reproduced. These show many new features hitherto unobserved. For instance, with elliptic dises, a number of bright and dark fringes parallel to the sides of the evolute are found inside it. Another interesting feature is the existence of quasi-elliptic rings outside the evolute, with their longer axis along the minor axis of the geometric shadow. These are found with elliptic apertures also, which besides exhibit bands parallel to the boundary of the ellipse and a fine criss-cross pattern inside the evolute. The patterns are explained in terms of the general theory proposed in Paper I. The transition from the Fresnel to the Fraunhofer pattern as the size of the aperture is diminished is also illustrated.