The interference effect is investigated in the form that appears at a finite distance in an arbitrary plane-mirror interferometer e.g., a Mach-Zehnder interferometer if the dimensions of the light source are not negligibly small. It is found that the most descriptive term for this interference is source-image transformation. The helical displacement between the source images in a plane-mirror interferometer gives rise to characteristic interference-fringe structures. Illustrations are given for these structures as found when the aperture stop is circular and are compared with their limiting cases as found earlier, especially wedge interference phenomena. The treatment will include the case of an eccentric position of the source.
Trans. of Optica Acta v11 p43-60, 131-143, 1964, by Stuart W. Kellogg.