Fresnel diffraction as an aperture edge integral

The standard Fresnel diffraction wave field from an aperture in a plane screen involves an integral over the aperture area. Here it is reduced to an aperture edge integral instead. The reduction really amounts to performing one integral but can be considered as the reduction of the ‘Maggi-Rubinovics’ edge formula from Kirchhoff optics to paraxial (i.e. Fresnel) optics.