On calculation of a scattering amplitude of closing in a complex field

The works shows that the expression for the closing scattering amplitude in the field, consisting of a set of flat waves satisfies to homogeneous Helmholtz equation out of a source of these waves on variable co-ordinates of closing. It has allowed to receive simple asymptotic rows on return degrees of distance between a source of waves and closing for scattering amplitude calculation. Examples of these rows use are given.