The paper reexamined the traditional equations for scanning imaging in far-field and found that it is inapplicable in near-field. By the introduction of a collection coefficient equations for both far- and near-field have been set up. The collection coefficient has been calculated using scalar Kirchhoff model and vector Bethe-Bouwkamp model respectively. It was found that the collection coefficient is proportional to the aperture diameter and it has a distribution about six ...
