The Huygens-Fresnel principle provides a conceptual understanding for wave propagation and diffraction. Recently the principle has been reexamined to suggest that it is also valid in the near field. We reformulate the problem in terms of nonradiative optics, focusing particularly on the obliquity factor inherent in the forward-directed propagation of light. In the near field of matter no explicit obliquity factor exists.
F. Depasse, M. A. Paesler, D. Courjon, and J. M. Vigoureux, "Huygens-Fresnel principle in the near field," Opt. Lett. 20, 234-236 (1995)