A general condition is derived for the distance beyond which the far-zone approximation can be used in studying propagation of light from a partially coherent source. The distance steadily increases as a function of the coherence radius across the source, reaching the usual value in the coherent limit.
© 2005 Optical Society of America
Coherence and Statistical Optics
Franco Gori, "Far-zone approximation for partially coherent sources," Opt. Lett. 30, 2840-2842 (2005)