A revised formulation of the image Light distribution of an incoherent
line source proposed by Steel [Rev. Opt. 31, 334-340 (1952)] is prese
nted. Analytical and numerical results based on this new representatio
n are given. We explicitly show that a major error in Steel's final ex
pression generates singularities, thereby preventing convenient numeri
cal computation. (C) 1997 Optical Society of America.