The relationship between the degree of spatial coherence of a statistically homogeneous planar source and the angular distribution of the radiant intensity is reinvestigated allowing for the finiteness of the source area. The approximate relations due to Wolf and Carter are reproduced in the limits of very large source area or very small coherence area. The generalized relation is illustrated by plotting the spatial frequency spectra and the spectral coherence areas of Bessel-correlated statistically isotropic free-field model sources that are bound by circular apertures. The effects of the variations of both the degree of spatial coherence and the source diameter are studied. In the case of the blackbody, the introduction of the finite aperture leads to deviations from the Lambert cosine law and removes the divergence of the coherence area obtained previously. Implications for the inverse scattering problem and the concept of generalized radiance are discussed.
© 1977 Optical Society of AmericaFull Article | PDF Article
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