  Despite the fact that incandescent sources are usually spatially incoherent,
it has been known for some time that a proper design of a thermal source can
modify its spatial coherence. A natural question is whether it is possible to
extend this analysis to electroluminescence and photoluminescence. A
theoretical framework is needed to explore these properties. In this paper, we
extend a general coherence-absorption relation valid at equilibrium to two
non-equilibrium cases: luminescent bodies and anisothermal bodies. We then use
this relation to analyse the differences between the isothermal and
anisothermal cases and to study the near-field emission of an
electroluminescent source.
