Alternative coherent-mode representation of a planar source

The problem of the coherent-mode representation of a planar source with unknown cross-spectral density function is considered. It is proposed the alternative coherent-mode representation of a source which does not involve the solution of the Fredholm integral equation but may be obtained from the results of radiometric measurements. The basic concept is illustrated by the example of the alternative coherent-mode representation calculated for the 1D Lambertian source.