A new method is proposed for determining the coherence properties of t
he wave fields, produced by a broadband source, from the spectral chan
ges produced on interference. The knowledge of the spectral degree of
coherence combined with the space-frequency equivalence principle can
be used to determine the intensity distribution across the source of t
he field, This method might be useful for enhancing the efficiency of
the existing imaging instruments over a broad range of frequencies, i.
e. radio, optical and X-rays. The application to the measurement of th
e angular diameters of stars is also considered.