Abstract

In an interesting recent paper Martinez-Herrero and Mejias established new existence theorems regarding the uniqueness of solutions to inverse problems involving homogeneous sources.¹ In my pa per some of the theorems are generalized to planar, secondary, quasi-homogeneous² sources, and explicit solutions are presented to two inversion problems with sources of this class, assuming that their normalized spectra are the same at each source point. I show that if the high spatial-frequency components of the degree of spatial coherence may be neglected, the far-zone spectrum of the emitted light uniquely determines both the normalized source spectrum and the degree of coherence of the source. It also follows from this analysis that the scaling law,³ previously derived as a sufficiency condition, is also a necessary condition for spectral invariance on propagation.

© 1990 Optical Society of America