Abstract

We report results from experimental studies dealing with the effects of partial coherence on the radiometric and imaging properties of beams generated by Gaussian Schell-model sources. The variable-coherence sources, represented by Gaussian distributions of optical intensity and spatial coherence, are realized by an optical system analogous to one introduced earlier.¹ The source coherence properties and those of the beam it produces are measured with a wavefront-folding interferometer. On changing the degree of coherence, the beams span the range from full coherence (laser beam) to full incoherence (geometrical optics). The quantities studied include the radiation pattern, an associated equivalence theorem, and the evolution of optical coherence on propagation. In imaging of Gaussian Schell-model sources, the invariant ratio of coherence length to beamwidth is examined. In addition, measurements are carried out on the coherence-dependent focal shift and magnification in focusing. Results are compared to theoretical predictions.²

© 1987 Optical Society of America