Imaging of Gaussian Schell-model sources

Imaging of Gaussian Schell-model sources by general lossless systems is analyzed with an extended ray-transfermatrix method. Algebraic expressions are derived for the location, size, and coherence area of the image waist and for the depth of focus and the far-field diffraction angle. These results are shown to provide a continuous transformation between laser-beam optics and geometrical optics. They also lead naturally to several equivalence and invariance relations pertaining to isotropic and anisotropic Gaussian Schell-model sources. As an application, the importance of effects due to partial spatial coherence in beam focusing is examined.