Non-Gaussian speckle contrast from a phase-perturbed random object field in a spatially partially coherent system is simulated. A quasi-monochromatic extended incoherent source is modeled as a collection of independent point sources distributed on a regular grid. The source illuminates a phase screen object in a Kohler configuration. Speckle is calculated from the incoherent sum of irradiances in the image plane generated from the point sources. Simulated speckle contrasts are verified by an experiment with a fractallike rough surface distribution that is fabricated using a grayscale maskless lithography tool. Characteristics of the simulation method and physical quantities affecting speckle contrast are discussed.
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