  We report on the experimental findings of a thin-slit grid diffraction of a
coherent light beam with sinusoidal amplitude. We create the sinusoidal
amplitude by placing a thin-slit grid at the center of the dark fringes of an
interference pattern resulting from laser light passing through a dual pinhole.
The experimental results show good agreement with diffraction calculations of a
thin-slit grid placed at the center of the dark fringes produced by two
coherent beams that intersect at small angle. The results are applied to
wire-grid diffraction in the Afshar experiment.
