A method and apparatus for reducing speckle during inspection of articles used
in the manufacture of semiconductor devices, including wafers, masks, photomasks,
and reticles. The coherence of a light beam output by a coherent light source,
such as a pulsed laser, is reduced by disposing elements in a light path. Examples
of such elements include optical fiber bundles; optical light guides; optical gratings;
an integrating sphere; and an acousto-optic modulator. These various elements may
be combined as desired, such that light beams output by the element combinations
have optical path length differences that are greater than a coherence length of
the light beam output by the coherent light source.
