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Apparatus and method for reducing spatial coherence and for improving uniformity of a light beam emitted from a coherent light source

  • US 6,081,381 A
  • Filed: 10/26/1998
  • Issued: 06/27/2000
  • Est. Priority Date: 10/26/1998
  • Status: Expired due to Fees
First Claim
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1. A method for eliminating speckle structures formed by speckle spots in an illumination plane of an optical system having a coherent light source by reducing spatial coherence of illumination, comprising:

  • providing at least one microlens array, which consists of a plurality of microlenses, in the optical path between said coherent light source and said illumination plane;

    igniting said coherent light source for generating a light beam;

    moving said at least one microlens array with the speed sufficient for introducing phase heterogeneity in the light wavefront for speckle elimination;

    passing said light beam through said rotating microlens array;

    and creating a speckle-free and uniform light distribution in said illumination plane, said coherent light source being a continuous laser which operates during an exposure time and wherein said rotation averages said speckle structures during said exposure time.

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