A diffractive optical element is positioned in an optical path between a coherent light source and a surface. The diffractive optical element is designed to disperse the light across one or more spots on the surface in a manner designed to create speckle patterns having substantially uniform intensi...http://www.google.de/patents/US7180669?utm_source=gb-gplus-sharePatent US7180669 - Method and system for generating substantially uniform speckle patterns
