A method and apparatus for monitoring the diffuse reflectivity of a portion of a surface. The method is particularly applicable to soil detection of banknotes. The method comprises exposing the surface portion (3) to a beam of radiation from a source (2). At least one part of the diffuse radiation reflected...http://www.google.fr/patents/US4988206?utm_source=gb-gplus-shareBrevet US4988206 - Methods are apparatus for monitoring the diffuse reflectivity of a surface
Methods are apparatus for monitoring the diffuse reflectivity of a surface
