The two measurements may be used in any manner, e.g. compared to one another, and voids are deemed to be present...http://www.google.fr/patents/US20060232768?utm_source=gb-gplus-shareBrevet US20060232768 - Evaluating a multi-layered structure for voids Recherche avanc???e dans les brevets Num???ro de publicationUS20060232768 A1Type de publicationDemande Num???ro de demandeUS 11/454,332 Date de pub