A method and apparatus for noninvasive, non-contacting measurement of stretches and deformations on the surface of a material or an object by utilizing changes which occur in the reflection characteristics of the material due to an applied stretch load is presented. The present invention may assume various...http://www.google.de/patents/US6324419?utm_source=gb-gplus-sharePatent US6324419 - Apparatus and method for non-invasive measurement of stretch
