An interferometric contact-free measuring method for sensing, by a laser beam, motional surface deformation of a workpiece subject to an ultrasonic vibration, comprising splitting the laser beam into a measuring beam incident upon a measuring point on the workpiece and a reference beam incident upon...http://www.google.de/patents/US4619529?utm_source=gb-gplus-sharePatent US4619529 - Interferometric contact-free measuring method for sensing motional surface deformation of workpiece subjected to ultrasonic wave vibration
