Air coupled piezoelectric detection of laser generated ultrasound

This paper presents the deployment of a pulsed laser to generate ultrasonic transients in samples of metal and their subsequent through air detection by a 1-3 connectivity composite transducer. Of particular interest is a class of reception devices that utilises the coupling of lateral vibrational modes to extend effectively the thickness-mode bandwidth. The characteristics of the laser generation/air-coupled detection hybrid system are evaluated through experimentation. In particular, detection of multiple reflections within thin materials is demonstrated with deconvolution techniques employed when necessary to enhance the relevant information. It is be concluded that the proposed approach has an acceptable sensitivity and bandwidth for many applications in which non-contact inspection is an advantage