On propose une nouvelle methode de caracterisation tres precise des materiaux. On mesure les caracteristiques de propagation des ondes de fuite a la limite entre l'eau et l'echantillon; la vitesse de phase et l'attenuation sont determinees a travers des mesures de la courbe V(z). On presente une methode d'analyse spectrale pour obtenir les proprietes acoustiques a partir des courbes V(z). Description des mesures effectuees en utilisant des materiaux isotropes ou anisotropes pour lesquels les vitesses s'etendent de 2000 a 11000 m/s. On examine tous les modes d'ondes de fuite impliques dans les phenomenes d'interferences dans les courbes V(z). Resultats experimentaux confirmant les resultats theoriques. Application a l'analyse de la structure des materiaux polycristallins

Material Characterization by Line-Focus-Beam Acoustic Microscope

It has been well recognized that the leaky surface wave plays an essential role both in imaging mode and in V(z) measuring mode of acoustic microscopy. To get further insight into the behavior and the role of the leaky surface wave we devised an acoustic lens that enables to generate broadband short pulses. With this lens, we could detect the leaky surface wave separately from the axial wave in time domain. The time interval between these two waves AtRdecreased as the velocity of leaky surface wave v increased. An analytical expression for predicting vzin terms of Atp and z was derived along with ray optics and was verified experimentally for glass, metals and ceramics. A new method for velocity measurement of leaky surface wave was developed that can be done without mechanical scanning of the lens nor the sample.

In acoustic microscopy

Characterization of Electronic Components by Acoustic Microscopy G. Pfannschmidt. Interaction of Acoustic Waves with Solid Surfaces Y. Tsukahara, et al. Scanning Acoustic Microscopy with Phase Contrast W. Grill, et al. Ultrasonic Focusing with Time Reversal Mirrors M. Fink, C. Prada.

Advances in acoustic microscopy

Absfmet-It is demonstrated that the reflectance function R(@) of a liquid-solid interface can be obtained by inverting the complex V(z) data collected with an acoustic microscope. The inversion algorithm is based on a nonparaxial formulation of the V(z) integral, which establishes the Fourier transform relation between R(@) and V(z). Examples are given to show that with this measurement technique, the acoustic phase velocities of the propagating modes in the solid medium can easily be determined and material losses can be estimated. The same technique is also used for characterizing imaging performance of focused systems. Applications In thin-6lm measurement are also discussed.

Material Characterization by the Inversion of V(z)

On utilise l'optique des rayons pour developper des expressions analytiques simples donnant la variation V(z) de la tension de sortie en fonction du deplacement z de la surface de l'objet par rapport au plan focal

Ray-Optical Evaluation of V(z) in the Reflection Acoustic Microscope

The output voltage of the reflection acoustic microscope depends on the location on the object surface in a way that is characteristic of its elastic properties. We present a ray model showing that this dependence is due to interference between a narrow bundle of axial rays and rays associated with the leaky Rayleigh wave excited on the surface.

W. Parmon

Papers

Ray interpretation of the material signature in the acoustic microscope