These curves contain all the material parameters which can be determined with the aid of the acoustic image. During the software-controlled displacement of the focal point from the surface into the sample, the intensity of the reflected ultrasonic signals is measured (V=voltage) and plotted against the distance the acoustic lens is lowered (z in thousandth of a millimetre).

The result is a frequency dependent curve of the material or layer combination, characteristic for the sample investigated: V(z) curves allow a completely new, non-destructive type of material characterisation in the micron range. V(z) curves are influenced by varieties in film thickness. V(z) curves reveal defect structures under the surface. V(z) curves are the key to a wide range of quantitative measurements.