Multi-layer ultrasonic imaging for non-destructive testing applications

In a multi-layer medium, interfaces between the layers refract the sound wave into lower layers, thereby playing the role of emitting sources for lower layers. We model the interfaces between the layers of a multi-layer medium as spatially distributed sources consisting of infinite number of point sources. Then, we use this model to develop a new model for array spatial signature for any point inside a multi-layer medium. This new model can be used in any imaging technique. In this paper, we present the application of our new model for array spatial signature in conventional beamforming algorithm in order to image the second layer of a two-layer medium.