Comparison and optimisation of fast array-based ultrasound testing

Phased array ultrasonic testing (PAUT) is now a widely used technique in industry for non-destructive testing. Arrays offer an intuitive view of the interior of a component from which geometric features and defects can be observed. Arrays also offer detailed information about the nature and extent of any defects. In recent years, full matrix capture (FMC) and the total focusing method (TFM) have attracted significant interest due to the high resolution of the images possible throughout an inspection volume. Due to the requirement of transmitting on each element separately, full matrix capture-based imaging techniques limit the maximum frame rate and scan speed achievable. Recently, to increase the speed of data acquisition, new techniques such as plane wave imaging (PWI) and virtual source aperture (VSA) have been introduced. They allow a significant reduction in the number of firings to be achieved without contributing to any major loss of image quality. In this paper, an in-depth comparison of these techniques using a hybrid linear system model and the analysis of experimental data is performed to assess the image quality of these emerging imaging algorithms and hence identify the optimal parameters for faster imaging.