Ultrasonic imaging technique in liquid and solid waveguides using spatio-temporal matched field (STMF) processing

Abstract

A new ultrasonic imaging technique devoted to detection of defects located inside a solid or liquid rectangular waveguide is presented. The technique, based on the spatio-temporal Green functions computation and cross-correlation technique, extends the concept of the matched field processing (MFP) technique used in ocean acoustics. The principle of the spatio-temporal matched field (STMF) processing relies on the cross-correlation between echographic B-SCAN signals detected with a linear transducer array and replica functions. These replica functions, derived from the Green functions, are designed to match as close as possible the time delays of direct and reflected acoustic wavefronts. Experiments conducted in liquid and Duralumin solid waveguides demonstrate the ability of the STMF processing to improve the spatial resolution of ultrasonic images in waveguides. An improvement factor up to five is achieved when the ultrasonic images in waveguides computed with the STMF processing are compared to that pre...