Calibration of ultrasonic phased arrays for industrial applications

This paper investigates the consistency in phased array element performance by extracting information from the Full Matrix Capture (FMC) of a reflection from a planar interface. The purpose of this work is to generate a robust methodology for tracking phased array performance over time, therefore, ensuring the reliability of measured data. To achieve this, a calibration method has been developed that quantifies the pulse length, sensitivity, bandwidth and phase error for each element in the array. This paper will highlight the variation across individual array elements and the experimental variation across FMC replicates. Finally, to illustrate the impact of the element performance variation, the phase error is included within the Total Focussing Method imaging algorithm, resulting in an 8% increase in ultrasonic image resolution.

I. Introduction and Motivation

Ultrasonic phased arrays are well-established in the field of non-destructive evaluation (NDE) for imaging into optically opaque structures, for example, these images can be used for the identification and characterisation of defects in steel [1]. In recent years, industrial uptake of phased arrays has increased, because the precise positioning of the active array elements permits accurate imaging of the load material.