Sparse total-focusing imaging of ultrasonic array sensor at the interface under an effective aperture

Total-focusing imaging based on full-matrix data, which makes the synthesis of sound waves at the focus point, has been widely used and shown to improve imaging resolution effectively. In traditional total-focusing imaging, it is considered that the echo signals received by all transmit–receive pairs contain the effective characteristic information from the focal point. However, by both acoustic theory and detection experiment, it is found that invalid array elements exist due to the directivity constraint. In this paper, aiming at the invalid and redundant ultrasonic signals in the full matrix data, a sparse total-focusing imaging method based on correlation criteria is proposed according to the characteristics of extracted reflected signals representing the interface information. Then, the total-focusing imaging of the interface defect was realized based on the full matrix dataset under an effective aperture. The imaging results demonstrated that the proposed algorithms can realize the detection of interface defects with higher imaging quality.