LAUSR

Metal workpiece imaging is of great significance for industrial nondestructive testing. However, current methods, such as radiographic or electromagnetic induction, are easily influenced by background noise, which leads to a short detection range and a high false detection rate. To overcome this issue, this article proposes a wide-focus imaging method for industrial metal workpieces using a tower-type transmitting coil and a magnetic sensing array. First, a single-loop coil excitation model is established to analyze the effects of transmitting current, coil radius, and other parameters on the radiation magnetic field. Second, a coaxial noncoplanar tower-type coil is designed, and a wide-focus optimization is achieved using a particle swarm algorithm, reconciling the conflict between high uniformity and high focusing degree requirements. Third, a wide-focus imaging system is developed, which combines a magnetic sensing array with cubic convolution interpolation algorithms to achieve 3-D imaging of metal workpieces. Experimental results demonstrate that the magnetic field uniformity achieved by the tower-type transmitting coil reaches 98.02%, representing a 43.82% improvement over the conventional single-loop coil. The proposed wide-focus imaging method leads to an average enhancement of 16.18% in imaging contrast and an average improvement of 37.33% in detection distance under various conditions, which increases the environmental adaptivity and decreases the false detection rate.