Enhancing scanning imaging in coplanar capacitive sensors via design optimisation

Coplanar capacitance scanning imaging (CCSI) has emerged as a promising non-destructive testing (NDT) method due to its advantages of low cost, high sensitivity, and non-destructive nature. In this study, a method was developed to improve the imaging quality of CCSI, with a focus on the optimisation of proximity edges. Coplanar capacitance sensors (CCS) designed with various edge sizes were investigated, and their sensitivity distribution and imaging quality were systematically evaluated through a combination of finite element modelling (FEM) and experimental validation. Additionally, the impacts of the defect size and shape on the scanned image quality were examined. Furthermore, image quality degradation was observed with excessive optimisation. The results show that through this optimisation strategy, the Pearson correlation coefficient increased from 0.71 to 0.76, and the imaging error decreased from 43.05% to 24.45%. This research may provide a reference for the sensor design and practical applications of CCSI.