Detection of surface defects in film-coated metals and measurement of coating thickness.

ABSTRACT

A novel sensor based on the interdigitated structure is presented to detect surface defects in film-coated metals and measure coating thickness. The detection and measurement are based on monitoring the shift of resonance frequency which is caused by the perturbation of electromagnetic field around the interdigitated structure. A 200-µm-wide defect was successfully detected in the experiment. In addition, the numerical simulations show that the designed sensor can detect a 50-µm-wide defect with a 220 MHz shift in the resonance frequency. The sensor is sensitive, inexpensive, portable, and can detect both defects and measure coating thickness.