Subsurface detection of small voids in low-loss solids

An open-ended coaxial probe method has been investigated for the detection of small subsurface voids in low-loss solids. Defects have been inserted into a 2 mm subsurface layer of wood veneer placed below an identical 2 mm layer of wood veneer without defects. The subsurface defect locations were correctly identified using this coaxial probe. Defects of various shapes with shallow depths (<0.5 mm) have been inserted into a 5.75 mm piece of Lexan placed below an identical 5.75 mm piece of Lexan without defects. The results of these initial measurements are discussed.