Wooden panel paintings investigation: an air-coupled ultrasonic imaging approach

In this paper, a method for the study of wooden panel paintings using air-coupled acoustical imaging is presented. In order to evaluate the advantages of the technique, several samples were made to mimic panel paintings along with their typical defects. These specimens were tested by means of both single-sided and through-transmission techniques using planar transducers. Image data were processed by means of a two-dimensional (2-D)-fast Fourier transform-based algorithm to increase the S/N ratio and 2-D representations (C-scans) were generated. The simulated defects were imaged using both configurations. Investigations were undertaken on four antique paintings from a private collection. The results presented and discussed in this investigation confirm both the robustness and the effectiveness of the technique in detecting defects such as delaminations and cracks in wooden panel paintings.