DEFECT IMAGING TECHNIQUE USING A SCANNING LASER SOURCE.

Considering the applications to in-line testing of products, water-free imaging technique is required. This study described defect imaging technique using a scanning laser source. Laser beam was emitted onto a surface of a plate, and then guided waves excited at the laser source were detected by ultrasonic transducers fixed on the plate surface. For a plate with rounded defects, amplitude distributions obtained by scanning the laser source corresponded to thickness distributions, but for plates with rectangular notches, unwanted artifacts were seen due to reflection, diffraction, and ultrasonic attenuation. Then, using multiple receiving transducers and synthesizing multiple images, distinct defect images were obtained for a flat plate and a curved plate with rectangular notches. [ABSTRACT FROM AUTHOR]