2015 Volume 101 Issue 7 Pages 351-357
Laser ultrasonics have been studying for many years as a promising technique for evaluating industrial materials. The non-contact technique, however, still have some problems in practical use for large structures such as pipes, tanks, bridges, etc. Authors have adopted the scanning laser source technique for imaging defects in a plate-like structure to solve one of the problems that elastic wave cannot be measured stably with laser interferometory due to the unstable detection of scattering light at rough and inclined surfaces of existing structures. In this study, a remote experimental system of the defect imaging technique with the scanning laser source, which does not require cables between receiving transducers and experimental equipments, was developed. In the experimental system, laser emission signal detected by a photo-detector was used as trigger signal that requires quick response for accurate measurements. The other data that does not require such quick responses were transffered with local area network (LAN) communications. Using the remote defect imaging system, we confirmed that defect images can be obtained clearly as the conventional cablewired experimental system was used. Moreover, we obtained defect images at the distances of 2.6 m and 7.6 m between the plate specimen and laser equipment.