Abstract:
A review of the efforts and recent achievements at the Industrial Materials Institute of the National Research Council of Canada to apply laser generation and optical detection of ultrasound to industrial inspection will be presented. The principles of generation used in the applications developed so far will be outlined. Penetrating light effects, key to generation in a variety of polymers and polymer matrix composites will be discussed. Detection schemes based on the use of a confocal Fabry--Perot in transmission or in reflection will be reviewed, as well as novel approaches based on the use of photorefractive crystals. These approaches include the one based on two-wave mixing, heterodyne interferometry combined with speckle beam cleaning with a double phase conjugation mirror and the photo electromotive force scheme. Two industrial demonstrations of the technology, the inspection of aeronautic parts made of polymer-matrix composite materials (in one case, the inspection was performed directly on an aircraft), and the wall thickness gauging of hot tubes directly on the production line will be presented. The inspection of composite aeronautic parts has been commercially developed and a production inspection system has been installed at a U.S. Air Force maintenance facility by our licensee UltraOptec, Inc.