Abstract:

Fiber optics lend increased flexibility to laser-based ultrasonic nondestructive evaluation (NDE). In this work, fiber-optic cables are used to transmit light from a laser to the detection site, and then from the detection site to a Fabry--Perot interferometer. The use of fibers allows both the detection laser and interferometer to be placed at a considerable distance from the object under test. A direct line-of-sight of the object from the main equipment is not required, since the fibers may be fed through walls and around obstacles. In addition, by containing the laser light in the fibers, the chance of accidental exposure to powerful laser beams that may otherwise be transmitted through air is decreased. Laser-based ultrasonics is generally less sensitive to traditional contact ultrasonics, and in addition, some light is lost in the coupling of laser light energy into optical fibers, further decreasing the sensitivity; thus the need for signal processing of the received signals is of great importance. In this work, the waveforms obtained using the Fabry--Perot interferometer and the corresponding signal processing performed on the data to enhance the resulting image for NDE are discussed.