Application of the magneto-optic Faraday effect in NDT

摘要

A magneto-optic/eddy current imaging device is presented in this paper to detect invisible defects on the surface and at the subsurface of metallic specimens. The device combines a magnetic inductor to induce eddy currents in the structure under test with an optical set-up to image the resultant magnetic field, thanks to the magneto-optic Faraday effect occurring in a magnetic-optic film which the linear polarised light penetrates. Finally, the image is received by Charge Coupled Device (CCD) to realise visual non-destructive testing. In this paper, the operation principle and the set-up of the new system are described, and the experimental results are discussed, according to which the method presented is proved feasible to non-destructive testing.