The purpose of this paper is to introduce a new device with eddy current microscope (ECM) to test the invisible and buried subsurface flaws in metallic specimens.
When coil is excited by intermittent impulse signal, the eddy current effect happens among the tested metal specimen which is near the coil. Because of magnetic‐optic effect caused by eddy current magnetic field, the magnetic‐optic film changes the polarization direction of the passing linear polarization beam. The beam, containing the defects' information, can be accepted by charge‐coupled device (CCD) after being reflected through beamsplitter, and the imperceptible flaws in subsurface of mental product can be visually tested.
Integrating the eddy effect fully with Faraday's magneto‐optic (MO) effect can realize the visual non‐destructive testing for the subsurface defects.
Manufacturing defected specimens and improving the resolving power of the MO image remain difficult and need further research. A better image processing system needs to be developed to ascertain the characters of the defects.
After additional experiments, this device may find practical application on the inspection of flaws under the surface of metal specimens.
The device presented in this paper can detect the small defects that are hardly seen by eyes at the surface and the subsurface of metal specimens, and have them detected by the CCD.
