Magnetooptic sensor for remote evaluation of surfaces

A new magnetooptic (MO) detection method utilizing changes in the optical path through a transparent MO thin film has been developed and studied for evaluation of surface deformation created by subsurface or internal defects in materials. Investigation of defects cannot be performed on nonconducting and nonmagnetic materials using conventional electromagnetic techniques such as eddy-current or magnetic flux leakage. The new method utilizes the controlled periodic displacement of a domain wall in the MO thin film and can be used to measure remotely mechanical deformation of a surface of any type of material by measuring the changes of width of the shoulder in the intensity versus time waveform.