Comparison of Magneto-Optical Faraday Effect Method and Magnetic Camera for Imaging the 2-D Static Leakage Magnetic Flux Density

Abstract

Magnetic flux leaks around the defect on the magnetized ferromagnetic specimen. The magnetic flux leakage testing (MFLT) use the magnetic sensor to measure the leaked magnetic flux density (LMFD). The high sensitivity of sensor need to increase the probability of detection (POD). Also the small size and high spatial resolution of sensor need to increase POD and to sizing defect. Uniform and small lift-off are another necessary to increase POD and sizing ability. Also, the real time imaging of magnetic flux density can increase the inspection time. So the period of planned preventive maintenance could reduce. Two dimensional semiconductor-based magnetic sensor array with high spatial resolution satisfies these requirements. Projection of magnetic flux density on a sensor itself would be another method. We compare the magnetic camera and the magneto-optical Faraday effect (MOE) for MFLT. Magnetic camera uses the two dimensional Hall sensor arrays to imaging the LMFD. And the MOE project LMFD. The plane of polarized light rotates inside of magneto-optical film (MOF). The Faraday rotation angle proportional to direction and intensity of magnetic flux density. Sensitivity, spatial resolution, magnetic hysteresis, repeatability, full-scaled operational range compared. Also shape of target specimen compares too.