The inspection of magnetic flux leakage from metal surface cracks by magneto-optical sensors

We investigated the feasibility of using magneto-optical sensors for measuring the magnetic leakage fields in non-destructive evaluation. We used magneto-optical garnet thin films as a sensor and the effect of crack dimension on the sensor's response were investigated via a simple Faraday rotation technique. Our results show that the sensor signal displays a linear increase as the length and depth of the cracks increase however; the change in crack width does not have a significant effect on the magnetic leakage field and the sensor's signal. This technique is capable of high resolution magnetic imaging of small surface cracks and thus has great potential for application in the magnetic flux leakage test industry.