Motion-based filtering of magneto-optic imagers

The magneto-optic imager (MOI) is a powerful device for the nondestructive inspection (NDI) of aging aircraft. MOI produces analog images of magnetic flux leakage associated with eddy current distribution around surface and subsurface structures. The main advantages of using MOI are its fast inspection speed and easy interpretation compared with conventional Eddy Current NDI instruments. However, due to the magnetic domain wall structures of the sensor, the MOI images are corrupted by noise, which lowers the MOI inspection capabilities. The domain walls produce serpentine pattern noise, which can be reduced by improving the sensor or by use of image processing methods. This paper introduces a motion-based image processing method to reduce the background noise. Initial results of implementing the algorithm on real field data are presented. q 2003 Elsevier B.V. All rights reserved.