REGISTRATION OF MULTI-MODAL NDI IMAGES FOR AGING AIRCRAFT
Zhenyu Liu, David S. Forsyth · Research in Nondestructive Evaluation · 2004
In the case of complex structures subject to various modes of corrosion and fatigue, it is unlikely that any single nondestructive inspection (NDI) technique will be able to fully characterize the structure. When multiple NDI methods are used on the same specimen, data fusion methods can be employed to combine and improve the information. In this article, sections of service-retired aircraft lap joints were inspected by numerous NDI techniques. All the inspections present the results as two-dimensional images. Before being further processed by a data fusion system, all the images must be registered to a common coordinate system. The registration operation will ensure that all pixels in every image can be located in a coordinate system associated with the physical specimen. In this study, an automatic image registration procedure is presented. The images are decomposed into sub-image components by a steerable pyramid, and registered in a multiresolution fashion. The registration parameters are searched and refined by matching the band-pass component of the decomposition through a coarse-to-fine procedure. Registration successfully transforms NDI data to a common coordinate system, and then multi-modal images can be input to a data fusion system for integration and combination.