Image Registration for Digital Radiographic Images and its Applications to Industrial NDT Inspection
Jianxin Gao, Gary Penney, Martyn Wright · 2006
Radiographic images taken under different conditions of the engineering structures in service need to be aligned properly prior to performing effectively any of the automatic defect detection. To this end, image registration techniques based on intensity correlation were employed in this paper in a coarse-to-fine multilevel manner to speed up the time- consuming calculation process. The original image with high spatial resolution was downscaled to several images, each with the resolution half of the previous level. The registration for the coarsest image pair resulted in the detection of predominant part of the displacement field associated with the image pairs, while the registration for the finest image pairs generated delicate corrections for the previously calculated displacement field. This image registration procedure was streamlined into a whole framework for digital radiographic processing for industrial NDT inspection. The aligned image sequences can be used subsequently for 3D defect assessment. Preliminary applications showed that the implementation of image registration improved considerably the effectiveness of the automatic defect detection.