Vehicle X-ray Scans Registration: A One-Dimensional Optimization Problem

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Over the years, image registration has been largely employed in medical applications, robotics and geophysics. More recently, it has increasingly drawn attention of security and defense industries, particularly aiming at threat detection automation. This paper first introduces a short overview of mathematical methods for image registration, with a focus on variational approaches. In a second part, a specific registration task is presented: the optimal alignment between X-ray scans of an inspected vehicle and an empty reference of the same car model. Indeed, while being scanned by dedicated imaging systems, the car speed is not necessarily constant which may entail non-rigid deformations in the resulting image. The paper simply addresses this issue by applying a rigid transform on the reference image before using the variational framework solved in one dimension. For convergence and speed purposes, line-search techniques and a multiscale approach are used.