A New CL Reconstruction Method under the Displaced Sample Stage Scanning Mode

X-ray computed laminography (CL), as a popular nondestructive testing technology, has unique advantages for the detection of plate-type structures. However, with the limitation of the detector size, the specimen, i.e., large flat-like components, may be beyond the field of view (FOV) of the CL system. For the cone-beam computed tomography (CBCT) system, which is analogous to the CL system, a traditional way to enlarge the FOV is the displaced sample stage scanning mode. In this article, a new CL reconstruction method with the displaced sample stage scanning mode is proposed to enlarge the FOV of the CL system. According to this method, a virtual detector is established to obtain a new CBCT system under the displaced sample stage. Then, the projection data are converted into the virtual detector and scanning geometric parameters are calculated. The Feldkamp-Davis-Kress (FDK) algorithm combined with the Parker weighting function can well reconstruct the cross sections of the specimen with acceptable quality. The numerical simulation and experiments demonstrate that the proposed approach can achieve image reconstruction with sufficient quality and low computational cost. The FOV of the CL system is enlarged effectively without changing the original scanning geometry, and thereby, it can be conveniently utilized in engineering applications.