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Advanced computed laminography using a priori information

: Schorr, Christian; Dörr, Laura; Maisl, Michael

Volltext urn:nbn:de:0011-n-3995368 (494 KByte PDF)
MD5 Fingerprint: a4a22903eb442c3bb93b1ba8150f49fd
(CC) by-nd
Erstellt am: 25.6.2016

International Committee for Non-Destructive Testing -ICNDT-; Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. -DGZfP-, Berlin:
19th World Conference on Non-Destructive Testing, WCNDT 2016 : Munich, Gemany, 13-17 June 2016; Proceedings; USB-Stick
Berlin: DGZfP, 2016
ISBN: 978-3-940283-78-8
Paper We.4.B.1, 9 S.
World Conference on Non-Destructive Testing (WCNDT) <19, 2016, Munich>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IZFP ()

Computed tomography (CT) is a very powerful tool in medicine and non-destructive testing but is unsuitable for planar objects. A solution can be found in the use of computed laminography (CL), a technique in which the object is irradiated by an oblique angle thereby circumventing the problems arising in CT. Due to the limited amount of angular coverage and the special geometric set-up, filtered back projection methods cannot be employed for the reconstruction in this case. More flexible iterative algorithms like SART (simultaneous reconstruction technique) provide an answer to this challenge. One of their important advantages when compared to filtered back projection methods is their ability to incorporate a-priori information about the object into the reconstruction process. Often the object's geometry is known from CAD files or other technical specifications. Especially in the case of limited-angle data, where only a part of the object can be measured, and laminographic geometries, additional information is of great importance. This geometrical a-priori knowledge can be exploited to restrict the reconstructed volume to areas where material is definitely present, resulting in correct object contours even in the limited-angle case. This reduces artefacts and increases contrast thereby allowing for a better defect detectability and thus an easier and more reliable inspection of the object. To use a-priori information correctly, a registration step between CAD file and measured projections is necessary. We have devised a registration algorithm which is able to compute the required 2D-3D-registration automatically. The concept of exploiting a-priori information to improve reconstruction quality can also be used in standard CT settings to reduce the amount of necessary projections or to solve limited angle problems.