idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
Fraunhofer IZFP offers its customers and research partners the entire range of nondestructive testing technologies, whether it involves basic or applied research. The institute's researchers, engineers and technicians develop solutions to address modern testing applications including feasibility studies, consulting, training and inspection services and creating prototype systems. From June 13 to 17, 2016, our researchers and engineers will present advanced computed laminography using a priori information at the 19th World Conference on Non-Destructive Testing (WCNDT) in Munich.
Computed tomography (CT) is a very powerful tool in medicine and nondestructive testing but is unsuitable for planar objects. A solution can be found in the use of computed laminography (CL), a technique where 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 backprojection 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 backprojection 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 reconstruction volume to areas where material is definitely present, resulting in correct object contours even in the limited-angle case. This reduces artifacts 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 an 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. We demonstrate the advantages of applying a priori knowledge by means of reconstructions of industrially relevant examples measured with our CLARA scanner.
Advanced Computed Laminography using a Priori Information
Source: Fraunhofer IZFP
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Advanced Computed Laminography using a Priori Information
Source: Fraunhofer IZFP
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