TY - JOUR A1 - Osterloh, Kurt A1 - Bücherl, T. A1 - Lierse von Gostomski, C. A1 - Zscherpel, Uwe A1 - Ewert, Uwe A1 - Bock, S. T1 - Filtering algorithm for dotted interferences JF - Nuclear instruments and methods in physics research A N2 - An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible. KW - Neutron KW - Radiography KW - Tomography KW - Filtering KW - Evaluation KW - NECTAR PY - 2011 DO - https://doi.org/10.1016/j.nima.2011.01.107 SN - 0168-9002 SN - 0167-5087 VL - 651 IS - 1 SP - 171 EP - 174 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-24917 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -