Detection of Knots in Logs Using X-ray Imaging

摘要

The basis for selecting x-ray technology for long inspection is its capability tosee the internal properties of objects. Producing several projection images with x-rays and applying the principle of computed tomography would yield three-dimensional data on the log. However, no such inspection systems have been realized because of the high speed requirements of the sawing process. The subject of the research work was a knot detection system with three fixed projections. It was known in advance that three projections cannot guarantee exact reconstruction of a 3-D object. Strong object details tend to hide weaker ones, or their shadows may combine into extra ghost details. However, utilizing knowledge of the properties of knots and stems, we were able to develop a method for determining the coarse shapes of the knots. The inherent uncertainty from insufficient information is managed with a confidence figure, which is calculated for each candidate knot to judge the usefulness of the results.