Signal Processing and Speech Communication Laboratory
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Description and Classification of 3-D Surfaces

2003 — 2006
Fons zur Förderung der wissenschaftlichen Forschung, FWF, (Project Nr.: J2243)
Research Areas

In steel industry there is an increasing demand for automatic inspection systems to control the quality of products. Through the economic pressure on the supplier to industry the inspection of a few samples from the production lot is insufficient. Especially, in car industry a complete, reliable, and automatic surface inspection is necessary. Hence, there is huge demand for vision based quality control systems in industry. The aim of the research project is to develop sophisticated methods for evaluating the surface quality of steel blocks. This means that irregularities have to be detected reliably. Further, they have to be classified as erroneous or as non-problematic. Due to the fact that an acceptable intensity image cannot be produced with intensity imaging the investigations are restricted to range imaging. The 3-D model of the surface is acquired be means of the light sectioning methods. The proposed research comprises of two key activities. Firstly, suitable features have to be investigated which represent the characteristics of the range data well. These descriptors are restricted to characterize the planar curves of the cross-sections. Secondly, the features are to be combined in order to locate the irregularities embedded in the surface data and further to decide between flawed and intact surface segment. There exists a huge variety of different classification algorithms. Special attention will be dedicated to Hidden Markov Models represented as Bayesian network. This model considers a sequence of random variables that are dependent on previous values. The issue of decision-making by means of probabilistic networks is a very fundamental approach which might be useful for many intelligent systems.