Multiresolution Texture Analysis of Surface Reflection Images Leena Lepistö 1 , Iivari Kunttu 1 , Jorma Autio 2 , and Ari Visa 1 1 Tampere University of Technology, Institute of Signal Processing P.O. Box 553, FIN-33101 Tampere, Finland {Leena.Lepisto, Iivari.Kunttu, Ari.Visa}@tut.fi http://www.tut.fi 2 Saanio & Riekkola Consulting Engineers Laulukuja 4, FIN-00420 Helsinki, Finland Jorma.Autio@sroy.fi http://www.sroy.fi Abstract. Surface reflection can be used as one quality assurance procedure to inspect the defects, cracking, and other irregularities occurring on a polished surface. In this paper, we present a novel approach to the detection of defects based on analysis of surface reflection images. In this approach, the surface im- age is analyzed using texture analysis based on Gabor-filtering. Gabor-filters can be used in the inspection of the surface in multiple resolutions, which makes it possible to inspect the defects of different sizes. The orientation of the defects and surface cracking is measured by applying the Gabor-filters in sev- eral orientations. A set of experiments were carried out by using surface reflec- tion images of polished rock plates and the orientation of the surface cracking was determined. In addition, the homogeneity of the rock surface was measured based on the Gabor features. The results of the experiments show that Gabor features are effective in the measurement of the surface properties. 1 Introduction During recent years, the number of industrial imaging systems has increased re- markably. The purpose of these digital imaging solutions is often the control of qual- ity or production. In these solutions, analysis of the image data is made by using some image processing method. One typical application for the image analysis system is to detect and analyze the defects occurring in the production. Image analysis is used to detect possible malfunctioning as soon as possible to minimize the economic losses. Another application is classification of the products in different categories. Surface reflection is a phenomenon that can be utilized in the detection of defects and microfracturing on different surfaces. In addition, based on the surface reflection, other surface properties can also be analyzed. These properties can be for example uniformity and smoothness of the surface. The reflection image obtained from the surface can be analyzed using methods and tools developed in the field of texture analysis. The majority of the texture analysis J. Bigun and T. Gustavsson (Eds.): SCIA 2003, LNCS 2749, pp. 4-10, 2003.  Springer-Verlag Berlin Heidelberg 2003