Automatic surface inspection using wavelet reconstruction

In automatic surface inspection, one has to solve the problem of detecting small surface defects which locally break the homogeneity of a texture pattern. Textures are generally classified into two major types, structural and statistical [1]. Structural textures are those that are composed of repetitions of some basic texture primitive, such as directional lines, with a deterministic rule of displacement. This type of texture arises in machined surfaces. Statistical textures cannot be described by primitives and displacement rules. The spatial distribution of gray levels in such textured image is rather stochastic. Sandpaper and leather, for instance, fall in this category.