Digital imaging based spectrometry applied to ceramic glass inspection

Materials surface characteristics can be investigated analyzing their spectral response when properly energized by a suitable source. When the source is represented by a light spectra of known characteristics the surface material response can thus be evaluated adopting a spectrophotometric approach. The analyses of the detected spectra can give useful information concerning the material characteristics and/or surface properties and status. In this perspective digital spectrophotometry can be considered as one of the basic techniques to characterize materials. The application of such a technique is usually confined in "high-tech" environments and can results quite expensive and difficult to apply in industrial "on-line" processes. In this paper recent advances in imaging spectrophotometry devices and techniques are presented with reference to the possibility of recognizing different glass fragments (cullets) according to their color and, most important thing, the presence of transparent polluting fragments, that is the distinction between glass from ceramic glass fragments. The work is specifically addressed on the spectral characterization of different ceramic glass products in order to define suitable inspection strategies to preliminary identify and then sort such a class of materials inside recycling plants to perform the required separation between useful (glass) and polluting (ceramic glass) materials.