Compact Disc players have problems playing discs with surface defects such as scratches and finger prints. The problem is that handling normal disturbances such as mechanical shocks etc, require a high bandwidth of the controllers which keep the Optical Pick-Up focused and radial tracked on the information track on the disc. In order for the controllers to handle the surface defects it is required that they are non-sensitive to the frequency contents of the defect, since a defect can be viewed as a disturbance on the measurements. A simple solution to this problem is to decrease the controller bandwidth during the defect. However, due to the variation of defects a more adaptive control strategy would be preferable. In this paper the defects are categorised into three groups. A discriminator is designed, based on the local most discriminating basis vectors of the Karhunen-Loève and Haar bases as well as the mean of defect groups vectors. In these bases the discrimination rule is simple. The defect in question is a member of the group it is closest too. The Karhunen-Loève basis gives a correct classification rate of more than 85.7% with 3 basis vectors and the Haar basis of more than 94.6% with 5 basis vectors.
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