A simulation model of focus and radial servos in compact disc players with disc surface defects

Compact disc players have been on the market in more than two decades. As a consequence most of the control servo problems have been solved. One large remaining problem to solve is the handling of compact discs with severe surface defects like scratches and fingerprints. This paper introduces a method for making the design of controllers handling surface defects easier. A simulation model of compact disc players playing discs with surface defects is presented. The main novel element in the model is a model of the surface defects. That model is based on data from discs with surface defects. This model is used to compare a high bandwidth with a low bandwidth controller´s performance of handling surface defects.