Surface evaluation of compact disks by electronic means

Compact disks (CDs) are widely used storage devices for audio- or computer data. Their relative immunity to damage or pollution of the surface is a major reason for their wide acceptance and commercial success. However, excessive defects on the surface can exceed the capabilities of the error correction circuits of the playback device. For audio CDs these defects may invoke error concealment algorithms in the signal processing circuits that may cause audible distortions of the playback signal. For data CDs, the damage can lead to completely destroyed data sets.