Abstract: A technique for verifying the authenticity of a particular breed of pirated optical discs. By comparing the original source disc with the pirated version in the cross-polarization laser light of a polarimeter, the stress of the pirated replication will be revealed, verifying the existence of piracy.

Abstract: A print scanner for detecting defects in the label of a compact disc or the like supported on a carrier moved through a label printing station into a substantially light-tight housing in which the disc is illuminated with diffuse light through a mask so that a video camera in the housing sees only the label area. A reference image derived from a multiplicity of video frames and a sample image derived from a plurality of video frames are subtracted each from the other, two histograms are computed from the subtraction results and respective figures of merit for missing ink and added ink are calculated from the histograms.