Scattering measurements on optical disks and their relation to media noise

We have conducted measurements of scattered light from bare polycarbonate and glass substrates and from complete optical disks using a He–Ne laser beam in different polarization states and at different angles of incidence. The results are compared with the measured media noise obtained from the same disks on a dynamic tester. Both the scattered light and the media noise originate from the jaggedness and other imperfections of the groove structure, the roughness of the substrate’s surface, and the inhomogeneities of the bulk of the substrate. Although some sources of media noise manifest themselves in the scattered light distribution, others cannot be easily detected by this type of measurement.