| 摘要 |
A disk-shaped optical storage medium for binary information, stored serially as a sequence of pits and lands along a spiral track in the form of pits and lands readable by means of a la- ser beam according to the principle of interference may be identified in a manner preventing confusing and unauthorized duplication in that a selected number of the total lands is formed in the optical reference surface as depressions which are shallow in comparison to the depth of the pits. This iden- tification feature of basically any form may be both so small that it can only be rendered visible by electron microscopic means and so large that it can be detected by the naked eye in diffused light. |
