Recognizable patterns in adjacent tracks of ROM record carriers for simultaneous scanning for copy protection

摘要

In order to distinguish a duplicated record carrier from an original record carrier, a pattern is included in a ROM type record carrier. The pattern is oriented perpendicular to the reading direction of the record carrier. During illegal duplication the spatial relationship is disturb which can be easily detected. The patterns can be read out simultaneously by the same single read-out spot by including both patterns within the diameter of the optical spot, thus guaranteeing that the read-out patterns are actually still spatially close together.