Indicator marks on an optical disk indicating that the disk has been previously accessed

摘要

A method for constructing an optical disk and a method of signal detection which permits a read only device, such as a CD-ROM or DVD-ROM reader, to create a permanent mark on a disk in such a way that it can be subsequently determined that the disk had been previously accessed is disclosed. Such a disk facilitates the operation of CD-ROM or DVD-ROM based systems where the behavior depends on whether or not the information on the optical disk had been previously accessed.