| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical storage medium with a protection code. <P>SOLUTION: The optical storage medium includes a substrate layer, and a data layer. The data layer includes data being arranged in tracks as marks and spaces. The protection code PC is coded in one of the tracks or a part of a track in the tracks including a code of a second mark smaller than the mark of a first size. The marks of the second size have a width being smaller than the width of the marks of the first size. To obtain the protection code, a method is used comprising the steps of reading a track or a part of a track with a first laser power for obtaining a first data signal D1, reading the same track or the same part of a track with a second laser power being different from the first laser power for obtaining a second data signal D2, and calculating the protection code by taking into account the first and the second data signals. The protection code may be calculated by a microprocessor of a respective data reading apparatus. <P>COPYRIGHT: (C)2010,JPO&INPIT |
