High data capacity storage medium with protection code, method for obtaining the protection code and respective data reading apparatus

摘要

The optical storage medium comprises a substrate layer (2), and a data layer (3) disposed on the substrate layer (2), the data layer (3) comprising data being arranged in tracks as marks and spaces. A protection code (PC) is coded in one of the tracks or a part of a track which code comprises marks (P) of a first size (w1) and marks (P) of a smaller, second size (w2). The marks of the second size (w2) have in particular a width being smaller than the width of the marks of the first size (w1). To obtain the protection code (PC), a method is used comprising the steps of reading a track or a part of a track (T) with a first laser power for obtaining a first data signal (D1), reading the same track or the same part of a track (T) in another step 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 for example by a microprocessor of a respective data reading apparatus.