OPTICAL DISK AND ITS REPRODUCING DEVICE AND OPTICAL DISK RECORDER

摘要

PROBLEM TO BE SOLVED: To easily judge whether an optical disk is hard copied or not by recording pit strings having a space frequency component above the reproduction threshold based on the optical transmission characteristic of an optical pickup for reproduction at prescribed positions. SOLUTION: A microcomputer 40 controls the information of the optical disk 1 so as to reproduce the information. This microcomputer compares the reproduction patterns outputted from a pattern extraction section 38 and the patterns recorded in a reference pattern recording section 41 and decides whether both coincide or not at the time of reproducing the prescribed position where the pit stings for remedy against copying are recorded. If both do not coincide, the microcomputer alarms or displays that the optical disk under reproduction is hard copied. Simultaneously, the microcomputer stops the reproduction action.