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AssigneeHitachi, Ltd.
InventorsTamotsu Ito, Hiroshi Banno, Ryuichi Koike, Takashi Takeuchi
Estimating the term…
A CD-ROM is provided with an area for forming a character/graphic pattern. The character/graphic pattern is formed in such a way that data, which generate on the CD-ROM two sorts of pit patterns having average reflectances different from each other to a perceptible extent, are respectively recorded inside and outside the character/graphic pattern. Unless an illegal copy disc is produced by duplicating the legal original disc of the CD-ROM at a very high precision, the character/graphic pattern of the copy disc is invisibly deformed by the discrepancy between the arrangements of the pit patterns of the copy disc and the original disc.
An information recording medium comprising:
An information recording medium comprising:
An optical disc comprising:
An optical disc as defined in 3, wherein the pit patterns formed in a bounds of tracks containing said specified tracks are formed in accordance with a CAV (constant angular velocity) system in which a rotational velocity of said optical disc is held constant, and the pit patterns formed on any tracks of said record surface except tracks contained in said bounds are formed in accordance with a CLV (constant linear velocity) system in which a tracking linear velocity of said tracks is held constant.
An optical disc comprising:
Dependencies are inferred from the claim text.