| 摘要 |
PURPOSE: A method for forming watermark image is provided to obtain an optical recording or storage medium having medium identification indicia which also offer protection against copying, with the indicia formed directly in an optical recording layer or in an optical storage layer of the medium. CONSTITUTION: A method of forming a watermark image in a hybrid optical master disc(10) for replication in a hybrid optical disc, comprises the steps of providing a master substrate(12); coating a photoresist layer(20) over a surface(22) of the master substrate; exposing at a laser beam groove exposure level a continuous spiral wobbled groove in the photoresist layer, the groove extending from a designated read-only memory(ROM) area(30) to a designated recordable area(50) of the master disc, and exposing at a laser beam depression exposure level depressions in the groove in the ROM area in response to data to be recorded therein; projecting a watermark image(100) over at least portions of the ROM area and the recordable area at a watermark exposure level which is lower than the groove exposure level; and developing the photoresist layer to provide the continuous spiral wobbled groove, the depressions in the ROM area, and portions of the watermark image remaining in lands between successive turns of the spiral groove.
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