Multi-layer recording method has been studied and developed since dual layer disk of DVD-ROM and the studied disk type has expanded from ROM to Rewritable disk. Multi-layer disk has new problems different from a single layer disk. One is an inter-layer cross-talk, which a component of a signal from adjacent layer leaks into a detected signal when the information data is reproduced from a target layer. Second is a recording power fluctuation, which the light power reached a target layer changes by marks on intermediate layers. There were many works that solve this problem. This causes severe problem for signal processing and recording performance. There was work that was proposed to design the structure of a multi-layer disk and an optical head. In this paper, we reported the consideration of a code in order to solve the problems.
To make higher density on optical disk, a new recording method- 2D recording-which can increase the track-density rather than the linear density was proposed. The performance of this method on increasing density is estimated by the simulation and confirmed by measuring the read-out signal. Consequently, it is clarified that this method can attain more than twice the areal density independently and realize the density of 2.2Gbit/in2 which is 8 times as large as that of first generation using 680 nm laser diode.
We have developed Sn-Sb-Se/Sb-Bi bi-layer phase-change media for high- density write-once optical disks. Crystallized marks as small as 0.5 micrometers are stably recorded without initialization. These phase-change media, compared to ablative type write-once media, have high carrier-to- noise ratio, low jitter, and long life. Mark-edge recording with multi- pulse laser irradiation on the media provides a linear bit density of 0.48 micrometers /bit and track pitch of 1.2 micrometers using a 690-nm-wavelength laser diode and 0.55 NA objective lens. This corresponds to 1.1 Gbit/in.2, or 14 GB formatted data capacity per both sides for a 12- inch-diameter disk with a zoned CAV format.
KEYWORDS: Optical discs, Edge detection, Modulation, Signal detection, Signal processing, Clocks, Optical storage, Data storage, Data archive systems, Process control
A large size optical disk (for example, in 300 mm diameter) has been applied to document files and archived coded data files. Recently, demands for larger capacity and higher speed are growing greatly. Therefore, we developed a write once optical disk (300 mm in diameter), which adopts the pit-edge recording method and the MCAV (modified constant angular velocity) method to achieve higher linear density. On optical disk system combining the above two methods has yet been developed. In addition, new techniques must still be developed to satisfy the requirements of large capacity and high speed using these two methods. In this paper, new techniques were have developed are discussed.
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