Isao Satoh

Key technology for high density rewritable DVD (DVD-RAM)

DVD-RAM requires a large storage capacity to write and read huge amounts of data such as MPEG2 and AV as well as computer data for full-scale multi-media applications. Its format is focused on unifying AV and computer files, and achieving read compatibility with DVD-ROM drive. DVD-RAM has been realized by using phase change media, 0.6 mm substrate, 650 nm laser and NA 0.6 lens. The track has a single-spiral wobbled land and groove format. Each sector in land and groove tracks can be accessed in a seamless manner by combining physical headers and the wobble signal. 8-16 modulated signal is overwritten on land and groove tracks with mark edge recording method. The sector position shifting of 8 bytes and two guard fields located at the top and end of the data field are introduced to prevent the signal deterioration caused by repeating overwrites. DVD-RAM disc has wide tolerances of laser power and disc tilt, and overwrite durability of over 10/sup 5/ cycles. It is also concluded that DVD-RAM is high reliable and compatible for reading by DVD-ROM drives.

Thin Injection Molded Substrate For High Density Recording Phase Change Retritable Optical Disk

First-generation phase change rewritable and MO optical disks have been commercialized. There are two approaches to high density optical recording. One is by applying shorter wavelength laser diodes. The second is using a large NA optical lens. Larger-NA optics are sensitive to disk tilt characteristics because of aberrations in the disk substrate. le propose a thin disk substrate to give wide disk tilt tolerance. This article will deal with the characteristics of thin injection molded polycarbonate disk substrate and crosstalk characteristics of phase change rewri table optical disks using large-NA optics.

Overwritable phase-change optical disk recording

Three key technologies have overcome the cycle issue of phase-change optical disks. The interchangeability testing data for Multimedia PD by different media makers has verified the values specified in ECMA-240 which has become a worldwide standard. Wide wavelength response will extend the capacity of 120 mm phase-change optical disk to 15 GB/side.

DVD-RAM for all audio/video, PC, and network applications

Rewritable DVD (DVD-RAM) 4.7 GBytes products such as DVD-RAM disc, DVD-RAM drive, and DVD Video Recorder have been developed. DVD-RAM can integrate all Audio, Video, Imaging, Computer, and Network applications with write compatibility between DVD-RAM 2.6 GBytes and read compatibility across the entire DVD format family. DVD-RAM disc and drive technologies such as high speed reliable recording, easy operability, secure copy protection functions, and DVD Video Recorder are presented. With the coming of blue light sources, the capacity of the DVD-RAM disc can be upgraded 3 to approximately 5 times, and furthermore could be expanded over 10 times in conjunction with a high-NA optics and a dual-layer disc technology, then 2 to approximately 4 hours high-definition video will be recorded.

Holographic disk recording of digital data with fringe stabilization

A novel 2-D holographic disk recording of binary data is proposed and discussed as an alternative to the bitby- bit recording disk. Using a double diffraction optical system with a holographic beam splitter, the disk holds interference fringes on a hologram recording disk stationary during exposure. The disk recording time is shortened by more than a factor of 100 compared with that of the conventional method, and the data transfer rate can be expected to exceed 100 Mbits/s. The light beam positioning control accuracy and the mechanical requirements of a disk are also discussed.

Holographic memory system for Kanji character generation.

A Fourier transform holographic memory has been developed and used for generating and storing sixteen thousand Kanji characters. The memory consists of four groups of holograms of 63 pages, recording 64 Kanji characters in each page, and has a packing density of 1.34 x 10(7) bits/cm (2). Digitized characters of sixteen sizes can be generated with natural letter faces and good image quality. This paper focuses on the recording and reconstruction of holographic Kanji memory using a pseudorandom diffuser and systematic solutions consistent with optical, mechanical, and digital systems.

A High-Density Phase-Change Optical Disk System Possessing Read/Write Compatibility with 90 mm Magneto-Optical Disks

High-density recording characteristics of phase-change optical disks were studied using 2-7 pulse-position-modulation (ppm) in-groove recording. Carrier-to-noise-ratio (CNR) was over 50 dB at a mark length of 0.60 µm and the crosstalk at the track pitch of 1.10 µm was less than -30 dB. In addition, a 256 MB 90 mm overwritable PC optical disk system having read/write compatibility with the ISO 128 MB MO disk has been developed based on the acquired results. The drive is based on the 90 mm MO drive at a wavelength of 780 nm and NA of 0.53. The user capacity of 256 MB was achieved using a mark length of 0.63 µm, track pitch of 1.25 µm, 2-7 ppm in-groove recording, and MCAV with 10 zones. The number of sectors per track was varied from 31 to 49.

High-Speed Access Mechanism for 90 mm 1-Inch-High Optical Disk Drive

A 90 mm, 1-inch-high optical disk drive with a 17-mm-high mechanism and a 27 ms seek time was developed using a separated optical system with an improved galvanomirror. This optical layout reduced the weight of the movable optical part to 7 g. The maximum acceleration of 127 m/s2 was driven by 8 W. The major component parts of the galvanomirror, such as the mirror holder and base, were made of anisotropic liquid-crystalline polymer. The use of this material, which has high rigidity and low thermal expansion, resulted in optical spot drifting due to mirror rotation of less than 3 µm from room temperature to 65°C.

Advanced dual-layer phase-change optical disc

Multi-layer optical recording is a promising technology for increasing a disc capacity using an optical pickup identical to that used for a single-layer optical disc. A capacity of 25 GB - 50 GB is required to record 2 - 4 hours HD-TV program. In this paper, the physical format of the dual-layer phase-change optical disc is studied and experimental results of an advanced dual-layer phase-change optical disc, of which first layer is characterized by a transmittance-balanced structure and prepared by a new replication process, are shown and discussed. The transmittance-balanced structure disc is realized by adopting Ge(Sn)-Sb-Te film that has appropriate optical constants and optimizing the thickness of dielectric layers. The signal of the second-layer in the transmittance-balanced structure disc is able to read and write without any influence of the first-layer. A capacity of over 50 GB is demonstrated by the transmittance-balanced structure disc.

Index-Free Full-Text Search Function Installed into Optical Disk Drive

An optical disk drive, equipped with additional SCSI commands for full-text search is developed. By hierarchical search architecture of parallel hardware, firmware and software, the system filters information almost at the disk-read speed. The basic search process is executed by a search engine sharing the function with a portion of the error-correcting LSI installed into the optical disk controller. The basic search performance of the developed system is 10 to 25 times faster than that of software. Also, introduction of an associative table for presearching results in performance more than 1000 times faster than that in the case in which no objective lines are found. Though our system does not have large-scale special-purpose hardware for text search, the retrieving speed of the free-text database is dramatically improved.