Yukinori Okazaki

PD (Powerfull Optical Disk System) for Multimedia.

The use of CD-ROM has become widespread. PC users have generally been satisfied with the performance CD-ROMs, however, there is also a demand for larger-capacity removable rewritable media for Multimedia applications. The PD system offers users an optical disk which is easily handled such as floppy disks presently in use. In addition, PD can also read CD-ROM at fourtimes of the speed using a single common slot for both CD-ROM and PD media. The PD system (name of the new optical disk system prososed by Matsushita Electric Industrial. Co., Ltd.) has good compatibility for pit and groove recording. We calculated the reflectivity, tracking error, and ROM modulation, and varied the groove depth and width to maximize performance. A signal was written on various pregroove depths, and the reproduced signal ratio was measured. We obtained good results by using a phase-change material with the PD optical disk.

Enhanced 8-10 conversion code for high density recording

A modulation code suitable for magneto-optical recording has been studied. The 8-10 code, proposed in this paper, is written in a 5/10, 2/10 or 8/10 code. The study clarifies that the 8-10 code enables high density recording in noisy conditions.

Optical Disc Memory System

The video and the audio disc systems have been realized and the progress of optical disc memory systems allows the new products such as the video file system and the document file system. The optical disc memory system has a number of advantages compared with the current magnetic disc memory. These are the large recording capacity, the high recording density (10 to 100 times more than ordinary magnetic disc) and the contact free record and retrieval of the information, which eliminates the Head Crush problems and realizes the reliable information storage system. However, high recording density and small track pitches (usually 1.6--2.5 micron meters) increases the probability of error rate of recording infomation. Bit error rate (BER) of the recorded optical disc sometimes presents 10-4-10-5 Which is much higher than the magnetic disc. This high BER strongly depends on the production process. Optical disc is preformatted with the address information and with the tracks for infor-mation recording. The pregrooved disc used to be produced by the optical mastering process and the U-V replication process, which needs the very high-grade clean room and the expensive facilities. Process control of the laser cutting on the resist coated glass master is quite sensitive and must be treated with extreme care. When the large quantity of mass produced optical memory discs is supplied, a new mastering process would be needed. One of the solutions of this problem is the dry mastering process with a mechanical cutting system.

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.