Eiji Nakagawa

Optical Disk System Using a High-Numerical Aperture Single Objective Lens and a Blue LD

An optical disk system using a blue laser diode and a single objective lens that has a numerical aperture of 0.7, is proposed. A sufficiently low jitter value was obtained with a read-only disk having 17-Gbyte capacity. The paper also includes discussion on the influence of the laser noise and RF modulation method on the playback signal.

A Format of High-Density Rewritable Optical Disk using Groove Recording

A new physical format using groove recording and new signal processing techniques is discussed. The signal reproduction of shallow pre-embossed pits was confirmed with a technique utilizing tangential push-pull (TPP) and a compatible partial response (PR) equalizing system. An evaluation in terms of the bit error rate by hardware experiments is demonstrated.

High-Density Rewritable Optical Disk Using Groove Recording

For an optical disk system using an objective lens of numerical aperture (NA) 0.7 and a GaN laser, the performances of the groove-recording scheme were investigated. A disk having 17 GB capacity showed the initial jitter of 11.9% with an equalizer for digital versatile disks (DVD). With an adaptive equalizer and a Viterbi decoder, sufficiently low bit error rates and wide tilt margins were obtained.

19.8 GBytes ROM disc readout using a 0.7 NA single objective lens and a violet laser diode

The performance of the proposed system with the noise reduced ROM optical storage disc and the error feedback (EF)-partial response maximum likelihood (PRML), composed of the error-select type adaptive equalizer and the adaptive Viterbi decoder, is demonstrated. The reproduced signal of the 19.8 GBytes ROM disc shows a sufficient low error characteristic.

Development of compact disk-write-once hybrid disk

We developed the new hybrid disk which has a read-only area (ROM), that is, a premastered area, and write-once area (WO), where writing is possible. To be compatible with a compact disk (CD), the disk is a single plate and organic dye is used for the recording layer. The disk has high productivity because there is the possibility of spin-coating the organic dye onto not only the WO area but to pits in the ROM area as well. Furthermore, the disk can have multiple ROM and WO areas as the users option. To satisfy the CD standards a high reflection rate is achieved by means of characterizing the shape of pits in the ROM area and pregrooves in the WO area. The disk yields good CD playback signals after recording.

High-Density Read-Only-Memory Disc Mastering Using Direct-Focus Laser Beam Recorder

The authors have developed a novel laser beam mastering apparatus using a deep-UV (DUV) laser for a high-density optical disc. A direct focusing mechanism, where the recording beam itself is also used for focusing, is applied in the laser beam recorder (LBR). The mechanism solves the focus depth issue and provides stable focusing. The evaluation results for the 23.3-Gbytes-capacity read-only-memory (ROM) disc revealed that uniform recording can be realized. Jitter variations in the tangential and radial directions were suppressed to less than 0.2% and 0.07%, respectively. A low residual tracking error signal was also attained. The measurement results for the 25-Gbyte-capacity disc show reasonable jitter not only for a resist/glass disc, but also for an injection-molded disc. The tilt margin of the disc confirmed that the disc was practical for application in the market. Furthermore, the evaluation of the 27 GByte disc indicated the possibility of higher density ROM disc mastering.

1-beam-mastering of groove recording disc with LPP address

This paper describes an unique mastering scheme to form the Land-Pre-Pit address along with the groove. The scheme expands the resolution limit and gives other advantages in the disc manufacturing. The authors produced the disc applying it on a 351nm mastering apparatus and confirmed the realization of 20 GBytes disc capacity per the DVD size. The scheme can be inherited in the future mastering using the shortened wavelength or the electron beam.

Laser beam mastering of high-density d=1 RLL code ROM disc

The paper describes a novel laser beam mastering system with technologies of direct focus servo, high contrast photoresist material, recording signal compensation. Although the optics consists of conventional 266 nm laser with numerical aperture (NA) 0.9 objective lens, it successfully realizes an over 20 Gbytes capacity Read-Only-Memory (ROM) disc.

Advanced Photoresist for High-Density Groove-Recording Disc

In high-density mastering process, the relationship between the groove noise of the groove-recording disc and the molecular weight of the photoresist was examined. With a decrease in the molecular weights of novolak resin and the photoactive compound used, the shape of the groove edge became smooth and the groove noise value was reduced. By optimizing the molecular weights of novolak resin and the photoactive compound, the groove noise value is reduced by 3.5 dB at a track pitch of 0.32 µm.