Hideaki Ohsawa

Experimental Study of High-Density Rewritable Optical Disk Using a Blue-Laser Diode

The read-write characteristics of an optical disk utilizing a blue-laser diode are examined, applying land and groove recording and partial response and maximum likelihood (PRML) to two optical disk systems: 1) 0.85 numerical aperture (NA) optical disk system consisting of an objective lens with NA of 0.85 and a thin cover layer on a disk with a thickness of 0.1 mm and 2) 0.65 NA optical disk system consisting of an objective lens with NA of 0.65 and a 0.6-mm-thick disk substrate. In the 0.85 NA optical disk system, the track pitch and the data bit length employed for the experiment are 0.29 µm and 0.0987 µm, respectively. These parameters correspond to a capacity of 30 GB/side. In the 0.65 NA optical disk system, they are 0.37 µm and 0.155 µm, respectively, corresponding to a capacity of 15 GB/side. A bottom channel bit error rate (ch.bER) of less than 5.0×10-5 can be obtained in these systems, and it is confirmed experimentally that the ch.bER remains below 1.0×10-4 up to 1000 cross-write cycles.

Experimental study of 28-GB optical disk using a blue laser

The possibility of an optical disk capacity of 28GB/side is studied. The read-write characteristics of a phase-change optical disk are examined using a thin cover layer, a blue laser diode, high NA objective lens and the PRML method. The wide tilt margins of high-density recording are achieved.

High Speed Accessing of a 90 mm Optical Disk Drive

High speed accessing is necessary for optical disk drives, which are used as computer peripheral equipments. A direct track seeking technique was introduced and a new light weight moving part was designed to make the track seeking time shorter. The average seeking time was reduced to 18 ms in an experimental optical disk drive, using an experimental 86 mm disk which was recorded in a sampled servo format.

Implement of a friction compensator for positioning control of a pickup head

Nonlinear friction on a pickup head mechanism causes an objective lens shift. Detrack that causes the objective lens shift makes deteriorates read signal quality. To reduce the objective lens shift, we implement a nonlinear friction compensator in the pickup head. Experimental results confirm this compensator reduces the objective lens shift a quarter of not used.

Experimental study of 30 GB/side rewritable optical disk using a blue-laser diode

The read-write characteristics of a land and groove disk have been examined using a blue-laser diode, high NA objective lens and the PRML method. The wide tilt and defocus margins have been obtained and no deterioration by CW has been observed at a data bit length of 0.0987 /spl mu/m and a track pitch of 0.29 /spl mu/m. These experimental results certify the feasibility of a rewritable optical disk with a capacity of 30 GB/side.

30 GB/side rewritable optical disk for HDTV utilizing a blue laser diode

This paper presents a rewritable optical disk with a capacity of 30 GB/side intended for the next generation of rewritable optical disks. The experimental results have shown that this optical disk has wide tilt margin and is a prospective candidate for supplanting VCR in the HDTV era.