Kenzo Ishibashi

Physical Characteristics and Format of a Two-Inch-Diameter Magneto-Optical Disk System with 3 GB Capacity

Recording at a high density four times that of a current digital versatile disk random access memory (DVD-RAM) has been achieved by applying the domain wall displacement detection (DWDD) technology using a conventional optical head with the same wavelength of 660 nm and numerical aperture (NA) of 0.60 as those the DVD head. It has been confirmed by using an alternating sampled servo, laser annealing of the inter track area and partial response maximum likelihood (PRML) that a recording density of 15 Gbit/inch2 with a track pitch of 540 nm and bit length of 80 nm has sufficient system margins. A newly developed 1-bit-distributed address format has achieved a redundancy of 23%. Furthermore, the edge shift compensation technique has reduced the recording magnetic field. These indicate that a capacity of 3 GB on a two-inch-diameter disk is now available for mobile use. If applied to a digital video camera, one hour or more of moving-picture-experts-group-2 (MPEG2) video contents can be recorded at a bit rate of 6 Mbps.

Compatability test for phase-change erasable and WORM media in a multifunction drive

We have presented configuration of the multifunction drive, interchangeability test, and reliability test consisting of temperature test and reading many cycles test. The multifunction drive could be realized by adding laser power control block and the polarity switch of reading amplifier without changing the WORMs head on a current WORM drive. Interchangeability test results showed having good interchangeability among multifunction drives or among WORM drives, and also the multifunction drive had full compatibility with current WORM drive on the current WORM disk. Reliability test results for the multifunction drive using a PCE disk and a WORM disk showed that writing sensitivities of both disks were much less dependent ont he temperature and the drive had stable writing characteristics in environments from 5 degree(s)C to 50 degree(s)C, and furthermore no error bit was observed while reading the most inner track of each disk 10 million cycles with the read power of 1.8 mW being 20% up to normal one at 6.1 m/s of disk velocity.