Akira Gotoh

Magneto-Optical Disk Structure with High Write/Erase Repeatability

Over 107 write/erase repeatability has been achieved in magneto-optical (MO) disk by optimizing thermo-structural design through thermal conduction analyses. By combining this technology with that for anti-corrosion measures, a highly reliable and durable 5 1/4 inch MO disk has been developed. Carrier level degradation through write/erase repetition, which was observed in the cource of the development, is thought to be interpreted as a structure relaxation by annealing leading to a localized change in magnetic properties.

Analysis of Leading Edge/Trailing Edge Independent Detection Method in Optical Disk

The effects of independent detection of leading edge / trailing edge on edge-shift and jitter are investigated for typical heat-mode recording processes using read-out pulse width, recording timing measurements and thermal simulation. In addition, in order to investigate the edge-shift reduction limit for this new method, a method is proposed to analyze what causes the edge-shifts; it statistically evaluates the relative edge intervals between adjacent edges of a particular worst-case recording pattern. Our results clarify that the new method is effective for reducing edge-shifts and jitter.

Highly reliable 7-GB, 1.2- to 2.2-MB/s, 12-inch write-once optical disk

In order to extend an application area of 12 inch write once optical disks, both a larger data capacity and higher data transfer rate are required, which in turn requires more advanced reliability and durability. This paper describers a double sided 7GB twelve inch diameter disk suitable for high data transfer (1.2-2.2 MB/s) application. A storage data capacity is increased by using both the pit- edge method and the Modified Constant Angular Velocity (MCAV) method. The corrosion resistant Te based ternary alloy recording layer has an excellent pit length characteristics and less thermal interference, which results in wide jitter margin in the pit edge detection. The high speed disk rotation gives the high data transfer rate. Acceleration tests prove a disk life longer than 45 years.

Highly reliable and durable 5.25-in. magneto-optical disks

By combining the optimization of Tb-rich TbFeCoX alloy composition with the optimization of thermo-structual design of recording layers, highly reliable and durable 5.25-inch magneto-optical disk has been developed.