Japanese manufacturers are convinced that over the next decade new emerging applications will pull the performance of optical storage systems and that evolving conventional optical storage technologies (DVD and MO) are capable of satisfying these demands for at least another seven to eight years (Fig. 1.7).
During the period of the WTEC site visits, PC manufacturers were heavily involved in the advanced R&D of 4.7 GB DVD-RAM products. The panel learned that PC manufacturers may combine higher NA optics with shorter wavelength blue lasers and single carrier independent pit edge recording (developed by SONY) together with radial direction partial response (RPR) encoding technique to achieve 15 GB capacity double layer disks required for the HDTV standard. Matsushita Electric Company (MEI) will be introducing a frequency doubled blue laser in some of its products within 1999. The panel also learned that MEI was experimenting with more transparent PC media layers that enable four-layer disks to be used in higher capacity products. In addition, various mastering techniques including UV laser, SIL lens, e-beam, and probe mastering are being developed to extend the effective areal density of DVD-ROM products to 50 Gb/in2 as described in Fig. 1.8.
All PC manufacturers seem to put highest priority, and therefore significant effort, into achieving backward and forward compatibility within a product line, and also on compatibility between different product lines within the DVD family.
In recent years, MO R&D activity has been revived through the ASMO consortium.
MO drive manufacturers now believe that the MO technology can be extended to 5.2 GB capacity in the near future, and then to 10.4 GB on a 5.25" double-sided disk using 680 nm wavelength and a lens with an NA of 0.55. Beyond that, they plan to rely on one of the magnetic super-resolution (MSR) techniques, either Magnetic Amplifying Magneto Optical Systems (MAMMOS) from Hitachi-Maxell or Domain Wall Displacement Detection (DWDD) from Canon, in addition to magnetic field modulation, to enable further capacity increases. By 2002 they may be able to achieve areal densities approaching 20 Gb/in2 by combining one of the MSR techniques with the use of a blue laser and larger NA optics. By adopting a format similar to DVD, MO researchers at Fujitsu are contemplating 36 GB capacity disc systems as VCR replacements. Finally, they envision using SIL lenses and parallel heads to extend the areal density and data rate of MO products to exceed 100 Gb/in2 and 1 Gb/s respectively.
Fig. 1.7. Example roadmaps describing performance potentials of (a) phase change media (Hitachi) and (b) MO media based systems (Fujitsu).
Fig. 1.8. A potential roadmap for mastering technology (OITDA).