Matsushita Electric Industrial Co., Ltd. and Canon Inc. have jointly developed a high-density 2-in. optical magneto disc with an improved recording capacity of 3GB per disc.
Its recording capacity enables about an hour of recording MPEG-2 coded moving pictures with the encoding speed of 6Mbps. Matsushita and Canon expect the disc to be used mainly for video cameras.
They have improved the data transmission rate to 24Mbps, and the disc's intermittent processing recording/playing helps lower the power dissipation.
As for the optical system, they have applied the red semiconductor laser with the wavelength of around 650nm and the numerical aperture (NA) 0.6 objective lens, which have been popular for current DVDs. They have realized the high-density recording per unit area to the level of around 15Gb/inch2 by combining the optical system with the domain wall displacement detection (DWDD) technology. High-density recording based on this technology is closing in on the next-generation optical disc standard "Blue-ray Disc," which uses a blue-violet laser with the wavelength of 405nm and an objective lens of NA 0.85. For comparison, areal density is 18Gb/inch2 for a 12cm-diameter 25GB media.
The disc structure including a hub in the center is similar to that of the current MD and is housed in a cartridge with a shutter. The disc substrate is 0.6mm thick, and records in grooves. Its track pitch is 540nm, and it has a bit recording length of 80nm.
The technologies used for this disc are already close to a practical level. According to both companies, evaluations for various specifications have met the criteria they set, including power margin, tilt margin, focusing and tracking error margins. Matsushita and Canon have succeeded in realizing the magnetic wall displacement during playing by selectively annealing only the areas adjacent to the grooves. As concerns the annealing process, they applied a blue-violet laser light focused by an NA 0.85 lens.