All of the erasable optical drives that have appeared so far have used the half-way house of opto-electronic technology where a laser alters the magnetic field at the spots on the disk – but this month Matsushita Electric Industrial Co will begin marketing a pure optical erasable drive – 3.5, storing 280Mb – according to Energy Conversion Devices Inc, Troy, Michigan which licensed the phase change thin film technology used on the disks to the Japanese firm. A single laser uses different temperatures to melt the spots, which change the phase of reflected light until heated again, and a lower temperature to read. As erase and record is one process, the drives are claimed to be twice as fast as the magneto-optic ones, which need erase and record passes.
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