In the mid-1980s, Japanese companies came out with a string of announcements of breakthroughs in the development of erasable optical media, but so far, we have seen in products only the magneto-optic technique that was essentially perfected much earlier. Now, reports Microbytes Daily, Matsushita Electric Industrial Co has come out with an erasable drive that uses an all-optical technology that measures the change in phase of light reflected from the recorded spot. Although phase change technology does not improve the access time over magneto-optic, it requires only a single pass to record a bit, where with magneto-optic, the previous bit must first be erased, and once the new one has been written, it must be verified. With the phase change technology – Matsushita is licensing it from Energy Conversion Devices Inc, Troy, Michigan – the disk medium includes a thin layer of material that changes with the application of laser light from a highly reflective crystalline state to a dull amorphous state depending on temperature, retaining either state when it cools, so that bits can be switched between the two states to create zeros and ones. Panasonic’s medium, which stores 1Gb – 500Mb per side – on a 5.25 platter – is claimed to withstand 100,000 writes, or 1m with error detection and correction. The average access time is 90mS but the disk transfers at 10Mbits per second, and the SCSI-2 transfer rate can reach 4M-bytes per second. Panasonic – the trade name under which Matsushita will market the drives expects the LF-7010 to be available in November at $5,000. The thing can also read – and write once, the 940Mb disks used in the LF-5010 write-once disk drive.
