LAS VEGAS, Jan. 9 (UPI) -- A recordable compact disc drive introduced at the Consumer Electronics Show triples a CD's storage capacity by altering the way lasers mark information on the disc.
The MultiLevel drive from Japanese electronics maker TDK is based on technology from Calimetrics, an Alameda, Calif.-based company.
Kenneth Campbell, Calimetrics' president, told United Press International on Wednesday that the ML drive stores up to 2,000 megabytes -- 2 gigabytes -- of data on ML-specific write-once -- CD-R and rewriteable -- CD-RW -- discs, enough capacity for more than 24 hours of digital music. The new drive can read current CDs, which hold about 650 megabytes of information, but current drives cannot read ML discs.
The ML drives carry an additional computer chip with special encoding and decoding instructions, but the primary difference between them and current CDs is how their lasers encode data onto the disc.
Current CD recorders turn their lasers on and off to "burn" marks of different lengths onto the disc, leaving much of the surface unused. MultiLevel drives leave their lasers on while writing data, Campbell said, varying the power level to leave an uninterrupted series of marks of different depths on the disc.
"What we do is we're able to measure ... the ratio of light to dark on the disc," Campbell said. "We can put one of eight different size spots (at a location) and measure the ratio; when we decode that, we turn that ratio, a continuously changing analog signal, into three bits per mark, instead of the one per mark on other discs."
An additional benefit of the ML approach is faster data transfer rates. All the bits are the same length and packed more closely together, Campbell said, so there's no need to vary the disc's rotation speed between the inner and outer sections of the disc, as occurs with today's drives.
The ML drive's rated speed for CD-R discs is 36X, compared with 24X for the fastest current drives; 48X rates will come when better discs are ready, Campbell said. For rewritable discs, the ML hums along at 24X, while 10X is about the best speed you'll find with today's CD-RW drives The ML scheme can also encode data the traditional way more quickly on standard discs, Campbell said.
Wolfgang Schlichting, an optical storage authority and research manager for the Storage Mechanisms program at International Data Corp. in Framingham, Mass., said the ML drive shows the rest of the computer industry the technology can work. Its appeal among the buying public might be limited, he told UPI, by the inability to read ML discs in older drives. The best shot for widespread ML acceptance is the drive's faster read and write rates, which could allow users to rely on the drive for all their CD-related functions while switching to ML discs.
The industry is likely to take notice of the technology, Schlichting said. The capacity and speed advantages can command a higher profit margin, he said, something equipment makers have been lacking as improved manufacturing methods drive down prices for mainstream equipment. The ML technology should also find a home with DVD recorders in a few years, he said.
(Reported by Scott R. Burnell of UPI Science News from Washington)
