George,
There must be something in the way that an optical disk shines gaudily under a bright light to account for the fact that everytime a new optical format like the DVD comes out, we get folks who invariably jump on the bandwagon that says that magnetic recording is dead and optical recording IS the future.
As Douglas indicated, nothing in a transition like that is ever easy, which is not to say that one is underway because optical recording right now is MORE EXPENSIVE and MUCH SLOWER than magnetic disk recording. It also doesn't have the capacity advantage of magnetic tape, e.g., Ampex's 330 GByte double density cartridge.
Below is an excerpt from a late '96 Bloomberg article that provides a snapshot of the state of optical recording.
"...A laser reads a compact disc much like a stylus reads a
phonograph record. Instead of the grooves on an LP, an optical
disc has pits or valleys. As the disc spins, the laser bounces light
off the surface, translating the pits and spaces in between as
digital ones and zeros.
Packing data more closely requires lasers that can focus on
smaller points. Light beams with short wavelengths have a
narrower focus, or point, than those with longer waves. Light waves
are shorter at the blue end of the color spectrum -- that's why blue
lasers are sparking such interest.
A specific type of laser called the semiconductor diode laser is
used to read an optical disc. The diodes are the size of an
electronic transistor and are made up of thin layers of chemically
enhanced film.
Making a semiconductor laser is no easy task. A lot depends on
getting finicky chemicals, some of which don't like each other, to
work together to create a light beam.
Before blue lasers will be ready for commercial use, scientists need
to show that the diodes can emit a continuous stream of blue light
for 10,000 hours at room temperature. No one has done that yet...."
Blue lasers are not even the panacea to the speed problem of optical recording because new media has to be developed to take advantage of the shorter wavelenght of blue lasers. Optical recording requires the laser diode to focus intense heat on the medium, changing the chemical state of the medium to a "pit" or "valley," when cooled and stable, signifying the 1's and 0's of digital recording. That's inherently more time-consuming than the process used in magnetic disk recording
And that's just the technical part. Standards have to be agreed upon in order to introduce the massive economies of scale necessary to bring down the costs. At the same time, the content providers have to be appeased with the most elaborate software/hardware encryption measures in order to persuade them to release titles. Without titles, formats die, as you probably know.
Meanwhile, magnetic disks continue to increase areal density at a rate of 60% per year while prices continue to go down EVERY quarter. And magnetic tape continues to lower the storage cost of each MB. Ampex alone has a road map that involves a combined use of narrower recording heads (read: narrower helical tracks) and slower tape movement to produce further increases in cartridge capacity. WITHOUT relying on the more risky approach of just using thinner (read: less reliable) tape, AXC could conceivably keep on doubling the tape capacity of their cartridges with further developments in head technology.
F-A-C-T-S are the ultimate reality check. Most of everything else is really just noise.
Gus |
