DVDs are the current standard for data
storage, and perhaps more importantly the publishing format
standard as well. The question is however, how much longer
will they be sufficient? A much anticipated battle, or
‘format war’ if you will, is in progress similar to that
seen in the 1980’s between VHS and Betamax. This time around
the same companies have fallen into the same camps and war
is ensuing between Blu-ray and HD DVD technology.
Knowing very little about either, I
decided to investigate these formats and what follows is
hopefully an unbiased presentation of facts. At this time it
is hard to say if there is a leader in this format race, or
if there will ever be one, with products still not available
in the retail market, and from what was shown at recent CES
2006 expo, manufacturers are still working hard on first
generation players, which will inevitably be replaced just a
few months later with more refined products once they reach
the masses. Hopefully after reading this article you will be
better informed about the two technologies, and why not,
pick your own favorite, or call the industry for a much
needed convergence (think of dual-format DVD±RW drives
nowadays).
Blu-ray Disc (BD) is one of the
next-generation optical disc formats currently being
proposed. It is designed for high-definition video and
high-density data storage. The technology was developed by a
group of companies working under the name Blu-ray Disc
Association (BDA). The main supporter of this technology is
Sony. As you can tell by now, the main competitor to Blu-ray
technology is HD DVD, which is backed chiefly by Toshiba.
HD DVD has been recognized as the only
format of approved next-generation technology by the DVD
Forum, which is a group of 230 companies who develop and
define DVD formats. Members of this forum include every big
name in music, movies and the computer industries, while
Toshiba is the organization maintaining the forum. The vote
to name HD DVD as the successor of DVD technology was 8 to
6, and many of the companies within the forum are backing
Blu-ray technology.
Blu-ray Technology
Blu-ray technology is currently
available only in Japan for recording HDTV. The US launch is
said to take place in early 2006, with other countries to
follow.
There are three types of Blu-ray formats
planned:
BD-ROM for pre-recorded media such as
software, games and movies
BD-R (recordable) for HDTV recording and
PC data storage
BD-RE (rewritable) for HDTV recording
and PC data storage
As with all new technology it will
initially be more expensive to run.
Capacities
Blu-ray supports more data capacity per
layer compared to HD DVDs. That is 25GB per layer versus
15GB of HD DVD. Technically it can fit three different
capacities; 25GB is merely the average, these capacities are
23.3GB, 25GB or 27GB. This equates to over 4 hours of high
definition video with audio.
There is also the option of dual-layers:
46.6GB, 50GB or 54GB, which is roughly 8 hours. Currently
BDA are researching 100GB and 200GB technology with 4 or 8
layers, this keeps the technology ‘future proof’. Also in
the works is an 8cm disc variation with a 15GB capacity,
rather than the regular 12cm discs.
The Name
The Blu-ray name comes from the
technology itself; it uses “blue” laser technology
(technically it is a blue/violet color), rather than the red
laser used for normal DVDs. The Blue laser uses a shorter
wavelength then the red laser; 405nm as compared to 650nm.
CDs use a 780nm wavelength.
The smaller wavelength allows more data
to be stored in the same amount of space. This is due to the
smaller ‘spot size’ that is achievable by using the blue
laser. The focus of a laser is limited by the amount of
diffraction. Diffraction is the bending and spreading of
waves, light waves in this case, when it meets an
obstruction.
In the case of laser technology however,
that light will naturally begin to spread the further it
gets from the laser itself (you can see an example of this
simply with a torch shining against a wall, the further away
from the wall, the more the light spreads.) This is where
other factors must be introduced to help focus the laser.
Those used in BD technology include an increased numerical
aperture than ones used previously (0.85 as compared to 0.6
used for DVDs), a higher quality dual-lens system, and using
a thinner cover layer on the disc to reduce optical effects.
