The Blu-ray Disc belongs to a new generation of optical discs capable
of staging high density data. Blu-Ray technology is based on a
blue-violet coloured laser. The blue laser operates at a wave length of
405 nm, while older technology such as DVDs and CDs are based on red
and infrared lasers that works at 650 and 780 nm. Since the wave length
is shorter with a blue laser, the new Blu-ray technology makes is
possible to store much more information
The advantage with the Blu-ray technology is that the laser beam can be
focused much more tightly at the surface of the disc. Tight focus means
that a smaller spot will be produced on the surface on the disc, and
when the spots become smaller there will naturally be room for more
information on each disc. The minimum spot size of any laser depends on
a naturally accruing phenomenon called diffraction. The narrow beam of
light sent out from a laser will always diverge into a wider beam
eventually, due to the natural diffraction of waves. Diffraction will
also occur the waves meet an obstruction. By reducing the wavelength of
a laser, we can affect the diffraction.
In Blu-ray technology, the diffractions is also affected by the fact
that the lens used to focus the light has a higher numerical aperture
than the lenses found in ordinary DVDs - 0.85 instead of 0.6. Blu-ray
technology based appliances are also equipped with a dual-lens system
of supreme quality, and the cover layer has been made thinner in order
to prevent unwanted optical effects. All this makes it possible for a
Blu-ray laser to focus on much smaller spots. The optical improvements
are accompanied with a new method for encoding data which makes it
possible to store even more data on the Blu-ray disc.
The standard for Blu-ray technology has been developed as a joint
venture between several major manufacturers of PCs and consumer
electronics, including Sony and Philips. The group is called the
Blu-ray Disc Association (BDA). The first Blu-ray recorder was launched
in Japan in 2003, by Sony. Today, Samsung, JVC, Matsushita (Panasonic)
and LG Electronics are all examples of companies using Blu-ray
technology in their products. Hewlett Packard has announced that they
will release desktop PCs equipped with Blu-ray technology in late 2005.
The main competitor for the Blu-ray technology is the HD DVD format
which is also capable of storing more information than a normal DVD.
The Blu-ray technology does however allow for more information per
layer than the HD DVD format – 25 GB compared to 15 GB. The Blu-ray
technology will on the other hand most likely be more expensive to
support, at least initially, which can make the HD DVD a tempting
alternative. In a Blu-ray disc, the data is stored extremely close to
the surface. This made the first Blu-ray discs extremely vulnerable to
scratching and many users preferred the tougher HD DVD discs. Since
2004, all Blu-ray discs are coated with a clear polymer called
“Durabis” which makes them much more durable. According to the
developers of Durabis, the TDK Corporation, a coated Blu-ray disc will
work even after being attacked with a screwdriver.
