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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.
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