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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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