Blu-Ray
2005 is here and the companies promoting
the next generation storage formats are ready for the last and most important
rounds in the “war”, which will probably answer the question: which
format will become the next standard for movie and data storage? HD-DVD
and Blu-ray: What are the technologies?
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These two formats are heralded as the successor to the current DVD technology.
Blu-ray and HD-DVD have both been developed to enable recording, playback and
rewriting of high definition video and data. The key to these technologies is
the blue-violet laser that is used to write the data to the disc. This blue laser
has a much shorter wavelength than the current red laser DVD system, which makes
it possible to read and write smaller pits, as a result, these discs can hold
up to 15 GB (HD-DVD) and 25 GB (Blu-ray) of data on a single sided single layer
12cm disc.
This additional storage capacity will be essential when HDTV
becomes mainstream, in order to allow storage of HD TV shows or movies on an optical
disc in the same high quality. You can record about 13 hours of standard TV but
only a bit more than 2 hours of uncompressed high definition TV on a 25GB disc.
When we take a closer look at the two competing formats, we can quickly
see that the dimensions of the discs and the use of a blue laser are about the
only similarities the two formats share. But before we start to compare
the two formats to find out the differences, let us explain some terms we will
need to know, to understand how it is possible to store that high amount of data
on discs that are looking like conventional CDs or DVDs. Numerical
Aperture (NA) The numerical aperture of an optical lens is a measure
of its ability to gather light and resolve fine specimen detail at a fixed object
distance. Together with the wavelength, this is how the NA or the resolution
of an optical system is determined. The NA and the wavelength also define the
size of the laser beam; the result of a higher NA and a shorter wavelength is
a smaller laser beam. This allows focusing the beam with much higher precision
and a reduction of the Track pitch. Track Pitch The
data track of an optical disc is a spiral starting from the centre of the disc;
the distance (in micro meters) between two rows of the track is the track pitch.
It is measured from the centre of the row to the centre of the next row. When
the Track Pitch can be reduced, this means that the distance between the rows
is lower and that the resulting track is much longer, thus you can store more
data.
Blu-ray vs. HD-DVD - Introduction
Posted by Herbert on 09
March 2005
Article: Blu-ray vs. HD-DVD
Authors: spath &
H3rB3i
Date: March 2005 | 
0207 722 0067
