- Educational & Career Guidance + Engineering and computer science students can get text book free of cost or on loan
from Sri Sumathi Vishal Book Bank. Application forms are available at Thirukumaran Apartment,
12, rameswaram Road, T nagar between 4 PM and 6 PM on weekdays and
between
10 Am to 1 PM on Sundays. You can also download the form from website www.ssvjbookbank.org. Last date for submitting application form is 10 July; you
can contact
them on phone 044-2436 0675 – info sent by Mr. B. Ramamoorthy
- Tell me How it Works?...
How Does A Blu-ray Disc Work?
- B. Ramamoorthy
The main feature of the Blu-ray disc that separates it from a
normal DVD is its storage capacity. The Blu-ray disc has five
times more storage capacity than DVDs. It can hold 25GB in a
single layer disc and 50 GB on a dual layer disc. A Dual Layer
Disc can have over 9 hours of high-definition (HD) video on a
25GB disc and over 22 hours of standard-definition (SD) video can
be had on a 50GB disc. The Blu-ray disc also offers other great
features, chief among these being a new dimension of
interactivity which allows you to connect to the internet and
download a wide variety of content.
In addition, you can also record HDTV without resulting in any
loss of video or audio quality. And Blu-ray has a transfer rate
of data of 36Mbps (megabits per second) so with a Blu-ray disc
25
GB of data can be recorded in around one and a half hours.
Essentially the Blu-ray disc is able to accomplish this because
of the way it is manufactured and how it reads the data stored on
the disc. The Blu-ray Disc is 1.2 millimeters thick, same as a
DVD.
With Blu-ray, data is stored directly on top of a 1.1mm thick
polycarbonate layer, then a protective hard coating layer is put
on the outside of the disc. This differs from a DVD in that, data
is stored on a DVD between two 0.6 mm polycarbonate layers. This
stacking of layers can cause the laser used to read the data, to
split into two different beams, resulting in problems reading the
disc correctly. Having data stored on top prevents the Blu-ray
disc laser from splitting.
The laser used to read the data is the main technical development
that separates the Blu-ray from the DVD. Video and Audio data is
stored digitally on spiral grooves which run from the middle of
the disc to the outer edges. To play the disc a laser is needed
to read these grooves. The smaller the grooves the more data can
be stored on the disc, however, with smaller grooves a more
precise laser is required.
Unlike the DVD, which uses a red laser, the Blu-ray uses a Blue
Laser. This blue laser has a shorter wavelength. The beam is more
precise and can read the grooves on the Blu-ray disc which are
made twice as small as the ones on a regular DVD. This is why the
Blu-ray disc can hold so much data and contain so many new
features. For these reasons, the Blu-ray disc will probably
become the medium of choice for the foreseeable future, until
something better comes along.
