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How DVD works

18 Aug 2013
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I hope you had seen and enjoyed the previous posts about ipod & LCD TV.
Today, i have come up with DVDs, While researching to creating this post i found some astonishing facts, i hope your are going to become surprise to know how a DVD stores its data and how those data are read / fetched  from it.

DVD
The storage capacity of a DVD, six times that of a traditional CD, has revolutionized the way digital
data is organized and stored in the decade since its appearance in 1997. The DVD explosion
resounded in the world of home movies thanks to its capability of storing entire feature films,
bonus material, and subtitles (in various languages) on only one disc. The evolution of technology,
however, has not stopped with DVDs. Recent years have seen the introduction of discs able to hold 12
times the data of the DVD




Reading with Light
Optical discs (CDs and DVDs) are read by a
laser beam to obtain information. This
information is transformed into a binary electric
signal that is later interpreted and converted into
sounds, images, and data.

click on the images to enlarge



1.Laser emitter
generates a laser beam of
a specific wavelength.
2.Mirrors
guide the ray by working in
coordination.
3.  Direction
In order to read the disc,
the laser beam must strike
the surface of the disc
perpendicularly.
4. Lens
focuses the laser beam
before it reaches the surface
of the disc.
5. Reading
The laser beam strikes the
disc's reflective surface. The
reflection varies according
to the pattern of pits on the
disc's surface.
6. Prism
changes the direction of the
laser beam that reflects from
the disc and contains the
data read from the disc.
7. Photodiodes
translate the variations in the
returning laser beam and
convert them into a digital
signal.
Blue  light
Because blue light has a shorter wavelength than
red light (which is used in CDs and DVDs), a blue
laser makes it possible to read smaller pits, which
accounts for Blu-ray's greater storage capacity.


From the CD to Blu-ray
This comparison traces the evolution of the compact disc—especially its storage capacity.


CD
DVD
HDDVD
BR-DVD

Maximum capacity (single layer)
875MB
4.7 GB
15 GB
27 GB
Maximum capacity (double layer)
--
8.5 GB
30 GB
54 GB
Laser wavelength
789 nm
650 nm
405 nm
405 nm
Transfer rate in megabits per second (Mbps)
6
11.1/10.1
36.55
36/54
Resistance to scratches and dirt
No
No
No
Yes
Maximum video resolution
--
576 pixels
1,080 pixels
1,080 pixels
Supported formats
-- VCD and
SVCD
DVD, VCD,
SVCD,
MPEG-2
MPEG-2, VC-1
(based on WMV),
H.264/MPEG-4 AVC
MPEG-2, VC-1,
MPEG-4 AVC

From the CD to Blu-ray, information storage has become
denser, and the wavelength of the reading beams has
become shorter.
1 millimeter = 1,000 micrometers (m)
1 micrometer = 1,000 nanometers (nm)

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I hope you had seen and enjoyed the previous posts about ipod & LCD TV. Today, i have come up with DVDs, While researching to creating this post i found some astonishing facts, i hope your are going to become surprise to know how a DVD stores its data and how those data are read / fetched  from it. DVD The storage capacity of a DVD, six times that of a traditional CD, has revolutionized the way digital data is organized and stored in the decade since its appearance in 1997. The DVD explosion resounded in the world of home movies thanks to its capability of storing entire feature films, bonus material, and subtitles (in various languages) on only one disc. The evolution of technology, however, has not stopped with DVDs. Recent years have seen the introduction of discs able to hold 12 times the data of the DVD Reading with Light Optical discs (CDs and DVDs) are read by a laser beam to obtain information. This information is transformed into a binary electric signal that is later interpreted and converted into sounds, images, and data. click on the images to enlarge 1.Laser emitter generates a laser beam of a specific wavelength. 2.Mirrors guide the ray by working in coordination. 3.  Direction In order to read the disc, the laser beam must strike the surface of the disc perpendicularly. 4. Lens focuses the laser beam before it reaches the surface of the disc. 5. Reading The laser beam strikes the disc's reflective surface. The reflection varies according to the pattern of pits on the disc's surface. 6. Prism changes the direction of the laser beam that reflects from the disc and contains the data read from the disc. 7. Photodiodes translate the variations in the returning laser beam and convert them into a digital signal. Blue  light Because blue light has a shorter wavelength than red light (which is used in CDs and DVDs), a blue laser makes it possible to read smaller pits, which accounts for Blu-ray's greater storage capacity. From the CD to Blu-ray This comparison traces the evolution of the compact disc—especially its storage capacity. CD DVD HDDVD BR-DVD Maximum capacity (single layer) 875MB 4.7 GB 15 GB 27 GB Maximum capacity (double layer) -- 8.5 GB 30 GB 54 GB Laser wavelength 789 nm 650 nm 405 nm 405 nm Transfer rate in megabits per second (Mbps) 6 11.1/10.1 36.55 36/54 Resistance to scratches and dirt No No No Yes Maximum video resolution -- 576 pixels 1,080 pixels 1,080 pixels Supported formats -- VCD and SVCD DVD, VCD, SVCD, MPEG-2 MPEG-2, VC-1 (based on WMV), H.264/MPEG-4 AVC MPEG-2, VC-1, MPEG-4 AVC From the CD to Blu-ray, information storage has become denser, and the wavelength of the reading beams has become shorter. 1 millimeter = 1,000 micrometers (m) 1 micrometer = 1,000 nanometers (nm)