DVD DRIVE STRUCTURE AND ITS WORKING

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Made By :-
Agrawal Kartik – 156170307001
Darshan Chavda – 156170307016
Subject Teacher :- Mrs. Charulata Parekh
Subject Code :- 3350701

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1. Description
2. Structure of DVD Drive
I. Disc Drive Mechanism
II. Optical System
III.Printed Circuit Board
3. Working Of DVD Drive

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• DVD Drive are devices that can read DVD discs on
a computer.
• Starting from 90s (1996 or later), most
computers comes with a DVD drive so that people
can play DVDs on a computer.
• In 2002, many manufacturers released DVD
drives that could for the first time allow people to
make their own DVD movies.
• DVD uses light of 650 nm wavelength.

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• The shorter wavelength allows a smaller pit on the
media surface compared to CDs, accounting in part
for DVDs increased storage capacity.
• The DVD player is not only used for playing the
data present in a DVD, but also to write the
content onto a DVD.
• There are two types of DVD Drives :-
1. Internal DVD Drives
2. External DVD Drives

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• The DVD player is not only used for playing the data present
in a DVD, but also to write the content onto a DVD
• DVD’s have pits and bumps in their track which holds the
information that is required to be played. This information can
be a video, audio or a mixture of both.
• When a DVD player reads this data, the smooth surface is
usually taken as a ‘0’ and pits are usually taken as a ‘1’.
• In order to create as well as read these data, a red laser with
a wavelength of 600 nanometers. This is about 180
nanometers lesser than the wavelength of CD, which enables
it to have a higher density of pits.

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• Thus the size of the DVD increases. Though the first released
DVD’s were only a single layer, 2 layered discs have been
released nowadays.
• Single layer can hold only up to 4.7 GB of data while double
layered DVD can hold up to 17 GB of data.
The DVD Drive consists of three fundamental
components :-
I. Disc Drive Mechanism
II.Optical System
III.Printed Circuit Board

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• The disc drive mechanism consists of a motor that will drive
the disc in a circular motion.
• The mechanism will also have a disc feed – a loading tray that
is used to accept the DVD from the user.
• Thus the entire disc drive is basically a spindle that holds the
disc and a motor that is used to circle the disc.
• The spindle is held in its position with the help of small gears
and belts that are attached internally.
• Some players have an automatic feed system in which, there
will be no tray.
• Instead the disc will be automatically recognized after
inserting a part of it.

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• The optical system mainly consists of the laser beam, lenses,
prism, photo-detectors and also mirrors. The output of this
mechanism will be the input for the disc-drive.
• The laser beam will be a red laser diode which works at a
wavelength of 600 nanometers.
• The optical system also requires a motor to drive it.
• The laser system and photo-detector is placed together on a
single platform.
• The laser diode as well as other diodes is made with the help
of glass.

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• The PCB is similar to that of any other electronic circuits.
• The electronic outline must be drawn on the PCB with the
correct placement of all the IC’s resistors as well as
capacitors.
• After the outline has been drawn, the components must be
soldered to their respective places.
• All this must be done in a very clean environment so that
the board does not become contaminated by dust.
• All the primary components of the electronic circuit should
be made out of silicon.

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• The pits and bumps in the DVD are hit by the laser from the
optical mechanism of the DVD player.
• This laser will be reflected differently according to the change
of pits and bumps.
• Though the laser hits a single spot, the DVD moves in a
circular motion so that the entire area is covered.
• Mirrors are also used to change the spot.
• These reflected laser beams are then collected by a light
sensor (e.g. photo-detector) which converts the different
signals into a binary code.
• In short, the optical system helps in converting the data from
the DVD into a digital code.

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• The binary signal is then sent to a Digital to Analog converter
which will be setup in the PCB.
• Thus the corresponding analog signal of the DVD is obtained.
• The PCB also has amplifiers which amplify the signal and then
sends it to the graphic and audio systems of the computer/TV.
• Thus, the corresponding audio/video signal is obtained.

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