39340191-Optical-Storage.ppt

BY
 03CP616 VIJAY
 03CP627 SHETUL
 COMPACT DISC
 DIGITAL VERSETILE DISC
 ULTRA DENSITY OPTICAL

What is a CD-ROM?
 A cd rom most resembles the vinyl long play
records still dear to the hearts of audio fanatics.
On a record, a single spiral in the vinyl winds
from the outside to the inside.
 74 minutes = 682MB
 80 minutes = 737MB
 Size: 120mm (4.72 inch) diameter ,
1.2mm (0.047 inch) thick plastic disc.

CDs: A Brief History
 In 1979 the phillips and sony corporation
joined forces to co-produce the CD-DA
(Digital Audio) standard.
 Phillips contributed most of physical design,
with has similar to the laser disc format. It
had previously created with regards to using
pits and lands on the disc that are read by
laser.
 Sony contributed the digital to analog
circuitry and digital encoding and error
correction code design.

 In 1980 the companies announced the
CD-DA standard which has since been
refer to as the red book format.
 The Red book included the specification
for recording , sampling, and 120mm
diameter physical format. This size was
chosen because it could contain all the 70
minutes of recording without interrupt.
 October 1,1982,sony has developed the
world’s first commercial CD recording-
Billy Joel’s 52nd street album.

 The tracks in the magnetic media is in the
discrete, concentric manner means one track
after another ,while in the optical storage
media the tracks are in spiral manner.
 Optical storage mostly have data only on one
side
>continue
What is the difference in optical
and magnetic storage media?

while in the magnetic storage the data may
be stored on both the sides.
 example :
 Magnetic storage: Hard-disks, floppy
disks.
 Optical storage: Compact disc

Why CD ROM invented?
 The industry needed high-capacity,
removable medium for multimedia and
software distribution, and the consumer
electronics industry had developed an
inexpensive, high-capacity digital
technology for distributing music.
 The window 98 operating system would
require more than 75 floppy disk while if we
use CD only 1 is required.

Structure of the compact disk:
 Track pitch : It is radial distance between
the two track spirals that is of 1.6 microns.
 The pits themselves are oval or sausage-
shaped depressions 0.15 micron deep and
0.5 micron wide.
 The length of the pit varies from 0.834 to 3
microns.

 Because a CD is read by a beam of light
instead of by an electromagnetic head, the
tracks can be much closer together than
the magnetic media.
 The track density of a CD is 16000 tracks
per inch (tpi) ,as compared to 96 tpi for a
floppy disk and an average of 400 tpi for a
hard disk.

CD ROM Technology
 A CD is made of a polycarbonate wafer,
1.2mm thick, with a 15mm hole in the
centre.
 This wafer base is stamped or molded with
a single physical track in a spiral
configuration starting from the inside of the
disk and spiraling outward.

 When viewed from the reading side the
disk rotates in counterclockwise.
 If you examined the spiral track under a
microscope, you would be able to see the
pits and lands.
 Here rised bump is called pits, and the
area between two pits are known as land.
 The pits are actually depression made in
the plastic.

 The stamped surface is coated with a
reflective layer of metal (Aluminum) to
make it reflective.
 The aluminum is coated with a thin
protective layer of acrylic lacquer and
finally a label or printing is added.

CAUTION:
 Do not write with pen with pressure on the
disc, don’t use the marker which are more
chemically reactive.
 Use only those markers which are
specially made for the CD’s.

Mass production of CD-ROMs
Commercial mass produced CDs are
stamped or pressed and not burned by a
laser as many people believe.
Using a laser to directly burn disk would be
impractical for the thousands of copies.

Steps of manufacturing the CDs
 Photo resist coating
 Laser recording
 Master development
 Electroforming
 Master separation
 Disc stamping operation
 Metallization
 Protective coating
 Finished product

 Photo resist coating:
A circular 240mm diameter piece of
polished glass 6mm thick is spin coated
with a photo resist layer about 150microns
thick and then hardened by backing at
80°c.
 Laser recording:
A laser beam fires pulses of blue laser light
to expose and shorten portion of the photo
resist layer on the glass master.

 Master development:
The NaCl solution is spun over the
exposed glass, which then dissolves the
areas exposed to the laser, thus etching
pits in the photo resist.
 Electroforming:
The developed master is then coated with
a layer of nickel alloy. This creates a metal
master called a father.

 MASTER SEPARATION:
The metal master father is then separated
from the glass master. The father is a
metal master that can be used to stamp
discs, and for short runs, it may in fact be
used that way. However , because the
glass master is damaged when the father
is separated, and because of troformed to
create, several reverse image mothers.
These mothers are then subsequently
electroformed to create the actual
stampers.

 Disc stamping operation:
A metal stamper is used in an injection
molding machine to press the data image
into approximately 18 gms of molten
polycarbonate plastic with a force of about
20,000psi.Normally 1 disc can be pressed
in 2-3 sec.
 Metallization: The clear stamp disc base is
then sputter-coated with a thin layer of
aluminum to make the surface reflective.

 Protective coating:
The metallization disc is then spin coated
with a thin layer of acrylic lacquer, which is
then cured (covered) with UV light. This
protects the aluminum from oxidation.
 Finished product :
Finally a label is affixed or printing is
screen-printed on the disc and cured with
UV light.

Pits and lands
 Reading the information back from a disc
is a matter of bouncing a low-powered
laser beam off the reflective layer in the
disc.
 Photo sensitive receptor detects when the
light is reflected back.
 When the light hits a land then the light will
be reflected back otherwise no light will be
reflected back.

 Pits on CD have 0.125 micron and 0.6 micron
wide.
 Both the pits and lands vary in land from about
0.9 micron at their shortest and 3.3
micron at their largest.
 The track is spiral with 1.6 micron between
adjacent turns.
 The pit height is exactly ¼ of the wavelength of
the laser light used to read the disc.
 So, the light striking a land travel ½ of the
wavelength of light further than the light striking
the top of a pit ( ¼ + ¼ = ½ ).

 This means the light reflected from a pit is
½ wavelength out of phase with the rest of
the light being reflected from a disc.
 The out of phase wave cancel each other
out, dramatically reducing the light that is
reflecting back and making the pit appear
dark at photo detector.

 The read laser in the CD drive is a 780nm
wavelength laser of about 1 milliwatt in
power.
 The polycarbonate plastic has a reflective
index of 1.55, so light travels through the
plastic 1.55 times more slowly then air.
 So, that 780nm light wave are now
compressed to 780/1.55 =500nm.
 ¼ of 500 nm is 125 nm, which is 0.125
microns - the specific height of the pit.

 Tray motor
 Ejects and pulls in CD tray
 Read head
 Shines light on CD and
reads reflection
 Spin motor
 Spins the CD at various
speeds

 Laser shines light on
disk
 Pits and lands reflect
light differently
 Reflected light is picked
up by sensor
 Sensor changes light to
electrical signal for the
computer
 Motor moves the head
to read all parts of the
spinning CD.

Drive mechanical operation
1. The laser diode emits a low energy
infrared beam towards a reflecting mirror.
2. The servo motor, on command from the
microprocessor, position the beam onto
the correct track on the CD rom by
moving the reflective mirror.
3. When the beam hits a disc, its reflected
light is gathered and focused through
the first lens and sent toward the beam
splitter.

4. The beam splitter detects the returning
laser light toward another focusing lens.
5. The last lens detects the light beam to a
photo detector that converts the light into
electric pulses.
6. This incoming pulses are decoded by the
microprocessor and send the analog to
the host computer as a data.

Tracks and sectors:
 The disc is divided into 6 main area :
1. Hub clamping area : The hub clamping
area is just that a part of a disc where the
hub mechanism in the drive can grip the
disc. No data and information is stored in
that area.
2. Power calibration area: This is found only
on CD-R/RW (writable) disc and is used
only by recordable drive to determine the
laser power necessary to perform and
optimum burn.

3. Program memory area: This is area where the
TOC (table of content) is temporary return until
a recording session is closed. After the session
is closed the TOC information is written to the
lead in area.
4. Lead-in:
a) The lead-in area contains the disc (or session)
TOC in the Q subcode channel. The TOC
contains the start address and length of all
tracks (songs or data), the total length of the
program area, and information about the
individual recorded sessions.

b) A single Lead-in area exists on a disc
recorded all at once ,or a Lead-in area
starts each session on the multi-session
disc. The Lead-in takes up 4500 sectors
on the disc (1 minute if measured in
time, or about 9.2MB worth of data).

5. Program area:
This area of the disc starts at a radius of
25 mm from the centre.
6. Lead-out:
The Lead-out marks end of the program
area or the end of the recording session
on a multi session disc. No actual data is
written in a Lead-out, it is simply marker.
Generally in single session disc has
6750 sectors long Lead-out.

CD capacity :
 A typical disc ( 74minutes) - each second
contain 74 block of 2048 bytes each.
 By calculating the storage capacity
681,984,000 bytes- rounded as a 650MB.

 B = byte (8 bits)
 KB = kilobyte (1000 bytes)
 Kib = kibibyte(1024 bytes)
Data capacity 74 minutes 80 minutes
B 681,984,000 737,280,000
KIB 666,000 720,000
KB 681,984 737,280
MIB 650.39 703.13
MB 681.98 737.29

Data encoding on the disc:
 After all 98 frame (audio or data)
composed for sector then the information
is run through a final encoding process
called EFM (eight to fourteen modulation).
 This scheme takes 8 bits and converts into
the 14 bits.
 These 14 bits conversion codes are
designed so that there are never less than
2 or more than 10 adjacent 0 bits .
 This is formed of Run Length Limited
(RLL) enconding called RLL 2,10 .

 This is designed to prevent long string of
0s which could more easily misread as
well as to limit the minimum and maximum
frequency of transition actually placed on
recording media.
 EFM codes start and end with a one or
more than 5 zeros.

Sampling :
 When music is recorded on CD it is sampled at a
rate of 44,100 times per second (Hz).
 Each sample have right & left channel (stereo).
 Each channel component is digitally converted
into a 16 bit number. This allows for a resolution
of 65,536 possible values which represent the
amplitude of the sound wave for that channel.
 The sampling rate determine the range of the
audio frequency that can be represented in the
digital recording.

Handling read errors:
 CD use parity and interleaving technique
called Cross-Interleave Reed- Solomon
Code (CIRC) to minimize the effect of
errors on the disc. This works at the frame
level.
 When being stored the 24data bytes in
each frame are first run through a Reed-
Solomon encoder produce a 4 byte parity
code called ‘Q’ parity.

 The resulting 28 bytes are than run
through another encoder that use a
different scheme to produce a additional 4
bytes parity called ‘P’ parity. So resulting
is 32 bytes
 An additional byte of tracking information
is then added so resulting in 33 bytes.

CD drive speed
CD rom speed
(max. if CAV)
Time to read
(74 minutes)
Transfer Rate
(bytes/ second)
1x 74.0 153,600
2X 37.0 307,200
10x 7.4 1,536,000
20x 3.7 3,072,000
40x 1.9 6,144,000
56x 1.3 8,601,000

Compact disc format
 Red book: The original CD audio standard on
which all subsequent CD standard are based.
 Yellow book: For data it divides in several sector
format (mode 1 and mode 2).
 Orange book: Define single session, multi session
and writing on recordable disc.
 White book: It store up to 74minutes MPEG-1 video
and ADPCM digital audio data.
 Blue book: Multi session format for stamped disc.

CD rom file system
 High sierra :
 ISO 9660 (based on high sierra):
 Joliet:
 UDF (Universal Disc Format):
 Mac HFS (Hierarchical file format):
 Rock ridge:

CD file system format:
CD file
system
Dos/win
3.x
Win
9x/ME
Win2000/
XP
Mac os
High sierra Yes Yes Yes Yes
ISO 9660 Yes Yes Yes Yes
Joliet Yes Yes Yes Yes
UDF No Yes Yes Yes
Mac HFS No No No Yes
Rock ridge Yes Yes Yes Yes

INTRODUCTION
 DVD stands for digital versatile disc.
 In simple terms it is a high capacity CD.
 A DVD can hold up to 4.7GB (single layer) or
8.5 GB (dual layer) on a single side of the disc.
 Which is more than 11 ½ times grater than a CD.
 Double sided DVD disc can hold up to twice that
amount, here DVD manually flip the disc over to
read the other side.

DVD history
 Hollywood video disc advisory group and
the Computer Industry Technical working
group banded together to form a
association to develop and control the
DVD standard.
 With this incentive, both groups worked
out an agreement on single ,new, high
capacity CD type disc in September 1995

 The new standard combine elements of
both previously proposed standards and
was called DVD.
 After agreeing on copy protection and
other items , the DVD ROM & DVD Video
standards were officially announced in
1996 .

DVD technology:
 DVD technology is similar to CD
technology and both use the same size.
 DVD can have two layer of recording on a
side and be double sided as well. Each
layer is separately stamped , and they are
all bounded together to make the final
1.2mm thick disc.
 DVD requires laser with a shorter
wavelength and focus on more closely to
the disc.

 Each recorded layer is coated with a thin film of
metal to reflect the laser light. The outer layer
has a thinner coating to allow the light to pass
through to read the inner layer.
 If the disc is single sided , label can be placed
on top.
 If it is double sided only a small ring near a
center provide room for labeling.
 The laser can shines a focus beam on the under
side of the disc and a photosensitive receptor
detects.
 The individual pits on DVD are 0.105 micron
deep and 0.4 micron wide.

 Both the pits and lands vary in length from
about 0.4 micron at their shortest to about
1.9 micron at their longest.
 The DVD disc pits and lands are much
smaller and closer together than those on
a CDs, allowing the same physical size
platter to hold much more information.
 In double sided DVD the second data
layer is written to a separate substrate
below the first layer which is then made
semi reflective to unable laser to
penetrate to the substrate.

DVD track and sectors
 In DVD the length of the total track is
11.8km and the track is consist of
sectors, with each sector containing
2048 bytes of data.
 The disc is divided into four main areas:
1. Hub clamping area:
2. Lead-in zone:
3. Data zone:
4. Lead-out:

These all above four areas of DVDs are similar to
that of the CDs in working.

DVD capacity :
Name Media structure Capacity (GB)
DVD-5
Single Side /
Single Layer
4.7
DVD-9
Single Side / Dual
Layer
8.54
DVD-10
Double Side /
Single Layer
9.4
DVD-18
Double Side / Dual
Layer
17.08
DVD-R
Single or Double
Side / Single Layer
3.95 / 7.9
DVD-RAM
Single or Double
Side / Single Layer
2.6 / 5.2

Future of optical
storage : UDO
(ULTRA DENSITY OPTICAL)

 The UDO invented by PLASMON company in
2003.
 In UDO we take advantage of higher density
blue lasers in place of lower density red laser.
 We take the advantage of the shorten
wavelength offered by blue laser to
dramatically increase the media capacity
(first generation blue laser offered as much as
30 GB)
 Another advantage of first generation UDO is
also available in rewritable.
 Company can’t disclose more about
construction of UDO.

39340191-Optical-Storage.ppt

More Related Content

Similar to 39340191-Optical-Storage.ppt (20)

Recently uploaded (20)

39340191-Optical-Storage.ppt