Sup DigitalMedia

8/10/2019 Sup DigitalMedia

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4/5/2004

Nguyen Chan Hung - Hanoi University of

Techonology 1

Digital Media &

Multimedia equipments


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4/5/2004 Nguyen Chan Hung - Hanoi University of Techonology 2

Outline

Digital Media Magnetic tape / Hard Disk

CDR CDRW DVD DVD ReWritable

Multimedia devices

Liquid Crystal Display (LCD) Plasma Display Panel (PDP)

Digital Still Camera

Video Camera (Camcorder)

The LATEST Technologies !!


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Digital Storage Introduction

Storage of audiovisual data has been analog for a long time, because

playing and recording should run in real-time

playing and recording should run during a long time (>1h).

The two most commonly used systems are:

magnetic storage systems, like hard-disks, video tapes and DAT

optical recording systems, like CD and DVD


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Magnetic Storage Recording head

magnetic flux

(clockwise)

magnetic

core

electric

current

magnetic

medium

d

b


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Magnetic Storage Recording head

Some considerations: v = . f v = speed of medium relative to head

f = frequency of electric current

= width of magnetic pattern on medium

A large head gap b results in more efficient recording, since the magnetic fluxin the medium will be large. Note that the gap is non-magnetic, in order to force

the magnetic flux to go through the medium. Also note that the final writing

occurs the moment after the tape leaves the magnetic flux area.

A small distance d between head and medium also results in more efficient

recording, for the same reason. If the head touches the medium (d = 0), wear

could damage the medium (more at high relative speeds).

Since the data density of the system is limited (there is a minimum ), and the

relative speed is also limited (mechanical problem), there is also a limit on the

bandwidth of the system (how fast data can be recorded).


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Magnetic Storage Losses

Data are read from a magnetic coating by another physical mechanism: by wayof the magnetic core and gap, the change of magnetic flux in the medium inducesa voltage over the conductor. When data are read, the signal is hard to read dueto:

Thickness loss: the reading head does not see the magnetized coating atdeep layers. Therefore the coating should not be too thick.

Separation loss:the distance d between reading head and coating should beas small as possible. Loss = 54.6 d/ dB.

Gap-width loss: If the gap-width b is too large, small wave-lengths can not bedetected. If b = , the output = 0 (why?).Since a recording head needs al large b, and a playing heada small b, often two different heads are used.


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Magnetic Storage Erasing

Due to the hysteresis effect, erasing is not that simple:

Bulk erasing: a strong external magnetic field is applied to the whole tape.This magnetic field follows a decaying oscillating pattern.

Erasing head: a special head with a large width is fed with a high-frequencysignal (which the playing head can not read).

Overwriting: the old data are overwritten with the new data.However, so called residual recording can distort the new data.


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Magnetic Storage Digital recording

In digital recordings, the magnitude of the magnetic flux in the coating is alwaysthe same (maximum remanent magnetization), only the polarity changes.

Recording /writing current

Flux in coatingN S S N N S S N N S S N

Playing /readingvoltage

The transitions are detected by use of an integrating circuit or a differentiatingcircuit (gated peak detector).


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Magnetic Storage Media

Area density factor= nr. of bits per unit area: 1970 3 kbit/mm2

1996 150 kbit/mm2

2002 > 1Mbit/mm2

Tape media: substrate 20-80 m, coating 0.2-8 mopen-reel or cassettecontact between head and medium wear

Disk media: surface is not protected sealing neededno contact between head and medium no wear

Tape decks are linear (track is parallel with tape) or

use helical scan mechanism (track is not parallelwith tape)


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Magnetic Storage Digital data cassette

The capstan is driven by some servo mechanism which keeps the linear speed ofthe tape constant. The pressure rollerin the tape ensures that there is enoughfriction between capstan and tape. The tension band prevents the tapebecoming loose, and thus uncontrollable.

head

assembly

tape motion

driven

capstan

This is an example of a linear tape deck. In general, these types are limited in

head-to-tape speed and thus bandwidth.

tension band

pressure

roller

supply reel take-up reel


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Magnetic Storage Helican scan

The threading pins enter behind the tape when the cassette is inserted and moveout of the cassette to wrap the tape around the scanner drum (dotted arrows).Note the position of the audio head.

audio

head

capstan

supply reel take-up reel

tension arm

tension arm

scanner drum


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Magnetic Storage Helican scan

The relative speed is increased sinceboth the tape moves, and the scannerrotates. The scanner contains two heads

to insure continuous contact betweenhead and tape.

scanner drum

two magnetic heads

tapemotion

tape

rotating

upper

drum

stationary

lower drum

tape

guide

head helix angle

The drum is not parallel with the tape, butat some angle, called the helix angle. Thesignal to be written has to be cut insegments. In analog recording, it

happens during the vertical blankinginterval. In digital recording, buffers areused. Often, also longitudinal tracks arewritten on the tape by external heads(see audio head on previous slide).


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Magnetic Storage Azimuth recording

In simple recording systems, the gap of the recording/playing head isperpendicular to the track. This results in the following magnetic pattern:

In advanced systems, several parallel tracks are written on the tape using

multiple recording heads. To diminish cross-talk between channels when theplaying heads are not perfectly aligned, the angle between adjacent tracks andthe gaps of their recording heads are slightly above or below 90. This is calledazimuth recording.

track 1

track 2

reading head


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Magnetic Storage DVCPRO specs

Video format Component 4:1:1 compressed intraframe only

Tape speed 3.4 cm/s

Tape usage 0.05 cm/s

Recording time 60 min. (M), 120 min. (L)

Channels for video 1

Record heads/channel 2

Total heads on scanner drum 6

Number of audio channels 2

Azimuth recording yes

Drum diameter 2.2 cm

Drum rotation speed 150 rps

Helical scan coding NRZI

Video writing speed 5.1 m/s

Video sample rate Y 13.5 MHz

Video sample rate chroma 3.375 MHz

Total video data rate (raw) 162 Mb/s

Total video data rate (compressed) 32.4 Mb/s

Audio sample rate 48 kHz

Audio bits/sample 16

Area density 150 kb/mm


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Magnetic Storage Comparison

Magnetic media

Tape Disk

slow access time (fast forwardor rewind buttons)

fast access time (few tens of ms)

contact between head andmedium sensitive to wear

no contact between head and medium

no wear

more storage capacity forremovable devices

less storage capacity for removabledevices (floppy disks, Hard Disk with

USB connection)


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Magnetic Storage Hard Disk

rotation: typically 7200 rpm

concentrictracks

head positioningmotor

flying head

density: > 1Mbit/mm2

capacity: 10GB to 80GBand more!

often consists of severaldisks

air film between disk andhead: few tenths of a m

hermetically sealing

transfer speed: 1-80MB/s

high cost per bit

alternative: floppy disk

directory: in first track(s)

sector


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Magnetic Storage Hard Disk Platters

head 0

head 1

head 2

head 3

head 4

head 5

head 6

head 7


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Magnetic Storage Hard Disk Interfaces

Normal use: IDE = Intelligent Drive Electronics

EIDE = Enhanced IDE

ATA = Advanced Technology

Attachment

Servers / Workstations: SCSI = Small Computer Systems Interface

higher rotation speed

shorter access time higher data transfer rate


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Magnetic Storage RLL example

1 0 0 0 1 1 1 1

FM : 13 reversals needed

1 0 0 0 1 1 1 1

MFM (floppy disk) : 7 reversals needed

10 0011 11

RLL (2,7) : 3 reversals needed higher density


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4/5/2004


Techonology 26

CDR CDRW


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Optical Storage Compact Disc

1 spiral track

12cm pits, bumps

or areas withdifferent

reflectivity

0.5m

1.6m

0.8

3-3m

0.8

3-3m

spot of laser


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0.5m

1.6m

Transparent Layer (polycarbon)

Reflective Layer (Al,Au)

Protecting Layer

focussing laser beam

0.1

5m

1.2mm

Mechanical recording

Reading & Optical recording

Optical Storage Compact Disc Cross-sectional View


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Optical Storage Compact Disc Reading Mechanism I

pit, bump or areawith non-optimal

reflectivity

no pit, no bump orarea with optimal

reflectivity

Arrivingbeam

Reflectingbeam

Intensity decrease! No Intensity decrease!


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Objectivelens

Quarter-waveplate

Polarization

beamsplitter

Optical Storage Compact Disc Reading Mechanism II

Reflectivelayer

LASERsource

Cylindrical

lens

Photodetector

"Focus" "Tracking"

Lens movements:


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Optical Storage CD Reading Mechanism Nice Picture


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Optical Storage Compact Disc Reading Mechanism III

The LASER source transmits polarized light (0).

The polarization beam splitter is transparant for this polarization (0), but reflectslight with an orthogonal polarization (90).

The quarter-wave plate turns the polarization with 45, so after two passes, the

polarization is 90.

The reflected light finally falls through a cylindrical lens (see focus) upon the

photodetector(s).

The diffraction grating produces several secondary LASER beams, such thatside-spots occur on the disk (see tracking).


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Optical Storage Focus mechanism

cylindrical lens

short

focus

correct

focus

long

focus

Correct focus should occur at the position of the multi-beam detector. If the

disk is out of focus of the objective lens, the cylindrical lens produces aneliptical spot (short or long focus) at the multi-beam detector which contains

a four-quadrant sensor (output = error signal).

4-

quadrantsensor

laser

spot

V+ 0 V-


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Optical Storage Focus mechanism

The objective lens (in the middle) can move up and down if a current flows

through the coil (electro-magnetic force: left-hand rule). The magnitude of

the current depends on the output of the four-quadrant sensor.

disk

moving-coil

focus actuator

flexible

dust seal

permanent

magnet

pole

pieces


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Optical Storage Tracking mechanism

center spot

side spot

side spotx

y

x

y

The three-spot method produces a tracking error signal by comparing the average

level of the side-spot signals (caused by diffraction grating). On the left, x < y,

which corresponds to mistracking. On the right, x = y: correct tracking. The side

spots have their own sensors.


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Optical Storage CLV versus CAV

Magnetic Hard Disks rotate at a Constant Angular Velocity (CAV), e.g. 5400 rpmor 7200 rpm, no matter where the data are located on the disk surface (inner trackor outer track).

Compact Discs have a uniform storage density, because the pit length limits(0.83-3m) do not change along the spiral track. This implies that a ConstantLinear Velocity (CLV) is needed. The angular velocity depends on thedistance rbetween the location of the data and the center of the disk:

r

CLV=


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Optical Storage Compact Disc Channel Coding I

Channel coding in CD: EFM = 8-to-14 Modulation

Meaning: every byte (8 bits) is converted to a waveform of length 14T

11310

invalid 11T


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Optical Storage Compact Disc Channel Coding II

Transitions in waveform occur only at integer multiple of T

minimal run-length = 3T: to stay below bandwidth of whole system

Tis the period of the master clock (4.3218 MHz)

maximal run-length = 11T: to guarantee enough 'clock content'set of allowed run-lengths = {3T, 4T, 5T, 6T, 7T, 8T, 9T, 10T, 11T}

There are 267 possible combinations of allowed run-lengths within 14T.

First and last interval may have smaller run-lengths, this is compensated for

by 'packing bits'.

Interval of 14Tis extended by interval of 3T= packing bits.

Purposes of packing bits: - to respect minimal run-length- to keep channel code DC free

- to ensure legal transitions between bytes- to avoid false 'syncs' (see below)

EFM is more efficient than MFM. MFM can change from bit to bit. Since themin. time for 1 bit is 3T, the min. time for 1 byte = 24T(instead of 17T)


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Optical storage CD read-out

slicing

levelpick-up

waveform

slicer output

clock

0 100 000 01 11 000000000000 000

channel bits

PLL

D QEX-

OR

clock

channel

bits


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Optical Storage CD Data Blocks

Sync SC 1 2 3 11 12 Q1 Q2 Q3 Q4 13 14 23 24 P1 P2 P3 P4

11T 11T 3T Subcode byte: 14T 3T

12 odd audiobytes

12 even audiobytes

4 bytes Predundancy

4 bytes Qredundancy

Sync: marks begin of data block

Subcode byte: marks begin of music tracks or files, also includes time informationAudio bytes are interleaved (not sequential) to reduce effect of 'burst errors'

P and Q bytes: from Reed-Solomon code, adds redundancy to data, enableserror detection and error correction


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Optical Storage Audio-CD

Purpose: to store high quality audio

playing time = 74 minutes = 4440 s

sampling rate = 44100 Hz

number of channels = 2 (stereo)

sampling resolution = 16 bit = 2 bytes

Capacity = 4440 s * 44100 Hz * 2 bytes * 2 = 780 MB

Data transfer rate = 44100 Hz * 16 bits * 2 = 1.41 Mb/s= 44100 Hz * 2 bytes * 2 = 176400 bytes/s

Alternative notation: CD-DA (Digital Audio)

Note: in the calculations 1 MB equals 1 million bytes, not 1024 * 1024 bytes


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Optical Storage Magneto-Optical disks

MO-Disk contains magnetic layer:

= direction of internal

magnetic field

laser beam

coil

current

magnetic field

The magnetic properties do not change at low temperatures.

LASER heats magnetic layer above Curie temperature. The magnetic propertiescan be altered now.

A current through the coil generates a magnetic field that changes the data.

Reading is done using a LASER. The Kerr effect causes the light polarizationto change in a direction depending on the direction of the magnetization.


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Optical Storage CD-Recordable

Transparant Layer (polycarbon)

Reflective Layer (Al,Au)

Protecting Layer

Dye layer

The recording LASER beam has high intensity, so the dye gets burned.It will reflect the reading LASER beam to a lesser extent.

The spiral track is already present on the blank CD to allow the trackingmechanism to operate properly.

The CD-R is sometimes called WORM disk (Write Once Read Many).


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Optical Storage CD-ReWritable

Dye layer of CD-R is replaced by exotic mix of Ag, In, Sb en Te.

A crystal structure is obtained if the mix is heated to a certain temperature andcooled down. This area will reflect light very well.

An amorph structure is obtained if the mix is heated to a highertemperature andcooled down. This area will reflect less light than a crystalline area.

Three different power levels of the LASER beam are needed:

2. Erasing power = high power making the area crystalline.

1. Writing power = very high power making the area amorph.

3. Reading power = low power not altering the area.


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Optical Storage Buffer underrun

IMPORTANT NOTE for old recorders: avoid buffer underrun!

When writing the data, the LASER can not be turned off easily.It should record continuously.

Therefore, the data to be recorded should always be available.

These data are stored in a memory buffer that should be kept filled.

If the buffer is empty, for instance because the link between PC and CD-Recorderis too slow, the recording process failed.

Modern recorders can deal with this problem: the recording process can resumeafter a buffer underrun.


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4/5/2004


Techonology 48

DVD DVD ReWritable


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Optical Storage DVD layers

Transparant Layer (polycarbon)

Reflective Layer (Al,Au)Protecting Layer

Semi-reflecting layer

Transparant Layer

LASER focuson lower layer

LASER focuson upper layer

Single double layer = 4.7 GB 8.5 GB (*1.81)

Single double sided = 9.4 GB 17 GB (*2)


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Optical Storage DVD Formats

DVD-ROM for PC

DVD-Video are replacing analog video tapes, uses MPEG-2

DVD-Audio Super-audio CD, more channels, more bits/samplehigher sampling rate

DVD-R DVD-Recordable

DVD-RAM DVD-RW of DVD+RW

Blu-ray disc new standard for DVD recorders,expected by end 2003


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Optical Storage DVD player

spindle

motor

EFM+ &

demod.

buffer

occupancy data buffer for

variable bit rate

error correction

& de-interleave

program

stream

demux

program

stream

data

audio

video MPEG-2

video

decoder

MPEG-2audio

decoder

focus &

tracking

control

& timing

system

user

controls


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Optical Storage Comparison CD with DVD

DVD = Digital Video Disc or Digital Versatile Disc

It can be regarded as a super CD. A lot more data can be stored on a DVD.

property CD DVD

laser 780 nm 635-650 nm

track pitch1.6 m 0.74 m

gain

*2.16

min. pit length 0.83 m 0.4 m *2.08

more efficient coding (EFM+)+ less overhead for error correction *1.35

capacity 780 MB 4.7 GB *6

speed of 1x 150 kB/s 1250 kB/s


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Displays Display types

emissive

non-emissive reflective

lightsource

non-emissive transmissivelight

source


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Displays Specifications

mediumhighlowhighpower

OKOKpersistenceflickerspeed

1112.2gamma

highhighmediumlowcost

mediumlightlightheavyweight

widewidenarrowwideviewing angle

mediumhighhighmediumcontrast ratio

lowhighmediumhighbrightness

projection40"15" (PC)35" (TV)size (typ.)

digitaldigitalanalog/digitalanaloginput

digitaldigitaldigitalanalogscanning

reflectiveemissivetransmissiveemissivetype

DMDPDPLCDCRTProperty


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Displays LCD crystal structure

0 grooved glass plate

90 grooved glass plate

polarized light beam

liquid-crystal material

Di l LCD l i


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Displays LCD polarizers

Di l LCD b i ht t l


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Displays LCD brightness control

Di l LCD ki i i l


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Displays LCD working principle

Liquid crystals are rod-shaped transparant molecules. When placed into a

container with slightly grooved surfaces, the crystals will align themselves with

the pattern of the grooves. The grooves in the top and bottom plate of a LCD are

placed at 90 to each other, causing the crystal alignment to twist as one movesthrough the cell from top to bottom.

If polarized light is applied to the cell with the polarization parallel to the top

grooves, the polarization will rotate by 90 going through the cell. A second

polarizer orthogonal to the first one is placed at the bottom of the cell, so that

light rotated by the cell will pass through it.

Another property of liquid crystals is that they will allign parallel to an applied

electric field. As a result, the light polarization is not rotated any more, and nolight will pass through the second polarizer.

Di l LCD i t i hit t


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Displays LCD passive matrix architecture

column electrodes

(on back plate)

row electrodes

(on front plate)

single pixel

In order to control a pixel, a voltage is applied between its row and column

electrode. Pixels are addressed in a sequence (scanning). The response of a

passive-matrix is slow: moving objects tend to smear. Also, the contrast ratio is

slow. The big advantage is the low cost.

side view

Di l LCD ti t i hit t I


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Displays LCD active matrix architecture I

Each pixel, being a capacitor, is controlled by a transistor switch and can be

addressed individually. This greatly improves the response speed and the

contrast ratio. This architecture, aka the Thin Film Transistor Technology, is

more expensive.

front plate

back plate

"pixel"

control

transistor =

switch

pixel data

high voltage = dark

low voltage = bright

gate = select

Di l LCD ti t i hit t II


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Displays LCD active matrix architecture II

rowselect(gate)

column select (pixel data)

Displa s LCD acti e matri architect re III


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Displays LCD active matrix architecture III

A row of pixels is selected by applying the appropriate select voltage to the select line connecting

the TFT gates for that row of pixels. When a row of pixels is selected, we can apply a desired

voltage to each pixel via its data line. When a pixel is selected, we want to apply a given voltage

to that pixel alone and not to any nonselected pixels. Those nonselected pixels should be

completely isolated from the voltages circulating through the array for the selected pixels. Ideally,the TFT active matrix can be considered as an array of ideal switches. The operation of this

active matrix would be as follows:

1) Appropriate select voltages are applied to the gates of the first row of the TFTs while

nonselect voltages are applied to the TFT gates in all other pixel rows.

2) Data voltages are applied at the same time to all of the column electrodes to charge

each pixel in the selected row to the desired voltage.

3) The select voltage applied to the gates in the first row of TFTs is charged to a

nonselect voltage.

Steps 1-3 are repeated for each succeeding row until all of the rows have been selected and

the pixels charged to the desired voltages. All rows are selected in one scanning period. Thus,

if there are 500 lines and the time to load data into each selected line is 50 s, then a single

scanning period is 25 ms, for a field-scanning rate of 40 Hz.

Displays LCD brightness and color


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Displays LCD brightness and color

Brightness is controlled by the voltage across the row and column electrodes

(passive matrix) or by the transistor switch (active matrix).

Note that lyquid crystals decay slowly to the unexcited state, after a voltage isapplied, resulting in persistence.

Coloris obtained by using separate pixels for red, green and blue. Thus, color

LCDs have three times the pixels in the horizontal direction: e.g., a 1024x768display has 3072x768 pixels.

color filters


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Displays LCD advantages


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Displays LCD advantages

The advantages of a LCD compared to a CRT are:

light weight

smaller size of total device

low power consumptionless heat production

no flicker

no focus problems

no high voltages or strong magnetic fields (EM radiation)

Displays PDP structure


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Displays PDP structure

Displays PDP cells


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plasma

Displays PDP cells

red phosfor green phosfor blue phosfor

anode

cathode

dielectri

c layer

front glass

rear glass

barriers

to viewer

Displays PDP working principle


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Displays PDP working principle

Basic principle: a high voltage accross a low-pressure gas (Ne, Xe) generates light.

1) A high voltage between anode and cathode generates a plasma = mixture of

electrons, positively charged ions and neutral particles.

2) The conducting plasma generates ultraviolet light.

3) The phosphoratoms emit visible light when hit by UV light.

Note that a cell is either on or off. Brightness is controlled by Pulse Width

Modulation (PWM).

Most PDPs areAC-PDPs: a cell is first charged (and lit) by a high write voltage.

Since the cell is a capacitor (dielectric layer), a charge remains on the cell.

Second, a small AC voltage (square wave) is applied across the cell, which

refires at each transition. Note that this does not happen if no write voltage is

applied in the first step. A special procedure is needed to erase the cell.

Displays PDP brightness control


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Displays PDP brightness control

time

erase & write periods

sustain periods

Time interval of sustain period n : n

n tt 2.0=

Erase period: capacitor is discharged.

Write period: capacitor is charged, cell by cell, if correspondig bit = 1 (cell fires).Sustain period: AC voltage is applied to all cells simultaneously, and all charged

cells keep firing during this period. Thus, first bit 0 is executedfor

all cells, then bit 1, and so on, till bit 7. All this happens so fast

that a viewer wont notice any flicker.

Di it l I i d i


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Digital Imaging devices

Digital Still Camera

Video Camera (Camcorder)


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How Digital Cameras Work

Light Lens CCD ADC DSP storage device(disk drive

or flash memory chip) computer

Light signal to electrical signal to digital signal to adjust and

compress to storage to computer

Digitization:


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Difference Between


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Difference Between

CCD and CMOS CCD : high-quality images ,lots of pixels ,excellent light

sensitivity.

CMOS: lower quality, lower resolution , lower sensitivity,

cheap, great battery life.

High-resolution cameras need a CCD sensor

Resolution


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Resolution

Different resolutions are available and typically increase directlywith price. Choose the resolution that best suits your needs:

640 x 480 Pixels = Minimum (email, Web pages) 1280 x 960 Pixels = Better (similar to a 4"x6" print)

1600 x 1200 Pixels = High (similar to a 8"x10" print)

1920 x 1600 Pixels = Very High (studio/professional )

lens


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lens

Aperture

Focal length

Optical zoom(x times zoom)

Digital zoom

Shutter Speed

Sensitivity(ISO)


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Focal Length


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Focal Length

300mm = Super Telephoto

Optical zoom (x times zoom)


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Optical zoom (x times zoom)

optical zoom works like the zoom on a traditional film camera.Elements within the lens move, reducing the field of view and

making the object you're shooting appear closer.

All the zoom describes is the lenses ability to multiply the size of

a subject between its minimum and maximum focal lengths.

Digital Zoom


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Digital Zoom

Digital zoom does not have moving parts. It is the electronic

enlarging of the middle of an image.

Resolution is reduced as the center pixels are enlarged to fill

the display.

Sensitivity (ISO)


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Sensitivity (ISO)

ISO stands for "International Standards Organization" and is a

measure of light sensitivity for film. The same sensitivitymeasurement that varies with different types of film has been

applied to the sensitivity of the digital camera's CCD. A higher

ISO rating means the camera will perform better in low-light

conditions.

Storage space


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Storage space

PCMCIA PC Card

CompactFlash

SmartMedia

Memory Sticks

Floppy disk

Writeable CD and DVD


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the most common format used today, Available

in capacities up to 256 MB.

Dimensions: 43.0 x 36.0 x 3.3mm


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Available in capacities up to 128 MB with 256 MB on the horizon


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These cards are only found on high end

processional digital SLR's(Single Lens Reflex).

Available in a large range of capacities up toseveral GB (gigabyte)

Dimensions: 85.6 x 54.0 x (Type I: 3.3mm,

Type II: 5.0mm, Type III: 10.5mm)


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thinner than Compact Flash.There is a controller chips in SmartMedia'spackage.



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The only difference between Type I and

Type II is the size of the package.



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Compression Formats

Most of today's cameras store their images in JPEG format; andyou might be able to select between "fine detail mode" and

"normal mode." Higher-end cameras may also support the TIFF

format. While JPEG compresses the image, TIFF does not, so

TIFF images take lots of space. The advantage of TIFF storageis that no data is lost to the compression process.


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Working Principles


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Working Principles

- The Basic Principle

- The CCD

- The CMOS

- X3 Technology


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Working Principles


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Working Principles

The CCD is the technology at the heart of most digital camera

Each CCD consists of millions of cells known as photosites orphotodiodes, and each acts as a pixel.

Read-out register

Charge Coupled Device (CCD)

Working Principles


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Working Principles

Charge Coupled Device (CCD) General Operation Principles

The photosites on a CCD actually respond only to lightnot

to color. Color is added to the image by means of red, greenand blue filters placed over each pixel.

The process of color interpolation

Continued

Working Principles


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Working Principles

Emerge as an alternative image capture technology to CCDs

Advantages: CMOS chips are significantly less expensive

significantly lower power requirements

multiple functions Problems: noisy images, an inability to capture motion correctly,

so has a way to go before reaching parity with CCD technology

Prospect: all entry-level digital cameras will be CMOS-based and

that only midrange and high-end units will use CCDs

Complementary Metal-oxideSemiconductor (CMOS)

Working Principles


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Working Principles

X3 technology The latest CMOS image sensor technology unveiled by Foveon

Corporation in 2002.

The conventional single layer of photo-detectors in a mosaicpattern

The new CMOS image sensor uses X3 technology: full-colordigital camera image sensor.

Variable Pixel Sizing (VPS): enable the grouping of smaller pixelinto larger pixels, "super pixels ".

Specifications


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Specifications

-Resolution-Storage

- Compression Formats

-Sensor Technology

-Lens

-Interface

-Exposure Control

-Image Stabilization

- Focus

-Batteries

- View Finder

-...

Features


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Features

Resolution

The amount of detail that the camera can capture is called the resolution, and it is

measured in pixels. In general, the more pixels your camera has, the more detail it

can capture. The more detail you have, the more you can blow up a picture before it

becomes "grainy," and starts to look out-of-focus.

Some typical resolutions that you find in digital cameras today include:

256 x 256 pixels = 65,000 total pixels.

640 x 480 pixels = 307,000 total pixels.

1216 x 912 pixels = 1,109,000 total pixels.

1600 x 1200 pixels = up to 3 million pixels.

...

Features


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Storage

Your camera needs to store its images somewhere, and it uses memory to do that.

Mostly they store it onto a Mini DV.

Example :

Format: Mini DV Tape

Memory Chip: None

Length: Available in 60 Minute Lengths

Storage Case: Plastic

Package contain 5 Pack of MiniDV Tape.31.25

Features


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Features


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Lens

You will find four different types of lenses on digital video cameras:

Fixed-focus, fixed-zoom lenses

Optical-zoom lenses with automatic focus

Digital-zoom lenses

Replaceable lens systems

Features


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Interface

The interface allows you to connect the camera to your computer and transfer the

movies. Once the movies are on your computer, you can edit them, e-mail them, load

them onto a Web site or print pictures out of the movie. There are at least four

different ways to move movies from the camera to the computer:

USB connection

Serial connection

Flash memory slots

IEEE 1394

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Exposure Control

Most cameras have completely automatic exposure. If you want exposure control, lookfor a manual exposure feature. Some cameras also offer special exposure settings for

specific situations like sports, indoor arenas, etc.

Image Stabilization

Some cameras offer a "steady cam" image stabilization system like video cameras have.A system like this can help you take clearer images.

FocusMost cameras have fixed focus, so you can not adjust the focus at all, or automatic focus.focus.

If you would like more control, choose a camera with a manual foIf you would like more control, choose a camera with a manual focus feature.cus feature.

BatteriesDigital cameras, especially those that use a CCD sensor and an LCD display, tend to use

lots of power - which means they eat batteries. Rechargeable batteries help to lower the

cost of using the digital camera, but rechargeable batteries are sometimes expensive.

View FinderSome cameras have no LCD panel, and instead use a simple optical viewfinder. Other

cameras have both an LCD panel and an optical viewfinder, in which case you can turn

off the LCD to save the battery. Some cameras have only an LCD panel, which also acts

as the viewfinder.

Canon - Sony - JVC


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- Canon ZR40 : USD 600

- Canon OPTURA 100MC : USD 1200

- Canon XM1 : USD 2000

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Compare Product


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Canon SonyDCR

JVC GR-DV

ZR40 Optura

100MC

XM1 TRV

140 D8

IP 5MicroMV

VX 2000 L 120 X 400 P 7

Measurement

of ccd-sensor1/6 5/18 3x 1/4 1/4 1/6 3x1/3 1/4 1/4 1/4

Resolution

(#Pixels) 290.000 690.000 3X320.000 540.000 680.000 3X450.000 680.000 800.000 1.020.000

Pixels on

memorycardNo Card

1280x960or

640x4801280x960 No Card No Card 640x480 No Card No Card 1280x960

Focus(mm) 1.6 - 2.9 1.6 - 42 4.2-84 3,6-72 3,6-36 6-72 1.8-18 3,6-36 3,8-38

Filterdiameter - 43 - 37 - 58 37 27 30

Image

StabilizerDigital Digital Optical Digital Digital Optical Digital Digital Digital

LCDresolution

112.000 200.000 122.000 61.600 211.000 200.000 110.000 112.000 200.000

Storage Type MiniDV

MiniDV

MiniDV

Digital8MicroMV

MiniDV

MiniDV

MiniDV

MiniDV

Connections IEEE1394

IEEE1394

IEEE1394

USBIEEE1394

IEEE1394

IEEE1394

RS 232IEEE &

USB

Key Points


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