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4/5/2004
Nguyen Chan Hung - Hanoi University of
Techonology 1
Digital Media &
Multimedia equipments
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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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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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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.
Dimensions: 45.0 x 37.0 x 0.76mm
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The only difference between Type I and
Type II is the size of the package.
Dimensions: 43.0 x 36.0 x 5.5mm
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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
Features
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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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