Transcript Display Devices and printers - Learn Hardware And Networking

DEFINATION:
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A display devices is a device for visual or
tactile presentation of images (including
text)acquired, Stored or transmitted in various
forms.
EX : Computer Monitor, TV Screen.
Also know as an information display
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CATHODE RAY TUBE (CRT)
LIQUID CRYSTAL DISPLAY (LCD)
PLASMA DISPLAY PANEL (PDP)
ORGANIC LIGHT EMITTING DIODE
(OLED)
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Pixel
Resolution
Display Size
Viewing Angle
Response time
Brightness
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Picture Element
It is the smallest element forming an
image
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No. of pixels per unit video display
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Video Graphics Array (VGA)
720x400 pixels down in text mode
b) 640x480 pixels down in graphics mode
a)
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Measured as distance from
one corner to the
diagonally opposite
corner
Usually measured in
INCHES.
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It is angle from which the screen can be
seen from side
It is larger for CRT as compared to LCD
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The minimum time necessary to change a
pixel’s color or brightness
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The amount of light emitted from the
display ( more specifically known as
luminance)
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CRT display works on :
Electron emission
 Electrons are emitted from the Cathode
tube
 Phosphorescence
 It is the emission of visible light, when
electron beam strikes phosphor material.
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 Cathode
 Grid
 Focusing anode
 Accelerating
anode
 Aquatic coating
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Electron guns
Electron beams
Focusing coils
Deflection coils
Anode connection
Mask for separating beams for red, green, and blue part of
displayed image
Phosphor layer with red, green, and blue zones
Close-up of the phosphor-coated inner side of the screen
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Offers greater resolution
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Widest viewing angle
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It is cheap as compared to LCD,PLASMA
display
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Thickness is much larger.
Cannot be used for smaller display, like
watches.
View area is less than the offered monitor
size.
It is more heavier.
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A Liquid Crystal Display is a thin, flat
display device made up of any number
of pixels arrayed in front of a light source
or reflector. It uses very small amounts of
electric power, and is suitable for use in
battery-powered electronic devices
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When electric current was
passed through the LCD
panel the liquid crystals
are aligned with the first
polarized glass
encountered and will
make 90 degree twist
when approaching the
other polarized glass at
the end
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When this happens the light from the
fluorescent backlight is able to pass through
and thus giving us a lighted pixel on the
monitor.
When there is no electric current the liquid
crystals will not twist and thus the light will
not pass through and a black pixel will be
shown.
The reason we see the colored images are due
to the color filter light passes through the
filtered cells creates the colors.
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Brightness
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Power Consumption
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Take up about 40% less desk space. LCDs are thin and compact.
Screen Shape
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Energy efficient. Consume less than 1/3 the
power of a comparable
CRT. Consume less electricity than a CRT and produce little heat.
Physical Aspects
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Produces very bright images due to high peak intensity. Very suitable for
environments that are brightly lit .
Completely flat screen.
Sharpness
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At the native resolution, the image is perfectly sharp. Adjustments are
required at all other resolutions which can result in measurable
degradation to the image.
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Aspect Ratio
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Contrast
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Considerably more expensive purchase price than comparable CRTs .
Resolution
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Color saturation is reduced at low intensity levels due to a poor blacklevel. Images are satisfactory, but not accurate due to problems with blacklevel, gray-scale and Gamma.
Cost
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Lower contrast than CRTs due to a poor black-level.
Color and Gray-Scale Accuracy
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The aspect ratio and resolution are fixed.
Works best at the native resolution. The native resolution can not be
changed. All other resolutions require adjusting procedures which can
cause considerable deterioration of the image.
Viewing Angle
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Restricted viewing angles. Viewing angles affect the brightness, contrast
and colors shown. Wide angles can lead to contrast and color reversal.
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A plasma display panel
(PDP) is essentially a
collection of very small
fluorescent-type lamps,
each a few tenths of a
millimeter in size
The plasma display itself
is a simple device
consisting of two parallel
glass plates separated by a
precise spacing of some
tenths of a millimeter and
sealed around edges
Slim profile
 Can be wall mounted
 Less bulky than rear-projection
televisions
 Produces deep blacks allowing for
superior contrast ratio
 Wider viewing angles than those of
LCD; images do not suffer from
degradation at high angles unlike LCDs
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Heavier screen-door effect when compared to LCD or
OLED based TVs
Susceptible to screen burn-in and image retention,
although most recent models have pixel orbiter
Phosphors lose luminosity over time, resulting in
gradual decline of absolute image brightness newer
models are less susceptible to this, having lifespan
exceeding 100,000 hours, far longer than older CRT
technology
Generally do not come in smaller sizes than 37 inches
For those who wish to listen to AM radio, or are
Amateur Radio operators Hams or Shortwave
Listeners SWL, the Radio Frequency Interference RFI
from these devices can be irritating or disabling.
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OLEDs are special
because they are
made-up of organic
polymer molecules
(otherwise known as
plastic) allowing light
to emit when a
voltage is applied
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Voltage is applied across the
OLED device allowing electron
to travel from the cathode
through the emissive layer to
make positively charged
electron holes in the conductive
layer where the anode draws
those electrons.
Quite simple, the anode is
drawing electrons through the
emissive layer to provide
positive electron holes in the
conductive layer
Then the positive holes and the
electrons collide and recombine
which leads to a drop in the
electron energy level as visible
light radiations is emitted
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They have the potential to be able to be produced
much more cheaply than conventional LED’s,
LCD’s and plasma televisions using processes
derived from ink-jet printing
Improved range of colors and brightness's
compared to LCD and plasma displays
Potentially very energy efficient
They can be deposited on large substrates enabling
large areas to be illuminated
Lighter than LED’s
Flexible
Can produce a true black and infinite contrast
ratios
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In computing, a printer
is a peripheral which
produces a hard copy
(permanent readable
text and /or graphics) of
documents stored in
electronic form, usually
an physical print media
such as paper or
transparencies
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Dot matrix printer
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Inkjet printer
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Laser printer
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The printer head is made up of a row of pins –
usually 9 or 25 pins forming a vertical bar. To form a
letter, the pins are “fired "in quick succession to
press the ribbon against the paper.
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low purchase cost.
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can handle multipart forms.
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cheap to operate, just new ribbons.
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rugged and low repair cost.
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noisy.
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low resolution. You can see the dots
making up each character.
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Not all can do colour.
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Colour looks faded and streaky.
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The Inkjet Printer is a common type of printer which
works by spraying a tiny drop of ink at paper. The
technology is probably best explained by this animated
picture.
The printing works the same way as the dot-matrix
print head above. the only difference is that we are
now using droplets of ink instated of hammers.
Inkjet works by having a print catridge with a series of
tiny electrically-heated chambers constructed by
photolithography
When the bubble, surplus ink is sucked back up from
the printing surface. the ink’s surface tension pumps
another charge of ink into the chamber through a
narrow channel attached to an ink reservoir
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Images are produced on a
drum
A laser beam sets
electrical charge on dots
on the drum
Magnetically charged
power called toner flies to
the electrified dots on the
drum
The drum rolls the toner
on the paper
A second drum burns the
toner on the paper
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The final stage is for the
paper to pass through
very hot “rollers "which
“melt "the ink on the
paper
The heat “seals” the ink
on to the paper instantly
making sure that you do
not get smudging or
crinkling as you can
with other printer types