Display Devices and printers
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Transcript of Display Devices and printers
DISPLAY DEVICES AND
PRINTERS
DISPLAY DEVICESDEFINATION:- 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
MONITOR TECHNOLOGIES
CATHODE RAY TUBE (CRT) LIQUID CRYSTAL DISPLAY (LCD) PLASMA DISPLAY PANEL (PDP) ORGANIC LIGHT EMITTING DIODE
(OLED)
RELATED TERMINOLOGIES
Pixel Resolution Display Size Viewing Angle Response time Brightness
PIXEL
Picture Element
It is the smallest element forming an image
RESOLUTION
No. of pixels per unit video display
Video Graphics Array (VGA)a) 720x400 pixels down in text modeb) 640x480 pixels down in graphics mode
DISPLAY SIZE
Measured as distance from one corner to the
diagonally oppositecorner
Usually measured in INCHES.
VIEWING ANGLE It is angle from which the screen
can be seen from side It is larger for CRT as compared to
LCD
RESPONSE TIME
The minimum time necessary to
change a pixel’s color or brightness
BRIGHTNESS
The amount of light emitted from
the display ( more specifically
known as luminance)
CRT MONITORcathode-ray tube
CRT : Principle
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.
CRT : WORKING Cathode Grid Focusing anode Accelerating anode Aquatic coating
1. Electron guns2. Electron beams3. Focusing coils4. Deflection coils5. Anode connection6. Mask for separating beams for red, green, and blue part
of displayed image7. Phosphor layer with red, green, and blue zones8. Close-up of the phosphor-coated inner side of the
screen
CRT DISPLAY : ADVANTAGES
Offers greater resolution
Widest viewing angle
It is cheap as compared to LCD,PLASMA display
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.
CRT DISPLAY : DIS ADVANTAGES
LCD : Liquid Crystal Display
LCD : DEFINITION
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
LCD : WORKING
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
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.
LCD : WORKING
LCD : ADVANTAGES
Brightness Produces very bright images due to high peak intensity. Very suitable
for environments that are brightly lit .
Power Consumption 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 Take up about 40% less desk space. LCDs are thin and compact.
Screen Shape Completely flat screen.
Sharpness 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.
Aspect Ratio The aspect ratio and resolution are fixed.
Contrast Lower contrast than CRTs due to a poor black-level.
Color and Gray-Scale Accuracy Color saturation is reduced at low intensity levels due to a poor black-
level. Images are satisfactory, but not accurate due to problems with black-level, gray-scale and Gamma.
Cost Considerably more expensive purchase price than comparable CRTs .
Resolution 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 Restricted viewing angles. Viewing angles affect the brightness, contrast
and colors shown. Wide angles can lead to contrast and color reversal.
LCD : DISADVANTAGES
PLASMA TECHNOLOGY
PLASMA : DEFINITION
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
PLASMA DISPLAY : WORKING
Plasma Display Advantages
Slim profileCan be wall mountedLess bulky than rear-projection
televisionsProduces deep blacks allowing for
superior contrast ratioWider viewing angles than those of
LCD; images do not suffer from degradation at high angles unlike LCDs
Plasma Display Disadvantages
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.
ORGANIC LIGHT EMITTING DIODE(OLED )
OLEDs : PRINCIPLE
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
OLEDs : WORKING
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
OLEDs : ADVANTAGES
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
PRINTERS
PRINTER : DEFINATION
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
PRINTER : TYPES
Dot matrix printer
Inkjet printer
Laser printer
DOT MATRIX PRINTER
DOT MATRIX PRINTER : WORKING
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.
DOT MATRIX PRINTER : ADVANTAGES
low purchase cost.
can handle multipart forms.
cheap to operate, just new ribbons.
rugged and low repair cost.
DOT MATRIX PRINTER : DISADVANTAGES
noisy.
low resolution. You can see the dots
making up each character.
Not all can do colour.
Colour looks faded and streaky.
INKJET PRINTER
INKJET PRINTER : WORKING
INKJET PRINTER : WORKING
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
LASER PRINTER
LASER PRINTER : WORKING
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
LASER PRINTER : WORKING
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
Q&A
THANK YOU