Monitor Screen - CRT, LCD, LED
One
of the most important output devices in computer system is its screen commonly
called monitor. It is an output device and displays all the programs and
applications which are running on the computer system. A Monitor is the visual
display unit of the computer system. It displays images generated from the
video output. It displays images without keeping a permanent record.
A
Graphic display is made up of a series of dots called ‘pixels’ (picture
elements) whose pattern produces images in computer system. Each dot on the
screen is defined as a separate unit which can be addressed separately. Since
each dot on the screen can be controlled separately it gives greater
flexibility in drawing pictures. The Number of dots per inch (dpi) is called
the resolution of the screen and represents the quality of the computer system.
The
resolution of a monitor means the number of pixels per inch appearing on its
surface. In general, the greater the number of pixels the sharper is the
images. Most modern monitors can display 1024 by 768 pixels. Some high-end
models of computer monitors can display 1280 by 1024, or even 1600 by 1200
pixels. Even 3280 by 2048 resolution monitors are available for special
purposes.
1.
Cathode Ray Tube Monitors (CRT)
Monitors display what is going on
in your computer. They can run at various resolutions. It is the part of
computer which looks like a TV set. After typing the characters from the
keyboard, we can see them on the monitor.
The main components of a CRT
monitors are the electron gun, the electron beam controlled by an
electromagnetic field and phosphor coated display screen. These older monitors
are bulky and require a lot of space for installation.
In CRT monitors, the image is
projected on the screen by directing the electron beam onto the computer
screen. To precisely direct the electron beams, copper steering coils are used
to create a magnetic field inside the tube. By applying varying voltages to the
copper coils a beam can be positioned at any point on the screen.
2.
Liquid Crystal Displays (LCD)
First introduced in watches and
clocks in the1970’s, LCDs are now used to display images in monitors. A newer
technology in computer screens is TFT LCD monitors. These are light weight
monitors and are used in laptop computers. Active-matrix structure is used by
most of the modern LCD monitors and television sets. In this technology, a
matrix of thin-film transistors (TFT) is added to the polarizing and color
filters. It enhances the display to make it look brighter and sharper. It can
also produce much better images and have quicker response times.
These monitors are portable,
reliable and consume less electricity. Images produced by these monitors are of
better quality than that of old CRT monitors. The LCD monitors have very high
resolution and emit less radiation than CRT monitors. The screen is also
flicker free.
3.
Light Emitting Diodes Monitors (LED)
Light Emitting Diodes (LED) is the
latest technology which is being used now a days for making high-definition TV
screens and monitors. It is a semi-conductor light source. In this technology
diodes are used to light up the screen instead of liquid crystal Diodes.
LED is known as light emitting
diode. It is an electronic device that lights up when electricity is passed
through it. LEDs are usually red. They are good for displaying images because
they can be relatively small, and they do not burn out. However, they require
more power than LCD monitors. LED is light weight monitors and is used in laptop
computers and in TV.
The Life of LED monitors is three
times than that of LCD monitors and they have less warm up time than that of
CRT or LCD monitors. These monitors require less space on the desk, less power
consumption and have flicker free screen.
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