Information Technology Reference
In-Depth Information
Output Devices
Computer systems provide output to decision makers at all levels of an organization so they
can solve a business problem or capitalize on a competitive opportunity. In addition, output
from one computer system can provide input into another computer system. The desired
form of this output might be visual, audio, or even digital. Whatever the output's content
or form, output devices are designed to provide the right information to the right person in
the right format at the right time.
Display Monitors
The display monitor is a device similar to a TV screen that displays output from the computer.
Because early monitors used a cathode-ray tube to display images, they were sometimes called
CRTs
. Such a monitor works much the same way a traditional TV screen does—the cathode-
ray tubes generate one or more electron beams. As the beams strike a phosphorescent com-
pound (phosphor) coated on the inside of the screen, a dot on the screen called a
pixel
lights
up. A pixel is a dot of color on a photo image or a point of light on a display screen. It appears
in one of two modes: on or off. The electron beam sweeps across the screen so that as the
phosphor starts to fade, it is struck and lights up again.
With today's wide selection of monitors, price and overall quality can vary tremendously.
The quality of a screen image is often measured by the number of horizontal and vertical
pixels used to create it. The more pixels per square inch, the higher the resolution, or clarity
and sharpness, of the image. For example, a screen with a 1,024 × 768 resolution (786,432
pixels) has a higher sharpness than one with a resolution of 800 × 600 (480,000 pixels).
Another way to measure image quality is the distance between one pixel on the screen and
the next nearest pixel, which is known as
dot pitch
. The common range of dot pitch is
from .25 mm to .31 mm. The smaller the dot pitch, the better the picture. A dot pitch
of .28 mm or smaller is considered good. Greater pixel densities and smaller dot pitches yield
sharper images of higher resolution.
The characteristics of screen color depend on the quality of the monitor, the amount of
RAM in the computer system, and the monitor's graphics adapter card. Digital Video Inter-
face (DVI) is a video interface standard designed to maximize the visual quality of digital
display devices such as flat-panel LCD computer displays.
Companies are competing on the innovation frontier to create thinner display devices
for computers, cell phones, and other mobile devices. In its effort to gain an edge, LG Phillips
has developed an extremely thin display that is only .15 mm thick, or roughly as thick as a
human hair. The display is also flexible so that it can be bent or rolled up without being
damaged. This flexible display opens up some exciting possibilities for manufacturers to make
cell phones, PDAs, and laptops with significantly larger displays but without increasing the
size of the device itself, as the screen could be rolled up or folded and tucked away into a
pocket.
42
pixel
A dot of color on a photo image or a
point of light on a display screen.
Plasma Displays
A
plasma display
uses thousands of smart cells (pixels) consisting of electrodes and neon and
xeon gases that are electrically turned into plasma (electrically charged atoms and negatively
charged particles) to emit light. The plasma display lights up the pixels to form an image
based on the information in the video signal. Each pixel is made up of three types of light—
red, green, and blue. The plasma display varies the intensities of the lights to produce a full
range of colors. Plasma displays can produce high resolution and accurate representation of
colors to create a high-quality image.
plasma display
A plasma display uses thousands of
smart cells (pixels) consisting of
electrodes and neon and xeon gases
which are electrically turned into
plasma (electrically charged atoms
and negatively charged particles) to
emit light.
Liquid Crystal Displays (LCDs)
LCD displays
are flat displays that use liquid crystals—organic, oil-like material placed
between two polarizers—to form characters and graphic images on a backlit screen. These
displays are easier on your eyes than CRTs because they are flicker-free, brighter, and don't
emit the type of radiation that makes some CRT users worry. In addition, LCD monitors
take up less space and use less than half of the electricity required to operate a comparably
sized CRT monitor.
Thin-film transistor (TFT) LCDs
are a type of liquid crystal display that
LCD display
Flat display that uses liquid
crystals—organic, oil-like material
placed between two polarizers—to
form characters and graphic images
on a backlit screen.
