COMPUTER SCREENS

Prepared By : Mohamed K. Mustafa

Introduced To : Mr. Ahmed Abu Mosameh

COMPUTER MONITOR

A monitor or display is an electronic visual

display for computers.

The monitor consists of :

o the display device

o circuitry

o enclosure

The display device in modern monitors is a Thin

film transistor - liquid crystal display (TFT-LCD)

. Older monitors use a cathode ray tube

(CRT).

SCREEN SIZE

The size of a rectangular display is usually

given as the distance between two opposite

screen corners, that is, the diagonal of the

rectangle.

The diagonal measurement of the rectangle is

equal to the diameter of the tube's face.

This method continued even when cathode ray

tubes {CRT} were manufactured as rounded

rectangles.

SCREEN SIZE

An example to show how the screen size can be calculated

PERFORMANCE MEASUREMENTS

The performance of a monitor is measured by the following :

1. Luminance is measured in candelas per square meter.

2. Viewable image size is measured diagonally. For CRTs, the

viewable size is 1  in (25 mm) smaller than the tube

itself.

3. Aspect ratios is the ratio of the horizontal length to the

vertical length. 4:3 is the standard aspect ratio

4. Display resolution is the number of distinct pixels in each

dimension that can be displayed.

5. Dot pitch is the distance between subpixels of the same

color in millimeters.

PERFORMANCE MEASUREMENTS

6. Refresh rate is the number of times in a second that a

display is illuminated.

7. Response time is the time a pixel in a monitor takes to go

from active (black) to inactive (white) and back to active

(black) again.

8. Contrast ratio is the ratio of the luminosity of the brightest

color (white) to that of the darkest color (black) that the

monitor produced.

9. Power consumption is measured in watts.

10. Viewing angle is the maximum angle at which images on the

monitor can be viewed, without distortion .

COMPARISON ‘ CRT ’

Adv.

• High dynamic range , excellent

color , low black level .

• No input lag

• Sub-millisecond response times

• Near zero color, saturation, contrast

or brightness distortion. Excellent

viewing angle.

• Usually much cheaper than LCD or

Plasma screens.

Disadv.

• Large size and weight

• High power consumption

• Geometric distortion

• Older CRTs are prone to screen burn-

in

• Produces flickers at low refresh

rates

CRT MOINTORS

COMPARISON ‘ LCD ’

Adv.• Very compact and light

• Low power consumption

• No geometric distortion

• Rugged

• Little or no flicker

Disadv.

• Limited viewing angle, causing color,

saturation, contrast and brightness

to vary , causing some distortion • Slow response times• Input lag • Dead pixels may occur during

manufacturing or through use.

LCD MOINTORS

COMPARISON ‘ PLASMA’

Adv.

• Compact and light.

• High contrast ratios excellent color,

low black level.

• High speed response.

• Near zero color, saturation, contrast or

brightness distortion

• No geometric distortion.

• Highly scalable, with less weight gain

per increase in size

Disadv.

• Large pixel pitch, meaning large screen.

• Flickers when viewed at close range

• High operating temperature and power

consumption

• Fixed bit depth

• Input lag

• Older ones may burn-in

• Dead pixels are possible during

manufacturing

PLASMA MOINTORS

PROBLEMS

o Phosphor burn-in

In older screens the phosphor layer of a CRT screen where it has

displayed a static bright image for many years. This results in a

faint permanent image 3:4 on the screen , even when turned off.

o Plasma burn-in

Burn-in is existing with early plasma displays , which are more

week to this than CRTs.

Screen savers with moving images may be used with these to

minimize burn.

PROBLEMS

o Glare

Glare is a problem caused by the relationship between lighting

and screen, or by using monitors in bright sunlight

o Color mis-registration

Most LCD screens , have mis-registration of the color channels,

that is, the centers of the red, green , and blue dots do not

line up perfectly.  

o Incomplete spectrum

RGB [registered] displays produce most of the visible color

spectrum, but not all. This can be a problem .

MONITORS USAGE

o Multiple monitors

More than one monitor can be attached to the same device. To

show the same image or each monitor can display a different

image.

o Multiple video sources

Multiple devices can be connected to the same monitor using a

video switch. It is designed to switch all of the user interface

devices for a workstation between different computers at once.

o Virtual displays

Much software and video hardware supports the ability to create

additional, virtual pieces of desktop, commonly known as

workspaces.

ADDITIONAL FEATURES

o Power saving Most modern monitors will switch to a power-saving mode.

This allows modern operating systems to turn off a monitor after a specified period

o Integrated accessories Many monitors have other accessories integrated. So no need

for another separate , camera , microphone , and speakers.o Glossy screen Some displays replace the traditional anti-glare matte finish

with a glossy one. The image is better . o Directional screen Narrow viewing angle screens are used in some security

applications .

ADDITIONAL FEATURES

o Auto polyscopic screen A directional screen which generates 3D images .

o Touch screen These monitors use touching of the screen as an input

method. Items can be selected or moved with a finger .

o Tablet screens A combination of a monitor with a graphics tablet. Such

devices are typically unresponsive to touch without the use of one or more special tools' pressure.

THANK YOU