Monitor technology

5 Monitor technology

Terminology

Aspect Ratio	The ratio of the width of a display screen to the height, e.g. 4 : 3
Bezel	The plastic or metal frame round a display screen
Brightness (Luminance)	The amount of light a LCD monitor produces in candela (cd) per square metre (m²), e.g. 250 to 350 cd/m²
Colour Depth	The number of bits used to give the colour of one pixel, and gives the number of different colours that can be displayed at one time, e.g.

• 1 bit depth gives 2 colours (black and white)

• 16 bit depth gives 65 563 colours that can be displayed

• 24 bit depth gives 16.8 million colours that can be displayed

Contrast RatioThe difference in intensity between the black and white on an LCD screen

• The higher the contrast ratio the better the detail

CursorA flashing marker on the screen which indicates where the next character is to be insertedDot PitchA measure of the sharpness or resolution of a screen

• DPM – dots per millimetre

• The higher the figure the better the resolution of the screen as the dots are closer together

LCDLiquid Crystal Display monitorMonitorA device very similar to a television, but which receives video signals directly from the computerNative ResolutionThe optimum resolution of a LCD monitor. If this is changed the image quality diminishes
Examples of native resolution:

• 17 inch screen = 1024 × 768

• 20 inch screen = 1600 × 1200

PixelPicture cell. A pixel is the smallest number of dots which can be used by a character on the display screenRefresh RateNumber of times the monitor is scanned by the electron beam per second

• The higher the refresh rate the less screen flicker

• A refresh rate of 85 Hertz means the screen is scanned 85 times each second

ResolutionThe number of ‘dots’ on a monitor screen defines the resolution of a system by describing the number of pixels horizontally and vertically, e.g. 1200 × 1200 gives a resolution of 1200 separate points horizontally and verticallyRGB InputThe colour input on a monitor. The signal from the computer is taken by the monitor as a basic Red, Green and Blue inputScreen SizeCathode ray tubes

• The diagonal measurement from the outer corners of the casing

Liquid Crystal Display screens

• The diagonal measurement from the corners of the screen

ScrollingThe movement of text or data on the display screen. Scrolling can be upwards, downwards or sidewaysThermionic EmissionThe release of electrons when a substance is heated

VDUVisual display unitViewing AngleThe maximum horizontal and vertical angle that a monitor screen can be viewed at to give a clear image with accurate colours, e.g.

• 120°

• 170°

VoxelA three-dimensional pixelInterlacingConsider one still picture on a cathode ray monitor (Figs 5.1, 5.2)

• The picture is made up of two fields which consist, in a 625 line system, of 312.5 lines each

• Each horizontal line is made up of minute dots (pixels)

• The picture is constructed by an electron beam scanning the tube phosphor from top left to bottom right in a series of horizontal lines

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