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Read the text and entitle each part. Write out all the terms connected with displays.






 

(1) ……

Displays often called monitors or screens are the most-used output device on a computer. They provide instant feedback by showing you text and graphic images as you work or play.

Most desktop displays use Liquid Crystal Display (LCD) or Cathode Ray Tube (CRT) technology, while nearly all portable computing devices, such as laptops, incorporate LCDs. Because of their slimmer design and lower energy consumption LCD monitors (also called flat panel or flat screen displays) are replacing CRTs because CRT-based displays are large, use a lot of energy, can flicker and emit electromagnetic radiation. However, annoying flicker can be eliminated by a high refresh rate. Refreshment rate is measured in Hz and shows how many cycles a beam makes to scan the screen. Since LCD displays hold the image in memory, the refresh rate is not critical.

 

(2) ……

The characters and pictures that we see on the screen are made up of dots. Resolution refers to the number of dots of colour, known as pixels (picture elements), contained in a display. A pixel is a combination of red, green and blue subpixels. Resolution is expressed by identifying the number of pixels on the horizontal and vertical axes. A typical resolution is 1024x768. If the number of pixels is very large, we obtain a high resolution and a sharp image. If the number of pixels is small, a low resolution is produced.

 

(3) ……

Two measurements describe the size of your display: the aspect ratio and the screen size. Historically, computer displays, like most televisions, have had an aspect ratio of 4: 3 – the width of the screen to the height is four to three. For widescreen LCD displays, the aspect ratio is 16: 9, very useful for viewing DVD movies, playing games and displaying multiple windows side by side. High definition TV also uses this format. The viewable screen size is measured diagonally, so a 19” screen measures 19” from the top left to the bottom right.

 

(4) ……

Inside the computer there is a video adapter or graphics card, which processes images and sends signals to the monitor. CRT monitors use VGA (video graphics adapter) cable which converts digital signals into analogue signals. LCD monitors use a DVI (digital video interface) connection.

 

(5) ……

Colour depth refers to the number of colours a monitor can display. This depends on the number of bits used to describe the colour of a single pixel. For example, an old VGA monitor with an 8-bit depth can generate 256 colours and a SuperVGA with a 24-bit depth can generate 16.7 million colours. Monitors with a 32-bit depth are used in digital video animation and video games to get certain effects.

 

(6) ……

An LCD is made of two glass plates with a liquid crystal material between them. The crystals block the light in different quantities to create the image. Active matrix LCDs use TFT (thin film transistor) technology in which one pixel has its own switch. The amount of light the LCD monitor produces is called brightness or luminance, measured in cd/m2 (candela per square metre).

A CRT monitor is similar to a traditional TV set. It contains millions of tiny red, green and blue phosphor dots that glow when stuck by an electronic beam that travels across the screen and create a visible image. To create different colours the intensity of the three electron beams is varied.

PCs can be connected to video projectors which project the image onto a large screen. They are used for presentations and home theatre applications.

In a plasma screen images are created by a plasma discharge which contains noble (non-harmful) gases. Plasma TVs allow for larger screens and wide viewing angles, making them ideal for movies.

Organic Light-Emitting Diodes (OLEDs) are thin-film LED displays that don’t require a backlight to function. The material emits light when stimulated by an electrical current which is known as electroluminescence. They consume less energy, produce brighter colours and are flexible – i.e. they can be bent and rolled up when they are not being used.

 


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