The monitor is an output device that displays images and text. Like any other component of the computer, it gets information from a data source. There exist several types of monitors: with tube (CRT), liquid crystal display (LCD) or plasma.
The CRT monitors are made from a tube having at one end an electrons coating. At the other end it has a screen with a phosphorus coating. It is based on the electrons bombardment on the screen, where the image is displayed as some points of different colors called pixels. When the phosphorus film is bombarded by electrons it emits light, but it is a very little light and therefore it should be bombarded continuously until the image is the one which should be presented to the viewer. A property of this process is called frequency.
Most monitors have a rate of about 70Hz which means that the screen presents 70 images per second. Or it can present, if you were watching a movie. Anyway, the human eye can’t distinct too many of those image movements and it is stressful for the eyes to put them to such a pain. This is seen especially in videos.
The CRT monitors are of two types: some based on bombs which distort the image slightly and others on the Trinitron technology, which are curved horizontally and vertically flat. The Trinitron offers a much better picture quality, but unfortunately their implementation cost more and thus they are much more expensive.
The LCD monitors generally have a poorer resolution than CRTs, but do not emit, nor consume too much electricity (about 5 watts compared to 100 watts as the tube monitors consume) which make them a bit more expensive. They are running on a different technology: a beam of light passes through special filters that turn into red, green or blue, and it directs electricity to each cell.
These cells contain three pixels that have the values red, green and blue (RGB). In general, flat-screen monitors are used in laptops, which occupy less space, but producers have taken this technology to other type of monitors and now the LCD monitors are made for desktops as well. The diagonal screen size for LCD monitors can reach up to 42 inches, while the CRT monitors stop at about 21 inches.
In general, the resolution on both monitors can be up to 1280×1024 pixels, with the mention that LCDs can go beyond this, reaching to 1600×1280 pixels and even more. The technology for the LCD screens is based on two major technologies: DSTN and TFT. The technology called DSTN (Dual Scan Twisted Nematic) uses multiple layers. The first is a piece of glass coated with a layer of metal oxide. The materials used are very transparent to maintain the image quality. Under this layer is one electrode which supplies the information needed. Then there is a small trench coat with liquid crystals that are aligned in the correct position, this position being changed frequently.
The colors seen on the screen are the result of filtering the beam of light through color filters. However, this process is slow and therefore a more rapid movement of the cursor on the screen or the watch of a video with a lot of movements in it may cause some troubles to the monitor in showing what exactly is happening.
Many companies have adopted the technology called TFT (Thin Film Transistor), which is based on an active matrix and has a good brightness and contrast, much like those seen on CRT screens. This technology uses a transistor for each color of each pixel. The responding speed is about 25ms.
The TFT monitors can be much thinner than DSTN, which makes them lighter. For a resolution of 1024×768, 2359296 transistors are used. They are arranged in one piece. The presence of any impurities can affect the whole system of transistors and so this could lead to big losses. This affects the price that is quite high.
Whether CRT or LCD, plasma or plastic, they all have something in common, they are two-dimensional. However the British in collaboration with major companies are developing new technology called HAD (holographic autostereoscopic display) screen that brings the real world in a three-dimension. The HAD is a simple conversion of LCD technology that replaces the light beam with an HOE (holographic optical element), which consists of two sets of horizontal bands each for every eye we posses.
Each eye sees a different image, which follows the 3D effect. Since this technology will be designed in 3D games, the producers decided to create a switch to go from 2D to 3D. This will be made by using a band and thus eliminating both eyes to see the same image.
The criterion of choosing a monitor or another consists in getting one that is compatible with video card and can support a good graphical mode: has a good resolution, a good restore rate and so on. If the monitor does not match the video card is possible that it will not show anything, or it can even be destroyed by this incompatibility. To choose a monitor, you should be informed about other properties except the resolution. These are: the energy consumption, the level of radiations emitted by them, the diagonal of the screen, the display type and price.
