Computers are a common part of the lives of most individuals. However, like the operation of many household appliances, computer desktop owners do not normally comprehend how their devices work. Visual display units or VDUs, are the monitor part of a desktop computer, which allow users to see the information they work with.
Three types of computer monitorsor visual display units are available. These are the LCD flat panel, the CRT or cathode ray tube monitor and the TFT-LCD monitor. CRT VDUs are enclosed in a large box-shaped casing and represent the older types of computer monitors that exist today. LCD, liquid crystal, monitors are flatscreen, thin visual display units that take up much less space than CRTs. In addition, the LCDs come in widescreen as well as standard screen models and can be designed with add-ons, such as Super Video Graphic Display Array and Digital Video Interface technologies. TFT-LCD monitors are thin film transistor monitors.
An electronic beam within the visual display unit consistently scans the screen and collects data from the memory. Display memory is then transferred into video signals and in turn, the video signals manipulate the electronic beam, affecting what is shown on the display. This type of scan is known as a Raster scan. Once the electronic beam has been altered, that beam focuses on the phosphorous material that coats the inside of the visual display unit, causing the screen to illuminate.
All electronic devices emit magnetic and electrical fields to some degree. Older visual display units that contain tubes inside the display screen have higher magnetic fields than flatscreen display units. Additionally, display units with internal tubes also emit low-intensity X-rays and non-ionizing radiation. Yet the radiation is quite minimal and not considered a health risk. Flatscreen display units, on the other hand, have no internal tubes and emit zero X-rays or radiation.
Visual display units come in a variety of sizes. Monitors are available in 15-inch, 17-inch, 19-inch and 21-inch styles. The size of the monitor is the size of the screen, not the size of the entire monitor. Fifteen-inch monitors are sufficient for casual computer users, while 17-inch screens are more acceptable for individuals that use their computers frequently. The 19-inch and 21-inch monitors, on the other hand, were created for individuals who use their computers for design and editing.