Monitor

A display screen used to present output from a computer, video camera, VCR or other video generator.

Another term for display screen. The term monitor, however, usually refers to the entire box, whereas display screen can mean just the screen. In addition, the term monitor often implies graphics capabilities.

There are many ways to classify monitors. The most basic is in terms of color capabilities, which separates monitors into three classes:

  • monochrome : Monochrome monitors actually display two colors, one for the background and one for the foreground. The colors can be black and white, green and black, or amber and black.
  • gray-scale : A gray-scale monitor is a special type of monochrome monitor capable of displaying different shades of gray.
  • color: Color monitors can display anywhere from 16 to over 1 million different colors. Color monitors are sometimes called RGB monitors because they accept three separate signals -- red, green, and blue.
  • After this classification, the most important aspect of a monitor is its screen size. Like televisions, screen sizes are measured in diagonal inches, the distance from one corner to the opposite corner diagonally. A typical size for small VGA monitors is 14 inches. Monitors that are 16 or more inches diagonally are often called full-page monitors. In addition to their size, monitors can be either portrait (height greater than width) or landscape (width greater than height). Larger landscape monitors can display two full pages, side by side. The screen size is sometimes misleading because there is always an area around the edge of the screen that can't be used. Therefore, monitor manufacturers must now also state the viewable area -- that is, the area of screen that is actually used.

    The resolution of a monitor indicates how densely packed the pixels are. In general, the more pixels (often expressed in dots per inch), the sharper the image. Most modern monitors can display 1024 by 768 pixels, the SVGA standard. Some high-end models can display 1280 by 1024, or even 1600 by 1200.

    Another common way of classifying monitors is in terms of the type of signal they accept: analog or digital. Nearly all modern monitors accept analog signals, which is required by the VGA, SVGA, 8514/A, and other high-resolution color standards.

    A few monitors are fixed frequency, which means that they accept input at only one frequency. Most monitors, however, are multiscanning, which means that they automatically adjust themselves to the frequency of the signals being sent to it. This means that they can display images at different resolutions, depending on the data being sent to them by the video adapters.

    Types of Monitors

     

    CRTs
    The most prevalent type of monitor today is the cathode ray tube (CRT). Despite its rather sci-fi sounding name, a CRT is the same as the picture tube inside your TV. They work by firing beams of electrons at phosphor dots on the inside of a glass tube. The phosphors in a CRT are chemicals that emit red, green or blue light when hit by electrons. These monitors are capable of multiple resolutions, give the best look to full-motion video and provide better control over color calibration for graphic artists.

    On the down side, they hog a lot of room and weigh more than several sacks of potatoes. You can get more compact CRTs called short-depth or short-neck monitors which are a couple of inches shallower than regular CRTs. Unless space is a primary consideration, most people buy a CRT display because they offer good performance at an affordable price.

     

    LCDs
    In the opposing corner are flat panel displays or LCDs (liquid crystal displays) commonly used in laptops and fast becoming popular as desktop monitors. Their major selling points are a slim profile and light weight. A CRT can be deeper than it is wide, whereas a LCD with a base is only about a handspan deep. No heavy lifting required with a LCD; they weigh less than half the average CRT. LCDs require half the power of CRTs and emit much less electromagnetic radiation which can interfere with other electronic devices.

    In the screen of a LCD monitor, each pixel is produced by a tiny cell which contains a thin layer of liquid crystals. These rod-shaped molecules bend light in response to an electric current. It's the same display technology that resides in your digital watch but more sophisticated.

    LCDs tend to be clearer than CRTs which can suffer from convergence or focus difficulties. Their improved clarity means that even small LCDs can display higher resolutions than the corresponding sized CRT. They also make small text easier to read. Unlike CRTs, LCD monitors have only one optimal resolution. At lower resolutions, the screen is redrawn as a smaller area or all the pixels in the image are blown-up to fill the screen. The latter solution can make images look jagged and blocky so be sure the resolution of the LCD is the resolution you want to use

     

     

     

     

     

    Other factors that determine a monitor's quality include the following:

  • bandwidth : The range of signal frequencies the monitor can handle. This determines how much data it can process and therefore how fast it can refresh at higher resolutions.
  • refresh rate: How many times per second the screen is refreshed (redrawn). To avoid flickering, the refresh rate should be at least 72 Hz.
  • interlaced or noninterlaced: Interlacing is a technique that enables a monitor to have more resolution, but it reduces the monitor's reaction speed.
  • dot pitch : The amount of space between each pixel. The smaller the dot pitch, the sharper the image.
  • convergence : The clarity and sharpness of each pixel.