Monitors

COMP1260 > Hardware

Introduction Your computer monitor is one of the most important parts of your computer. However, many people don't think much about the monitor when they're out to buy a new computer. It is important to know about monitors so that you can find the right one for you. Monitors are the medium that allows you to see everything your computer can do. As the computer becomes a more integral part of everyday life (and increases in complexity), it is essential to have a good monitor, and to understand what it does. A top quality monitor will greatly enhance your computing experience. This article will explain some early developments with monitors. Then we will go into the two common types of monitors used today. It will also touch upon which type of monitor is best for you, and where the world of monitors is going.

...by students CRT Monitors and Magnets. Do not try this on your good monitor!! Little kids all over the world have taken a magnet to their parent's computer screen. The image gets distorted, if not completely lost and there is a lot of angry faces. Just in the middle of that deadline for that important project. Why does this happen? Well the magnet attracts the electrons in the screen of a CRT monitor causing them to be dispersed and not hit the screen where they should. This causes a rainbow of neat colors and distorted images How do you fix this? Removing the magnet is the first step to fixing this problem. Most monitors have a degauss button by the screen, which when pressed may help. If there is no button, it may be located in the monitor setup menu. If none of this works, a new monitor may be in your future. Now go find a old monitor and try it out!

Early Developments

Computers have come leaps and bounds since the 1970's - back then all we had were blinking green monitors. The developments at IBM noted below show the progress and early development of computer monitors. This will give you a brief idea of how quickly things moved along.

• 1981 - IBM introduced the first Color Graphics Adapter (CGA). It was capable of rendering only four colors and a maximum resolution of 320 by 200 pixels.
• 1984 - IBM introduced the Enhanced Graphics Adapter (EGA). It made great improvement over the CGA in terms of improving appearance and readability of text. It was capable of producing 16 colors and a screen size of 640 by 350 pixels.
• 1987 - A Video Graphics Array (VGA) display system was released and had a standard resolution of 640 by 480 pixels. Some of these are still in use today.
• 1990 - The Extended Graphics Array came into production and made great strides in the area. It produced 16.8 million colors or more commonly known as true color. It also had a improved resolution of 800 by 600 pixels. It could also do a larger 1024 by 768 pixel but only in 65,536 colors.

CRT Monitors

CRT Monitors look very similar to televisions sets. They are characterized by their very deep size. CRT stands for cathode ray tube projection. The monitor contains millions of tiny red, green and blue dots that glow their colour when hit with an electron beam. This beam travels across the screen to create a visible image.

Typical CRT Monitor

In a cathode ray tube, the actual cathode is a heated filament which is inside of vacuum created glass tube. The ray is a stream of electrons which is generated by an electron gun. The screen of the monitor is coated with phosphor, which is an organic material. It glows when struck by the electron stream. There are three ways to filter the electron beam in order to obtain the correct image on the screen. The first of the three is Shadow Mask. This techniques uses a thin metal screen filled with tiny holes that the electron beam passes through to focus on a single point. It uses the shadow mask to help improve accuracy of the election beam so that is strikes at just the right place. Any unwanted beams of light are blocked out. The second way is called the Aperture-grill method, and uses tiny vertical wires. The beam passes through a grill to illuminate the phosphor on the screen. The advantage to this approach is that it allows the screen to be flatter and causes less distortion. The third and final way is called Slot Mask. It is the least common of the three. Slot Mask is sort of a hybrid between the previous two methodologies. It uses vertical slot like the aperture grill, but on a setup like the shadow mask display. This design allows for a greater screen brightness.

CRT monitors are measured by the area you view information on and the plastic outside the screen.
So on a 19 inch monitor you may only get 17 inches of screen.

LCD Monitors

LCD stands for Liquid Crystal Display technology. This technology works by blocking varying amounts of light to show colors. Two pieces of polarized glass with a liquid crystal material between them. A light behind the first piece of glass shines through that first piece then through the liquid crystal material then past the second pane. While the light is shining through the two panes of glass an electrical current is aligning the liquid crystal molecules to change the amount of light shining through. The light that goes through the second pane of glass is what you actually see displayed on the monitor.

Typical LCD Monitor

There are two types of LCD monitors. The first type is active matrix technology. Tiny transistors and capacitors are arranged by a thin film transistor in a matrix on the glass of the display. In order to change a particular pixel, the row in which the pixel resides in turn on then a electrical charge is sent down that column. Since all the other rows are turned off, only that pixel is affected. The second type is passive matrix. A conductive metal grid is used to charge each pixel. Although this type is inexpensive compared the other to produce, it is rarely used because of the slow response time.

LCD monitors are measured by the area on which you view information only.
 So you get the full 19 inches you pay for.

Which one to choose

Each monitor has its pros and cons over other types of monitors. These are some of the differences:

• LCD monitors require less power than the power-hungry CRT monitors. A 19 inch CRT monitor typical uses about 100 watts of power while a LCD of the same size will consume about 45 watts. Because of this, LCD monitors also produce less heat.
• LCD monitors are a lot smaller and weigh less then CRT counterparts. Since LCD monitors can weigh more then half as a much they can be mounted on a wall, therefore saving even more space.
• LCD monitors are more adjustable, since they are able to tilt, swivel, mount on a wall or switch orientation from horizontal or vertical. CRT monitors are very fixed when it come to position.
• LCD monitors are more friendly to the user by causing less eye strain to the user. CRT monitors produce a harmful flicker and display text poorly.
• CRT monitors are less expensive than the newer LCD models but LCD technologies are coming down in price with time.
• CRTs shows colors better then LCD models. Although the difference was quite noticeable at first; the difference is become smaller with time.
• CRT monitors have a faster time to redraw the screen. However just like color representation, LCD monitors are getting better with time. The faster a screen redraws the less problems you have with ghosting and blurring.
• CRT monitors give you the ability to change screen resolutions very easily. LCD monitors have a harder time doing this.
• CRT monitors are bigger and there for more rugged and harder to damage then the comparatively fragile LCD monitors.

Two Heads Better Then One

As the old saying goes two heads are better than one, but is this really the case for monitors. Adding a second monitor is a great way to add more display to your computer. It makes viewing large spreadsheets easy. Also if you make on a web page you can see the results of your changes on the other monitor. Finally it is great for having two applications open such as when you are working on that essay and need a Word document and a Web browser open at once. All the additional technologies you need is a video adapter with two display outputs. Be sure to make sure that your computer supports the use of dual monitors, so you don't waste your money in case it doesn't. Common operating systems such as Windows XP, 2000, ME, and 98 all support dual monitors. If you want even more display, three monitors is a realistic option now a days.

New Technologies

The world of computer monitors is ever changing. Here are a few of the latest developments in the field:

• Touch Screen Monitors

These displays allow you to control the program you are working with by simply touching the screen. You can input information or navigate through programs simply by using a stylus. Infra-red sensors, pressure-sensitive resistors or electronic capacitors are just some of the ways of implementing this technology. The most common example of this is the tablet laptop, that a lot of professors use.

• Wireless Monitors

Use many different technologies in order to connect your computer to the monitor. It can be very similar to a tablet PC since the wireless monitors often have controls for web surfing or mouse movement. Some even have touch screen capabilities outlined above.

• DisplayPort Standard

This new technology works with both LCD and CRT display and supports protected digital outputs for high definition while providing an interface for this. The inventors want to enable support for a wider range of source and display devices. The audio and video signals will be sent over the same cable and have a smaller video connection so that it can connect to smaller devices such as notebooks.

• Organic Light-Emitting Diode

This technology uses thin film LED's that don't require a back light to operate. The LED's emit light when stimulated with a electrical current. They contain red, green, and blue lights which combine to form the desired color. Some advantages of this is less power consumption, less expensive manufacturing process, and the ability to bend the screen if need be.

• Surface-Conduction Electron Emitter Displays

This is similar to a CRT and uses electrons and a phosphor coated screen to create images. But instead of a deep tube with one electron gun uses tiny electron emitters and a flat panel display.

Terms To Know

Analog (VGA) Connection - Used for CRT monitors which require the signal to be a continuous electronic signal or waves.
DVI Connection - Keeps data in digital form from the computer to the monitor when using LCD monitors. They send pulses equivalent to 1's and 0's.
Bezel - The plastic or metal surrounding the screen on a LCD monitor
Contrast Ratio - The difference in light intensity between black and white on a LCD display. A high contrast makes it easier to see details.
Ghosting - A blurring of images caused by slower response time also called latency.
Luminance - The level of light put out by the monitor. Also called brightness.
Response Time - How fast a monitor can changed the colors of the pixels.
Stuck Pixels - A pixel that is either illuminated or not all the time irregardless of what the image that the LCD is displaying.
Native Resolution - The actual size of the monitor measured in pixels horizontal by pixels vertical.
Dot Pitch - The sharpness of a CRT monitor measured in millimeters (mm). The smaller the number, the sharper the image.
Refresh Rate - The number of times the image on a CRT monitor is drawn each second.
Aspect Ratio - The ratio of the horizontal size of the display area to the vertical size.

Futher Readings

• http://en.wikipedia.org/wiki/Computer_display
• http://simple.wikipedia.org/wiki/Computer_monitor
• http://www.bizrate.com/computer-monitors/buying_guides/basics.html

References

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