What Is A Flat Panel Display?

Flat panel displays are electronic displays that occupy a small volume, weigh little, and require modest amounts of power.

Major Types of Flat Panel Displays:

Liquid Crystal Displays (LCDs)

LCDs are, by far, the most commercially important flat panel technology because they are used  in notebook computers.  In 1998, around 11 million notebooks were sold.  Almost all (over 99 percent) of those notebooks had an LCD in it.

As their name suggests LCDs exhibit some properties of a liquid and some associated with a crystal. They flow like liquids and share much of a liquid's dependence upon temperature, stress, electric fields, and chemical environment.
LCDs can be subdivided into the following types:

Advantages:

Disadvantages:

 

Field Emission Displays(FEDs)

This technology is essentially a flat CRT with a thousand cathodes (emitters) per pixel eliminating thereby the long throw distance of the single scanning electron beam of the CRT. Most of the advantages of CRT image quality accrue, without the bulk or power inefficiency of the deflection system, and shadow mask.

Advantages:

Disadvantages:

 

Light Emitting Diodes (LEDs)

Display applications are classified either as low information content (where a limited amount of information is being displayed, refresh rates are slow, and the nature of information being displayed is predictable), or as high information content (where the opposite conditions apply). Broadly speaking LEDs, ELs, and VFDs are best suited to the former, while plasma and all types of LCDs are appropriate for the latter.
 
 

Plasma Display Panels (PDPs)

This Flat Panel Display (FPD) technology is based on the glow discharge that occurs when ionized gas undergoes recombination. Electrons are removed from atoms to produce ions, later recombining with the ions to release energy in the form of light.

Advantages:

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Electroluminescent Displays (ELs)

This technology is very similar to that of LEDs. However, ELs are doped (as a semiconductor) with specific impurities to provide energy states that lie slightly below those of the mobile electrons and those slightly above states inhabited by electrons bound to atoms. Impurity states are used to provide initial and final states in light emitting transitions.

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Vacuum Fluorescent Displays (VFDs)

A form of cathodoluminescent display that can operate at low voltages, since very thin layers of highly efficient phosphors are coated directly onto each transparent anode. These displays are limited to a matrix of widely-spaced phosphor dots, and are designed for use in low-information-content applications.

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Organic Light Emitting Diodes (OLEDs)

Relatively more recent in origin that the other flat panel display technologies, OLEDs use organic compounds as sources of light emissions.  They are quite similar in construction to inorganic EL displays in that they are thick films and are less expensive to construct than LCDs.  It is currently thought that OLEDs will not only be cheaper to make than TFT-LCDs, but that they will make possible the depositing of high-quality displays on plastic and/or flexible substrates.

The following are types of displays that are not flat panel displays that compete with FPDs in the overall display marketplace:

 

Cathode Ray Tubes (CRTs)

Cathode Ray Tubes are well established and form the basis for most displays commonly in use today. Their broad market acceptance is based upon their long-standing in the marketplace and low cost. However, CRTs are being replaced in a wide variety of markets because they require a large physical space in which to operate and comparatively large amounts of power.  People who use CRTs as computer monitors often switch to flat panel displays that have less "flicker" and give off less harmful electromagnetic radiation despite their higher cost.
 

Projection Displays

There are many kinds of projection displays.  One way of classifying them is in terms of the imaging source.  Many projection displays on the market use very bright, small CRTs as their imaging source.  Others use LCDs or digital light processors (DLPs) as their imaging sources.  Projection displays may project the image forward onto a flat wall or screen that is several feet or more distant from the projector (called "forward projection) or they may project the image onto a screen that is relatively close to the projector (called "rear projection").   Forward projection is used primarily in business and education for the presentation of computer and video materials.  Rear projection is used primarily in homes in large-screen televisions.

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