Many people are unsure as to what the difference is between LCD flat screen TVs and plasma TV sets. In fact it is only the screen and the way that the the image is created that is different between these two, and even between them and your big cathode ray tube TV : the rest is pretty much the same.
Let's look first of all at what LCD and plasma really are. Most people are acquainted with LCD from the display on their calculators but have never come across plasma before. So what is plasma? It has nothing to do with the clear fluid in the blood, but is a fluid of a sort in that it is a gas (which is technically a fluid).
The plasma in a TV screen is formed from neon and xenon gases that, when electrically charged, turn into what are known as ions. As the energy passes through this ionic cloud of gas they start moving faster and faster, and the negative and positive particles that make up the ionic gas become attracted to each other. When they collide they release a photon of energy. A photon is akin to a 'particle' of energy that is part particle and part wave.
This plasma is contained between two plates of glass with a tiny space between them. The inside surface of the plate that you view is coated with hundreds of thousand of tiny cells, each of which are coated with phosphor, a substance that emits light when hit by a photon. These can be excited to produce either blue, green or red light, and which are excited by the photon is determined by the energy of that photon.
The TV signal is converted to electrical energy that excites the photons of the plasma gases to specific energies according to the color of the original subject, and so excite the particular set of phosphor needed to produce the color. As red, blue and yellow can produce just about every other color of the rainbow, so red, blue and green do the same with photon sensitive phosphors.
On the other hand, an LCD (liquid crystal display) screen is totally different, and much more difficult to explain. To put it in simple terms, a liquid crystal is one that is more liquid than solid, and whose structure can be oriented by electromagnetic fields to either block polarized light or allow it through. Polarized light is light that is arranged so that its vibrations occur only in one plane, so that it is easily filtered.
Basically an LCD works by cells either allowing light through or not. This is colored by the use of red, blue and green filters in the front of each pixel, so that if light is passed through a pixel it is colored. If it is not passed through, then it is not colored. Therefore, both systems work through the use of the same three colors of light, just as the old cathode ray color TV does. With CTR the screen also contains red, blue and green phosphors, just as with the plasma screen, which are excited by a beam of electrons aimed at each specific pixel.
The choice between plasma TVs and LCD flat screen TVs depends on your specific needs that are beyond the scope of this article, but suffice it to say that each has its own merits and drawbacks, and whichever you choose will likely be a compromise. The situation will remain thus for many years since High Definition TV is not dependent on any particular system, other than it it is certainly not the old CTR, or Cathode Ray Tube TV.
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