Plasma television - Understanding the technology
Plasma screen technology is fascinating. It is by far the coolest name and - once you look at it in more detail - by far the most exciting technology. From an engineering point of view plasmas are almost as impressive as cathode ray. Some say they are an even bigger achievement.
Plasma screen, from the very beginning, were designed with television in mind. And this you can tell by simply looking at the result. A plasma looks like a television rather than a blown up laptop screen. Plasmas produce a vibrant colourful picture and crisp contrast. Since they are also fairly slim built they basically brought together the best from both worlds.
Manufacturers put great effort and considerable resources into developing and perfecting this technology. The ultimate goal was nothing less than to produce a big fat ass wide screen television that had the ability to make a middle aged man weep. They looked for nothing less than tears of joy from a bunch of men watching a match.
The engineers probably phrased it slightly different in their original proposal but let’s face it; a big screen TVs suitable for sporting events is the holy grail of modern television technology. And plasma delivers!
Plasma – as a word – is Greek and describes the fourth state of matter. Since it is quite important for the understanding of the technology behind plasma screens, let’s go into a little more detail.
Plasma is very similar to gas except that a certain number of particles are ionized; quite a portion actually. An ion - just as a reminder - is an atom where the number of electrons (-) is not equal to the number of protons (+). Ions as a result have a positive or negative charge.
This charge has quite an effect on the whole. Plasma responds rather strongly to electromagnetic fields. Much more interesting; because of an effect called "spontaneous emission" plasma emits visible and ultraviolet light. Plasma screens use that effect. In some ways they work on the same principle as fluorescent tubes except that they use noble gas.
In a plasma screen this gas is trapped in tiny little chambers that are placed between two glass plates. Three chambers – one is red, on is green, one is blue – make up a pixel. You can see where this is going.
There is more to these chambers though. They are filled with Neon and Xenon (some manufacturers add Helium as well) but the pressure is significantly lower than standard. That's for a very simple reason. Because of the "depression" in the chambers the in our next step required "reaction" can happen at a relatively low temperature. After all; you want your television to radiate light not heat.
The next step is quite important. To create a picture we need light. You can probably guess that at this stage the noble gas comes to play. In order
to produce light it has to be "stimulated".
This is achieved by something rather old-fashioned: a transistor.
Each chamber has its own transistor that "ignites" the chamber by basically ionising it. The gas turns into plasma, the spontaneous emission kicks in and ultraviolet light is produced. Ultraviolet light?
This bit is quite ingenious. UV light is invisible as you know BUT it has some interesting qualities to it. It is energy-rich for example and it causes a strong reaction in certain substances.
And from there it is surprisingly simple. The chambers are covered with different fluorescent substances (phosphor). The ultraviolet light reacts with the phosphor which then emits visible light.
The colour of this light is determined by the kind of phosphor in the chamber. And depending on how long you ignite the chamber the light is less or more bright.
You have got to admit that this is an awesome piece of technology!
The advantages of Plasma technology are obvious. Unlike LCD televisions the little chambers, filled with gas glow by themselves. They do not require an additional light source. When they are off there is no light.
Traditionally this meant that the contrast was much higher than LCD. Because of the screens actively emitting light rather than blocking it out the effective viewing angle is much wider. There is a problem though; Plasma screens are made of glass. In your average living room reflections from other light sources will determine where you can sit and enjoy the experience.
There is more bad news. LCDs have caught up as far as contrast and vibrant colours are concerned. And because the surface is matt it doesn’t reflect as much light from other sources such as windows.
Plasmas are also a bit more fragile and then there is the problem with image retention. Static pictures used over a longer time frame can result in ghost images. They are similar to the burn-in we know from CRTs. Plasmas are therefore less than ideal for displays panels and the likes.
It is true that with low resolution Plasmas (HD Ready) are more energy efficient that a LCD but with the arrival if LED technology even this is likely to changes. On top comes that with a Plasma you never really know how much energy it consumes. It depends on what you watch. Because of the design it is cheaper to watch a film noir than let’s say ice skating, where a lot of bright light is required.
The biggest pro for Plasma televisions from a manufacturers point of view seems to be, that they are cheaper to produce. Unless this is reflected at the price for the actual device though there is very little chance that the technology will survive long. LCD seems to be the thing of the future.
It is a shame. The technology behind the Plasma screens is astonishing and in many ways the more obvious for use in a television. From a manufacturers point of view it probably makes more sense to research and maintain one technology instead of two but as a consumer I feel a certain sense of loss.
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