The plasma TV or plasma display panel (PDP) is a type of HDTV that is growing in popularity, largely because of the quality of picture it provides. Its major advantages over other technology such as LCD TV are in the higher contrast ratio and brilliant color quality. There is also a minimum of motion blur which is great for viewing fast moving action on the TV screen. With the current MPEG4 compressed movies, this is an important consideration.
However, a plasma TV also has its own share of disadvantages, such as being bulky, fragile, and most importantly not functioning properly at high altitudes. There are several excellent resources throughout Bright Hub discussing plasma TVs. An article series called HDTV Buying Guide will help when choosing between an LCD TV or a plasma TV. Additionally, read Plasma vs LCD - Which is the Best? for more tips on buying an HDTV.
So, how does a plasma TV work?
How does plasma TV work ?
The core of the plasma TV or PDP’s operation boils down to two things, the plasma and the concept of cells. First let’s take a look at what a cell is like. As with any other display technology, the overall image is composed of a number of pixels. Each pixel is individually produced or displayed on the screen for each and every image. In plasma TV each pixel is produced by corresponding cells (in a monochrome display there will be one cell per pixel and in color there will 3 per pixel). Thus, depending on the screen’s resolution there will be many thousands of such cells which help in producing the image. For example in a standard 1080p display this means there will be 1920x1080 = 2073600 (over 2 million) pixels, which imply up to over 6 million cells.
In a plasma TV these cells are held between two plates of glass. Each individual cell contains gas - xenon, neon and helium. The figure below shows a color PDP with the 3 cells (one each for red, green and blue) forming a pixel. Behind the rear plate of glass and in front of the forward plate are electrodes, which are held in an insulating dielectric medium. The combination of electrodes – horizontal and vertical – causes the cells to be individually excited. In particular, a voltage difference is setup between the forward electrode and the rear one, causing the gas that is in the cell to ionize into a plasma.
Whenever a proportion of the particles of a gas are ionized it is said to be in plasma form. The gas conducts electricity in the plasma form. In a plasma TV the electrical conduction properties are used to excite the phosphor lining at the back of the plasma TV cell. Once the phosphor is excited it emits light of a certain color. The intensity or brightness of the light produced is controlled by a technique called pulse-width-modulation, whereby the pulse-width (amount of time that the current is applied) controls the individual cell’s perceived intensity. Also, by controlling the combination of the three cells, the desired color can be produced.
Picture Quality and Other Issues
Since plasma displays do not depend on blocking light (there is no backlight, such as in LCD), but produces light, this results in a PDP having darker blacks, and thus a higher contrast ratio. This contrast ratio in turn improves the picture quality. Similarly, because the cells produce light they are viewable over wider angles. PDPs are able to produce many times more colors than LCDs (68 billion vs. 16.7 million) and this leads to more accurate color reproduction, improving the picture quality further.