How-it-Works Plasma Display Technology

An easy-to-follow explanation


Plasma televisions have been around for consumer use since 2003, yet there still remains a lot of consumer confusion about what plasma display technology is really all about.

If you would like to know more on the subject, here is a short easy-to-follow article that describes the basic operational principles behind flat-panel plasma TV technology.

Panasonic VIERA 55-inch TC-P55ST60

Since the first plasma TVs appeared on the market less than a decade ago, a lot has changed in plasma display panel technology. The plasma TVs of today are more robust, less prone to burn-in, more energy efficient, thinner—some are just an inch-thick—and equally important, they are capable of a superior picture.

It is thus no surprise that plasma display technology represents by far the most popular display technology among videophiles and home theater enthusiasts looking for the best cinematic picture over large screen TVs.

The reality is that if you want the best in overall picture performance, a plasma display can deliver the best shade of black among flat-panel televisions, including the latest and more expensive LED TVs.

Black-level performance is a most important aspect in picture quality as it helps improve the realism of dark scenes while making colors look richer and more saturated.

The only display technology that may eventually surpass plasma in terms of picture quality and overall performance is OLED. But OLED represents an extremely expensive display technology, and one that still has to prove itself especially in the long term color stability despite claims by OLED TV makers that the new technology is now ready for the consumer market.

In this respect, we still say that plasma display technology will remain the king of the big screen HDTV for a number of years to come, at least till the new technology proves itself over time and prices of OLED TVs become more within reach of the average household budget.

In this article, we explain the technology that makes this display technology so much capable of a superior picture performance.

Plasma Display Technology Explained

A Few ‘Electron Physics’ Basics First!

By definition, plasma is a state of matter (gas) where atoms are ionized by adding energy; in this case electrical energy is added by applying a voltage between two electrodes, which then leads to the flow of an electric current. In the process, positive and negative charged particles move fast towards the respectively opposite charged electrodes.

During this fast flow of particles, numerous collisions take place between electrons and atoms. These collisions cause electrons in an atom to jump to a higher energy level. However, it will soon fall back to its original energy level while releasing the extra energy in the form of a light photon.

The photon is that elementary particle responsible for all electromagnetic phenomena; it carries electromagnetic radiation, from gamma to radio. If it falls within the light spectrum, visible or otherwise, it is called a light photon.

The released light photons are in effect ultraviolet photons, meaning that the emitted radiation is invisible to the human eye. Ultraviolet light photons can be used to produce visible light by exciting phosphor atoms. Phosphors are substances that give off visible light photons when their atoms are hit by ultraviolet photons. The collision causes electrons to jump to a higher energy level; this energy is then released in the form of a visible light photon when the electron returns to its normal energy level. Different phosphor formulations yield different colors of light.

How does all this apply to a Plasma Display?

In a plasma display, electricity is used to excite the gas atoms inside the miniature cells forming the display panel; this in turn releases ultra-violet photons. The radiated UV causes the phosphor lining on these minute cells to emit energy in the form of visible colored light – the color of which depends on the type of phosphor used to line the cell.

 

Each of these cells is further sub-divided into three sub-cells as will be explained further on, each representing one of the primary light colors (click on the image for more details).

Sandwiched between the glass-plates are long electrodes on both sides of the cells. The address electrodes sit behind the cells along with the rear glass plate while transparent display electrodes sit in front of the cells covered by a protective layer along the front glass plate.

When a voltage is applied between the plasma display electrode and the respective address electrode, an electric current flows through the gas in the cell; this simulates the gas atoms to release ultraviolet photons. This ultraviolet radiation excites the phosphor lining on the inside wall of the cell – giving off energy in the form visible light.

The phosphors in a plasma display are arranged to give off colored light—red, green or blue—to build a color image. As already indicated earlier on, each picture element in a display panel is made up of three sub-pixels—each acting as a miniature light source, one for each of the primary light colors.

These colors blend together to create the final color of the pixel; this is very much the same with the way colors blend in CRTs and LCDs.

Pixel Brightness: The pixel brightness in a plasma display is controlled by using pulse-width modulation techniques. This means that by varying the duration of the voltage pulses applied to the sub-pixel electrodes several thousand times per second, it is possible to control the intensity of the resultant current pulses flowing through the individual cells.

This in turn energizes each sub-cell phosphor at different levels to generate increased or decreased intensity of colored light in line with the picture content. This makes it possible for plasma displays to generate billions of different shades of colors, leading to extremely accurate color reproduction and smooth film-like image.

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