Plasma Display

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Definition

  • A plasma display panel is a type of panel display common to large TV displays 30 inches or larger. They are called ?plasma? displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent lamps.

First off, what is plasma?

  • In physics and in chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize (reduce the number of electrons in) its atoms, thus turning it into plasma. So basically plasma is ionized gasses which contain positive ions and negative electrons.

Characteristics of a plasma display

  • Plasma displays are bright (1,000 lux or higher for the module), have a wide color gamut, and can be produced in fairly large sizes?up to 150 inches diagonally. They have a very low-luminance "dark-room" black level compared to the lighter grey of the un-illuminated parts of an LCD screen (the blacks are blacker on plasmas and greyer on LCDs). The display panel itself is about 6 cm thick, generally allowing the device's total thickness (including electronics) to be less than 10 cm. Plasma displays use as much power per square meter as a CRT or an AMLCD television. Power consumption varies greatly with picture content, with bright scenes drawing significantly more power than darker ones ? this is also true of CRTs. Typical power consumption is 400 watts for a 50-inch screen. 200 to 310 watts for a 50-inch display when set to cinema mode. Most screens are set to 'shop' mode by default, which draws at least twice the power (around 500?700 watts) of a 'home' setting of less extreme brightness. The lifetime of the latest generation of plasma displays is estimated at 100,000 hours of actual display time, or 27 years at 10 hours per day. This is the estimated time over which maximum picture brightness degrades to half the original value.
  • Plasma display screens are made from glass, which reflects more light than the material used to make an LCD screen. This causes glare from reflected objects in the viewing area.

??????? How plasma displays work

  • A panel typically has millions of tiny cells in compartmentalized space between two panels of glass. These compartments, or "bulbs" or "cells", hold a mixture of noble gases and a minuscule amount of mercury. Just as in the fluorescent lamps over an office desk, when the mercury is vaporized and a voltage is applied across the cell, the gas in the cells forms plasma.
  • With flow of electricity (electrons), some of the electrons strike mercury particles as the electrons move through the plasma, momentarily increasing the energy level of the molecule until the excess energy is shed. Mercury sheds the energy as ultraviolet (UV) photons. The UV photons then strike phosphor that is painted on the inside of the cell. When the UV photon strikes a phosphor molecule, it momentarily raises the energy level of an outer orbit electron in the phosphor molecule, moving the electron from a stable to an unstable state; the electron then sheds the excess energy as a photon at a lower energy level than UV light; the lower energy photons are mostly in the infrared range but about 40% are in the visible light range. Thus the input energy is shed as mostly heat (infrared) but also as visible light. Depending on the phosphors used, different colors of visible light can be achieved. Each pixel in a plasma display is made up of three cells comprising the primary colors of visible light. Varying the voltage of the signals to the cells thus allows different perceived colors.
  • A plasma display panel is an array of hundreds of thousands of small, luminous cells positioned between two plates of glass. Each cell is essentially a tiny neon lamp filled with rarefied neon, xenon, and other inert gases; the cells are luminous when they are electrified through "electrodes?. A plasma display panel is an array of hundreds of thousands of small, luminous cells positioned between two plates of glass. Each cell is essentially a tiny neon lamp filled with rarefied neon, xenon, and other inert gases; the cells are luminous when they are electrified through "electrodes".
  • The long electrodes are stripes of electrically conducting material that also lie between the glass plates, in front of and behind the cells. The "address electrodes" sit behind the cells, along the rear glass plate, and can be opaque. The transparent display electrodes are mounted in front of the cell, along the front glass plate. As can be seen in the illustration, the electrodes are covered by an insulating protective layer.[23] Control circuitry charges the electrodes that cross paths at a cell, creating a voltage difference between front and back. Some of the atoms in the gas of a cell then lose electrons and become ionized, which creates electrically conducting plasma of atoms, free electrons, and ions. The collisions of the flowing electrons in the plasma with the inert gas atoms lead to light emission.
  • Every pixel is made up of three separate sub pixel cells, each with different colored phosphors. One sub pixel has a red light phosphor, one sub pixel has a green light phosphor and one sub pixel has a blue light phosphor.

Advantages and Disadvantages
Advantages

  • Picture quality - superior contrast , Wider viewing angles than those of LCD and Less visible motion blur, thanks in large part to very high refresh rates and a faster response time, contributing to superior performance when displaying content with significant amounts of rapid motion
  • Physical ? Slim profile, can be wall mounted, less bulky than CRTs

Disadvantages

Picture quality ? may suffer from burn-ins, phosphor may degrade over time, early models susceptible to ?large area flicker?, more noticeable screen-door effect when compared to LCD or LED TVs

Physical ? Generally do not come on smaller sizes than 37 inches, heavier than LCD and LED because of the requirement of glass to hold the gasses.

Other ? Uses more electricity, on average, than LCD TVs, performance suffers at high altitudes due to the difference between the external air pressure and the pressure of the gasses within the screen, High radio frequency interference output.

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