We're all familiar with the common cathode-ray tube (CRT) technology that has been the backbone of television for decades. Inside each CRT, an electron gun similar to a laser fires a negatively charged beam of electrons at groups of gas molecules (the pixels), which causes them to change color; producing the pictures we see everyday. These televisions work well and produce very crisp pictures, but they are notoriously bulky and heavy. This is because as the screen gets larger, the electron gun must be moved farther back so that it has a good angle to hit every pixel with its beam. Thus, the larger the screen, the deeper the TV. Enter the plasma flat panel television. Arriving with the turn of the millennium, these televisions come in large, widescreen models that measure only 6 or 7 inches deep; a huge improvement over CRT. This dramatic change in shape results from individual transistor electrodes at each pixel. We no longer need the laser to hit every inch of the TV and, without the laser, manufacturers can eliminate most of the traditional bulk. The individual pixels in a plasma TV are composed of 3 fluorescent light cells: one red, one blue, and one green. The television produces pictures by varying the intensity of each cell to produce a unique color at every pixel without a laser. These lights give the television its name because they contain free flowing ions called plasma. The plasma, when hit with an electrical charge, produces light. Traditional CRTs used the electron gun, or laser, to charge each pixel and create colored light. Plasma TVs instead have two sets of electrodes, one set running vertically and one set running horizontally. The horizontal set, which runs across the front of the screen, and the vertical electrodes, which run across the rear of the screen to form a grid like a checkerboard. The computer, by sending specific charges through a single vertical and a single horizontal row, can color one pixel of plasma at a time. When the various sub-pixels are charged, the gas molecules inside release light particles called photons. The problem here is that photons are typically in the ultraviolet spectrum, and invisible to the naked eye. However, as they are released, they strike the surrounding surface of the cell. These surfaces have been specially coated with phosphors. A phosphor is a chemical that produces light, but only after being hit by another source of light. So, the invisible, ultraviolet photons strike the phosphor, creating a spectrum of light that our eyes can see. Depending on how the three sub-pixels are charged, we may see a greener, redder, or bluer shade. These primary colors may combine to produce one of a million different colors. If you think about the basics of this technology, each light cell is a miniature fluorescent light. This produces the brilliant, flicker-less picture we see when we watch a plasma television. Now you understand the technology behind the plasma flat panel television. To make longer: expand on the cathode ray's need for space. |
