The technology employed to convert electrical signals into images on a television screen has become a great deal more complicated and varied then it was back in 1959 when I opened my radio and television repair shop in my uncle’s garage. Back in those days, all we had was the good old bulky CRT (Cathode Ray Tube). It didn’t matter whether we were dealing with a black and white set or a color set, it still employed a picture tube whose operation was straightforward and easy to understand. It was simply a matter of the number of electron guns that were located in the neck of the picture tube, one if it was a black and white set or three if it was a color set. Those ole picture tubes were a lot easier to test then some of this newer technology because all we had to do was plug that old CRT into a tube tester and we knew within a matter of seconds if the tube was good or bad. Testing is not so easy with today’s modern display technology.
Flat screen tubes, LCDs (Liquid Crystal Displays), Plasma screens, and LPDs (Light Processing Displays) have replaced that heavy, curved screen CRT. There are still television made that employ our old friend the CRT but there’s coming a time in the very near future when the CRT display will be phased out all together. Laser technology is the new kid on the block but before we take a deeper look at that technology let’s look at the other technologies being used today the LCD and Plasma screen displays.
Plasma screens, like LCD screens are flat screen displays. The plasma screen replaced our old friend the electron gun with tiny gas filled cells that convert electrical charges into individual pixels (picture elements) that make up the picture you see on the screen. The phosphorous coatings on the plasma screen produce colors that are as near lifelike as possible, which was one of the qualities we loved about the older color CRT sets. Plasma screen colors are richer, more cinematic then the colors produced by a LCD screen. Like with all good things there are a few negative aspects to consider. Plasma screen displays are subject “burn-in” which can be a serious problem if you use your TV to play games involving stationary images. “Burn-in,” or permanent image retention, for those of you who may not be familiar with the terms is where a permanent image is burned into the screen’s phosphorous coating and is visible behind whatever image is being watched. This burned-in image is visible as a dark ghost image on the screen even when the set is turned off. Another problem with plasma screen displays is that it is possible for the gas-filled cells to lose their gas through leakage over time.
The LCD television set employs the same technology that has been used in calculators and other electronic devices. Simply put, they consist of liquid crystal sandwiched between positive and negative grids that control the charged conditions of the individual crystals. The charged crystals make up the individual pixels. LCD sets are lighter then the plasma screen sets, use less electrical energy then the plasma set, and are not subject to “burn-in,” but the negative is that the picture they produce appears less natural then the pictures produced by the plasma screen.
Digital Light Processing technology is different then either Plasma or LCD technology because it is employed in projection TV sets and not thin screen technology. In the original projection sets of yesteryear, three tubes were employed to generate red, green, and blue light signals. These individual beams were focused on a screen where they combined to form the picture you were viewing. DLP technology replaced the three tubes with a single very bright light source; because of this projection, sets using DLP technology became thinner too. DLP sets employ a special chip that produce the red-green-blue signals that strike the screen when the single, finely focused light beam strikes it. DLP sets produce an extremely clear picture, which makes them ideal for watching high-definition programming. Another advantage that they have over normal projection technology is that the viewing angle and distance isn’t as critical. The major problem with DLP sets is that they employ a very expensive mercury lamp as their single light source and this lamp has a tendency to burn out much sooner then the rest of the components that make up these sets.
Laser technology solved most of the problems and gives us the best of both worlds. Using a laser beam that can be even more tightly focused then the light beam used DLP technology we get a picture that equals that of the Plasma display in a display that is almost as thin and light as the LCD unit. Laser displays use plastic instead of glass so the displays are more durable and last longer. They also consume less electrical energy then any of the other display types.
When laser technology televisions finally hit the market they are supposed to be compatible, cost wise, with the top plasma sets currently on the market. The newest kid on the block will hit the ground running.
