TV Technology Demystified

Demystified,Plasma Technology

Plasma TVs, the first TVs to have a thin, flat, “hang-on-wall” form factor, have been in use since the earlier 2000s, but in late 2014, the last remaining plasma TV makers (Panasonic, Samsung, and LG) discontinued manufacturing them for consumer use. However, many are still in use, and you may still be able to find one refurbished, used, or on clearance.

Plasma TVs employ interesting technology. Similar to a CRT TV, a plasma TV produces images by lighting phosphors. However, the phosphors are not lit by a scanning electron beam. Instead, the phosphors in a plasma TV are lit by superheated charged gas, similar to fluorescent light.

All the phosphor picture elements (pixels) can be lit at once, rather than having to be scanned by an electron beam, as is the case with CRTs.

All the phosphor picture elements (pixels) can be lit at once, rather than having to be scanned by an electron beam, as is the case with CRTs.

Also, since a scanning electron beam is not necessary, the need for a bulky picture tube (CRT) is eliminated, resulting in a thin cabinet profile.

Demystified,LCD Technology

Demystified,Taking another approach, LCD TVs also have a thin cabinet profile like a plasma TV. They are also the most common type of TV available. However, instead of lighting up phosphors, the pixels are merely turned off or on at a specific refresh rate.

In other words, the entire image is displayed (or refreshed) every 24th, 30th, 60th, or 120th of a second. Actually, with LCD you can engineer refresh rates of 24, 25, 30, 50, 60, 72, 100, 120, 240, or 480 (so far). However, the most commonly used refresh rates in LCD TVs is 60 or 120. Keep in mind that the refresh rate is not the same as frame rate.

It must also be noted that LCD pixels do not produce their own light. In order for an LCD TV to display a visible image, the LCD’s pixels have to be “backlit.” The backlight, in most cases, is constant. In this process, the pixels are rapidly turned on and off depending on the requirements of the image. If the pixels are off, they don’t let the backlight through, and when they are on, the backlight comes through.

The backlight system for an LCD TV can either be CCFL or HCL (fluorescent) or LED. The term “LED TV” refers to the backlight system used. All LED TVs are actually LCD TVs.

There are also technologies used in conjunction with the backlight, such as global dimming and local dimming. These dimming technologies employ a LED-based full array or edge backlight system.

Global dimming can vary the amount of backlight hitting all of the pixels for dark or bright scenes,

while local dimming is designed to hit specific groups of pixels depending on which areas of the image need to be darker or lighter than the rest of the image.

In addition to backlighting and dimming, another technology is employed on select LCD TVs to enhance color: quantum dots. These are especially “grown” nanoparticles that are sensitive to specific colors.

Quantum dots are either placed along the LCD TV screen edges or on a film layer between the backlight and the LCD pixels.

Samsung refers to their quantum-dot-equipped TVs as QLED TVs: Q for quantum dots,

and LED for LED backlight—but nothing that identifies the TV as an actual LCD TV, which it is.

For more LCD TVs, including buying suggestions, also check out our Guide to LCD TVs.