Television Technologies

Television Technologies

How many of us truly understand the differences between LCD / LED / OLED and Plasma? Granted, a significant few only.

Here we will try to de-mystify a large part of some of the technological terms applied to television viewing, that is the screens.

LCD: 

LCD has been in widespread use since the early 1970s when it first appeared in digital watches. As its name suggests, Liquid Crystal Display is a fluid which has been sandwiched between two plates, and it changes when a current is applied to it.

We’ve had black-and-white LCDs for a few decades, but color LCDs are a lot more recent, however,  the technology is somewhat the same. As we all know, you need to press a button to read a watch in the dark, and an LCD TV is no different. It needs a light source because it emits no light of its own.

There are basically two common methods of backlighting in LCD flat panels: Cold-cathode fluorescent lamp (CCFL) and LED (light-emitting diode). CCFL used to be the most widespread method of backlighting for LCD TVs, and consists of a series of tubes laid horizontally down the screen. Fully backlit LCDs and Edgelit LCds exist.

However, with the advances LED televisions, the traditional LCD counterparts are now almost extinct, so there is little reason to know much more about LCD technology, but if your interest has been awakened, by all means look up references in some more authority sources like wikipedia. Certainly as far as the major brands are concerned, LCD now have better options. We however take the view that for secondary television needs (bedrooms, kitchen, guest rooms, etc) there are fantastic bargains around in LCD Tvs.

LED:

While the giant display in a sports stadium, for example, is made up of thousands of LEDs that are used to directly produce an image, “LED” TVs are actually LCDs. That’s right, they’re not LED TVs at all. These “so-called” LED TVs use a series of LED bulbs to light up the screen. Confused? Don’t be!

1. An LED TV is not a new kind of TV.

An LED TV is just an LCD TV that’s backlit with light-emitting diodes (LEDs) instead of standard cold-cathode fluorescent lights (or CCFLs). And though they became well-known recently with various ultrathin models, LED-backlit LCDs have been on mainstream store shelves since about 2007-2008.

Unlike plasma and OLED, which are emissive technologies where each pixel is its own discrete light source, LCD is a transmissive technology where each pixel has to be illuminated from behind, or backlit.

2.There are two LED backlight configurations

Initially, LED-based displays  were backlit by what’s referred to as a “full array” of LEDs behind the LCD, across the back of the panel–just like a standard CCFL backlight. But to create even thinner TVs, engineers needed to eliminate that extra layer of LEDs and move it to the sides of the display. With this form of backlighting, the LEDs are affixed to all four sides of the TV and light is projected inward to the middle of the TV via “lightguides.” These types of TVs are commonly referred to as “edge-lit” LED-based LCDs, and are by far the most common available today.

3. Each configuration may also offer “local dimming.”

Local-dimming LED backlights can dim or turn off individually as needed.

Most current LED-based LCDs with rear-placed, full-array LED backlighting feature a technology called “local dimming.” With local dimming, portions of the backlight can be dimmed or brightened independently when different areas of the picture get darker or brighter. For example, the LEDs behind the words in a credit sequence can illuminate while the ones behind the black background remain dim.

With standard CCFL backlighting and most edge-lit LED backlighting, the entire backlight dims or brightens at once

4. Edge-lit TVs are really thin.

The key benefit to an edge-lit LED-backlighting scheme is that manufacturers can make thinner TVs. However, the downside is that the backlighting isn’t quite as uniform.

5. LED backlighting of either variety doesn’t improve LCD’s  off-angle viewing.

Unlike with plasma, one of the big downsides to LCD TVs is that the picture degrades if you’re sitting off to the side or the TV is placed too high or low, based on your eye level.

6. LED backlighting is even more efficient than standard fluorescent backlighting.

It’s definitely true that LED backlighting can cut down on power use, and some LED-backlit LCDs are, inch for inch, the most efficient flat panels available. On the flip-side, standard fluorescent backlighting is getting more efficient itself.

On the other hand, it’s also worth noting that LCD TVs of both varieties continue to be significantly more energy efficient than plasma TVs.

7. LED backlighting will get better–but how much better is debatable.

Though it’s true that manufacturers’ backlighting schemes will continue to improve with time, we’ve heard from industry insiders that the real advancements will be in edge-lit technology. Engineers are trying to improve edge-lit backlighting to the point that it equals or even surpasses full-array LED backlighting.

One of the issues with full-array backlighting (that features local dimming) is that to truly perfect it would require 2.1 million LEDs to individually light 2.1 million pixels (in a 1080p TV). Adding that many LEDs simply isn’t cost efficient, and sources tell us that for the foreseeable future, engineers have maxed out the number of LEDs they can add to a panel without making the end product prohibitively expensive.

8. Top LED TVs can come close to the picture quality of the best plasmas, but they still have drawbacks.

LCD TVs have long been knocked for not producing the deep blacks of plasma TVs. Well, with the introduction of LED backlighting with local dimming, blacks on the best LED TVs can go toe-to-toe with the blacks on some of the best plasmas, and the picture is outstanding. Also, as noted, LED-backlit LCD TVs are more energy efficient than plasmas and weigh less. But off-angle viewing and picture uniformity remain a sticking point. With plasma, by comparison, you can sit to the side of the TV and the picture won’t degrade, and blooming and other uniformity problems are non-existent.

9. If you don’t have your picture settings correct, LED or non-LED won’t make a difference.

You can have the best HDTV in the world with the latest and greatest technology, but if it’s not set up correctly, it can look pretty run of the mill.  So, do try to get the settings configured professionally if possible.

OLED:

An OLED TV screen uses a new display technology called OLED (Organic Light Emitting Diodes). OLED televisions are brighter, more efficient, thinner and feature better refresh rates and contrast than either LCD or Plasma. OLED TVs deliver the best picture quality ever, so are the “real thing” today.

OLEDs are made by placing thin films of organic (carbon based) materials between two conductors. When electrical current is applied, a bright light is emitted. The OLED materials emit light and do not require a backlight (unlike LCDs). Each pixel is a small light-emitting diode, in fact. OLED TV panels offers several advantages over LCDs:

  • Faster refresh rate, better contrast and better color reproduction
  • Thin and light
  • Better viewing angle – almost 180 degrees
  • Greener: OLEDs use less power, and contain no toxic metals
  • OLED panels can potentially be made flexible and/or transparent.

As competition increases, no doubt the familiar Brands will have their OLED offerings very soon. Technology gets fascinating by the day.

 

PLASMA:

plasma display panel (PDP) is a type of flat panel display common to large TV displays 30 inches (76 cm) or larger. They are called “plasma” displays because the technology utilizes small cells containing electronically charged ionised gases, or what are in essence chambers more commonly known as fluorescent lamps.

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