LCD television - Understanding the technology
LCD on paper was the last system to enter the market. While this is true for televisions it ignores the fact that the technology has been around for quite a while. LCD was originally developed for laptops and computer screens. The demands there are different from the television world but with multimedia application, streaming and computers being used as entertainment centres this slightly changed. Computer screens more and more had to cover the one area televisions have to be really good at: moving pictures.
It was only a question of time until someone would come up with the idea to use LCD in TV sets as well. First they had to overcome a few problems though.
LCD screens were hugely popular as computer and laptop screens. The biggest challenge with computer screens was always the prevention of burned in and ghost pictures. LCD by default was much better than CRT based screens but it had another big advantage: Size.
If you think about it, it’s quite obvious. Building a laptop would have been impossible without a flat screen. Why not use the advantage for pc screens as well? It took some developing and perfecting but eventually they did.
The combination of slim design, ever bigger sizes and the fact that manufacturers could now produce a proper flat screen, with proper corners made LCDs so popular they literally wiped CRTs off the market. That didn’t necessarily make them a good TV but this is where it started.
Let’s look at how they work then.
LCD stands for "Liquid Crystal Display" and that’s what they are. Liquid crystals are fascinating the least to say. Without going into too much detail; they are made of organic material and basically work as a light switch. It is quite simple really. A TV screen is made of thousand of these tiny little light switches. They are placed in front of a light source and let the light through depending on the demand.
If you go very close to your computer screen you can actually see them. Every single little pixel in a LCD screen is a liquid crystal and every single one of them is controlled by an electronic control unit. This unit controls the electrical charge that is send to the pixel. Depending on the charge more or less light is being let through.
So far our picture is only black and white. How do we get the colour?
The solution is surprisingly simple. In front of the liquid crystals are filters. They come in the three colours; red, blue and green. These are the three basic colours of the light spectrum (RGB). From combining red, green and blue it is possible to create every single colour a human eye can perceive.
There can only be one filter per pixel, in order to create a picture we therefore have to group three liquid crystals to get a colour pixel. Since these crystals are tiny this is no problem. Individual pixels are invisible to the human eye and that’s a trick colour CRTs relied in exactly the same way.
Summary: A LCD display needs a light source, liquid crystals and coloured filters. Depending on the electronic charge that is used different amounts of light are let through by the crystal. By adding red, green and blue filters and combining three pixels it is possible to generate any given colour.
This all sounds very simple and extremely cool so one could ask why bother with anything but LCD. Well, there are drawbacks and the biggest of them all is actually quite obvious.
The background light in an LCD is constantly switched on. Besides the energy that is being wasted it does present a big problem: How to generate Black?
Black is the absence of light and that’s quite difficult to achieve with a bright light source right behind a thin screen made of liquid crystals. As a result grey became the new black.
With computer screens this made no difference. There are very few scenarios where a computer screen has to display wide areas of black. Television is a different story. Manufacturers eventually found solutions but up until LED technology arrived power consumption and black were the two areas where LCD was no match for CRT and Plasma.
Another problem was speed. The crystals initially weren’t quick enough. With fast moving pictures this produced undesirable effects. No problem when you type a document but no good for gamers and fans of fast moving action. This was eventually addressed by manufacturing ever faster screens. We are now well below 5 ms refresh rate which is good enough by any means.
Once the main pain points were addressed LCD were introduced to the wonderful world of television. The black is not as black as with CRT and Plasma and some sport fans claim the screens are still to slow but generally speaking LCD was welcomed. The technology allowed ultra slim and robust TV sets and that to many people was more important than minor flaws in the display of black. All that this stage was missing was size and a competitive price.
Coming from the computer world LCDs weren’t exactly massive; at least by living room standards. While as a result LCD first broke in to the under-40-inch screens market. To establish it in the big screen section (where the money is) took considerably longer.
Since there in theory is no real limit for the size of such screen it was surprising. Apparently the lack of big screen LCDs was at least partly due to the difficulty of manufacturing them.
Because of the background light every single fault was immediately obvious. One single pixel that didn't work would ruin the entire screen. For a manufacturer this is a nightmare and even worse: costly. The bigger the size the bigger the loss.
It seems very much like they have perfected the manufacturing process. LCDs are now available in all sizes and at a competitive price. As a matter of fact; the price in our days is more determined by features than by technology which probably means that LCD will eventually do to the television market what it did to computer screens. It will dominate.
With the latest LED technology there simply is no reason to buy a Plasma. The only way back to Plasma would be the price and as it stands no company wnats to go down that route.
What is LED ?