Have you ever wondered how an LCD TV works? Just what are liquid crystals, and how do they create the wonderful colour image we see on our screens?
LCD is short for Liquid Crystal Display. These tiny “liquid crystals” which make up the image are not really liquid as such, but their behaviour is more like that of a liquid than a solid. They are sort of a half-way point between the two states. They are solid in that they are able to stay in one place, but liquid-like in their ability to change shape.
When creating the image that you see on the screen, LCD TV screens use the same technology that is used to give polarising sunglasses their unique effect. A large bright light at the back of the screen projects light forwards. A horizontal polarising filter sits in front of this light, blocking any light waves that are not vibrating horizontally. This means that it only lets horizontal light waves through the filter.
The many tiny dots which make up the TV image comprise many tiny liquid crystals. A transistor sits behind each of these liquid crystals, controlling the amount of electricity that flows through them. Each of the liquid crystals is twisted, and a vertical polarising filter in front of them only lets vertical waves of light get through.
In response to electricity passing through it, the liquid crystal straightens out and blocks all light from going through. To let light through the crystals, the electrical current is turned off, causing the crystal to twist and therefore allow the light to bend through the filters and pass out the other side.
However, it is not just a case of turning the electrical current on or off. The voltage can actually be varied to produce 256 different shades of brightness. “But what about colour?” you may be wondering. This involves the use of three sub pixels for each dot of the image, one each for red, green and blue. By varying the intensity of brightness of each of these primary colours, any colour can be created on your LCD TV screen.
While this may all seem hugely complicated, it is all technology based on the very first generation of television. LCD televisions allow consumers to win back some space and decide the extent to which their TV dominates the room in which it is installed in their home.