How it works - LCD TV

After several unsuccesful attempts, I now have a simple answer to the question: How does an LCD TV work?

The reason I thought about getting to grips with an explanation of how LCD TVs work was a discussion with industry insiders about "Backlight" that left me wanting to find out more. The backlight is one of the critical bits of an LCD panel. But why? It's all down to the way that the picture is generated. Without wishing to over-simplify the technology, I'll try to explain it in layman's terms...

The TV's screen is an LCD panel, made up of several layers. A bright white light shines away at the back of the panel. Millions of colour filters sit in front of this light, each one acting as a single pixel. Changing the strength of these colour filters allows varying amounts of the backlight through the front of the screen and into the room. With all of the filters switched off, the screen shines bright white. With all of the filters fully on, the screen will go nearly black. There are three elements to each filter - one each for the red, green and blue light that makes up the white visible spectrum. Each of the three colours can be adjusted for each filter, allowing each dot on the screen to have a different colour and brighness at the same time.

To get an idea of the size of each pixel, a full high-definition TV has 1,080 rows of pixels in 1,920 columns. The brightness and colour of each of these pixels can be controlled separately by adjusting its colour filters, to create the full colour picture across the whole screen.

Television pictures are made up of a series of still images displayed one after another in quick succession, to give the impression of movement. Therefore it important that the pixels should be able to change colour and brightness very quickly. If they change too slow, any fast movement on the screen will look blurred, with a smeared edge behind the moving object. The speed with which the pixels can change colour and brightness is called the "refresh rate". The faster the refresh rate, the less blurry and smeared the picture. Top-range LCD TVs currently refresh in 4 milliseconds, but lower priced LCD TV's don't achieve this rate and often suffer from noticeable motion-blur as a result.