by J.R. Powell

Created on: February 25, 2007   Last Updated: May 04, 2007

How high definition TVs work:

There are different types of high definition TVs, and each work slightly differently.

* LCD

An LCD TV has a layer of liquid crystals between two layers of polarised glass. A backlight shines through the liquid crystals, and through colour filters to create a full colour image.

* Plasma

A plasma screen is made of tiny chambers of gas . When given an electric charge, they turn into plasma, giving off light. This excites the phosphors in the chambers, giving off coloured light. A group of 3 chambers (for red, green and blue) makes up a single pixel on the screen.

* CRT

There are very few CRT high definition TVs. The ones that do exist work on the same principle as standard definition CRT TVs. An electron gun hits RGB phosphors to create a full colour image on the screen.

LCD Rear-Projection TVs

The TV picture is split into red, green and blue and sent to three different LCD panels. These 3 are then brought together and projected onto a screen.

DLP Rear Projection TVs

These use a spinning colour wheel and tiny mirrors. Their disadvantages include a 'rainbow' effect caused by the spinning colour wheel, noise from the cooling fans and the need to replace the projection bulbs).

A future potential future HDTV system is SED. This stands for surface conduction electron-emitter display. This is a fixed pixel display (as with LCD) but has many similarities to CRT displays. Unlike CRT, it has a separate electron emitter for each pixel.

My recommendation for a current HDTV would be a high quality LCD. This is because they don't suffer from screen-burn like Plasma TVs can. LCD TVs can also produce brighter images. Though LCD TVs can suffer more problems with motion than Plasma TVs. I would suggest viewing a demonstration of the HDTV you want before buying. I would also check that it is fully HD ready, it's picture resolution and that it has all the connections and features you may require (such as a digital tuner, 7-day episode guides, multiple HDMI sockets, etc).

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