Rear Projection TV Systems
Rear Projection TVs project an image onto the screen from the back of the TV. It is a bit like having a miniature cinema inside your TV. The upside of this is that they are pretty cheap to manufacture, but the downside is that they have poor viewing angles and a big and bulky. Modern rear projection televisions are much smaller than older models, but they remain bigger and bulkier than the LCD and Plasma displays that are increasingly dominating the market. These modern rear projection televisions use one of two technologies; LCD projector or DLP (Digital Light Processing) projector.
LCD projector TVs project light from the back of the TV through liquid crystals that are manipulated by electrical signals to control how much light passes through them. DLP projection televisions use a digital micromirror device that is made up of a large matrix of mirrors. The mirrors are then rotated to control how much light is projected on the display. Colour is produced in one of two ways, either with a spinning colour wheel that has filters for red green and blue, or by using three separate chips, each of which produces the red, green or blue primary colours.
Rear projection televisions are generally much less expensive to produce than modern flat panel displays, either LCD or Plasma. DLP projectors in particular do an excellent job of producing deep blacks and accurate colours. They also have very good viewing angles. The major negative of rear projection televisions is their size. Although they have become slimmer in recent years, they are still generally larger, and in particular thicker, than LCD and Plasma televisions, and cannot be mounted on walls. This has made them less popular than other television technologies.