How Projection Television Works

Projection TVs can have front- or rear-projection.

Enormous televisions and home theaters used to be a real luxury. But in the last few years, many people have started to view large screens with great pictures as necessary for watching TV and movies at home. Although old-fashioned cathode ray tube (CRT) TVs can provide a great picture, they can't support the screen size that people look for today. Projection TVs can provide a much bigger picture than CRT sets can, and front- and rear-projection models can suit a range of rooms and budgets.

In this article, we'll discuss the differences between front- and rear-projection TVs. We'll also explain the differences between the various types of projection TV technology and what to look for when you go shopping.

A good way to understand how a projection TV works is to compare it to a standard TV. A conventional television uses a cathode ray tube (CRT) to create a picture.

A CRT fires a beam of electrons at a phosphor-coated screen. Every time an electron comes into contact with the screen, that point, called a pixel, glows. Color CRT televisions use three electron beams and separate phosphors for red, green and blue. When you watch, you're looking directly at the surface that the TV uses to create the picture. That's why traditional CRT sets are called direct-view displays.

­ CRTs are very reliable and have good picture quality. But they do have one big drawback -- since the screen is made of glass, size is limited. The largest CRT screens measure about 40 inches diagonally. A CRT TV with a screen that size is deep, heavy and unwieldy.

That's the main reason for projection TVs. Even though some models can't rival the quality of a direct-view CRT set, they can be much bigger. Instead of using a direct-view setup, a projection TV creates a small picture and then uses a beam of light to display that picture at a much larger size. Next, learn about projection TV configuration.