LCD, which is an abbreviation of liquid crystal display, is not a strange word nowadays. LCD products are around us everywhere, entrance guard, mobile phone, watches, computers and many electronics.
LCD are used in TV screen as well. An LCD TV screen uses the sunglasses trick to switch its colored pixels on or off. At the back of the screen, there’s a large bright light that shines out toward the viewer. In front of this, there are the millions of pixels, each one made up of smaller areas called sub-pixels that are colored red, blue, or green. Each pixel has a polarizing glass filter behind it and another one in front of it at 90⁰. That means the pixel normally looks dark. In between the two polarizing filters there’s a tiny twisted, nematic liquid crystal that can be switched on or off (twisted or untwisted) electronically. When it’s switched off, it rotates the light passing through it through 90 degrees, effectively allowing light to flow through the two polarizing filters and making the pixel look bright. When it’s switched on, it doesn’t rotate the light, which is blocked by one of the polarizers, and the pixel looks dark. Each pixel is controlled by a separate transistor (a tiny electronic component) that can switch it on or off many times each second.
For many of us, the most attractive thing about LCD TVs is not the way they make a picture but their flat, compact screen. Unlike an old-style TV, an LCD screen is flat enough to hang on your wall. That’s because it generates its picture in an entirely different way.