How Does an LCD TV Work?

Basic Structure

A Liquid Crystal Display TV is made of two flat sheets of glass. These sheets are treated or "polarized" to allow certain wavelengths of light to pass through while blocking others. Because of this, the sheets are known as substrates. Between the substrates is a liquid crystal solution. A back light is shown through the rear substrate toward the viewer. Molecules of the liquid crystal shift by means of a varying electrical current. This causes them to become transparent in some areas and opaque in others, allowing certain wavelengths to pass through.

How Does an Active Matrix Display LCD TV Work?

The Active Matrix Display is the more common of the two types of LCD TVs because of its quick refresh rate. The front substrate is lined with a matrix of transparent, thin film transistors. While the general image is created by the manipulation of the liquid crystal medium, the detail is picked out by an array of pixels layered directly over the matrix. The matrix receives the video signal and switches on the appropriate transistor, which connects with each color pixel across the entire matrix, creating a picture. This configuration of lighted pixels remains the same until the next cycle occurs and a new configuration is sent electronically, creating the next picture. The speed at which this is done is called the refresh rate. Acting at a rate of more than 100 cycles per second, it's three times faster than traditional reel-film projectors.

How Does a Passive Matrix Display LCD TV Work?

This type of LCD TV is cheaper and easier to produce as it does not use a matrix of film transistors. Instead, it uses a lattice work of conductive metals to carry the electrical signal charge to the pixels. This method is imprecise as the metals are slower to carry a charge and only able to activate a larger number of pixels in any given area, resulting in a significantly lower resolution.