A type of display used for computer monitors (especially those found in laptops), as well as many other electronic devices such as fax machines, photocopiers, cellular phones, digital watches, video games, etc. Essentially, an LCD forms a picture by the selective absorption and reflection of light. Two light polarization filters enclose a group of liquid crystals. When light passes through the first polarization filter, it is polarized, or in other words the light rays are oriented in one particular direction. Each pixel of the display is controlled by the liquid crystals. When an electric field (produced by a transistor) is imparted to the crystals controlling the display of a pixel, it causes the liquid crystals to align, which then causes the light ray to pass unimpeded tghrough the crystal layer. When it hits the second polarization filter, it is absorbed and does not pass out of it. If there is no electric field imposed on the crystals, they cause the light ray to orient itself in the direction that will allow it to pass through the second polarization filter.
There are two varieties of LCDs. A passive-matrix display has one transistor that controls a whole line of pixels by itself. In contrast, an active matrix has one transistor per pixel, and consequently has faster screen updates and allows the display to be clearly viewed at wider angles. Active-matrix LCDs, however, are substantially more expensive and consume more power.