Liquid Crystal Display

LCDs are organic molecules, naturally in crystalline state, and they get liquified while excited by heat or E field. Crystalline state twists polarized light through 90º. Like light- emitting diode (LED) and gas-plasma technologies, LCDs permit displays to be much thinner than cathode ray tube (CRT) technology. LCDs get through much less power than LED and gas-displays because they work on the principle of blocking light rather than emitting it.

An LCD is made with either a passive matrix or an active matrix (a polysilicate layer provides thin film transistors at each pixel, permitting direct pixel access and constant illumination) display grid. The active matrix LCD is also called as a thin film transistor (TFT) display. The passive matrix LCD contains a grid of conductors with pixels located at each intersection in the grid. A current on the grid is sent across two conductors to control the light for any pixel. An active matrix has a transistor situated at each pixel intersection, requiring less current to control the luminance of a pixel. For this cause, the current in an active matrix display can be switched on and off more frequently, by improving the screen refresh time. For instance, mouse shall appear to move more smoothly across the screen.

Some passive matrix (Pixels are illuminated in scanline order like a raster display but the lack of phospherescence causes flicker) LCDs contain dual scanning, meaning that they scan the grid twice with current in the same time that it took for one scan in the original technology. Though, active matrix is yet a superior technology. As stated before, display devices utilizing CRT and LCD technology have to refresh the screen before the picture disappears.