LCD

•       Liquid crystal display.

•       The liquid crystal material has properties similar to solid.

•       In ordinary crystals molecules will be random but in liquid crystals they have a special pattern.

Construction

•       A liquid crystal cell is sandwiched between two glass sheets.

•       Glass sheets have transparent metal film electrodes.

•       Two thin polarizing optical fibers are placed on the surface of each glass fiber.

•       Commonly used type is twisted nematic cell.

 

Working

•       LCD twists the light passing through when not energized

•       This twisting allows light to pass through polarizers so it appears semi-transparent.

•       When energized the liquid molecules are reoriented so that no twisting occurs and no light can pass through.

•       The energized cell appears dark in a bright background.

•       It can also be manufactured to appear bright in dark background.

Types

•       Reflective type

•       Transmittive type

•       Transreflective type

Reflective

•       Relies on reflected light.

•       When not energized its just a reflective surface

•       When energized it does not allow light to pass and hence becomes dark in the bright background.

Transmittive Type

•       Allows light to pass when not energized.

•       When energized block the light and hence appears dark in the bright background.

Transreflective Type

Combination of reflective and transmittive type