• 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
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