Liquid Crystal Display

A display technology using a thin layer of liquid polymers that can be used to transmit or block light according to whether a charge is applied.

Most personal mobile devices use liquid crystal displays (LCDs) to get a thin, low-power display.

The LCD is not the source of light; instead, it controls the transmission of light.

How It Works

  • A typical LCD includes rod-shaped molecules in a liquid that form a twisting helix that bends light entering the display, from either a light source behind the display or less often from reflected light.
  • The rods straighten out when a current is applied and no longer bend the light. Since the liquid crystal material is between two screens polarized at 90 degrees, the light cannot pass through unless it is bent.
  • Today, most LCDs use an active matrix display:
    • We use a transistor each individual pixel to control the transmission of light
    • For coloured display, we use three transistor switches at each point (RGB)


pixel = The smallest individual picture element

  • We use 8 bits for each of channel of a given pixel, which is why it ranges from 0-255. ()
  • Since we have 3 channels, RGB, we use 24 bits per pixel