How LCD Screens Work: Liquid Crystals & Pixels

Look at this text. It’s black on white. But your screen is actually a flashlight shining through window blinds. LCD = Liquid Crystal Display.

The Sandwich

1. Backlight: A bright white LED panel at the back.
2. Polarizer 1: A filter that only lets “Vertical” light waves through.
3. The Liquid Crystal: A layer of goo.
   • State ON: The molecules twist the light 90 degrees (Vertical -> Horizontal).
   • State OFF: The molecules do nothing.
4. Polarizer 2: A filter that only lets “Horizontal” light through.
5. Color Filter: Red, Green, Blue glass.

The Valve

• To make a Black Pixel, we apply electricity to the crystal. It untwists. The Vertical Light hits the Horizontal Filter and gets blocked. Darkness.
• To make a White Pixel, we turn off electricity. The crystal twists the light. It passes through. Brightness.

Dead Pixels

Sometimes, a transistor gets stuck. The valve is stuck Open (Bright Green dot) or Closed (Black dot). It’s a tiny mechanical failure in a sea of 2 million valves. Robots don’t care about screens, but they care about Polarization. We put Polarizing Filters on our cameras to remove glare from the shiny field tiles so we can see the game elements clearly.