Liquid-Crystal Display (LCD)

  Flat-screen technologies now dominate. The liquid-crystal display (LCD) screen is an example. It has individual cells containing a liquid crystal to create each pixel. The pixel matrix is illuminated by back-lighting and each pixel can affect the transmission of this light to create the on-screen display. The back-lighting is usually provided by light-emitting diodes (LEDs). Polarised light is directed towards the pixel matrix and a further polarizer is placed between the pixel matrix and the screen. If a voltage is applied to an individual pixel cell the alignment of the liquid crystal molecules is affected. This changes the polarisation of the light and so changes what is displayed on the screen. 

A liquid-crystal display (LCD): a screen back-lit by light-emitting diodes and with liquid crystal cells sandwiched between polarisers