LCD Screens ‘How it works?’

LCD ScreensOutput devices LCD Screens Liquid crystal display (LCD) screens are visual display units. An LCD is made up of an array of pixels or picture elements. An Array of pixels (liquid crystal display) Each pixel contains red, blue and green

LCD ScreensOutput devices LCD Screens There is a back light that shines through the pixel creating an image. Back light shines through pixels (usually lit from bottom of the monitor) Each pixel contains red, blue and green An Array of pixels

LCD ScreensOutput devices LCD Screens Different combinations of red, blue and green are used to change the image. Back light shines through pixels Each pixel contains red, blue and green An Array of pixels

LCD ScreensOutput devices LCD Screens The pixels are positioned between two polarised grills. Direction of light Two polarisation filters or grills that are orientated 90 degrees to each other. Filter A Filter B

LCD ScreensOutput devices LCD Screens The pixels are positioned between two polarised grills. The polarised light must rotate through 90 degrees to pass through the other filter. Filter B Filter A Light twisting through 90 degrees

LCD ScreensOutput devices LCD Screens Here are the pixels between the polarised grills. Back light shines through pixels The liquid crystals twist the light through 90 degrees Two polarised grills Light shines through This allows the light to pass through filter B. Filter B Filter A

LCD ScreensOutput devices LCD Screens An electric current is applied to the crystals. Back light shines through pixels Two polarised grills An electric current is applied to the crystals Light shines through

LCD ScreensOutput devices LCD Screens When an electric current is applied separately to the red, blue and green crystals, the amount of twist in each one can vary the intensity of each and the final colour output. Back light shines through pixels An Array of pixels Two polarised grills. An electric current is applied to the crystals. Light shines through. The electricity passes through the crystals and changes how the crystals react, allowing some light and blocking other light.

LCD ScreensOutput devices LCD Screens The electricity passed through the crystal, controls whether red, blue or green is output depending on the voltages applied to each crystal. Back light shines through pixels Two polarised grills An electric current is applied to the crystals Light shines through

LCD ScreensOutput devices LCD Screens The diagram below shows an individual crystal, made up of red, blue and green light. In reality these are very small. Electricity controls the colour twist and the amount of each light let through. Red, blue and green crystals sandwiched between two polarised filters RedBlue Green

LCD ScreensOutput devices LCD Screens How it works: Made up of an array of pixels with red, blue and green light or picture elements. A backing light shines through the array of pixels that show different amounts of red, blue and green light. The array of pixels are sandwiched between two polarised grills. When a current is applied to each crystal, the red, blue and green light is twisted at different degrees, combining to make different colour pixels of light. The combination of mixing/blocking light forms the picture.

LCD ScreensOutput devices LCD Screens Advantages: Smaller and lighter than equivalent CRT. More energy efficient than CRT. Disadvantages: Viewing angles can be smaller than from a CRT. Dead pixels can be a problem with LCD Screens.