Question: how does a screen/display work? how does touch screen work?

Daisy Shearer answered on 10 Nov 2020:

Great question. Originally, screens were made of something called a cathode ray tube. These screens were super bulky and were basically a vacuum with electron guns that were directed at a phosphorescent screen which made the image. But now we have much more advanced types of screen– usually liquid crystal display (LCD). LCDs have a panel made of something called a liquid crystal which is illuminated by a backlight. The liquid crystals switch pixels in the screen on and off using light polarizing properties– their properties can be controlled using electrical current. If a pixel is lit up, then it is coloured using a red, blue or green filter. The combination of the pixels gives you the image on the screen.

Touch screens are really fascinating! There are quite a lot of different types, so I’ll just explain the most common types. Resistive touch screens are basically two layers of material which are separated until you touch it with your finger. When you do this, the top layer bends to touch the bottom layer, causing a change in the current of the bottom layer. This is detected and the co-ordinates of your touch are sent to the device where it will carry out whatever function is needed. There are also capacitative touch screens (which are becoming more common) where your finger completes an electrical circuit which causes a voltage drop at that point which can then be detected. These types of touch screen don’t work when you’re wearing gloves because you need something conductive to complete the circuit like your finger.