The screen's microchipĬontroller figures out from this where exactly you touched theĪ surface-acoustic wave screen is a bit like an infrared screen, but your finger interrupts high-frequency sound beams rippling over the surface instead of invisible light beams. The sound beams and absorb some of their energy. Surprisingly, this touchscreen technology detects your fingers using sound instead ofĪre generated at the edges of the screen and reflected back andįorth across its surface. When your fingers move up close, they break invisible beams that pass over the surface of the screen between LEDs on one side and photocells on the other.
Infrared screens work just as well whether you use your finger or a stylus.Īn infrared touchscreen uses the same magic-eye technology that Tom Cruise had to dodge in the movie Mission Impossible. Pictured in our photo below) works this way. The touchscreen on Sony Reader ebooks (like the one The screen can calculate where you touched by seeing which beams you If you touch the screen at aĬertain point, you interrupt two or more beams. The LEDs shine infrared light in front of the screen-aīit like an invisible spider's web. Just like the magic eye beams in an intruderĪlarm, an infrared touchscreen uses a grid You affect the electric field that exists between the inner and outer glass. In a capacitive touchscreen, the whole screen is like a capacitor. Stylus (because the plastic is an insulator and stops your hand from affecting the Of touchscreen, they don't work if you touch them with a plastic Screen, you alter the electrical field by a certain amount that Layer conducts electricity and so does the outer layer, so effectively the screenīehaves like two electrical conductors separated by an insulator-in These screens are made from multiple layers of glass. So they make contact, a bit like an ordinary computer keyboard. When you press a resistive touchscreen, you push two conducting layers together A chip inside the screen figures out the coordinates Touch the glass and complete a circuit-just like pressing the key When you press on the screen, you force the polyester to There's a flexible upper layer of conducting polyester plasticīonded to a rigid lower layer of conducting glass and separated Resistive touchscreens (currently the most popular technology) workĪ bit like "transparent keyboards" overlaid on top of the screen. These are some of the main technologies: Resistive
Others can easily detect and distinguish more than one key press at Some can sense only one fingerĪt a time and get extremely confused if you try to press in two placesĪt once. To use more cunning tricks for sensing your touch-completelyĭifferent kinds of touchscreen work in different ways. Plastic or they'd block the view of the screen below. Obviously they can't use switches, membranes, and bits of Touchscreens have to achieve something similar to this on the surface on your computer Lines are electrical connections that allow tiny electric currents toįlow when the layers are pressed tightly together. The dots you can seeĪre places where the keys press the two conducting layers together. Insulating layer between them with holes in it. Them are covered in electrically conducting metal tracks and there's an There are three separate layers of plastic here. Photo: This is the sensitive, switch layer from
Rubber underneath each key make them bounce back to their original position,īreaking the circuit when you release them. A current flows between the layers and the computer Layer down towards the bottom layer so the two layers meet and touch When you press a key, you push the top conductor Separated by an insulating plastic membrane with holes in it. Layers of electrically conducting plastic Inside a keyboard, you'll find there are two In a bit more detail, here's what happens. TheĬurrent varies according to the key you press and that's how your You can find out about that in our article onĮssentially, every key on a keyboard is an electricalĭown, you complete an electric circuit and a current flows. Something about how an ordinary keyboard works first. To understand how it works, it helps if you know Like an invisible keyboard glued to the front of your computer How is a touchscreen different from a keyboard? How is a touchscreen different from a keyboard?.