How does the touch screen work?
touch screen
The use of smart phones and tablets has spread in this era, and it has become an essential and vital part of our daily life. Many of us wonder how touch screens work, and how the phone responds and carries out the required command when touching a specific place on the screen, so we will present in a simple and clear manner how touch screens work.
We can define the touch screen as the transparent layer that is located above the display screen in smart phones and tablets, where hand movements or writing with the device's pen are sensed.
Touch screen components
- The top layer is made of polyester, and this layer is coated with a transparent conductive metallic paint.
- A layer of adhesive material, which is placed under the top layer, to fix it.
- The glass layer is coated with a transparent conductive metallic lacquer.
- A layer of adhesive on the back glass, in order to increase the volume.
Touch screen technologies
Resistivity technology
The resistive touch screen consists of an acrylic or glass layer, covered by two layers, one of which is a conductive layer, the second is a resistive layer, and there is an invisible separation between the two layers. The touch screen, when pressing on the screen with a finger, the conductive and resistance layers combine, allowing an electric current to pass over the touched area, then sending signals to the processor after converting these signals from analogue to digital, and then the processor translates the digital signals or data and appears on the screen in front of us.
Resistive touch screens have the advantage of requiring a stylus, needing forceful pressure on the screen to respond, and are cheap compared to other technologies.
Capacitive technology
The screen consists of a thin layer of oxidized tin, located on a glass slide, and there are four electrodes on the screen, which are connected to vibrating electrical circuits. The capacitance technology screen depends on the change in the electrical capacitance, as a result of the electrostatic field distortion when touching the screen.
When touching the screen or pressing with a finger, the tin layer absorbs the charge leaving the finger, and the electrodes transfer it to the oscillating circuitry, reaching the signals to the waveguide, and transmitting it to the processor to translate the data into output. This technology is more advanced than the resistance technology, and more responsive when touching the screen with a human finger.
Surface sound wave technology
It works with surface sound wave technology, and when you touch the touch screen with a finger or a stylus, an electric field is produced, and then these signals are transmitted to the control unit, and then to the processor to translate this data into output that appears on the screen. Although this technology is advanced, it is affected by external factors such as pollutants that form on its surface.
Infrared technology
This technology works by blocking the beams of light, as the screen is equipped with a panel of invisible wires, with photoelectric cells, a network of infrared rays, light and color-sensitive diodes. When the screen is touched, an electric field is created, which sends signals to the processor and subsequently transforms it into data that appears on the screen. The infrared technology is characterized by its high ability to withstand shocks and impacts.