Loads of people use touch screens. Few of them have wondered how it works, and even fewer have taken the trouble to check out how it actually works. In this post, I'll try to shed some light on how touch screens work.
Touch screens use electricity to work (like you didn't know already) and there are three main systems used to detect touch, which are: resistive, capacitive and surface acoustic waves.
Resistive
In this system, two thin resistive transparent layers, which are usually made of Indium Tin Oxide because it is transparent, are placed over the display, which are separated by a thin gap in between. Then, a scratch-proof insulating layer is placed upon the whole system, which is what you will be touching. Electricity passes through these two layers and when they come into contact, the exact location of the touch is figured out by the computer. The resistive system is the cheapest, but allows only about 75% of light from the monitor to pass through.
Capacitive
"Capacitance is the capability of a material object or device to store electric charge."[3]
A thin transparent capacitive film is placed over the screen. And when you touch the screen, some of the charge on the capacitive film flows into your hand. This disturbance in the charge in the capactive film is detected by the computer and the exact location of touch is calculated. The capacitive system allows about 90% of the light from the display to pass through. It is widely used in smartphone touch screens.
Surface Acoustic Waves
This system involves the use of sending transducers, receiving transducers and reflectors. The sending transducer generates ultrasonic waves (known as surface acoustic waves because they move on the surface) which travel along edges of the surface of the screen in the X and Y axes. The reflectors then reflect these waves onto the screen forming a grid. These waves are then reflected onto the receiving transducers by reflectors on the other end. When your finger the screen, the surface acoustic waves are absorbed by the finger and as this wave won't reach the receiving transducer, it is able to detect the exact location of touch. As there are no metallic surfaces on the screen, it allows 100% of the light to pass through.
I hope you liked the post and please feel free to suggest changes.
Regards,
Lightspeed (new here)
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