How It Works — Touchscreens
Sitting at home with a broken phone during quarantine is a different kind of torture . Especially when you spend a lot of time on it (an unhealthy amount of time according to my mother). The fact that you had to get the screen replaced just a couple of months ago, thanks to your own clumsiness does not make you feel any better.
Whilst scouring the internet for Python programming tutorials , an interesting video popped up in my recommendations; ‘How Touchscreen Works In Simple Words’. One thing lead to another, it’s 2 A.M. and I’m in uncharted waters trying to write about something I just wrapped my head around.
The first touchscreen is considered to be invented by E.A.Johnson at the Royal Radar Establishment, Malvern,UK in the 1960’s . Dr.Sam Hurst of the University of Kentucky developed a touch sensor, the “Elograph” in 1971. In 1974 Dr.Hurst and the Elographics managed to develop a transparent touch screen and by 1977 managed to develop a device with a curved glass touch sensor interface.
In the decades that followed the technology was improved and utilized by companies of the likes of Hewlett-Packard with the HP-150 in the 1980’s , Apple and IBM in the 1990’s and Microsoft in the early 2000’s till the iPhone put the world on notice of this technology
In the simplest of terms, a touch screen is an input/output device which allows users to interact by touching areas on the screen. It primarily consists of 3 components .
- Touch Sensor : A clear glass panel with a touch responsive surface.Different types of sensor technologies are used to detect touch inputs. The sensors have an electrical current/signal going through it and contact with the screen results in a change in voltage or signal. This change is used to determine the location of the touch on the screen
- Controller : The component that connects the touch sensor with the device. The voltages/signals from the touch sensor are taken by the controller and converted into information that could be understood by the device
- Software Driver : The software that facilitates the smooth operation of the touch screen and the device. Through this a device’s operating system is directed on how touch event information sent from the controller is to be interpreted.
There are a variety of different technologies that are used to create touchscreens. Of those, Resistive Touchscreens and Capacitive Touchscreens are the most popular.
Resistive Touchscreens are one of the most commonly used types of touchscreens, initially developed by Dr. Sam Hurst in 1977. It is used in ATM machines and other Point of Sale devices. The screen consists of 2 layers that can conduct electricity, one of which is conductive while the other is resistive and are separated by spacers; tiny dots that keep the layers apart until there is contact upon the screen. An electrical current constantly flows through the 2 layers and once a user presses upon the screen, the two layers come into contact and the electric current changes ,the device software registers the change and carries out the relevant functionality accordingly. This type of touchscreen is very durable but can handle only one touch at a time.
Capacitive Touchscreens function differently to Resistive Touchscreens. There are 2 types of capacitive screens; Projective displays and Surface displays. A Projective display uses a tight grid of special sensor chips while a Surface display uses Sensors in the corners and a paper-thin film evenly distributed over the screen. Modern day mobile phones consist of Toughened Glass, Projected Capacitive Touchscreen and AMOLED Display. The projected capacitive touchscreen that senses the presence of conductive materials is made up of 2 transparent diamond grid patterns made from Indium Tin Oxide which acts as a conductor with an insulator layer in the middle. Simply put, when a finger or other conductive material touches the screen it disrupts the electric field leading to a voltage drop at the point of contact and the processor locates this and registers it as a touch. One reason as to why the phone does not respond to gloves is because clothes do not conduct electricity ( Check out How Do Touchscreens Work for a more in-depth analysis)
Other types of technologies utilized are Infrared Touchscreens where the display shines a grid of infrared rays in front of the screen. When touched, the device software can determine the suitable course of action. Surface Acoustic Wave Touchscreens sends acoustic waves across a clear glass panel with a series of transducers and reflectors. When a finger touches a screen, the waves are absorbed, causing a touch to be detected at a point.
References :
How Touchscreen Works In Simple Words
