Touch Screen: What Is It And How Does it Works?

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In late 20th century, no one believed the so-called touch screen technology. The technology which allows you to interact with any device by a mere touch of your fingertips. The  initial devices to come with this technology are HP series 100 HP-150 c which is said to be the earliest commercial touchscreen computer and IBM simon personal communicator. With an increase in the number of smartphone users, most of them using touch screen technology. One must be pondering how a touchscreen works?.

What is Touchscreen?

Touchscreen is an input device. Unlike other input devices like keyboard and a mouse, a touch screen is layered over a visual electronic display of a computer, for example, your daily smartphones, tablets and laptops. Some touch screens can be used only when the user uses a special glove or a stylus.

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Types of Touchscreen Technology

Generally a touch screen is sensitive to pressure it points the exact location in an X-Y graph form. There are mainly four types of touchscreen technology which are mainly

#1. Resistive

#2. Capacitive

#3.Surface Acoustic Wave

#4. Infrared

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Resistive Touch Screen Technology

Used in a majority of devices mainly in ATM devices lost it significance after Apple started manufacturing  devices using capacitive touchscreen technology.

Resistive touchscreen consists of two layers coated with Indium tin oxide also known as ITO and then spaced with the spacers. The upper layer is flexible since it is made up of PET (polyethylene). Current flows through both the layers. When the user touches the screen the upper flexible layer presses the bottom layer, as a result a change in current  gets noticed by the device  and its coordinates are detected. Which it parses into readable signals for the operating system  and the operating system then reacts to give an output accordingly.

Popular devices using resistive touch-screens are-  Sony Ericsson Satio, Nintendo Ds and Nokia N97.

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Capacitive Touch Screen

Capacitive touch screen works with anything that carries a charge which is opposite to how resistive touchscreen works. Since capacitive touchscreen doesn’t  use pressure it gets difficult to work if the screen is wet.

Capacitive touch screen is made up of a layer of insulating materials coated more precisely a glass with an electrostatic grid of tiny wire(wire being very thin  not visible to naked eye).

These are made up of copper or indium tin oxide. The wire layered below the glass of the monitor stores electric charge. This can be used by anyone who is carrying a charge including human.

When the user touches the screen a change in current is detected. Capacitive touchscreen use capacitors layered in a row and column grid to notice such electrical change. And give necessary input to the operating system to react accordingly. Also because of this multi-touch is possible. It transmits 90% of the display light to the monitor as compared to resistive technology which transmits 75% light.

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Surface Acoustic Wave Touch Technology

Surface Acoustic Wave touch Technology uses ultrasonic waves for detection of the point where a person has touched. This technology is often abbreviated as S.A.W. The device having this technology works on a simple principle similar to what bats use to detect their prey.

Surface Acoustic Wave touch screen consist of one glass panel with reflectors. Two receiving  transducers at the corner of the glass panel and two transmitting transducers.

The transmitting transducers emit ultrasonic sound waves travel over the panel surface which gets reflected and then received by the  receiving transducers.

If a user touches the panel surface the ultrasonic sound generated by transducer gets absorbed by the finger or in simple words the finger stops the saw travelling towards reflectors. Since these waves do not reach the receiving transducer the sensor will come to know which point was touched.

There are few cons to this technology these are, vulnerable to surface contaminates and water which might absorb saw  creating a snag in tracking  location touched by the user. It also requires soft touch inputs plus the sensor won’t outlast the display and periodic calibration is needed.

The advantage of this technology is pressure sensitive, durable glass construction and high transmission and optical clarity i.e, the resolution is high and visibility is excellent.

SAW touchscreen technology are generally used to build large touch screen-based displays. Such as Arcade gamings, Kiosks, medical equipment etc.

Infrared Touch Screen Technology

Similar to Surface Acoustic Wave technology but instead of ultrasonic waves. This technology works with the help of light.

Instead of using a glass surface or any other surface it uses frames. The led light and light receivers are situated on the opposite side of the frame.

When an object touches the screen the infrared light not visible to naked eye gets interrupted. Causing a drop in the signal received by the receivers or photo sensors. This information gets parsed into machine language readable by the operating system which gives output accordingly.

It is suitable for large screens. It does not require physical touch or electric interference because of which it is highly durable. The transmission of light in this touchscreen technology is 100% sine no film or glass surface is required.

This touch screen technology is generally used in factory automation and ATMs.

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