A touchscreen is a popular electronic device used to display information. A touchscreen functions by detecting the presence and location of a touch within the display area. The term 'touchscreen' is a direct reference to interaction with the display screen to perform tasks.
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Figure 1.1 - Touchscreen
The touchscreen allows you to interact with the information displayed without the use of a mouse or a pad. These displays can be attached to computers as well as to networks as terminals. They are popularly used in the design of many digital appliances including mobile phones, PDAs (personal digital assistants), satellite navigation devices, video games etc.
They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games.
Construction
A touchscreen can be built in various ways. The main focus is to:
Recognize one or more fingers that touch the screen.
Command interpretation.
Communicating as per the command.
There are four layers in the most popular techniques.
At the top, Polyester layer is coated with transparent metallic conductive coating on the bottom.
The backside of the glass has an adhesive layer for mounting.
Adhesive spacer.
The glass layer is coated with a transparent metallic conductive coating on the top.
When the surface is touched by a user, system is able to record the change in the flow of electrical current. The piezo-electric effect can be calculated with the Dispersive - signal technology.
Two infra red based approaches are present. In one of them, finger touch is sensed by an array of sensors and in the other, touching of the screen is recorded by the infrared cameras mounted at the bottom.
The system can recognize the commands by the user's touch.
Working
Touch screen monitors have become more popular as the rates have dropped down. Three fundamental systems used to identify the persons touch are:
Resistive system - This system is made of a normal glass panel covered with a conductive and resistive metallic layer. These layers are kept separated from each other with the help of spacers. On top of the entire set up, a scratch resistant layer is positioned. When the monitor runs, electrical current runs through the two layers. The two layers get connected when a user touches the screen. This creates a change in the electrical field. The computer can now calculate the coordinates of the point of contact. With the help of these coordinates, a special driver can recognize the touch and translate the touch for the operating system to understand. The resistive system is the cheapest as compared to other systems. For example, Nintendo DS uses resistive touchscreen technology.
Capacitive system - In this system, the electrical charge that is stored is positioned on glass panel of the monitor. Some of the electrical charge is transferred to the user when the user touches the monitor with the finger. This reduces the charge of the capacitive layer and gets deposited at the corner of the monitor. A relative difference in charge, thus occurs,at each corner of the monitor which is calculated by the computer. This information is transferred to the touch screen driver software. For example: Apple's iPhone, iPod Touch and HTC's T-Mobile G1. Compared to the resistive system, capacitive system transfers 90% of light from the monitor which can display a clearer image on the monitor.
Surface acoustic wave - This technology uses ultrasonic waves passing over the touchscreen panel. Two transducers, a receiver and a transmitter, are positioned on the x and y axes of the glass plate of the monitor to form the surface acoustic wave system. Reflectors are located on the glass in order to reflect the electrical signal from one transducer to another. The receiving transducer can recognize if the electrical wave was disturbed by a touch. Metallic layers are absent in wave set up. This allows 100% transfer of light in order to display a clearer image. Surface acoustic wave system is considered as the best system to display graphics in detail. This system is expensive comparatively.
As long as the two layers are connected in the resistive system, the touch can be registered for a long period. For the capacitive system, finger should be the conductive input to register the touch. For the surface acoustic wave system, the touch can be done with any object apart from hard objects.
Applications
Public Information Displays - The demand for touch screen has increased rapidly since the older generation find the touch screen easier to use. The public information displays appear as information kiosks, trade show displays, tourism displays and so on.
Retail Systems - Time is a major factor to determine the efficiency and effectiveness of transactions in certain conditions. The touch screen can increase the ability of software in terms of visual communication of options and decrease the time required to feed the information. These systems play a vital role in the field of seat and reservation systems, cash registers, order entry station by making the data entry process simple and quick.
Customer Self-Service - Waiting in queue or lining up for things can be avoided with the use of this technology. In order to improve customer service, self screen touch screen terminals are used at restaurants, stores and transportation hubs. Examples are ATMs, railway enquiry terminal, airport e-ticket terminals. This technology enables the customer to complete transactions by themselves which can help them save time.
Computer Training - In education systems, the speed of training can be increased by using this technology. The computer beginner's can find it easy to understand the use of this system for efficient training.
Industrial And Manufacturing - The integration of touch screen technology has increased in industrial parts and product manufacturing field. The high speed to feed data and easier way for visual communication has improved and increased the usage of this system when compared to the older data input systems.
History
Doctor Sam Hurst, the instructor of University of Kentucky launched the first Touch Sensor in the year 1971. This touch sensor was named Elograph and was patented by the University of Kentucky Research Foundation. In 1974, Sam Hurst and Elographics lauched a new touch screen incorporated with a transparent surface.
With the invention of the computer assisted learning terminal in 1975, the touch screens got recognition. Industries make use of touch screens for point of sale systems, ATM's, PDA's, kiosk systems in retail and tourist settings and many more.
During the period 1979-1985, light pen technology was used by a high end musical sampling and re-synthesis workstation named Fairlight CMI. With this technology, the user can provide and control sample and synthesis data and can have the right to use various menus within the operating system. Instead of light pen, Fairlight series III used graphics tablet.
HP-150 launched the world's first touchscreen computer. It had 9" Sony Cathode Ray Tube which was flanked by infrared transmitters and receivers. This touchscreen computer could detect the position of any non-transparent object on its screen.
Till now, the touch screens can sense only one point of contact at a time. Some touch screens required hard touching by the user to sense it.
Touchscreens and its controller based firmware are well liked by system integrators, display manufacturers, and chip manufacturers.
Advantages
Touchscreen devices have simple interfaces that are more instinctive. For example, iPhone.
Big screen makes it ideal for web browsing, viewing the picture and movies.
Touchscreen equipments have less buttons for operation.
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Figure 1.2 - Big screen for web browsing, viewing picture and movies
Disadvantages
The screen becomes filthy.
Big screens tend to have low battery life.
These screens cannot be read clearly in direct sunlight.
The touchscreen have very low precision because of virtual QWERTY keyboards.
Some interfaces require a stylus for operation which means using both hands.
Devices need to have immense computing power which will lead to slower the operations and shorten the battery life.
These devices are expensive as compared other devices.
