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Touch screen

Touch Screen

Touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touch or contact to the display of the device by a finger or hand. Touchscreens can also sense other passive objects, such as a pen. However, if the object sensed is active, as with a light pen, the term touchscreen is generally not applicable. The ability to interact physically with what is shown on a display (a form of “direct manipulation”) typically indicates the presence of a touchscreen.

The touchscreen has two main attributes. First, it enables one to interact with what is displayed directly on the screen, where it is displayed, rather than indirectly with a mouse or touchpad. Secondly, it lets one do so without requiring any intermediate device, again, such as a stylus that needs to be held in the hand. Such displays can be attached to computers or, as terminals, to networks. 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.

Touchscreens are popular in heavy industry and in other situations, such as museum displays or room automation, where keyboard and mouse systems do not allow a satisfactory, intuitive, rapid, or accurate interaction by the user with the display’s content.

Historically, the touchscreen sensor and its accompanying controller-based firmware have been made available by a wide array of after-market system integrators and not by display, chip or motherboard manufacturers. With time, however, display manufacturers and chip manufacturers worldwide have acknowledged the trend toward acceptance of touchscreens as a highly desirable user interface component and have begun to integrate touchscreen functionality into the fundamental design of their products.


There are a number of types of touchscreen technology.


Surface acoustic wave


  • Surface capacitance
  • Projected capacitance

Strain gauge

Optical imaging

Dispersive signal technology

Acoustic pulse recognition

 Coded LCD: Bidirectional Screen


Working of Touch Screen
Touch screen has 3 main components: a touch sensor, a controller and a software driver. To make a complete touch input system, a touch screen is combined with a display and a PC or other device.

1) Touch screen censor
A touch screen sensor is a glass plate having touch responsive surface. The touch sensor is positioned over a display screen so that the responsive area of the plate covers the maximum viewable area of the video screen. There are number of touch sensor technologies available in the market today, each using a different approach to detect touch input. The sensor has an electrical current or signal passing through it and touching the screen causes change in voltage or signal. This voltage or signal change is used to find out the location of the touch to the screen.

2) Controller
The controller used in touch screen is a small PC card that interconnects between the touch sensor and the PC. Controller takes data from the touch sensor and converts it into information that PC can understand. For integrated monitors, the controller is usually installed inside the monitor or it is placed in a plastic case for external touch add-ons/overlays. The controller is useful to determine what type of interface/connection you will need on the PC. Integrated touch monitors are provided with an extra cable connection on the back for the touch screen. Controllers are available by connecting to a Serial/COM port (PC) or to a USB port (PC or Macintosh).

3) Software Driver
The driver is software for the PC system that permits the touch screen and computer to work together. It tells operating system of computer how to interpret the touch event information that is sent from the controller. Today’s touch screen drivers are a mouse-emulation type driver. This makes touching the screen the same as clicking your mouse at the same location on the screen. This permits the touch screen to work with existing software and provide new applications to be developed without the need for touch screen specific programming. Some devices such as thin client terminals, DVD players and specialized computer systems either do not use software drivers or they have their own in -built touch screen driver.

Uses of Touch Screen
The touch screen is one of the simplest PC interfaces to use, making it the interface of choice for a large number of applications. Following are uses of touch screen.

1) Public Information Displays
Tourism displays, trade show displays, Information kiosks and other electronic displays are used by large number of people that have little or no computing experience. The touch screen interface is easier to use than other input devices especially for novice users. A touch screen is useful to make your information more easily accessible by allowing users to navigate your presentation by simply touching the display screen.

2) Retail and Restaurant Systems
In retail or restaurant environment, touch screen systems are easy to use so employees can get work done faster and also training time can be reduced for new employees. As input is present right on the screen, valuable counter space can be saved. Touch screens can be used in order entry stations, cash registers, seating, reservation systems and more.

3) Control and Automation Systems
The touch screen device is useful in systems ranging from industrial process control to home automation. Valuable workspace can be saved by integrating the input device with the display. In real-time by simply touching the screen and with a graphical interface, operators can monitor and control complex operations.

4) Computer Based Training
The touch screen interface is more user-friendly than other input devices so overall training time for computer novices and therefore training expense can be reduced. It can also more useful to make learning more fun and interactive, which can lead to a more beneficial training experience for both students and educators.

5) Assistive Technology
The touch screen interface is very useful for those having difficulty using other input devices such as a mouse or keyboard. When touch screen used with software such as on-screen keyboards or other assistive technology, they can help make computing resources more available to people that have difficulty using computers.

Technology 4-Wire SAW 5-Wire Infrared Capacitive
Durability 3 year 5 Year 5 Year 5 Year 2 Year
Stability High Higher High High Ok
Transparency Bad Good Bad Good Ok
Installation Built-in/Onwall Built-in/Onwall Built-in/Onwall Onwall Built-in
Touch Anything Finger/Pen Anything Finger/Pen Conductive
Intense light-resistant Good Good Good Bad Bad
Response time <10ms 10ms <15ms <20ms <15ms
Following Speed Good Low Good Good Good
Excursion No Small Big Big Big
Monitor option CRT or LCD CRT or LCD CRT or LCD CRT or LCD CRT or LCD
Waterproof Good Ok Good Ok Good