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In this article:
- What are touchscreens?
- Uses of touchscreens
- Types of touchscreens
What are touchscreens?
Touchscreens, also called touch panels or even touchscreen panels are display overlays which are typically either pressure-sensitive (resistive), electrically-sensitive (capacitive), acoustically-sensitive or photo-sensitive (infra-red). This type of an overlay makes the display unit act as an input device at the same time hence removing the need to use a keyboard or mouse or a pair of the two for interacting with the content being displayed on the screen. Touchscreens can be attached to computers or terminals.
Uses of Touchscreens
The touchscreen interface was invented in 1971 by Dr. Samuel C. Hurst. Since then, touchscreens have been used in a variety of ways and are available in a wide range of shapes and sizes. Touchscreen interfaces can be found on point of sales systems in retail and wholesale stores. Automatic Teller Machines (ATMs) and Personal Digital Assistants (PDAs) also make use of touchscreen interfaces for input where the graphical interface is manipulated with the help of one’s bare fingers or with a stylus. More recently, touchscreens have found their place on smart phones, portable video games and other such devices. Among the oldest devices that feature a touchscreen interface was the HP-150. The onboard infrared transmitters on the device could detect the position of an object on the screen provided that the object is opaque or translucent.
Touchscreens are usually used in areas where there is a need to provide a quick, precise and intuitive way of interaction with the content being displayed. Thus, touchscreens can be found in situations where heavy industrial goods are being used or where room automation is being done. They are also common in museums.
Types of Touchscreens
Touchscreen interfaces are distinguished from one another on the basis of the underlying technology they use. On that ground, the types of touchscreens in use today are:
- Resistive
This type of touchscreen is coated with an electrically conductive but resistive layer which is thin and is made up of metal. When the screen is ‘touched’, there occurs a change in the electrical current being transferred which is interpreted as an event and the internal controller of the system performs the necessary operation corresponding to the event. These types of touchscreens are widely used and are popular due to the fact that they are very affordable. Though their resistant layer may be damaged by the use of sharp objects, they are resistant to dust and water etc.
- Surface wave
These types of touchscreens employ ultrasonic waves. These waves travel over the touch screen panel. When the surface is touched, some of these waves are absorbed which is translated into a touch event and communicated to the controller. The controller then does the processing and takes the necessary action. The limitation of this type of touchscreens is that they can be easily damaged by outside elements and inhibit their proper functioning.
- Capacitive
These types of touchscreens have a coating on their panels which is usually indium tin oxide. A continuous electrical current is maintained over the sensor giving it capacitance. When this field is disturbed by another capacitive field (eg., a human finger), the sensor detects it as an even and the necessary action is taken by the controller. The major limitation here is that a non-conductor such as a stylus cannot be used to operate them.
- Infrared
Infrared touchscreens make use of an array of IR sensors that detect disturbances in a modulated light beam on the surface. They may also operate by detecting thermal induced changes on the surface, though this is a limiting factor as it would require a warm object to operate the system.
- Optical Imaging
The modern technology of optical imaging is used by touchscreens to detect a touch event by placing two or more image sensing devices on the edges of the screen. The camera fitted into these devices helps detect the position or location of the touch on the screen and in turn, helps the controller to determine the action to be taken. These touchscreens are versatile and affordable and are becoming widely used day by day.
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