Introduction
A touchscreen is an electronic device that allows the input of information through touch motions. It commonly refers to making contact with the display area using a finger, touchscreens can also detect other inert items such as a stylus and a fingernail. This technology is common in tablet PCs such as Apple’s iPad or Motorola’s Xoom, smartphones such as Apple’s iPhone, and laptop computers.
A touchscreen has three major advantages. First, it allows a user to input information directly into the processing unit. Secondly, it does not require any peripheral devices to be attached to the computer, such as a keyboard or a mouse. Thirdly, a smartphone doubles up as an input and an output device hence increasing response time and further reducing the number of additional devices required. This makes the device easily portable and it can easily be held by hand. Touchscreens are commonly attached to computers, they also find use in smartphones, video game consoles, satellite navigation equipment, and media devices such as iPods and televisions.
A Brief History
The first touch-sensing device was designed by Dr. Sam Hurst in 1971, the sensor was referred to as the “Elograph”. Although the Elograph was not as advanced as today’s touch screens, it was a major step in touchscreen technology. Three years later, the first genuine touchscreen with an integrated transparent surface appeared, designed by Sam Hurst and his company, Elographics. Then in 1977, the firm came up with a 5-wire resistive technique, the most widely used technology in touchscreen systems presently. The company changed its name to Elo Touchsystems in 1994 and continues to design and develop touchscreen devices based on modern technology.
Other historical papers indicate that the first touchscreen systems were developed by E. A. Johnson, an employee at Royal Radar Establishment in the UK. He later described the possible use of this technology in air traffic control (Potter et al, pp. 59).
The HP-150 was one of the earliest computer systems that used touchscreen technology, the device used infrared technology to detect the position of anything opaque or translucent on the screen. With the commercialization of touchscreen technology, touchscreens are now a common sight, e.g. they exist in smartphones, tablet PCs, industrial control switchboards, and even at hospitals. Other areas that commonly make use of this technology, include kiosks, museums, and airports (Holzinger, pp. 390).
Types of Touchscreens
Touchscreen devices vary on the technology that they use. Some of these technologies are outlined below.
Resistive Touchscreen
This comprises a glass pane fitted with a conductive material and a metal film placed on top. The two layers are separated by conductors, and a scratch-resistant finish is placed on the uppermost part. An electric current flows through the two layers when the device is operating such that when a person touches the display area, the two layers come into contact in that precise position. The variation in the electrical field is detected and the coordinates of the spot of contact are computed by the computer.
Once the coordinates are identified, a specialized driver converts the touch motion into something that can be read by the operating system, similar to the way a computer converts the motions of the mouse into a click. The displays generally have high resolution (4096 X 4096 DPI) and this increases the accuracy of the finger or touch device used on the touchscreen (Hartson & Hix, pp. 24).
Capacitative System
In this setup, a thin film that stores charge is placed on the display plane. When a person touches the display area, some charge moves onto the touch object, causing a drop-off charge. The decrease is computed by circuits located on the display area. The computer then calculates the position of the touch-based on the difference in charge of the four circuits, then transmits this information to the touchscreen driver, which then translates it into information that can be read by the operating system (Shneiderman, pp. 93).
One major advantage of the capacitative display over the resistive display is that it conveys nearly 90% of all the information it receives from the display, however, the resistive system only conveys approximately 75 percent. Display in this type of touchscreen is clearer and sharper than that of the resistive touchscreen.
Surface Acoustic Wave Touchscreen (SAW)
This type of touchscreen makes use of two transducers, the first receives information while the second transmit it to the control unit. The two transducers are placed along the x and y axes of the display area. SAW consists of reflectors, which reflect away electrical current passing between the two layers. The recipient transducer can detect whether the wave has been altered by a touch motion at any point, and can find an accurate position of this touch. The wave system does not have any metallic layers on its surface as in the resistive system, hence, it allows all of the light to pass through, contributing to graphic and video clarity. This makes the SAW best fitted for viewing detailed graphics. One downside of the surface acoustic wave is that it cannot identify touch from hard or pointed objects such as a pin.
Other differences between the three systems stem from the contact that is sensed as a touch. A resistive system records a touch as long as the two layers come into contact, this feature makes it detect touch from all objects, i.e. both a finger and a stylus. By contrast, a capacitative touchscreen must have a conductive touch device, such as a finger. The surface acoustic wave setup functions similarly to the resistive system, allowing input from any touch object, except hard and pointed objects (Sears and Shneiderman, pp. 602).
The resistive touchscreen costs the least of the three types, but has the poorest display quality, its layer can also be scratched easily. The SAW display is the most costly system.
Conclusion
Modern touchscreen technologies have altered the world’s expectations of a touchscreen device, especially with the release of Apple’s iPhone and iPad. The two devices are considered trendsetters in the use of touchscreen technology in smartphones and tablet PCs respectively, and as new technologies come to the fore, touchscreen technology will undergo development. One area that holds the key to the success of future touchscreen technology is its fusion with other technologies, such as a touchscreen system that also recognizes gesture and translates it into a form that can be read understood by the operating system, or a system that would recognize finger motion and translate particular finger movements as scrolling, clicking, and mouse movement.
Works Cited
Hartson, Rex H., and Hix, Deborah. Advances in human-computer interaction, Volume 3. New Jersey: Ablex Publishing Corporation, 1992.
Holzinger, Andreas. Finger Instead of Mouse: Touch Screens as a Means of Enhancing Universal Access. Lecture Notes in Computer Science, Volume 2615/2003, 387-397.
Potter, Ralph, Weldon, Luke & Shneiderman, Ben. Improving the accuracy of touch screen: An experimental evaluation of three strategies. Washington, DC: ACM Press. 1988.
Sears, Andrew, and Shneiderman, Ben. High precision touchscreen: Design strategies and comparison with a mouse. Int. J. of Man-Machine Studies 34 (4): 1991, 593–613.
Shneiderman, Ben. Touch screens now offer compelling uses. IEEE Software 8 (2): 1991, 93–94.