A touchscreen is a display which 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 stylus. However, if the object sensed is active, as with a light pen, the term touchscreen is generally not applicable. The ability to interact directly with a display typically indicates the presence of a touchscreen.
Until the early 1980s, most consumer touchscreens could only sense one point of contact at a time, and few have had the capability to sense how hard one is touching. This is starting to change with the commercialisation of multi-touch technology.
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 and mobile phones.
History
One of the the Nintendo DS' main selling points is its second screen on the bottom, which is a touch screen. Touchscreens emerged from academic and corporate research labs in the second half of the 1960s. One of the first places where they gained some visibility was in the terminal of a computer-assisted learning terminal that came out in 1972 as part of the PLATO project. They have subsequently become familiar in kiosk systems, such as in retail and tourist settings, on point of sale systems, on ATMs and on PDAs where a stylus is sometimes used to manipulate the GUI and to enter data. The popularity of smart phones, PDAs, portable game consoles and many types of information appliances is driving the demand for, and the acceptance of, touchscreens.
The HP-150 from 1983 was probably the world's earliest commercial touchscreen computer. It doesn't actually have a touchscreen in the strict sense, but a 9" Sony CRT surrounded by infrared transmitters and receivers which detect the position of any non-transparent object on the screen.
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 System On Chip (SOC) 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. In the portable consumer electronics space, the touchscreen has evolved from the Electronic Organizer to the Apple iphone, Samsung Eternity, LG Vu, and Blackberry Storm.[1]
Technologies
There are a number of types of touchscreen technology.
Resistive
A resistive touchscreen panel is composed of several layers. The most important are two thin metallic electrically conductive and resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at a certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing.
Resistive touchscreen panels are generally the most affordable technology but offer only 75% clarity[citation needed] (premium films and glass finishes allow transmissivity to approach 85%[citation needed]) and the layer can be damaged by sharp objects. Resistive touchscreen panels are not affected by outside elements such as dust or water and are the type most commonly used today. The Nintendo DS is an example of a product that uses resistive touchscreen technology.
Surface acoustic wave
Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.[2]
Capacitive
A capacitive touchscreen panel is coated with a material, typically indium tin oxide, that conducts a continuous electrical current across the sensor.[3][4] The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. Capacitive sensors work based on proximity, and do not have to be directly touched to be triggered. It is a durable technology that is used in a wide range of applications including point-of-sale systems, industrial controls, and public information kiosks. It has a higher clarity than Resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus. Capacitive touch screens can also support Multitouch. A good example of this is Apple Inc.'s iPhone and iPod touch.
Projected Capacitance
Projected Capacitance Touch technology is a type of capacitive technology which involves the relationship between an XY array of sensing wires embedded within two layers of non-metallic material, and a third object. In touchscreen applications the third object can be a human finger. Capacitance forms between the user’s fingers and projected capacitance from the sensing wires. A touch is made, precisely measured, then passed on to the controller system which is connected to a computer running a software application. This will then calculate how the user’s touch relates to the computer software.[5]
Visual Planet’s ViP Interactive Foil is an example of a product that uses Projected Capacitance Touch technology. This technology allows a gloved hand to make the touch, resulting in Projected Capacitance Touch technology now being common in external "through window" touch applications (i.e. those where no direct physical contact with the touchscreen is made).
Strain gauge
In a strain gauge configuration the screen is spring-mounted on the four corners and strain gauges are used to determine deflection when the screen is touched.[6] This technology can also measure the Z-axis. Typically used in exposed public systems such as ticket machines due to their resistance to vandalism.
Optical imaging
A relatively-modern development in touchscreen technology, two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the camera's field of view on the other sides of the screen. A touch shows up as a shadow and each pair of cameras can then be triangulated to locate the touch or even measure the size of the touching object (see visual hull). This technology is growing in popularity, due to its scalability, versatility, and affordability, especially for larger units.
Dispersive signal technology
Introduced in 2002, this system uses sensors to detect the mechanical energy in the glass that occurs due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch. The technology claims to be unaffected by dust and other outside elements, including scratches. Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Also, since mechanical vibrations are used to detect a touch event, any object can be used to generate these events, including fingers and stylus. A downside is that after the initial touch the system cannot detect a motionless finger.
Acoustic pulse recognition
This system uses more than two piezoelectric transducers located at some positions of the screen to turn the mechanical energy of a touch (vibration) into an electronic signal.[7] The screen hardware then uses an algorithm to determine the location of the touch based on the transducer signals. This process is similar to triangulation used in GPS. The touchscreen itself is made of ordinary glass, giving it good durability and optical clarity. It is usually able to function with scratches and dust on the screen with good accuracy. The technology is also well suited to displays that are physically larger. As with the Dispersive Signal Technology system, after the initial touch, a motionless finger cannot be detected.
Building touch screens
There are several principal ways to built a touch screen. The key goals are to recognize one or more fingers touching a display, to interpret the command that this represents, and to communicate the command to the appropriate application.
In the most popular techniques called the capacitive or resistive approach, manufactures coat the screen with a thin, transparent metallic layer. When a user touches the surface, the system records the change in the electrical current that flows through the display.
Dispersive-signal technology which [3M] created in 2002, measures the piezoelectric effect- the voltage generated when mechanical force is applied to a material- that occurs chemically when a strengthened glass substrate is touched.
There are two infrared-based approaches. In one, any array of sensors detects finger touching or almost touching the display, there by interrupting light beams projected over the screen. In the other, bottom-mounted infrared cameras record screen touches.
In each case, the system determines the intended command based on the controls showing on the screen at the time and the potation of the touch.
Development
Virtually all of the significant touchscreen technology patents were filed during the 1970s and 1980s and have expired. Touchscreen component manufacturing and product design are no longer encumbered by royalties or legalities with regard to patents and the manufacturing of touchscreen-enabled displays on all kinds of devices is widespread.
The development of multipoint touch screens facilitated the tracking of more than one finger on the screen, thus operations that require more than one finger are possible. These devices also allow multiple users to interact with the touchscreen simultaneously.
With the growing acceptance of many kinds of products with an integral touchscreen interface the marginal cost of touchscreen technology is routinely absorbed into the products that incorporate it and is effectively eliminated. As typically occurs with any technology, touchscreen hardware and software has sufficiently matured and been perfected over more than three decades to the point where its reliability is unassailable. As such, touchscreen displays are found today in airplanes, automobiles, gaming consoles, machine control systems, appliances and handheld display devices of every kind. With the influence of the multi touch-enabled iPhone, the touchscreen market for mobile devices is projected to produce US$5 billion in 2009.[8]
The ability to accurately point on the screen itself is taking yet another step with the emerging graphics tablet/screen hybrids.
Ergonomics and usage
Finger stress
An ergonomic problem of touchscreens is their stress on human fingers when used for more than a few minutes at a time, since significant pressure can be required and the screen is non-flexible. This can be alleviated with the use of a pen or other device to add leverage, but the introduction of such items can sometimes be problematic depending on the desired use case (for example, public kiosks such as ATMs). Also, fine motor control is better achieved with a stylus,. a finger being a rather broad and ambiguous point of contact with the screen.>>
Fingernail as stylus
These ergonomic issues of direct touch can be bypassed by using a different technique, provided that the user's fingernails are either short or sufficiently long. Rather than pressing with the soft skin of an outstretched fingertip, the finger is curled over, so that the top of the forward edge of a fingernail can be used instead. (The thumb is optionally used to provide support for the finger or for a long fingernail, from underneath.)
The fingernail's hard, curved surface contacts the touchscreen at a single very small point. Therefore, much less finger pressure is needed, much greater precision is possible (approaching that of a stylus, with a little experience), much less skin oil is smeared onto the screen, and the fingernail can be silently moved across the screen with very little resistance, allowing for selecting text, moving windows, or drawing lines.
The human fingernail consists of keratin which has a hardness and smoothness similar to the tip of a stylus (and so will not typically scratch a touchscreen). Alternately, very short stylus tips are available, which slip right onto the end of a finger; this increases visibility of the contact point with the screen. Oddly, with capacitive touchscreens, the reverse problem applies in that individuals with long nails have reported problems getting adequate skin contact with the screen to register keystrokes (note that ordinary styli do not work on capacitive touchscreens nor do gloved fingers).
The concept of using a fingernail trimmed to form a point, to be specifically used as a stylus on a writing tablet for communication, appeared in the 1950 science fiction short story Scanners Live in Vain.
Fingerprints
Touch screens also suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduced the visible effects of fingerprint oils.
"Gorilla arm"
Gorilla arm was a side-effect that destroyed vertically-oriented touch-screens as a mainstream input technology despite a promising start in the early 1980s. Designers of touch-menu systems failed to notice that humans are not built to hold their arms at waist- or head-height, making small and precise motions. After a short period of time, cramp may begin to set in, and arm movement becomes painful and clumsy — the operator looks like a gorilla while using the touch screen and feels like one afterwards. This is now considered a classic cautionary tale to human-factors designers; "Remember the gorilla arm!" is shorthand for "How is this going to fly in real use?".[9] Gorilla arm is not a problem for specialist short-term-use devices such as ATMs, since they only involve brief interactions which are not long enough to cause gorilla arm. Gorilla arm also can be mitigated by the use of horizontally-mounted screens such as those used in Tablet PCs, but these need to account for the user's need to rest their hands on the device. This can increase the amount of dirt deposited on the device, and occludes the user's view of the screen.
See also
References
- ^ Evolution of portable consumer electronics from the Electronic Organizer to Apple's iPhone.
- ^ Patschon, Mark (1988-03-15), Acoustic touch technology adds a new input dimension, Computer Design, pp. 89-93, http://rwservices.no-ip.info:81/pens/biblio88.html#Platshon88
- ^ Kable, Robert G. (1986-07-15), Electrographic Apparatus, United States Patent 4,600,807, http://rwservices.no-ip.info:81/pens/biblio86.html#Kable86
- ^ Kable, Robert G. (1986-07-15), Electrographic Apparatus, United States Patent 4,600,807 (full image), http://www.freepatentsonline.com/4600807.pdf
- ^ Truetouch Projective Capacitance Technology
- ^ Minsky, M.R. (1984-08-15), Manipulating simulated objects with real-world gestures using a force and position sensitive screen, Computer Graphice, Vol 18 No 3, pp. 195-203, http://rwservices.no-ip.info:81/pens/biblio85.html#Minsky84
- ^ Acoustic Pulse Recognition Touchscreens, Elo Touch Systems, 1888-07-31, http://www.elotouch.com/Products/Touchscreens/AcousticPulseRecognition/default.asp, retrieved on 25 August 2008
- ^ http://www.abiresearch.com/press/1231-Touch+Screens+in+Mobile+Devices+to+Deliver+$5+Billion+Next+Year
- ^ "Jargon File - Gorilla Arm". www.catb.org. Retrieved on 2008-11-17.
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
- Andreas Holzinger: Finger Instead of Mouse: Touch Screens as a means of enhancing Universal Access, In: Carbonell, N.; Stephanidis C. (Eds): Universal Access, Theoretical Perspectives, Practice, and Experience. Lecture Notes in Computer Science. Vol. 2615. Berlin, Heidelberg, New York: Springer, 2003, ISBN 3-540-00855-1, 387–397.
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