A touchscreen is an input device and output device normally layered on the top of an electronic visual display of an information processing system. A user can give input or control the information processing system through simple or multi-touch gestures by touching the screen with a special stylus or one or more fingers. Some touchscreens use ordinary or specially coated gloves to work while others may only work using a special stylus or pen. The user can use the touchscreen to react to what is displayed and, if the software allows, to control how it is displayed; for example, zooming to increase the text size.
The touchscreen enables the user to interact directly with what is displayed, rather than using a computer mouse, touchpad, or other such devices (other than a stylus, which is optional for most modern touchscreens).
Touchscreens are common in devices such as game consoles, personal computers, electronic voting machines, and point-of-sale (POS) systems. They can also be attached to computers or, as terminals, to networks. They play a prominent role in the design of digital appliances such as personal digital assistants (PDAs) and some .
The popularity of smartphones, tablets, and many types of information appliances is driving the demand and acceptance of common touchscreens for portable and functional electronics. Touchscreens are found in the medical field, heavy industry, automated teller machines (ATMs), and kiosks such as museum displays or room automation, where keyboard and mouse systems do not allow a suitably 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. Display manufacturers and chip manufacturers have acknowledged the trend toward acceptance of touchscreens as a user interface component and have begun to integrate touchscreens into the fundamental design of their products.
In 1972, a group at the University of Illinois filed for a patent on an optical touchscreenF. Ebeling, R. Johnson, R. Goldhor, Infrared light beam x-y position encoder for display devices, , granted November 27, 1973. that became a standard part of the Magnavox Plato IV Student Terminal and thousands were built for this purpose. These touchscreens had a crossed array of 16×16 infrared position sensors, each composed of an LED on one edge of the screen and a matched phototransistor on the other edge, all mounted in front of a monochrome plasma display panel. This arrangement could sense any fingertip-sized opaque object in close proximity to the screen. A similar touchscreen was used on the HP-150 starting in 1983. The HP 150 was one of the world's earliest commercial touchscreen computers. The H.P. Touch Computer (1983) . YouTube (2008-02-19). Retrieved on 2013-08-16. HP mounted their infrared and receivers around the bezel of a 9-inch Sony cathode ray tube (CRT).
In 1984, Fujitsu released a touch pad for the Micro 16 to accommodate the complexity of kanji characters, which were stored as Tile engine graphics. Japanese PCs (1984) (12:21), Computer Chronicles In 1985, Sega released the Terebi Oekaki, also known as the Sega Graphic Board, for the SG-1000 video game console and SC-3000 home computer. It consisted of a plastic pen and a plastic board with a transparent window where pen presses are detected. It was used primarily with a drawing software application. A graphic touch tablet was released for the Sega AI computer in 1986. New Scientist (March 26, 1987), page 34 Technology Trends: 2nd Quarter 1986 , Japanese Semiconductor Industry Service - Volume II: Technology & Government
Touch-sensitive control-display units (CDUs) were evaluated for commercial aircraft flight decks in the early 1980s. Initial research showed that a touch interface would reduce pilot workload as the crew could then select waypoints, functions and actions, rather than be "head down" typing latitudes, longitudes, and waypoint codes on a keyboard. An effective integration of this technology was aimed at helping flight crews maintain a high-level of situational awareness of all major aspects of the vehicle operations including the flight path, the functioning of various aircraft systems, and moment-to-moment human interactions.Biferno, M.A., Stanley, D.L. (1983). The Touch-Sensitive Control/Display Unit: A promising Computer Interface. Technical Paper 831532, Aerospace Congress & Exposition, Long Beach, CA: Society of Automotive Engineers.
In the early 1980s, General Motors tasked its Delco Electronics division with a project aimed at replacing an automobile's non-essential functions (i.e. other than throttle, transmission, braking and steering) from mechanical or electro-mechanical systems with solid state alternatives wherever possible. The finished device was dubbed the ECC for "Electronic Control Center", a digital computer and software control system hardwired to various peripheral sensors, servos, solenoids, antenna and a monochrome CRT touchscreen that functioned both as display and sole method of input. The ECC replaced the traditional mechanical Vehicle audio, fan, heater and air conditioner controls and displays, and was capable of providing very detailed and specific information about the vehicle's cumulative and current operating status in real time. The ECC was standard equipment on the 1985–1989 Buick Riviera and later the 1988–1989 Buick Reatta, but was unpopular with consumers—partly due to the technophobia of some traditional Buick customers, but mostly because of costly technical problems suffered by the ECC's touchscreen which would render climate control or stereo operation impossible.
Multi-touch technology began in 1982, when the University of Toronto's Input Research Group developed the first human-input multi-touch system, using a frosted-glass panel with a camera placed behind the glass. In 1985, the University of Toronto group, including Bill Buxton, developed a multi-touch tablet that used capacitance rather than bulky camera-based optical sensing systems (see Multi-touch#History of multi-touch).
The first commercially available graphical point-of-sale (POS) software was demonstrated on the 16-bit Atari 520ST color computer. It featured a color touchscreen widget-driven interface. The ViewTouch restaurant system by Giselle Bisson The ViewTouch POS software was first shown by its developer, Gene Mosher, at the Atari Computer demonstration area of the Fall COMDEX expo in 1986.
In 1987, Casio launched the Casio PB-1000 pocket computer with a touchscreen consisting of a 4×4 matrix, resulting in 16 touch areas in its small LCD graphic screen.
Touchscreens had the bad reputation of being imprecise until 1988. Most user-interface books would state that touchscreen selections were limited to targets larger than the average finger. At the time, selections were done in such a way that a target was selected as soon as the finger came over it, and the corresponding action was performed immediately. Errors were common, due to parallax or calibration problems, leading to user frustration. "Lift-off strategy" was introduced by researchers at the University of Maryland Human–Computer Interaction Lab (HCIL). As users touch the screen, feedback is provided as to what will be selected: users can adjust the position of the finger, and the action takes place only when the finger is lifted off the screen. This allowed the selection of small targets, down to a single pixel on a 640×480 Video Graphics Array (VGA) screen (a standard of that time).
Sears et al. (1990)
In 1990, HCIL demonstrated a touchscreen slider, which was later cited as prior art in the lock screen patent litigation between Apple and other touchscreen mobile phone vendors (in relation to ).
An early attempt at a handheld game console with touchscreen game controller was Sega's intended successor to the Game Gear, though the device was ultimately shelved and never released due to the expensive cost of touchscreen technology in the early 1990s.
Touchscreens would not be popularly used for video games until the release of the Nintendo DS in 2004. Until recently, 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 has changed with the commercialization of multi-touch technology.
Resistive touch is used in restaurants, factories and hospitals due to its high tolerance for liquids and contaminants. A major benefit of resistive-touch technology is its low cost. Additionally, as only sufficient pressure is necessary for the touch to be sensed, they may be used with gloves on, or by using anything rigid as a finger substitute. Disadvantages include the need to press down, and a risk of damage by sharp objects. Resistive touchscreens also suffer from poorer contrast, due to having additional reflections (i.e.: glare) from the layers of material placed over the screen.Lancet, Yaara. (2012-07-19) What Are The Differences Between Capacitive & Resistive Touchscreens? . Makeuseof.com. Retrieved on 2013-08-16. This is the type of touchscreen used by Nintendo in the DS family, the 3DS family, and the Wii U GamePad.
A capacitive touchscreen panel consists of an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location is then sent to the controller for processing.
Unlike a resistive touchscreen, one cannot use a capacitive touchscreen through most types of electrically insulating material, such as gloves. This disadvantage especially affects usability in consumer electronics, such as touch tablet PCs and capacitive smartphones in cold weather. It can be overcome with a special capacitive stylus, or a special-application glove with an embroidered patch of conductive thread allowing electrical contact with the user's fingertip.
Leading capacitive display manufacturers continue to develop thinner and more accurate touchscreens. Those for are now being produced with 'in-cell' technology, such as in Samsung's Super AMOLED screens, that eliminates a layer by building the capacitors inside the display itself. This type of touchscreen reduces the visible distance between the user's finger and what the user is touching on the screen, creating a more-direct contact with the image of displayed content and enabling taps and gestures to be more responsive.
A simple parallel-plate capacitor has two conductors separated by a dielectric layer. Most of the energy in this system is concentrated directly between the plates. Some of the energy spills over into the area outside the plates, and the electric field lines associated with this effect are called fringing fields. Part of the challenge of making a practical capacitive sensor is to design a set of printed circuit traces which direct fringing fields into an active sensing area accessible to a user. A parallel-plate capacitor is not a good choice for such a sensor pattern. Placing a finger near fringing electric fields adds conductive surface area to the capacitive system. The additional charge storage capacity added by the finger is known as finger capacitance, or CF. The capacitance of the sensor without a finger present is known as parasitic capacitance, or CP.
This technology was first developed by Ronald and Malcolm Binstead in 1984, when a simple 16 key capacitive touchpad was invented which could sense a finger through very thick glass, even though the signal to be sensed was significantly smaller than the capacitance changes caused by varying environmental factors such as humidity, dirt, rain and temperature.
Accurate sensing was achieved due to :
1) the slow but continuous updating of the “no-touch” reference value for each key, eliminating medium to long term problems associated with dirt and ageing.
2) the change in value for each key being compared with the relative change in value for each of the other keys, to see if the pattern of change corresponded to the change that would be expected to be caused by a nearby finger, as opposed to localised heating, rain, or other environmental factors .
A simple to manufacture x/y multiplexed version of this touch screen was invented in 1994. This could use Indium Tin Oxide, or 10 to 25 micron diameter insulation coated copper wires as the sensing elements. The first version enabled 64 touch positions to be detected with just 16 inputs.
Due to their low cost and ability to survive in hostile environments, 7000 of these were used by JPM International in their 'Monopoly' pub gaming machines.
Later this term was modified by Zytronic Displays to ‘Projected Capacitance’ .
Some modern PCT touch screens are composed of thousands of discrete keys,www.google.co.uk/patents/US7663607B2 but most PCT touch screens are made of a matrix of rows and columns of conductive material, layered on sheets of glass.
This can be done either by etching a single conductive layer to form a grid pattern of [[electrode]]s, or by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form a grid.In some designs, voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact with a PCT panel, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance. If a finger bridges the gap between two of the "tracks", the charge field is further interrupted and detected by the controller. The capacitance can be changed and measured at every individual point on the grid. This system is able to accurately track touches.Knowledge base: Multi-touch hardware
Due to the top layer of a PCT being glass, it is sturdier than less-expensive resistive touch technology. Unlike traditional capacitive touch technology, it is possible for a PCT system to sense a passive stylus or gloved finger. However, moisture on the surface of the panel, high humidity, or collected dust can interfere with performance.
These environmental factors, however, are not a problem with 'fine wire' based touchscreens due to the fact that wire based touchscreens have a much lower 'parasitic' capacitance, and there is greater distance between neighbouring conductors .
There are two types of PCT: mutual capacitance and self-capacitance.
An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. These LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch. A major benefit of such a system is that it can detect essentially any opaque object including a finger, gloved finger, stylus or pen. It is generally used in outdoor applications and POS systems which cannot rely on a conductor (such as a bare finger) to activate the touchscreen. Unlike capacitive touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system. Infrared touchscreens are sensitive to dirt and dust that can interfere with the infrared beams, and suffer from parallax in curved surfaces and accidental press when the user hovers a finger over the screen while searching for the item to be selected.
In the capacitive resistive approach, the most popular technique, there are typically four layers:
Dispersive-signal technology 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, an array of sensors detects a finger touching or almost touching the display, thereby interrupting infrared light beams projected over the screen. In the other, bottom-mounted infrared cameras record heat from screen touches.
The x/y layout, commonly used in touchscreens, has also been improved by using a diagonal lattice layout, where there are no dedicated x or y elements, but each element may be transmitting or sensing at different times during a scan of the touchscreen. This means that there are nearly twice as many cross-over points for a fixed number of terminal connections and no 'bussed' connections around the edges of the touchscreen .
In each case, the system determines the intended command based on the controls showing on the screen at the time and the location of the touch.
With the growing use of touchscreens, the cost of touchscreen technology is routinely absorbed into the products that incorporate it and is nearly eliminated. Touchscreen technology has demonstrated reliability and is found in airplanes, automobiles, gaming consoles, machine control systems, appliances, and handheld display devices including cellphones; the touchscreen market for mobile devices was projected to produce US$5 billion by 2009.
The ability to accurately point on the screen itself is also advancing with the emerging graphics tablet. Polyvinylidene fluoride (PVFD) plays a major role in this innovation due its high piezoelectric properties.
TapSense, announced in October 2011, allows touchscreens to distinguish what part of the hand was used for input, such as the fingertip, knuckle and fingernail. This could be used in a variety of ways, for example, to copy and paste, to capitalize letters, to activate different drawing modes, etc.
Guidelines for touchscreen designs were first developed in the 1990s, based on early research and actual use of older systems, typically using infrared grids—which were highly dependent on the size of the user's fingers. These guidelines are less relevant for the bulk of modern devices which use capacitive or resistive touch technology.
From the mid-2000s, makers of operating systems for smartphones have promulgated standards, but these vary between manufacturers, and allow for significant variation in size based on technology changes, so are unsuitable from a human factors perspective.
Much more important is the accuracy humans have in selecting targets with their finger or a pen stylus. The accuracy of user selection varies by position on the screen: users are most accurate at the center, less so at the left and right edges, and least accurate at the top edge and especially the bottom edge. The R95 accuracy (required radius for 95% target accuracy) varies from in the center to in the lower corners. Users are subconsciously aware of this, and take more time to select targets which are smaller or at the edges or corners of the touchscreen.
This user inaccuracy is a result of parallax, visual acuity and the speed of the feedback loop between the eyes and fingers. The precision of the human finger alone is much, much higher than this, so when assistive technologies are provided—such as on-screen magnifiers—users can move their finger (once in contact with the screen) with precision as small as 0.1 mm (0.004 in).
In addition, devices are often placed on surfaces (desks or tables) and tablets especially are used in stands. The user may point, select or gesture in these cases with their finger or thumb, and vary use of these methods.
Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with designed to reduce the visible effects of fingerprint oils. Most modern smartphones have oleophobic coatings, which lessen the amount of oil residue. Another option is to install a matte-finish anti-glare screen protector, which creates a slightly roughened surface that does not easily retain smudges.