Touchscreen

A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area(SONY VGP-BPS8 battery). The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus(SONY VAIO VGN-FZ Battery).

The touchscreen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a cursor controlled by a mouse or touchpad. Secondly(SONY VAIO VGN-FZ11S Battery), it lets one do so without requiring any intermediate device that would need to be held in the hand. Such displays can be attached to computers, or to networks as terminals(SONY vgp-bps9 battery). 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(sony vgp-bpl9 battery).

History

In 1971, the first "Touch Sensor" was developed by Doctor Sam Hurst (founder of Elographics) while he was an instructor at the University of Kentucky. This sensor, called the "Elograph," was patented by The University of Kentucky Research Foundation(SONY VAIO VGN-FZ32 Battery). The "Elograph" was not transparent like modern touch screens; however, it was a significant milestone in touch screen technology. In 1974, the first true touch screen incorporating a transparent surface was developed by Sam Hurst and Elographics(SONY VAIO VGN-FZ440N Battery). In 1977, Elographics developed and patented five-wire resistive technology, the most popular touchscreen technology in use today.

Touchscreens first gained some visibility with the invention of the computer-assisted learning terminal, which came out in 1975 as part of the PLATO project(SONY VAIO VGN-FZ280E Battery). Touchscreens have subsequently become familiar in everyday life. Companies use touch screens for kiosk systems in retail and tourist settings, point of sale systems, ATMs, and PDAs, where a stylus is sometimes used to manipulate the GUI and to enter data(SONY VAIO VGN-FZ460E Battery). The popularity of smart phones, PDAs, portable game consoles and many types of information appliances is driving the demand for, and acceptance of, touchscreens(SONY VAIO VGN-FZ190 Battery).

From 1979–1985, the Fairlight CMI (and Fairlight CMI IIx) was a high-end musical sampling and re-synthesis workstation that utilized light pen technology, with which the user could allocate and manipulate sample and synthesis data, as well as access different menus within its OS by touching the screen with the light pen(SONY VAIO VGN-FZ150E Battery). The later Fairlight series III models used a graphics tablet in place of the light pen.

The HP-150 from 1983 was one of the world's earliest commercial touchscreen computers. It did not have a touchscreen in the strict sense; instead, it had a 9" Sony Cathode Ray Tube (CRT) surrounded by infrared transmitters and receivers, which detected the position of any non-transparent object on the screen(SONY VAIO VGN-FZ260E Battery).

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 is starting to change with the commercialization of multi-touch technology(SONY VAIO VGN-FZ140E Battery).

Touchscreens are popular in hospitality, and in heavy industry, as well as 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(SONY VAIO VGN-FZ11l Battery).

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(SONY VAIO VGN-FZ11z Battery). 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(SONY VAIO VGN-FZ11m Battery).

Technologies

There are a variety of touchscreen technologies.

Resistive

Main article: Resistive touchscreen

A resistive touchscreen panel is composed of several layers, the most important of which are two thin, electrically conductive layers separated by a narrow gap. When an object, such as a finger(SONY VAIO VGN-FZ18m Battery), presses down on a point on the panel's outer surface the two metallic layers become connected at that point: the panel then behaves as a pair of 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(SONY VAIO VGN-FZ21m Battery).

Surface acoustic wave

Main article: Surface acoustic wave

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched(SONY VAIO VGN-FZ410 Battery), 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 touch screen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen(SONY VAIO VGN-FZ21 Battery).

Capacitive touchscreen of a mobile phone

Main article: Capacitive sensing

A capacitive touchscreen panel is one which consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As the human body is also a electrical conductor(SONY VAIO VGN-FZ160 Battery), 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(SONY VAIO VGN-FZ210CE Battery).

Surface capacitance

In this basic technology, only one side of the insulator is coated with a conductive layer. A small voltage is applied to the layer, resulting in a uniform electrostatic field. When a conductor, such as a human finger, touches the uncoated surface(SONY VAIO VGN-FZ38M Battery), a capacitor is dynamically formed. The sensor's controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel. As it has no moving parts(SONY VAIO VGN-FZ31z Battery), it is moderately durable but has limited resolution, is prone to false signals from parasitic capacitive coupling, and needs calibration during manufacture. It is therefore most often used in simple applications such as industrial controls and kiosks(Sony Vaio VGN-FZ31S battery).

Projected capacitance

Projected Capacitive Touch (PCT) technology is a capacitive technology which permits more accurate and flexible operation, by etching the conductive layer(SONY VAIO VGN-FZ31E Battery). An X-Y grid is formed either by etching a single layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form the grid (comparable to the pixel grid found in many LCD displays) (SONY VAIO VGN-FZ31J Battery).

The greater resolution of PCT allows operation without direct contact, such that the conducting layers can be coated with further protective insulating layers, and operate even under screen protectors, or behind weather and vandal-proof glass(SONY VAIO VGN-FZ31M Battery). Due to the top layer of a PCT being glass, PCT is a more robust solution versus resistive touch technology. Depending on the implementation, an active or passive stylus can be used instead of or in addition to a finger(SONY VAIO VGN-FZ31B Battery). This is common with point of sale devices that require signature capture. Gloved fingers may or may not be sensed, depending on the implementation and gain settings. Conductive smudges and similar interference on the panel surface can interfere with the performance(HP PAVILION DV6000 battery). Such conductive smudges come mostly from sticky or sweaty finger tips, especially in high humidity environments. Collected dust, which adheres to the screen due to the moisture from fingertips can also be a problem. There are two types of PCT: Self Capacitance and Mutual Capacitance(SONY VGP-BPS13 Battery).

Mutual capacitance

In mutual capacitive sensors, there is a capacitor at every intersection of each row and each column. A 12-by-16 array, for example, would have 192 independent capacitors. A voltage is applied to the rows or columns(SONY VGP-BPS13B/B Battery). Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field which reduces the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis(SONY VGP-BPS13/B Battery). Mutual capacitance allows multi-touch operation where multiple fingers, palms or stylus can be accurately tracked at the same time(Sony VAIO VGN-FZ15T Battery).

Self-capacitance

Self-capacitance sensors can have the same X-Y grid as mutual capacitance sensors, but the columns and rows operate independently. With self-capacitance, the capacitive load of a finger is measured on each column or row electrode by a current meter(Sony VAIO VGN-FZ15G Battery). This method produces a stronger signal than mutual capacitance, but it is unable to resolve accurately more than one finger, which results in "ghosting", or misplaced location sensing(SONY VGP-BPS13A/S Battery).

Infrared

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(SONY VGP-BPS13AS Battery). 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 input including a finger, gloved finger, stylus or pen(SONY VGP-BPS13S Battery). It is generally used in outdoor applications and point of sale systems which can't rely on a conductor (such as a bare finger) to activate the touchscreen(SONY VGP-BPS13B/S Battery). Unlike capacitive touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system(SONY VAIO PCG-5G2L battery).

Optical imaging

This is a relatively modern development in touchscreen technology, in which two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared back lights are placed in the camera's field of view on the other side of the screen(SONY VAIO PCG-5G3L battery). A touch shows up as a shadow and each pair of cameras can then be pinpointed 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(SONY VAIO PCG-5J1L battery).

Dispersive signal technology

Introduced in 2002 by 3M, 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(SONY VAIO PCG-5K2L battery). 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(SONY VAIO PCG-5L1L battery). 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(SONY VAIO PCG-5J2L battery).

Acoustic pulse recognition

This system, introduced by Tyco International's Elo division in 2006, uses piezoelectric transducers located at various positions around the screen to turn the mechanical energy of a touch (vibration) into an electronic signal(SONY VAIO PCG-6S2L battery). The screen hardware then uses an algorithm to determine the location of the touch based on the transducer signals. 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(SONY VAIO PCG-6S3L battery). 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. However, for the same reason, the touch recognition is not disrupted by any resting objects(SONY VAIO PCG-6V1L battery).

Construction

There are several principal ways to build a touchscreen. 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(SONY VAIO PCG-6W1L battery).

In the most popular techniques, the capacitive or resistive approach, there are typically four layers;

Top polyester layer coated with a transparent metallic conductive coating on the bottom

Adhesive spacer(SONY VAIO PCG-7111L battery)

Glass layer coated with a transparent metallic conductive coating on the top

Adhesive layer on the backside of the glass for mounting.

When a user touches the surface, the system records the change in the electrical current that flows through the display(SONY VAIO PCG-6W3L battery).

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(SONY VAIO PCG-7113L battery).

There are two infrared-based approaches. In one, an array of sensors detects a finger touching or almost touching the display, thereby interrupting light beams projected over the screen. In the other, bottom-mounted infrared cameras record screen touches(SONY VAIO PCG-7133L battery).

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(SONY VAIO PCG-7Z1L battery).

Development

Most 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 use of touchscreen-enabled displays is widespread(SONY VAIO PCG-7Z2L battery).

The development of multipoint touchscreens 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(SONY VAIO PCG-8Y1L battery).

With the growing use of touchscreens, the marginal cost of touchscreen technology is routinely absorbed into the products that incorporate it and is nearly eliminated. Touchscreens now have proven reliability(SONY VAIO PCG-8Y2L battery). Thus, touchscreen displays are found today in airplanes, automobiles, gaming consoles, machine control systems, appliances, and handheld display devices including the Nintendo DS and the later multi-touch enabled iPhones; the touchscreen market for mobile devices is projected to produce US$5 billion in 2009(SONY VAIO PCG-8Z2L battery).

The ability to accurately point on the screen itself is also advancing with the emerging graphics tablet/screen hybrids(SONY VAIO PCG-8Z1L battery).

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 for certain types of touchscreen(SONY VAIO PCG-7112L battery). This can be alleviated for some users with the use of a pen or other device to add leverage and more accurate pointing. The introduction of such items can sometimes be problematic, depending on the desired use (e.g., public kiosks such as ATMs) (SONY VAIO PCG-6W2L battery). Also, fine motor control is better achieved with a stylus, because a finger is a rather broad and ambiguous point of contact with the screen itself(SONY VAIO PCG-5K1L battery).

Fingernail as stylus

Pointed nail for easier typing. 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(SONY VGP-BPS21A/B Battery).

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(SONY VGP-BPS21B Battery), the finger is curled over, so that the tip 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. This method does not work on capacitive touch screens(SONY VGP-BPS21 Battery).

The fingernail's hard, curved surface contacts the touchscreen at one very small point. Therefore, much less finger pressure is needed, much greater precision is possible (approaching that of a stylus, with a little experience) (SONY VGP-BPS21/S Battery), much less skin oil is smeared onto the screen, and the fingernail can be silently moved across the screen with very little resistance[citation needed], allowing for selecting text, moving windows, or drawing lines(SONY VGP-BPS13A/Q Battery).

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(SONY VGN NR11Z/T battery).

Fingerprints

Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduce the visible effects of fingerprint oils, such as the oleophobic coating used in the iPhone 3G S, or by reducing skin contact by using a fingernail or stylus(SONY VGN NR11Z/S battery).

Combined with haptics

The user experience with touchscreens without tactile feedback or haptics can be difficult due to latency or other factors. Research from the University of Glasgow Scotland [Brewster, Chohan, and Brown 2007] demonstrates that sample users reduce input errors (20%), increase input speed (20%), and lower their cognitive load (40%) when touchscreens are combined with haptics or tactile feedback(SONY VGN NR11M/S battery).

Gorilla arm

The Jargon File dictionary of hacker slang defined "gorilla arm" as the failure to understand the ergonomics of vertically mounted touch screens for prolonged use(SONY VGN NR11S/S battery). The proposition is that the human arm held in an unsupported horizontal position rapidly becomes fatigued and painful, the so-called "gorilla arm". It is often cited as a prima facie example of what not to do in ergonomics(SONY VGP-BPS13B/Q Battery). Vertical touchscreens still dominate in applications such as ATMs and data kiosks in which the usage is too brief to be an ergonomic problem(SONY VGP-BPS13Q Battery).

Discomfort might be caused by previous poor posture and atrophied muscular systems caused by limited physical exercise. Fine art painters are also often subject to neck and shoulder pains due to their posture and the repetitiveness of their movements while painting(SONY Vaio VGN-FW21M Battery).