Touchscreen

 ( American Inventions ) 

In 1972, a group at the University of Illinois filed for a patent on an optical touchscreenEbeling, F.; R. Johnson; R. Goldhor. "Infrared light beam x-y position encoder for display devices", , granted 27 November 1973. that became a standard part of the Magnavox Plato IV Student Terminal. These touchscreens had a crossed array of 16×16 infrared position sensors mounted in front of a monochrome plasma display panel, capable of sensing any fingertip-sized opaque object in close proximity to the screen.

In 1977, American company Elographics—in partnership with Siemens—began work on developing a transparent implementation of an existing opaque touchpad technology developed by Elographics' founder George Samuel Hurst. The resulting resistive technology touch screen was first shown at the World's Fair at Knoxville in 1982.

Also in 1983, an optical touchscreen utilizing infrared and receivers was used on the HP-150, making it one of the world's earliest commercial touchscreen computers. Bob Boie of AT&T Bell Labs used capacitance to track the mechanical changes in thickness of a soft, deformable overlay membrane when physical objects interacted with it, allowing the flexible surface to be easily replaced if damaged. While derivative sources retrospectively described this as a major multi-touch advancement, no evidence indicates Boie ever patented a rugged multi-touch capacitive touchscreen suitable for modern mobile devices.

The 1980s saw touchscreens integrated into various consumer and industrial applications. Touch-sensitive control-display units (CDUs) were evaluated for commercial aircraft flight decks in the early 1980s to reduce pilot workload and improve situational awareness.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. General Motors also tasked its Delco Electronics division with replacing an automobile's non-essential functions with a monochrome CRT touchscreen known as the Electronic Control Center (ECC). Featured on the 1985–1989 Buick Riviera and 1988–1989 Buick Reatta, the ECC ultimately proved unpopular due to technical problems and consumer technophobia. In 1985, the first commercially available graphical point-of-sale (POS) software, ViewTouch, was demonstrated on the 16-bit Atari 520ST color computer. The ViewTouch restaurant system by Giselle Bisson During Expo 88 in Brisbane, Australia, 56 touch screen information consoles (modified Sony Videotex Workstations) were deployed to provide expo visitors with digital information.

Consumer electronics also adopted early touch technology. Fujitsu released a touchpad for the Micro 16 in 1984 to accommodate complex kanji characters. Japanese PCs (1984) (12:21), Computer Chronicles Sega released graphic tablets like the Terebi Oekaki for the SG-1000 in 1985, and a graphic touch tablet for the Sega AI Computer in 1986. Technology Trends: 2nd Quarter 1986 , Japanese Semiconductor Industry Service - Volume II: Technology & Government Casio launched the Casio PB-1000 pocket computer in 1987 with a 4×4 matrix touchscreen.

Touchscreens had a reputation for being imprecise until 1988, when researchers at the University of Maryland Human–Computer Interaction Lab (HCIL) introduced the "Lift-off strategy." This provided visual feedback as users touched the screen, allowing them to adjust their finger position before the action took place upon lift-off, enabling the selection of tiny targets down to a single pixel on a VGA screen.

Between 1991 and 1992, the Sun Microsystems Star7 prototype PDA implemented a touchscreen with inertial scrolling. In 1993, IBM released the IBM Simon, widely considered the first touchscreen phone, while Bob Boie of AT&T Bell Labs patented a capacitive keypad/mouse. Despite early interest, Sega abandoned plans for a touchscreen successor to the Game Gear in the early 1990s due to the high cost of the technology, and touchscreens were not popularly used for video games until the release of the Nintendo DS in 2004.

The technology saw a massive commercial breakthrough in the 2000s. Apple patented its multi-touch capacitive touchscreen for mobile devices in 2004, and the first mobile phone to feature a capacitive touchscreen was the LG Prada, released in May 2007, shortly before the first iPhone. By 2009, touchscreen-enabled phones were rapidly gaining popularity, and by the fourth quarter of 2009, a majority of smartphones shipped globally featured touchscreens rather than traditional physical keys. In April 2015, the Apple Watch introduced consumer force-sensitive displays, allowing screens to sense how hard a user is touching the surface in addition to tracking multi-touch points.

Some 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, reducing the thickness and weight of the display, which is desirable in .

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.

Although some standard capacitance detection methods are projective, in the sense that they can be used to detect a finger through a non-conductive surface, they are very sensitive to fluctuations in temperature, which expand or contract the sensing plates, causing fluctuations in the capacitance of these plates. These fluctuations result in a lot of background noise, so a strong finger signal is required for accurate detection. This limits applications to those where the finger directly touches the sensing element or is sensed through a relatively thin non-conductive surface.

High frequency voltage pulses are applied to these conductors, one at a time. These pulses capacitively couple to every conductor that intersects it.

Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field, which in turn reduces the capacitance between these intersecting conductors. Any significant change in the strength of the signal sensed is used to determine if a finger is present or not at an intersection.

The capacitance change at every intersection on the grid can be measured to accurately determine one or more touch locations.

Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.The greater the number of intersections, the better the touch resolution and the more independent fingers that can be detected. This indicates a distinct advantage of diagonal wiring over standard x/y wiring, since diagonal wiring creates nearly twice the number of intersections.

A 30 i/o, 16×14 x/y array, for example, would have 224 of these intersections / capacitors, and a 30 i/o diagonal lattice array could have 435 intersections.

Each trace of an x/y mutual capacitance array only has one function, it is either an input or an output. The horizontal traces may be transmitters while the vertical traces are sensors, or vice versa.

Traces are sensed, one after the other until all the traces have been sensed. A finger may be detected anywhere along the whole length of a trace (even "off-screen"), but there is no indication where the finger is along that trace. If, however, a finger is also detected along another intersecting trace, then it is assumed that the finger position is at the intersection of the two traces. This allows for the speedy and accurate detection of a single finger.

Although mutual capacitance is simpler for multi-touch, multi-touch can be achieved using self-capacitance.

Self-capacitive touch screen layers are used on mobile phones such as the Sony Xperia Sola, the Samsung Galaxy S4, Galaxy Note 3, Galaxy S5, and Galaxy Alpha.

Self-capacitance is far more sensitive than mutual capacitance and is mainly used for single touch, simple gesturing and proximity sensing where the finger does not even have to touch the glass surface. Mutual capacitance is mainly used for multitouch applications. Many touchscreen manufacturers use both self and mutual capacitance technologies in the same product, thereby combining their individual benefits.

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 hybrids. Polyvinylidene fluoride (PVDF) plays a major role in this innovation due its high piezoelectric properties, which allow the tablet to sense pressure, making such things as digital painting behave more like paper and pencil.

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 2000s, 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 touch 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.

Unsupported touchscreens are still fairly common in applications such as ATMs and data kiosks, but are not an issue as the typical user only engages for brief and widely spaced periods.

Some devices have a mode which increases the sensitivity of the touchscreen. This allows the touchscreen to be used more reliably with gloves, but can also result in unreliable and phantom inputs. However, thin gloves such as medical gloves are thin enough for users to wear when using touchscreens; mostly applicable to medical technology and machines.