history of touch screens

8/8/2019 History of Touch Screens

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INDEX

i. Certificateii. Index

1.What is touch screen technology?.............................................12.History of touch screens....23.Patents....24.Basic Types of touch screens

a. Resistive..3b.Capacitive....4c. Surface wave Technology5d.Infra-red Matrix Touch Screens6e. Strain Gauge Touch Screens7

5.Things to consider....76.Main Touch Screen Components.....97.Applications and Uses.10


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What is Touch Screen Technology?

Touch screens best suit applications that require frequent interaction with non-technical users or

must work in dirty environments. The devices are easy to use and can tolerate dirt and moisturethat would quickly disable a keyboard or a mouse. Some Touch screens can work through a 2-

inch thick barrier. This feature can protect both the system from user abuse and the user from the

systems environment. Compact designs can also benefit from touch screen technology. Because

Touch screens are integral to the display device, the screens eliminate the need for a separate

keypad. You can make hand-held devices with Touch screens as small as the display itself.

Touch screen technology comprises a variety of options that let you match the technology to

your application. For example, a touch screens sensor uses one of five mechanisms; resistance,

capacitance, acoustics, optics, and mechanical force. The first step in successfully applying

Touch screens, therefore, is to understand these options.


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History of touch screens

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. 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 came on the scene

developed by Sam Hurst and Elographics. In 1977, Elographics developed and patented five-

wire resistive technology, the most popular touch screen technology in use today. On February

24, 1994, the company officially changed its name from Elographics to Elo TouchSystems.

Patents

US3662105: Electrical Sensor Of Plane Coordinates

Inventor(s)

Hurst; George S. , Lexington, KY

Parks; James E. , Lexington, KY

Issued/Filed Dates:May 9, 1972 / May 21, 1970

US3798370: Electrographic Sensor For Determining Planar Coordinates

Inventor(s)

Hurst; George S. , Oak Ridge, TN

Issued/Filed Dates:March 19, 1974 / April 17, 1972


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Basic types of systems used for touch screens

There are three basic systems that are used -

Resistive

The resistive system consists of a normal glass panel that is covered with a conductive and aresistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer

is placed on top of the whole setup. An electrical current runs through the two layers while themonitor is operational. When a user touches the screen, the two layers make contact in that exact

spot. The change in the electrical field is noted and the coordinates of the point of contact arecalculated by the computer. Once the coordinates are known, a special driver translates the touch

into something that the operating system can understand, much as a computer mouse drivertranslates a mouse's movements into a click or a drag.


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Capacitive

In the capacitive system, a layer that stores electrical charge is placed on the glass panel of themonitor. When a user touches the monitor with his or her finger, some of the charge istransferred to the user, so the charge on the capacitive layer decreases. This decrease is measured

in circuits located at each corner of the monitor. The computer calculates, from the relativedifferences in charge at each corner, exactly where the touch event took place and then relays

that information to the touchscreen driver software. One advantage that the capacitive system hasover the resistive system is that it transmits almost 90 percent of the light from the monitor,

whereas the resistive system only transmits about 75 percent. This gives the capacitive system amuch clearer picture than the resistive system.


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Surface acoustic wave

On the monitor of a surface acoustic wave system, two transducers (one receiving and onesending) are placed along the x and y axes of the monitor's glass plate. Also placed on the glassare reflectors -- they reflect an electrical signal sent from one transducer to the other. The

receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant,and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for

100-percent light throughput and perfect image clarity. This makes the surface acoustic wavesystem best for displaying detailed graphics (both other systems have significant degradation in

clarity).

Another area in which the systems differ is in which stimuli will register as a touch event. Aresistive system registers a touch as long as the two layers make contact, which means that it

doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the otherhand, must have a conductive input, usually your finger, in order to register a touch. The surface

acoustic wave system works much like the resistive system, allowing a touch with almost anyobject -- except hard and small objects like a pen tip.


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Infra Red Matrix Touch Screens

It use an array of photodiodes on two adjacent screen edges with correspondingphoto sensors on the opposite edges. These diode/sensor pairs establish an optical grid across the

screen. Any object that touches the screen breaks the optical-grid lines that cross the touch point,causing drops in the corresponding photo sensor output signals. These drops indicate the touch

point coordinates. Rather than simultaneously establishing all grid lines, IR screen controllerstypically scan through the array. This type has no glass panel construction that may reduce

visibility of the display. It also has no tactile sense so the user may falsely activate a touch sincethe activation will happen before the user actually feels the touch of the display withtheir finger. The life span is excellent - infinity.


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The Strain-gauge Touch Screen

This screen have pressure sensors that measure at each corner the stresses that a touchto the screen produces. The ratio of the four readings indicates the touch point coordinates. The

platform touch screen doesnt use a screen. Instead, the monitor or display device rests on aplatform with force measurement sensors at the corners of the base. A touch to the display device

translates to forces at the platforms base corners. The platforms controller performs the vectorcalculations that determine the touch point from the four force measurements through rigid body

mechanics. The controller tracks out static forces, such as gravity, and repetitive forces, such asvibration. This type also has no glass panel construction that may reduce visibility of the

display. The platform type is a good concept in theory because there is no integration of touchcomponents into the display. You need only set the display on the touch base, calibrate and go.

Practically, problems occur when the display is moved only a very small amount on the platform

base or if even the display is tipped up or down fordifferent heights of viewing. This throws off the base vector values as initially calibrated andtherefore the calibration. The life span is excellent - infinity.

Things to Consider

Once you understand the touch screen mechanisms, your next step is to consider the conditions

under which your system must work. Moisture, grease, dust, and other contaminants that have noeffect on some touch screens but can cripple others. You need to know if a bare finger, a gloved

finger, a stylus, or any combination will activate your system. Keep in mind also, the type ofhandling the system will receive. A system in a hospital will receive more reasonable care than a

public information kiosk, which is more susceptible to vandalism. Other factors may also have a bearing on your applications. By understanding basic touch screen technology and your

operating environment, you can begin to evaluate the range of choices. The comparison chartshows some of the tradeoffs for various touch screen options. Although most of the technologies

are comparable in price, Resistive touch screens are typically the least expensiveoption. Four wire resistive Touch screens, however, are highly susceptible to wear out and all

Resistive types aresusceptible to surface damage because of their flexible outer layer.

Touch screen vendors, such as Elo Touchsystems and MicroTouch, have addressed the damage

and wear out problems of Resistive touch screens with the creation of tougher outer coatings andthe adoption of the five wire approach. Resistive touch screens wear out because repeated flexing

of the membrane can crack its resistive coating. Four wire touch screen membranes need uniformsurface resistivity for the sensor to accurately determine touch points. Cracks quickly ruin that

uniformity. Five wire screens, in contrast, require only that the membrane be somewhatconductive. Cracking must be severe to affect the five wire systems membrane. The

five wire screens, therefore, have 35 million touches per point, whereas four wire systems offeronly 1 to 4 million touches per point.


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Five wire screens are also less affected by surface damage, such as cuts, than are four wirescreens. A cut in a four wire screens membrane compromises the membranes ability to

establish a uniform voltage gradient, making accurate touch point determination impossible. Thefive-wire systems membrane, however, is merely a probe, so cuts, and even holes, do not affect

its accuracy. Cuts and holes may create dead spots on the screen but dont totally disable the

system.

Unlike Resistive touch screens, Capacitive touch screens are all glass and have no flexing parts.

As a result, Capacitive touch screens are highly resistant to physical surface damage. Despite theovercoat of a protective thin layer of glass, the conductive coating will eventually wear off

through repeated touches. This is accelerated when used in dirty environments where the dirt hasabrasive properties. Their main drawback is that the screens depend upon the users conductivity

for operation and typically dont work if the user is wearing gloves. Vendors have developedsome Capacitive systems, however, that work with gloves and other insulating barriers.

Capacitive touch screens had other drawbacks, such as accuracy limits and drift (the change ofsensor calibration over time). Vendors have corrected both limitations such as improving the

accuracy of capacitive screens using a multi-point calibration procedure built into the controllerand software. The calibration procedure prompts the user to touch a series of points on the

display screen. The controller then calculates correction factors that accommodate irregularitiesin both the touch screen and the display. The correction factors improve position

accuracy to within 1%. In settings in which the system must be water and contaminationresistant, Acoustic touch screens prove troublesome. Dust, grease and water drops on the

screens surface can disturb the acoustic signal enough todegrade accuracy or even generate false touch indications. Unless you apply it carefully, any

sealant that you use to make the touch screen water resistant dampens the acoustic signal. Thesealant may also make the screen inoperable. Vendors of the SAW type have come up with a

gasket material which has open pores and allows the sound energy to pass through but this maynot be enough as the open pores collect dust and dirt and in time cause the same problems of

degraded accuracy.The Strain-gauge Platform Touch Bases are the simplest to install in the field. You simply set the

display on the pedestal. Their drawback is the need for frequent calibration. When you place thedisplay on the platform, you must then calibrate the sensors. The sensors need recalibration

whenever the display changes position on the pedestal. The sensors are also subject to falsereadings based on shock and vibration to the pedestal.

One technology that appears to be declining is the Infra Red Matrix touch screen. IR screens aresusceptible to dust and other contaminants, need special bezels for daylight use, have more

possible points of failure, and cost in scale with the array size. IR screens also suffer fromparallax problems when used with curved screens.

Because the light must travel in a straight line from source to sensor, the optical grid that formsthe touch-sensing surface must be flat. If used with CRT displays having curved faces, the

optical grid floats above the screen. This displacement causes parallax between the display andthe optical grid, resulting in possible misalignment between the measured and intended touch

points if the user views the screen from an angle. The effect is mostpronounced at the corners. Having the optical sensor grid float above the screen also causes the

touch sensor to register a touch before the users finger reaches the display screen. This featuredeprives the user of tactile feedback and could result in unintended activation of the screen.


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The primary advantages of IR Touch screens are their clarity and immunity to drift. The LEDand sensor arrays of an IR touch screen need no substrate, so the touch screen doesnt place

anything between the display and the user that might reduce the displays brightness. Further,because the array forms a stationary optical grid, the touch point positioning cannot drift. These

advantages may outweigh IRs limitations in many applications.

The many tradeoffs between touch screen technology options are subject to change. Vendors areconstantly improving their technology to reduce or eliminate the drawbacks inherent in eachchoice. Vendors are also creating packaging that extends the utility of their Touch screens.

As far as price, the resistive system is the cheapest; its clarity is the lowest of the three, and its

layers can be damaged by sharp objects. The surface acoustic wave setup is usually the most

expensive.

Main Touch Screen Components

Touch Sensor

A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over

a display screen so that the responsive area of the panel covers the viewable area of the display

screen.

The sensor generally has an electrical current or signal going through it and touching the screen

causes a voltage or signal change. This voltage change is used to determine the location of thetouch to the screen.

Controller

The controller is a small PC card that connects between the touch sensor and the PC. It takes

information from the touch sensor and translates it into information that PC can understand.


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Software Driver

The driver is a software that allows the touch screen and computer to work together. It tells the

operating system how to interpret the touch event information that is sent from the controller.

Most touch screen drivers today are a mouse-emulation type driver. This makes touching the

screen the same as clicking your mouse at the same location on the screen.

Application & Uses

Uses of Touch Screen

The touch screen is one of the simplest PC interfaces to use, making it the interface of choice for

a large number of applications. Following are uses of touch screen.

1) Public Information Displays

Tourism displays, trade show displays, Information kiosks and other electronic displays are used

by large number of people that have little or no computing experience. The touch screen

interface is easier to use than other input devices especially for novice users. A touch screen is

useful to make your information more easily accessible by allowing users to navigate your

presentation by simply touching the display screen.

2) Retail and Restaurant Systems

In retail or restaurant environment, touch screen systems are easy to use so employees can get

work done faster and also training time can be reduced for new employees. As input is present

right on the screen, valuable counter space can be saved. Touch screens can be used in order

entry stations, cash registers, seating, reservation systems and more.


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3) Control and Automation Systems

The touch screen device is useful in systems ranging from industrial process control to home

automation. Valuable workspace can be saved by integrating the input device with the display. In

real-time by simply touching the screen and with a graphical interface, operators can monitor and

control complex operations.

4) Computer Based Training

The touch screen interface is more user-friendly than other input devices so overall training time

for computer novices and therefore training expense can be reduced. It can also more useful to

make learning more fun and interactive, which can lead to a more beneficial training experience

for both students and educators.

5) Assistive Technology

The touch screen interface is very useful for those having difficulty using other input devices

such as a mouse or keyboard. When touch screen used with software such as on-screen

keyboards or other assistive technology, they can help make computing resources more available

to people that have difficulty using computers.

history of touch screens

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