406 Touch Screen

8/2/2019 406 Touch Screen

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INTRODUCTIONA touchscreen is a display that can detect the

presence and location of a touch within the displayarea, generally refers to touch or contact to thedisplay of the device by a finger or hand.touchscreen is also an input device. The screensare sensitive to pressure; a user interacts with thecomputer by touching pictures or words on thescreen,Touchscreens can also sense other passiveobjects, such as a stylus, The touchscreen has twomain attributes. First, it enables one to interactwith what is displayed directly on the screen,where it is displayed, rather than indirectly withamouse or touchpad. Secondly, it lets one do sowithout 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, asterminals, to networks. They also play a prominentrole in the design of digital appliances such as thepersonal digital assistant (PDA),satellite navigationdevices, mobile phones, and video games


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TECHNOLOGIESThere are a number of types of touchscreentechnology available now

1.RESISTIVEA resistive touchscreen panel is composed

of several layers, the most important of which aretwo thin, metallic, electrically conductive layersseparated by a narrow gap. When an object, suchas a finger, presses down on a point on the panel's

outer surface the two metallic layers becomeconnected at that point: the panel then behaves asa pair of voltage dividers with connected outputs.This causes a change in the electrical current whichis registered as a touch event and sent to thecontroller for processing. In another way Theresistive system consists of a normal glass panel

that is covered with a conductive and a resistivemetallic layer. These two layers are held apart byspacers, and a scratch-resistant layer is placed ontop of the whole setup. An electrical current runsthrough the two layers while the monitor isoperational. When a user touches the screen, thetwo layers make contact in that exact spot. The

change in the electrical field is noted and thecoordinates of the point of contact are calculatedby the computer. Once the coordinates are known,a special driver translates the touch into something


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that the operating system can understand, muchas a computer mouse driver translates a mouse'smovements into a click or a drag.

2.SURFACE ACOUTIC WAVESurface acoustic wave (SAW) sumit

technology uses ultrasonic waves that pass overthe touchscreen panel. When the panel is touched,a portion of the wave is absorbed. This change inthe ultrasonic waves registers the position of the

touch event and sends this information to thecontroller for processing. Surface wave touchscreen panels can be damaged by outsideelements. Contaminants on the surface can alsointerfere with the functionality of thetouchscreen,an din surface acoustic wave system,two transducers (one receiving and one sending)

are placed along the x and y axes of the monitor'sglass plate. Also placed on the glass are reflectors -- they reflect an electrical signal sent from onetransducer to the other. The receiving transducer isable to tell if the wave has been disturbed by atouch event at any instant, and can locate itaccordingly. The wave setup has no metallic layers

on the screen, allowing for 100-percent lightthroughput and perfect image clarity. This makesthe surface acoustic wave system best fordisplaying detailed graphics .


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3.Capacitivecapacitive touchscreen panel consists of aninsulator such as glass, coated with a transparent

conductor such as indium tin oxide (ITO).[2][3]Asthe human body is also a conductor, touching thesurface of the screen results in a distortion of thelocal electrostatic field, measurable as a change incapacitance. Different technologies may be used todetermine the location of the touch. The locationcan be passed to a computer running a software

application which will calculate how the user'stouch relates to the computer software. And incapacitive system, a layer that stores electricalcharge is placed on the glass panel of the monitor.When a user touches the monitor with his or herfinger, some of the charge is transferred to theuser, so the charge on the capacitive layer

decreases. This decrease is measured in circuitslocated at each corner of the monitor. Thecomputer calculates, from the relative differencesin charge at each corner, exactly where the touchevent took place and then relays that informationto the touch-screen driver software. Oneadvantage that the capacitive system has over the

resistive system is that it transmits almost 90percent of the light from the monitor, whereas theresistive system only transmits about 75 percent.This gives the capacitive system a much clearer


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picture than the resistive system

4.SURFACE CAPACITANCEIn 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 auniform electrostatic field. When a conductor, suchas a human finger, touches the uncoated surface, acapacitor is dynamically formed. The sensor'scontroller can determine the location of the touchindirectly from the change in the capacitance asmeasured from the four corners of the panel. As it

has no moving parts, it is moderately durable buthas limited resolution, is prone to false signalsfrom parasitic capacitive coupling, and needscalibration during manufacture. It is thereforemost often used in simple applications such as


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industrial controls and kiosks.

5.PROJECTED CAPACITANCE

Projected Capacitive Touch (PCT)technology is a capacitive technology whichpermits more accurate and flexible operation, byetching the conductive layer. An XY array is formedeither by etching a single layer to form a gridpattern 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 manyLCDdisplays).Applying voltage to the array creates a grid ofcapacitors. Bringing a finger or conductive stylusclose to the surface of the sensor changes the localelectrostatic field. The capacitance change at every

individual point on the grid can be measured toaccurately determine the touch location.[5] Theuse of a grid permits a higher resolution thanresistive technology and also allows multi-touchoperation. The greater resolution of PCT allowsoperation without direct contact, such that theconducting layers can be coated with further

protective insulating layers, and operate evenunder screen protectors, or behind weather andvandal-proof glass.PCT is used in a wide range of applications


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SSSincluding point of sale systems, smartphones,and public information kiosks. Visual Planet's ViPInteractive Foil is an example of a kiosk PCT

product, where a gloved hand can register a touchon a sensor surface through a glasswindow.[6]Examples of consumer devices usingprojected capacitive touchscreens include AppleInc.'s iPhone and iPod Touch, HTC's HD2, G1, andHTC Hero, Motorola's Droid, Palm Inc.'s Palm Preand Palm Pixi and more recently the LG KM900

Arena, Microsoft's Zune HD, Sony Walkman Xseries, Sony Ericsson's Aino and now Vidalco'sEdge, D1 and Jewel, and the Nokia X6 phone.

6.INFRAREDConventional optical-touch systems use an array ofinfrared (IR) light-emitting diodes (LEDs) on two

adjacent bezel edges of a display, withphotosensors placed on the two opposite bezeledges to analyze the system and determine atouch event. The LED and photosensor pairs createa grid of light beams across the display. An object(such as a finger or pen) that touches the screeninterrupts the light beams, causing a measured

decrease in light at the correspondingphotosensors. The measured photosensor outputscan be used to locate a touch-point coordinate.Widespread adoption of infrared touchscreens has


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been hampered by two factors: the relatively highcost of the technology compared to competingtouch technologies and the issue of performance in

bright ambient light. This latter problem is a resultof background light increasing the noise floor atthe optical sensor, sometimes to such a degreethat the touchscreens LED light cannot bedetected at all, causing a temporary failure of thetouch screen. This is most pronounced in directsunlight conditions where the sun has a very high

energy distribution in the infrared region.However, certain features of infrared touch remaindesirable and represent attributes of the idealtouchscreen, including the option to eliminate theglass or plastic overlay that most other touchtechnologies require in front of the display. Inmany cases, this overlay is coated with an

electrically conducting transparent material suchas ITO, which reduces the optical quality of thedisplay. This advantage of optical touchscreens isextremely important for many device and displayvendors since devices are often sold on theperceived quality of the user display experience.Another feature of infrared touch which has been

long desired is the digital nature of the sensoroutput when compared to many other touchsystems that rely on analog-signal processing todetermine a touch position. These competing


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analog systems normally require continual re-calibration, have complex signal-processingdemands (which adds cost and power

consumption), demonstrate reduced accuracy andprecision compared to a digital system, and havelonger-term system-failure modes due to theoperating environment.

7.STRAIN GUAGEIn a strain gauge configuration, also called

force panel technology, the screen is spring-mounted on the four corners and strain gauges areused to determine deflection when the screen istouched. This technology has been around sincethe 1960s but new advances by Vissumo and F-Origin have made the solution commercially viable.It can also measure the Z-axis and the force of a

person's touch. Such screens are typically used inexposed public systems such as ticket machinesdue to their resistance to vandalism.

8.OPTICAL IMAGINGA relatively-modern development in

touchscreen technology, two or more image

sensors are placed around the edges (mostly thecorners) of the screen. Infrared backlights areplaced in the camera's field of view on the othersides of the screen. A touch shows up as a shadow


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and each pair of cameras can then be triangulatedto locate the touch or even measure the size of thetouching object (see visual hull). This technology is

growing in popularity, due to its scalability,versatility, and affordability, especially for largerunits.Dispersive signal technologyIntroduced in 2002 by 3M, this system uses sensorsto detect the mechanical energy in the glass thatoccurs due to a touch. Complex algorithms then

interpret this information and provide the actuallocation of the touch.[10] The technology claims tobe unaffected by dust and other outside elements,including scratches. Since there is no need foradditional elements on screen, it also claims toprovide excellent optical clarity. Also, sincemechanical vibrations are used to detect a touch

event, any object can be used to generate theseevents, including fingers and stylus. A downside isthat after the initial touch the system cannotdetect a motionless finger.

9.ACOUSTIC PULSE RECOGNITIONThis system, introduced by Tyco International's Elo

division in 2006, uses more than two piezoelectrictransducers located at some positions of thescreen to turn the mechanical energy of a touchinto an electronic signal. The screen hardware then


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uses an algorithm to determine the location of thetouch based on the transducer signals. This processis similar to triangulation used in GPS. The

touchscreen itself is made of ordinary glass, givingit good durability and optical clarity. It is usuallyable to function with scratches and dust on thescreen with good accuracy. The technology is alsowell suited to displays that are physically larger. Aswith the Dispersive Signal Technology system, afterthe initial touch, a motionless finger cannot be

detected. However, for the same reason, the touchrecognition is not disrupted by any resting objects.10.CODED LCD: Bidirectional ScreenA new system that turns LCD displays into giantcameras that provide gestural control of objectson-screen was introduced by MIT Media Lab inDecember, 2009. Instead of an LCD, an array of

pinholes is placed in front of sensors. Light passingthrough each pinhole strikes a small block ofsensors producing a low-resolution image. Sinceeach pinhole image is taken from a slightlydifferent position, all combined images provide agood depth information about the sensed image.Pinholes are problematic because they allow very

little light to reach the sensors, requiringimpractically long exposure times. Instead ofpinholes, an array of liquid crystals could worksimilarly but more effectively: The LCD's panel is


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composed of patterns of 19-by-19 blocks, eachdivided into a regular pattern of differently sizedblack-and-white rectangles. Each white area of the

bi-colored pixels allows light to pass through.Background software uses 4D light fields tocalculate depth map, changes the scene, andcollects gesture information. The LCD alternatesbetween mask pattern display and a normal scenedisplay at a very high frequency/rate.

First computers became more visual, thenthey took a step further to understandvocal commands and now they have gonea step further and became TOUCHY', that

is skin to screen.A touchscreen is an easy to use inputdevice that allows users to control PCsoftware and DVD video by touching the
http://www.seminarprojects.com/newthread.php?fid=53


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display screen. A touch system consists ofa touch Sensor that receives the touchinput, a Controller, and a Driver. The most

commonly used touch technologies arethe Capacitive & Resistive systems. Theother technologies used in this field areInfrared technology, Near Field Imaging &SAW (surface acoustic wave technology).These technologies are latest in this fieldbut are very much expensive.

The uses of touch systems as GraphicalUser Interface (GUI) devices for computerscontinues to grow popularity. Touchsystems are used for many applicationssuch as ATM's, point-of-sale systems,industrial controls, casinos & public kiosksetc. Touch system is basically an

alternative for a mouse or keyboard.Various companies involved indevelopment of touch systems mainly arePhilips, Samsung etc. Even touch screenmobile phones have been developed byPhilips.

A touchscreen is an easy to

use input device that allows users tocontrol PC software and DVD video bytouching the display screen.A touch system consists of a touch Sensor


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that receives the touch input, a Controller,and a Driver. The touch screen sensor is aclear panel that is designed to fit over a

PC. When a screen is touched, the sensordetects the voltage change and passes thesignal to the touch screen controller. Thecontroller that reads & translates thesensor input into a conventional busprotocol (Serial, USB) and a softwaredriver which converts the bus information

to cursor action as well as providingsystems utilitiesAs the touch sensor resides between theuser and the display while receivingfrequent physical input from the uservacuum deposited transparent conductorsserve as primary sensing element. Vacuum

coated layers can account for a significantfraction of touch system cost. Cost &application parameters are chief criteriafor determining the appropriate typedetermining the system selection.Primarily, the touch system integratormust determine with what implement the

user will touch the sensor with & whatprice the application will support.Applications requiring activation by agloved finger or arbitrary stylus such as a


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plastic pen will specify either a low costresistive based sensor or a higher costinfra-red (IR) or surface acoustic wave

(SAW) system. Applications anticipatingbare finger input or amenable to atethered pen comprises of the durable &fast capacitive touch systems. A higherprice tag generally leads to increaseddurability better optical performance &larger price.

The most commonly used systems aregenerally the capacitive & resistivesystems. The other technologies used inthis field are Infrared technology & SAW(surface acoustic wave technology) thesetechnologies are latest in this field but arevery much expensive.

How Does a Touchscreen Work?A basic touchscreen has three maincomponents: a touch sensor, a controller,and a software driver. The touchscreen isan input device, so it needs to becombined with a display and a PC or otherdevice to make a complete touch input

system.


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I.TouchSensorA touch screen sensor is a clear glass panelwith a touch responsive surface. The

touch sensor/panel is placed over adisplay screen so that the responsive areaof the panel covers the viewable area ofthe video screen. There are severaldifferent touch sensor technologies on themarket today, each using a differentmethod to detect touch input. The sensor

generally has an electrical current or signalgoing through it and touching the screencauses a voltage or signal change. Thisvoltage change is used to determine thelocation of the touch to the screen.2. ControllerThe controller is a small PC card that

connects between the touch sensor andthe PC. It takes information from thetouch sensor and translates it intoinformation that PC can understand. Thecontroller is usually installed inside themonitor for integrated monitors or it ishoused in a plastic case Tor external touch

addons/overlays. The controllerdetermines what type ofinterface/connection you will need on thePC. Integrated touch monitors will have an


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extra cable connection on the back for thetouchscreen. Controllers are available thatcan connect to a Serial/COM port (PC) or

to a USB port (PC or Macintosh).Specialized controllers are also availablethat work with DVD players and otherdevices.3.Software DriverThe driver is a software update for the PCsystem that allows the touchscreen and

computer to work together. It tells thecomputer's operating system how tointerpret the touch event information thatis sent from the controller. Most touchscreen drivers today are a mouse-emulation type driver. This makestouching the screen the same as clicking

your mouse at the same location on thescreen. This allows the touchscreen towork with existing software and allowsnew applications to be developed withoutthe need for touchscreen specificprogramming. Some equipment such asthin client terminals, DVD players, and

specialized computer systems either donot use software drivers or they have theirown built-in touch screen driver.


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Comparing Touch TechnologiesEach type of screen has uniquecharacteristics that can make it a better

choice for certain applications.

Touchscreen Specifications

Touch Type: Screen Sizes: Cable Interface:Touch Resolution: Response Time:Positional Accuracy: Light Transmission:

Life Expectancy: Temperature:Humidity:Chemical Resistance: Software Drivers:

Software, Cables, and AccessoriesSoftware:Touchscreen related software, including

presentation development software andother utilities

1. MYTSOFTMy-T-Soft On-Screen Keyboard Software2. RIGHTTOUCHRightTouch Right-Click

Utility Software


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APPLICATIONSThe touch screen is one of the easiest PCinterfaces to use, making it the interface

of choice for a wide variety ofapplications. Here are a few examples ofhow touch input systems are being usedtoday:1. Public Information DisplaysInformation kiosks, tourism displays, tradeshow displays, and other electronic

displays are used by many people thathave little or no computing experience.The user-friendly touch screen interfacecan be less intimidating and easier to usethan other input devices, especially fornovice users. A touchscreen can helpmake your information more easily

accessible by allowing users to navigateyour presentation by simply touching thedisplay screen2. Retail and Restaurant SystemsTime is money, especially in a fast pacedretail or restaurant environment.Touchscreen systems are easy to use so

employees can get work done faster, andtraining time can be reduced for newemployees. And because input is doneright on the screen, valuable counter


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space can be saved. Touchscreens can beused in cash registers, order entrystations, seating and reservation systems,

and more3. Customer Self-ServiceIn today's fast pace world, waiting in line isone of the things that has yet to speed up.Self-service touch screen terminals can beused to improve customer service at busystores, fast service restaurants,

transportation hubs, and more. Customerscan quickly place their own orders orcheck themselves in or out, saving themtime, and decreasing wait times for othercustomers. Automated bank teller (ATM)and airline e-ticket terminals are examplesof self-service stations that can benefit

from touchscreen input.4. Control and Automation SystemsThe touch screen interface is useful insystems ranging from industrial processcontrol tc home automation. Byintegrating the input device with thedisplay, valuable workspace can be saved.

And with a graphical interface, operatorscan monitor and control complexoperations in real-time by simply touchingthe screen.


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4. Computer Based TrainingBecause the touch screen interface ismore user-friendly than other input

devices, overa training time for computernovices, and therefore training expense,can be reduced. It can also help to makelearning more fun and interactive, whichcan lead to a more beneficia trainingexperience for both students andeducators.

5. Assistive TechnologyThe touch screen interface can bebeneficial to those that have difficultyusing other input devices such as a mouseor keyboard. When used in conjunctionwith software such as on-screenkeyboards, or other assistive technology,

they can help make computing resourcesmore available to people that havedifficulty using computers.ADVANTAGES OVER OTHER POINTINGDEVICESTouch screens have several advantagesover other pointing devices;

Touching a visual display of choicesrequires little thinking and is a form ofdirect manipulation that is easy to learn. Touch screens are the fastest pointing


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devices. Touch screens have easier hand eyecoordination than mice or keyboards.

No extra work space is required as withother pointing devices. Touch screens are durable in publicaccess and in high volume usage.Disadvantages User's hand may obscure the screen. Screens need to be installed at a lower

position and tilted to reduce arm fatigue. Some reduction in image brightnessmay occur. They cost more than alternativedevices.ConclusionTouch systems represent a rapidly growing

subset of the display market. The majorityof touch systems include touch sensorsrelying on vacuum-deposited coatings, sotouch coatings present opportunity forsuppliers of vacuum coatings and coatingequipments.Touch sensor manufactures currently

require thin films in the areas oftransparent conductors, opticalinterference coating and mechanicalprotective coatings. Touch sensors


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technical requirements dovetail well withthose of the flat panel and display filtermarkets. The reality should provide value

added opportunities to operationsparticipating in these areas.

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406 Touch Screen