Touch screen report

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Touch screen report

  1. 1. Working of Touchscreen Amit Bhardwaj ContentsIntroduction……………………………………………………………………………..21.1 Four-Wire Resistive: ........................................................................................................ 7 1.2 Eight-Wire Variation: .......................................................................................... 8 1.3 Six- and Seven-Wire Variations: ......................................................................... 9About Touch Screen Displays:.............................................................................................. 14Pros and Cons of Touch screens: .......................................................................................... 18Touch screen Cons: ................................................................................................................ 18Advantages and Disadvantages:……………………………………………………………19Hand movements (if used with keyboard):.......................................................................... 18 Size: ................................................................................................................................. 23 Sequential Input:............................................................................................................ 23 Feedback: ........................................................................................................................ 23 Drag Operations: ........................................................................................................... 23Reference:……………………………………………………………………………………26 1
  2. 2. Working of Touchscreen Amit BhardwajINTRODUCTION:A touch screen is computer display screen that is sensitive to human touch, allowing a user tointeract with the computer by touching pictures or words on the screen. Touch screen areused with information kiosks (an interactive computer terminal available for public use, asone with internet access or site specific information), computer based training devices, andsystem designed to help individuals who have difficulty in manipulating a mouse orkeyboard.Touch screen technology can be used as an alternative user interface withapplication that normally requires a mouse, such as a web browser. Some applications aredesigned specifically for touch screen technology, often having larger icon and link thantypical PC application. Monitors are available with built in touch screen kit. A touch screenkit includes a touch screen panel, a controller, and a software driver. The touch screen panelsare is a clear panel attached externally to the monitors that plug in to a serial or a universalserial Bus (USB) port a bus Card installed inside the computer. The touch screen panelregisters touch event and passes these signal to controller.The controller then processes thesignals and sends the data to the processor. The software driver translates the touch eventsinto mouse events. Driver can be provided for both Window and Macintosh operatingsystems.Internal touch screen kits are available but require professional installation becausethe must be installed inside the monitors. Fig 1.1 2
  3. 3. Working of Touchscreen Amit BhardwajHISTORY OF TOUCH SCREEN MONITORS:Dr. Sam Hurst, founder of Elo-graphics, developed the first ―touch screen‖while he was aninstructor at the university of Kentucky in 1971.Ten stockholders founded Elo-graphics, Inc. in March 1971, to produce Graphical dataDigitizers for use in research and industrial application, with the, principal being Dr. SamHurst. He was on leave from the Oak Ridge National Laboratory to tech at the University ofKentucky for two years, where he was faced with a need to read a huge stack of strip chartdata. It would have taken two graduate student s approximately two month to do the task. Hestarted to thinking of a way to read the and during the process, the ―Elo-graph‖ (Electronicgraphics) coordinate measuring system and Elo-graphics the company were born. TheUniversity Kentucky research foundation applied for and was granted a patent on the Elo-graph. The foundation granted an exclusive license to Elo-graphics.The touch screen is one of the easiest to use and most intuitive of all PC interface of choicesfro a wide variety of applications. A touch interface to allows users to navigate a computersystem by touching icon or links on the screen.WHY TOUCH SCREEN:User interface PCs are quickly becoming the control device of choices for the plant floor,machine control and any application where the user interface is important. This change hasnot been without its difficulties. One challenge industrial PC manufacturers have faced issimplifying the human machine interface while maintaining accuracy of input. Industrialgrade touches Screen system have quickly become the input device of choice for severalreasons. Touch systems generally have no additional hardware to mount and protect, such asa mouse or keyboard. A flat panel display can also be sealed by the factory to prevent damagefrom dust and water. The ultra thin nature of a touch screen on a LCD saves critical space,which is a vital for most application.Durability is tested to over 35 million finger touches with no over performance degradation.1million-touch life max. 3
  4. 4. Working of Touchscreen Amit BhardwajDesign Flexibility: -Advanced design allows flat and spherical design.Touch screen are very intuitive; it is natural for people to respond to their environment bytouching. Touch screen are usually manipulated with ease and require minimalinstrumentation training for a user. Best of all, touch screens draw an operator ―into‖ theapplication, improving accuracy attention span and speed of response. Although the touchscreen system for the rigors of everyday life, for rugged environments and the best solutionfor your application.Touch screen Characteristics: Speed: high Accuracy: low (finger), high (pen) Speed control: yes Continuous movement: yes Directness: direction, distance, speed Fatigue: high Footprint: no Best uses: point, select 4
  5. 5. Working of Touchscreen Amit BhardwajThe touch screen can be operated by two ways:.1.Finger-Operated: 2.Stylus operated: Fig 4.1 fig 4.2Types of Touch Screen Technologies: 1. Resistive Touch Screen 2. Capacitive Touch Screen 3. Surface Acoustic Wave Touch Screen 4. Infrared Touch Screen 1. ResistiveA resistive touchscreen panel is composed of several layers, the most important of which aretwo thin, metallic, electrically conductive layers separated by a narrow gap. When an object,such as a finger, presses down on a point on the panels outer surface the two metallic layersbecome connected at that point: the panel then behaves as a pair of voltage dividers withconnected outputs. This causes a change in the electrical current which is registered as atouch event and sent to the controller for processing. 5
  6. 6. Working of Touchscreen Amit Bhardwaj fig 5.1All types of resistive touch screens:Resistive touch screens are used in more applications than any other touch technology– forexample, PDAs, point-of-sale, industrial, medical, and office automation, as well asconsumer electronics.All variations of resistive touch screens have some things in common: fig 5.1.1They are all constructed similarly in layers-a back layer such as glass with a uniform resistivecoating plus a polyester coversheet, with the layers separated by tiny insulating dots. Whenthe screen is touched, it pushes the conductive coating on the coversheet against the coatingon the glass, making electrical contact. The voltages produced are the analog representationof the position touched. An electronic controller converts these voltages into digital X and Ycoordinates which are then transmitted to the host computer.Because resistive touch screensare force activated, all kinds of touch input devices can activate the screen, including fingers,fingernails, styluses, gloved hands, and credit cards. All have similar optical properties,resistance to chemicals and abuse. 6
  7. 7. Working of Touchscreen Amit Bhardwaj fig 5.1.2Both the touch screen and its electronics are simple to integrate into imbedded systems,thereby providing one of the most practical and cost-effective touchscreen solutions.1.1 Four-Wire Resistive:Four-wire resistive technology is the simplest to understand and manufacture.It uses both theupper and lower layers in the touchscreen "sandwich" to determine the X and Y coordinates.Typically constructed with uniform resistive coatings of indium tin oxide (ITO on the innersides of the layers and silver buss bars along the edges, the combination sets up lines of equalpotential in both X and Y.In the illustration below, the controller first applies 5V to the backlayer. Upon touch, it probes the analog voltage with the coversheet, reading 2.5V, whichrepresents a left-right position or X axis.It then flips the process, applying 5V to thecoversheet, and probes from the back layer to calculate an up-down position or Y axis. At anytime, only three of the four wires are in use (5V, ground, probe). fig 5.1.3The primary drawback of four-wire technology is that one coordinate axis (usually the Yaxis), uses the outer layer, the flexible coversheet, as a uniform voltage gradient. The constantflexing that occurs on the outer coversheet with use will eventually cause microscopic cracksin the ITO coating, changing its electrical characteristics (resistance), degrading the linearityand accuracy of this axis.Unsurprisingly, four-wire touchscreens are not known for their 7
  8. 8. Working of Touchscreen Amit Bhardwajdurability. Typically, they test only to about 1 million touches with a finger-far less whenactivated by a pointed stylus which speeds the degradation process. Some four-wire productseven specify 100,000 activations within a rather large, 20 mm x 20 mm area. In the real worldof point-of-sale applications, a level of 100,000 activations with hard, pointed styluses(including fingernails, credit cards, ballpoint pens, etc.) is considered normal usage in just afew months time.Also, accuracy can drift with environmental changes. The polyestercoversheet expands and contracts with temperature and humidity changes, thereby causinglong-term degradation to the coatings as well as drift in the touch location.While all of thesedrawbacks can be insignificant in smaller sizes, they become increasingly apparent the largerthe touch screen. Therefore, Elo normally recommends four-wire touch screens inapplications with a display size of 6.4" or smaller. However, the relative low cost, inherentlow power consumption, and common availability of chipset controllers with support fromimbedded operating systems, makes four-wire touch screens ideal for hand-held devices suchas PDAs, wearable computers, and many consumer devices.1.2 Eight-Wire Variation:Eight-wire resistive touchscreens are a variation of four-wire construction. The primarydifference is the addition of four sensing points, which are used to stabilize the system andreduce the drift caused by environmental changes. Eight-wire systems are usually seen insizes of 10.4" or larger where the drift can be significant.As in four-wire technology, themajor drawback is that one coordinate axis uses the outer, flexible coversheet as a uniformvoltage gradient, while the inner or bottom layer acts as the voltage probe. The constantflexing that occurs on the outer coversheet will change its resistance with usage, degradingthe linearity and accuracy of this axis.Although the added four sensing points helps stabilizethe system against drift, they do not improve the durability or life expectancy of the screen. 8
  9. 9. Working of Touchscreen Amit Bhardwaj1.3 Five-Wire Resistive: fig 5.1.4As we have seen, four- and eight-wire touchscreens, while having a simple and elegantdesign, have a major drawback in terms of durability in that the flexing coversheet is used todetermine one of the axes. Field usage proves that the other axis rarely fails. Could it bepossible to construct a touch screen where all the position sensing was on the stable glasslayer? Then the coversheet would serve only as a voltage probe for X and Y. Microscopiccracks in the coversheet coating might still occur, but they would no longer cause non-linearity’s. The simple buss bar design is not sufficient and a more complex linearizationpattern on the edges is required. In the five-wire design, one wire goes to the coversheet (E)which serves as the voltage probe for X and Y. Four wires go to corners of the back glasslayer (A, B, C, and D). The controller first applies 5V to corners A and B and grounds C andD, causing voltage to flow uniformly across the screen from the top to the bottom. Upontouch, it reads the Y voltage from the coversheet at E.Then the controller applies 5V tocorners A and C and grounds B and D, and reads the X voltage from E again.So, a five-wiretouchscreen uses the stable bottom layer for both X- and Y-axis measurements.The flexiblecoversheet acts only as a voltage-measuring probe. This means the touchscreen continuesworking properly even with non-uniformity in the coversheets conductive coating. The resultis an accurate, durable and more reliable touchscreen over four- and eight-wire designs.1.4 Six- and Seven-Wire Variations:There are some manufacturers who claim improved performance over five-wire resistive withadditional wires.The six-wire variation adds an extra ground layer to the back of the glass. Itis not needed for improved performance, and in some cases is not even connected to thecompanion controller.The seven-wire variation adds two sense lines, like with the eight-wire 9
  10. 10. Working of Touchscreen Amit Bhardwajdesign, to decrease drift due to environmental changes. The proprietary "Z border" electrodepattern is a better solution to prevent drift. 2. Capacitive:A capacitive touch-screen panel is a sensor typically made of glass coated with a materialsuch as indium tin oxide (ITO). The sensor therefore exhibits a precisely controlled field ofstored electrons in both the horizontal and vertical axes - it achieves capacitance. The humanbody is also an electrical device which has stored electrons and therefore also exhibitscapacitance. Capacitive sensors work based on proximity, and do not have to be directlytouched to be triggered. It is a durable technology that is used in a wide range of applicationsincluding point-of-sale systems, industrial controls, and public information kiosks. It has ahigher clarity than Resistive technology, but it only responds to finger contact and will notwork with a gloved hand or pen stylus. Capacitive touch screens can also support Multi-touch. Examples include Apple Inc.’s iPhone and iPod touch, and HTC’s G1 & HTC Magic.Two types are available: Capacitive technology & Pen-touch CapacitiveFig 5.2 fig 5.3 3. Surface Acoustic WaveSurface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touch-screen 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 the location. Surface wave touchscreen panels can be damaged by 10
  11. 11. Working of Touchscreen Amit Bhardwajoutside elements. Contaminants on the surface can also interfere with the functionality of thetouchscreen. Fig 5.4 4. Infrared touch screen:Conventional optical-touch systems use an array of infrared (IR) light-emitting diodes(LEDs) on two adjacent bezel edges of a display, with photo sensors placed on the twoopposite bezel edges to analyze the system and determine a touch event.The LED and photo sensor pairs create a grid of light beams across the display. An object(such as a finger or pen) that touches the screen interrupts the light beams, causing ameasured decrease in light at the corresponding photo sensors.The measured photo sensor outputs can be used to locate a touch-point coordinate.Widespread adoption of infrared touch screens has been hampered by two factors: therelatively high cost of the technology compared to competing touch technologies and theissue of performance in bright ambient light.Another feature of infrared touch which has been long desired is the digital nature of thesensor output when compared to many other touch systems that rely on analog-signalprocessing to determine a touch position. Infrared touch is capable of implementing multi-touch, something most other touch technologies cannot easily achieve. 11
  12. 12. Working of Touchscreen Amit BhardwajFig 5.5 12
  13. 13. Working of Touchscreen Amit BhardwajWORKING OF TOUCH SCREEN MONITORS:A basic touchscreen has three main components: a touch sensor, a controller, and a softwaredriver. The touchscreen is an input device, so it needs to be combined with a display and a PCor other device to make a complete touch input system. fig 6.11. Touch Sensor :A touch screen sensor is a clear glass panel with a touch responsive surface. The touchsensor/panel is placed over a display screen so that the responsive area of the panel coversthe viewable area of the video screen. There are several different touch sensor technologieson the market today, each using a different method to detect touch input. The sensorgenerally has an electrical current or signal going through it and touching the screen causes avoltage or signal change. This voltage change is used to determine the location of the touchto the screen.2. Controller :The controller is a small PC card that connects between the touch sensor and the PC. It takesinformation from the touch sensor and translates it into information that PC can understand.The controller is usually installed inside the monitor for integrated monitors or it is housed ina plastic case for external touch add-ons/overlays. The controller determines what type ofinterface/connection you will need on the PC. Integrated touch monitors will have an extracable connection on the back for the touchscreen. Controllers are available that can connectto a Serial/COM port (PC) or to a USB port (PC or Macintosh). Specialized controllers arealso available that work with DVD players and other devices. 13
  14. 14. Working of Touchscreen Amit Bhardwaj3. Software Driver :The driver is a software update for the PC system that allows the touchscreen and computerto work together. It tells the computers operating system how to interpret the touch eventinformation 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 thesame location on the screen. This allows the touchscreen to work with existing software andallows new applications to be developed without the need for touchscreen specificprogramming. Some equipment such as thin client terminals, DVD players, and specializedcomputer systems either do not use software drivers or they have their own built-in touchscreen driver.About Touch Screen Displays:Touch screen displays are the most user-friendly PC interface. They are input devices, a wayto communicate with the PC. The user touches the screento select options presented on thescreen. Associated hardware and software are used to determine the location of thepress. Touch screen displays can be either internally mounted, or externally mounted on anexisting screen. An internally mounted screen is a touch screen input device that is designedto be installed on the inside of a PC monitor. It is commonly a touch sensitive glass panel thatuses a touch screen controller and a software driver to interface with a PC system. Theinternal touch screen requires a sometimes-technical installation, as the monitor needs to beopened and in some cases the touch screen controller needs to be wired to a power sourceinside the monitor. An external touch screen panel is a touch screen input device that isdesigned to mount on the outside of a PC monitor. The external touch screen does not requireany difficult installation or opening of the monitor. It is commonly a touch sensitive glasspanel that uses an external touch screen controller and a software driver to interface with aPC system. There are five basic types of touch screen displays: resistive, capacitive, infrared,surface acoustic wave (SAW) and strain gauge. Resistive and capacitive touch screendisplays are the most common. Resistive touch screens consist of a glass or acrylic panel thatis coated with electrically conductive and resistive layers. The thin layers are separated byinvisible separator dots. During operation, an electrical current moves through the screen.When pressure is applied to the touch screen, the layers are pressed together, causing achange in the electrical current and a touch event to be registered. A capacitive touch screenconsists of a glass panel with a capacitive (charge storing) material coating its surface. 14
  15. 15. Working of Touchscreen Amit BhardwajCircuits located at corners of the screen measure the capacitance of a person touching theoverlay. Frequency changes are measured to determine the X and Y coordinates of the touchevent.Infrared touch screens are similar to resistive products. Infrared touch screens projecthorizontal and vertical beams of infrared light over the surface of the screen. When a fingeror other object breaks those beams, the X/Y coordinates are calculated. Surface acousticwave (SAW) technology sends acoustic waves across a clear glass panel with a series oftransducers and reflectors.When a finger touches the screen, the waves are absorbed, causinga touch event to be detected at that point. In a strain gauge touch screen, the screen is springmounted on the four corners and strain gauges are used to determine deflection when thescreen is touched. This touch screen display technology can also measure the Z-axis 15
  16. 16. Working of Touchscreen Amit BhardwajComparing Touch TechnologiesEach type of screen has unique characteristics that can make it a better choice for certainapplications. The most widely used touchscreen technologies are the following:4-Wire Resistive Touchscreens4-Wire Resistive touch technology consists of a glass or acrylic panel that is coated withelectrically conductive and resistive layers. The thin layers are separated by invisibleseparator dots. When operating, an electrical current moves through the screen. Whenpressure is applied to the screen the layers are pressed together, causing a change in theelectrical current and a touch event to be registered.4-Wire Resistive type touch screens are generally the most affordable. Although clarity is lessthan with other touch screen types, resistive screens are very durable and can be used in avariety of environments. This type of screen is recommended for individual, home, school, oroffice use, or less demanding point-of-sale systems, restaurant systems, etcAdvantages Disadvantages•High touch resolution•Pressure sensitive, works with any stylus• Not affected by dirt, dust, water, or light• Affordable touchscreen technology • 75 % clarity• Resistive layers can be damaged by a sharp object• Less durable then 5-Wire Resistive technologyTouchscreen SpecificationTouchType:4-WireResistiveScreen Sizes: 12"-20" DiagonalCable Interface: PC Serial/COM Port or USB PortTouch Resolution: 1024 x 1024Response Time: 10 ms. MaximumPositional Accuracy: 3mm maximum errorLight Transmission: 80% nominalLife Expectancy: 3 million touches at one pointTemperature: Operating: -10°C to 70°C 16
  17. 17. Working of Touchscreen Amit BhardwajStorage: -30°C to 85°CHumidity: Pass 40 degrees C, 95% RH for 96hoursChemical Resistance: Alcohol, acetone, grease, and general household detergentSoftware Drivers: Windows XP / 2000 / NT / ME / 98 / 95, Linux, Macintosh OS5-Wire Resistive Touchscreens5-Wire Resistive touch technology consists of a glass or acrylic panel that is coated withelectrically conductive and resistive layers. The thin layers are separated by invisibleseparator dots. When operating, an electrical current moves through the screen. Whenpressure is applied to the screen the layers are pressed together, causing a change in theelectrical current and a touch event to be registered.5-Wire Resistive type touch screensare generally more durable than the similiar 4-WireResistive type. Although clarity is less than with other touch screen types, resistive screensare very durable and can be used in a variety of environments. This type of screen isrecommended for demanding point-of-sale systems, restaurant systems, industrial controls,and other workplace applications.AdvantagesDisadvantages• High touch resolution• Pressure sensitive, works with any stylus• Not affected by dirt, dust, water, or light• More durable then 4-Wire Resistive technology• 75 % clarity• Resistive layers can be damaged by a sharp object 17
  18. 18. Working of Touchscreen Amit BhardwajPros and Cons of Touch screens:The following overview lists advantages and disadvantages of touchscreens and summarizestheir characteristics.Touchscreen Pros:Direct: Direct pointing to objects, direct relationship between hand and cursor movement(distance, speed and direction), because the hand is moving on the same surface that thecursor is moving, manipulating objects on the screen is similar to manipulating them in themanual worldFast (but less precise without pen)Finger is usable, any pen is usable (usually no cable needed).No keyboard necessary for applications that need menu selections only -> saves desk spaceTouchscreen Cons:.Dirt: The screen gets Low precision (finger): Imprecise positioning, possible problems witheye parallaxis (with pen, too), the finger may be too large for accurate pointing with smallobjects -> a pen is more accurate.Hand movements (if used with keyboard): Requires that users move the hand away fromthe keyboard; a stylus requires also hand movements to take up the pen.Fatigue: Straining the arm muscles under heavy use (especially if the screen is placedvertically).Sitting/Standing position: The user has to sit/stand close to the screenScreen coverage: The users hand, the finger or the pen may obscure parts of the screen.Activation: Usually direct activation of the selected function, when the screen is touched;there is no special "activation" button as with a light pen or a mouse. 18
  19. 19. Working of Touchscreen Amit BhardwajUses for Touch screens:Best Suited to Applications Where... Opportunity for training is low Frequency of use is low Accurate positioning is not required Little or no text or numerical input is required Desk space is at a premium The environment may be chemically or otherwise "aggressive"Not Suited to Applications... Requiring training/trained users With high-frequency use Requiring accuracy Requiring a lot of typingUses of touch screen in regular life: The touch screen is one of the easiest PCinterfaces to use, making it the interface of choice for a wide variety of applications. Here area few examples of how touch input systems are being used today:Public Information DisplaysInformation kiosks, tourism displays, trade show displays, and other electronic displays are used by many people that have little or no computing experience. The user- friendly touch screen interface can be less intimidating and easier to use than other input devices, especially for novice users. A touch screen can help makeyour information more easily accessible by allowing users to navigate your presentation bysimply touching the display screen.Retail and Restaurant Systems Time is money, especially in a fast paced retail or restaurant environment. Touch screen systems are easy to use so employees can get work done faster, and training time can be reduced for new employees. And because input is 19
  20. 20. Working of Touchscreen Amit Bhardwajdone right on the screen, valuable counter space can be saved. Touch screens can be used incash registers, order entry stations, seating and reservation systems, and more.Customer self-services In todays fast pace world, waiting in line is one of the things that has yet to speed up. Self-service touch screen terminals can be used to improve customer service at busy stores, fast service restaurants, transportation hubs, and more. Customers can quickly place their own orders or check themselves in or out,saving them time, and decreasing wait times for other customers. Automated bank teller(ATM) and airline e-ticket terminals are examples of self-service stations that can benefitfrom touch screen input.Control and Automation Systems the touch screen interface is useful in systems ranging from industrial process control to home automation. By integrating the input device with the display, Valuable workspace can be saved. And with a graphical interface, operators can monitor and control complex operations in real-time by simply touching the screenComputer Based Training because the touch screen interface is user-friendlier than other input devices, overall training time for computer novices, and therefore training expense, can be reduced.It can also help to make learning more fun and interactive, which can lead to a morebeneficial training experience for both students and educators.Assistive Technology the touch screen interface can be beneficial to those that have difficulty using other input devices such as a mouse or keyboards. When used in conjunction 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. 20
  21. 21. Working of Touchscreen Amit BhardwajAnd many more uses...The touch screen interface is being used in a wide variety of applications to improve human- computer interaction. Other applications include digital jukeboxes, computerized gaming, Student registration systems, multimedia software, financial And scientificapplications, and more. 21
  22. 22. Working of Touchscreen Amit BhardwajPROBLEM WITH TOUCH SCREEN MONITORS ANDTROUBLESHOOTING:ATM system is one of the application of touch screen monitors.Hardware failure can occur in touch screen monitors.We have mentioned some of the most common hardware problems of touch screen and havegivensome of the troubleshooting’s.Hardware problems:  Touch screen does not respond  Portions of the touch screen do not respond  Touch screen is very slow to respondTroubleshooting:The first step in troubleshooting a touchscreen system is to determine whether the problem isrelated to the display, software, or hardware: Do not confuse display problems with touchscreen problems—the two are unrelated. Software problems are determined by a basic hardware functionality test. If the hardware transmits touch coordinates correctly, then the problem is with the driver or application software. Hardware problems may be caused by the touchscreen, controller, cabling, power supply, or by the integration of the touchscreen components in the display. The easiest way to verify a hardware failure is by substitution, if you have more than one unit to try. 22
  23. 23. Working of Touchscreen Amit BhardwajLimitations of Touchscreens:Size:Fingers have a certain size, So, screen elements have to have a minimum size, to ensure thata touch screen can be operated with few errors. Even with a stylus, which makes possible touse smaller screen elements, there are limiting factors.Sequential Input:Input on a touch screen is inherently sequential:One finger is used for clicking. This slows input down compared to keyboard input whereseveral fingers can be used virtually in parallel.Strain:Keying in many numbers or letters by pointing with the finger is also very straining andtiring. Therefore, touch screens make no sense in workplaces, where much text or numberinput is required.Feedback:On touch screens, there is no analogue to mouse-move events. Mouse users can move themouse pointer over screen elements, get feedback about the selected element (e.g. byhighlighting), and may confirm the selection by clicking the mouse button.Touch screen usersdirectly point on a screen element.If they are lucky, they can withdraw their finger if theytouched the wrong screen element.On other touchscreens, the touch immediately initiates anaction - there is no opportunity to cancel the action.Drag Operations:Dragging is generally not well suited to finger-operated touchscreens,Here, pointing is thepreferred interaction. However, this is different for stylus-operated touchscreens. Heregestures and handwriting offer promising possibilities for making interaction withcomputers easier and more intuitive.But here, too is the limitation of strictly sequentialinput.There are also no means to constrain drag operations to, e.g. straight lines, like withmouse-based interfaces. 23
  24. 24. Working of Touchscreen Amit BhardwajREFERENCES http://en.wikipedia.org/wiki/Touchscreen http://www.buzzle.com/editorials/2-21-2005-66062.asp http://orissa.gov.in/e- magazine/Orissareview/jun2005/engpdf/touch_screen_system.pdfhttp://orissa.gov.in/ e-magazine/Orissareview/jun2005/engpdf/touch_screen_system.pdf 24

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