INTRODUCTION A touch screen is an input devicethat allows users to operate adevice by simply touching thedisplay screen. The display screen has asensitive glass overlay placed onit and we can give the desiredinput by touching on it. The term generally refers totouch or contact to the displayof the device by a finger orhand.
HOW DOES A TOUCH SCREENWORK…??? There are three basic systems that areused to recognize a persons touch:• Resistive• Capacitive system• Surface Wave
(i)RESISTIVE A touch screen sensor is a clear glasspanel surface with a touch responsivesurface which is placed over a displayscreen. The sensor generally has an electriccurrent or signal going through it andtouching the screen causes a voltage ora signal change.
(ii) CAPACITIVE SYSTEM This is a small device card thatconnects the sensor and the mainhardware device. It takes information from the sensorand translates it into information thatdevice can understand.
(iii) SURFACE WAVE It is the software that allows the touchscreen and the device to work together. It tells the main hardware device how tointerpret the touch event informationthat is sent from the controller. Most of the devices are a mouse-emulation type driver.
RESISTIVE TOUCH SCREEN A resistive touch screen panelis composed of several layers,the most important of whichare two thin, electricallyconductive layers separatedby a narrow gap. When an object, such as afinger, presses down on apoint on the panels outersurface the two metalliclayers become connected atthat point This causes a change in theelectrical current, which isregistered as a touch eventand sent to the controller forprocessing.
SURFACE ACOUSTIC WAVE TOUCHSCREEN Surface acoustic wave(SAW) technology usesultrasonic waves that passover the touch screenpanel. When the panel istouched, a portion of thewave is absorbed. This change in theultrasonic waves registersthe position of the touchevent and sends thisinformation to thecontroller for processing.
CAPACITIVE TOUCH SCREEN A capacitive touch screenpanel is one which consistsof an insulator such asglass, coated with atransparent conductorsuch as Indium tin oxide(ITO). As the human body is alsoa conductor, touching thesurface of the screenresults in a distortion ofthe screens electrostaticfield, measurable as achange in capacitance.
INFRARED TOUCH SCREEN An infrared touch screen usesa ray of X-Y infrared LED andphotodetector pairs aroundthe edges of the screen todetect a disruption in thepattern of LED beams. These LED beams cross eachother in vertical andhorizontal patterns. This helpsthe sensors pick up the exactlocation of the touch. A major benefit of such asystem is that it can detectessentially any input includinga finger, gloved finger, stylusor pen.
ACOUSTIC PULSE RECOGNITION This system uses piezoelectric transducers located atvarious positions around the screen to turn the mechanicalenergy of a touch (vibration) into an electronic signal. The screen hardware then uses an algorithm to determinethe location of the touch based on the transducer signals. This touchscreen technology gives good durability andoptical clarity. It is usually able to function with scratches and dust onthe screen with good accuracy. The technology is also well suited to displays that arephysically larger.
3M Dispersive Signal Technology (DST) Traditional touch technologies detect touch locations byinterrupting acoustic waves, optical fields or infrared lightabove the surface of the touch screen. Dispersive Signal Technology (DST), however, preciselycalculates touch locations within the glass substrate byanalyzing the bending waves created by the users touch. This allows for fast, accurate and reliable touch performancethat is unaffected by contaminants, scratches or staticobjects on the screen, as well as enabling stylus support andmulti-user capability. 3M Dispersive Signal Technology (DST) is poised to becomethe touch technology standard for large-format interactivedisplays.
USAGE Finger stress:With stressing the finger on the desiredarea of the touch screen, the input is taken bythe sensors of the screen. Finger nail as stylus:With the help of touching the screen withthe finger mail which acts as the stylus, inputcan be taken by the sensors.
MULTI-TOUCH TECHNOLOGY On touchscreen displays, multi-touch refersto the ability to simultaneously register threeor more distinct positions of input touches.
ADVANTAGES User friendly Fast response Error free input User finger, finger nail, gloved hand,stylus or any soft tip pointer to operate Make computing easy, powerful and fun
DISADVANTAGES 1)Finger stress:Stress on human fingers when usedfor more than a few minutesat a time. (for example, ATMs). 2)Fingerprints:Touchscreens can suffer from theproblem of fingerprints on the display.
CONCLUSIONThough the touch screen technologycontains some limitations with it, it isfast, accurate, user friendly and fun tooperate .It is being widely accepted.With some modifications, it cancompletely replace mouse and keyboardcompletely in the near future.