1.Touch Screen Sensor Quanling zheng

2. How Does a Touchscreen Work?A basic touchscreen has three main components:1 Touch sensor;2 Controller;3 Software driver.The touchscreen is an input device, so it needs to becombined with a display and a PC or other device tomake a complete touch input system. 3. Touch Sensor A touch screen sensor is a clear glass panel with a touchresponsive surface. The touch sensor/panel is placedover a display screen so that the responsive area of thepanel covers the viewable area of the video screen.There are several different touch sensor technologies onthe market today, each using a different method todetect touch input. The sensor generally has anelectrical current or signal going through it and touchingthe screen can cause a voltage or signal change. Thischange is used to determine the location of the touch tothe screen. 4. Controller The controller connects between the touch sensor andthe PC. It takes information from the touch sensor andtranslates it into information that PC can understand.The controller determines what type ofinterface/connection you will need on the PC. Controllersare available that can connect to a Serial/COM port (PC)or to a USB port. Specialized controllers are alsoavailable that work with DVD players and other devices. 5. Software Driver The driver allows the touchscreen and computer to worktogether. It tells the computers operating system how tointerpret the touch event information that is sent from thecontroller. Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screenas same as clicking your mouse at the same location onthe screen. This allows the touchscreen to work withexisting software and allows new applications to bedeveloped without the need for touchscreen specificprogramming. 6. Touchscreen Technology Resistive touchscreen Capacitive touchscreen Infrared touchscreen Surface acoustic wave (SAW)touchscreen Strain gauge touchscreen Optical imaging touchscreen Dispersive signal technology touchscreen 7. Resistive touchscreen StructureResistive touch screensconsist of a glass oracrylic panel that iscoated with electricallyconductive and resistivelayers made with indiumtin oxide (ITO) .The thinlayers are separated byinvisible spacers. 8. 4-wire resistive touchscreen 9. 5-wire resistive touchscreen The construction of the panels are similarwith 4-wire technology, but for a 5-wiretouch screen all four bus bars areconnected to the lower, non-flexible layerof the screen. The flexible layer is alwaysused as a sense layer to read the voltageconnection point to the bottom layer. 10. 8-wire resistive touchscreen 11. Resistive touchscreenCharacters:1. Cost effective solutions2. Activated by a stylus, a finger or gloved hand3. Not affected by dirt, dust, water, or light4. 75%~85% clarify5. resistive layers can be damaged by a very sharp object 12. Projected-capacitive touchscreen StructureProjected capacitivetouchscreens have front andback protective glassproviding optical and strengthenhancement options.Its middle layer consists of alaminated sensor grid ofmicro-fine wires, andoptical enhancement options. 13. Projected-capacitive touchscreen During a touch, capacitance forms between thefinger and the sensor grid.The embedded serialcontroller in the touchscreen calculates touchlocation coordinates and transmits them to thecomputer for processing. 14. Surface-capacitive touchscreen Structure Surface capacitive technology consists of a uniform conductive coating on a glass panel. Electrodes around the panels edge evenly distribute a low voltage across the conductive layer, creating a uniform electric field. 15. Surface-capacitive touchscreen Working principleA human body is an electric conductor, so when you touch the screenwith a finger, a slight amount of current is drawn, creating a voltagedrop. The current respectively drifts to the electrodes on the fourcorners. Theoretically, the amount of current that drifts through the fourelectrodes should be proportional to the distance from the touch point tothe four corners. The controller precisely calculates the proportion of thecurrent passed through the four electrodes and figures out the X/Ycoordinate of a touch point. 16. Capacitive touchscreen Characters:1. Durable and resistant to scratches for demanding applications2. Faster and more responsive3. Immune to surface contaminants4. Superior optical clarity, brighter display and less surface reflection5. Must be touched by finger, will not work with any non-conductive input 17. Infrared touchscreen Infrared (IR) technology relies on the interruption of anIR light grid in front of the display screen. The touchframe contains a row of IR-light emitting diode (LEDs)and photo transistors, each mounted on two oppositesides to create a grid of invisible infrared light.The IR controller sequentially pulses the LEDs to createa grid of IR light beams. When a stylus, such as a finger,enters the grid, it obstructs the beams. One or morephoto transistors from each axis detect the absence oflight and transmit signals that identifies the x and ycoordinates. 18. Infrared touchscreen 19. Infrared touchscreenCharacters:1. Clear as glass, improves reading ability2. Most durable surface 20. SAW touchscreen Principle Surface waves are readily absorbed when a soft object such as a fingertip touches the substrate. SAW Touch Screen use pure glass with transmitting and receiving piezoelectric transducers for both the X and Y axes. The touch screen controller sends an electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass. When you touch the screen, you absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculate. 21. SAW touchscreen 22. SAW touchscreenCharacters:1. Durable glass construction2. High optical clarity3. Activated by a finger, gloved hand or soft tip4. Not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environment 23. TechnologyCapacitiveSAWInfrared ResistiveTransparenceVery good Very goodVery good75%~85% >92%>92% >92%ResolutionGoodGood Limited due to good spacing of IR sensorsSurface Resistant toAdverselyPotential forUnaffected byContaminantsmoisture andaffected byFalse activation Surface/durability other surface moisture oror dead zonescontaminants.contaminantsSurfaceFrom Surface Polyester topcontaminants Contaminants sheet is easilyscratchedSensor substrate Glass with ITO Glass with ITO Any substratePolyester top coatingcoating sheet, glasssubstrate withITO coatingDisplay size8.4"-21"10.4"-30"10.4"-60"up to 19"Touch methodHuman touch finger, gloved Can use anyCan use any pointing devicepointing devicehand or soft tip 24. Multi-touch technology Multi-touch denotes a set of interactiontechniques which allow computer users tocontrol graphical applications with severalfingers. Products: Apple iPhone, iPod touch, MacBook Air,and MacBook Pro Microsoft Surface