INTRODUCTION Most sophisticated computer access technology. Detect the presence and location of a touch. Eliminates the need for the mouse and keyboard.
HISTORYEmerged in the second half of the 1960s.In 1971, Sam Hurst, invented first touch sensorIn 1977 , "touchscreen."
1) SURFACE ACOUSTIC WAVE: Uses ultrasonic waves. It is based on sending waves across a clear glass panelwith a series of transducers and reflectors.
DisadvantagesTouched by finger, glovedhand, or soft-tip stylus.Not completely sealable.
TECHNOLOGIES2) RESISTIVE: Composed of two thin, metallic, conductive layers. Change in current is registered as touch event.
DISADVANTAGESOffer only 75% clarity.The layer can be damaged.Cannot press hand down on the screen while writing.
3) CAPACITIVE:Consists of insulator coated with a transparentconductor.Touching results in a distortion of the electrostatic field.
4) INFRARED:It employs one of two very different methodologies.Use an array of infrared light-emitting diodes.
5) Strain gauge : The screen is spring-mounted on the four corners. Used to determine deflection when the screen istouched.
6) Optical imaging: Two or more image sensors are placed around the edges ofthe screen. Revolutionizes the way we interface with computertechnology.
7) Dispersive signal technology:Chemically-strengthened glass substrate with piezosmounted on each corner.Determines position by pinpointing the source of“bending waves”.
Comparison of touchscreen technologiesTechnology 4-Wire SAW 5-Wire Infrared CapacitiveDurability:5 year 5 Year 3 Year 3 Year 2 YearStability:High Higher High High OkTouch:Anything Finger/Pen Anything Sharp ConductiveResponsetime:<10ms 10ms <15ms <20ms <15msMonitoroption:CRT CRT CRT or LCD CRT or LCD CRT or LCDWaterproof:Good Ok Good Ok Good
CONSTRUCTIONThree main components:1) Touch SensorTouch response surface.It is a clear glass panel.
2) ControllerInterface between a touch screen sensor and the devicethe sensor is used to control.Determines what type of interface/connection.
3) SoftwareDriverSoftware update for thePC system.Allows the touchscreenand computer to worktogether.
APPLICATIONS Public Information Displays. Retail and Restaurant Systems . Customer Self-Service. Control and Automation Systems. Computer Based Training. Assistive Technology.