Touch screen technology

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Touch screen technology

• Researcher Eng. Tamer Sherif Mohamed ElMasry.
• Supervisor Prof.D. Mohamed Besheer

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What are Touch Screens?

• It is the most user friendly input device used to
  interface with a PC.
• The user touches the screen
• to select options presented
• on it, where associated hardware and software
  locate that touch.

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History and Development

• In 1971 Dr. Sam Hurst, founder of Elographics
  developed the first touch opaque sensor
  Elograph at the University of Kentucky.
• In 1974 He developed the first real touch screen.
  
• In 1977, Elographics developed the five-wire
  resistive technology then with the backing of
  Siemens Corporation, developed a curved glass
  sensor called the touch screen.
• The new transparent technology, AccuTouch, was
  later developed by the founders of Elographics,
  Dr. Hurst and Bill Colwell.

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Why use Touch Screens?

• Enable first-time users to interface with
  computers instantly, without any training.
• Eliminate operator errors because users make
  selections from clearly defined menus.
• Eliminate keyboards and mice, which many novice
  users find difficult to use.
• Rugged enough to stand up to harsh conditions
  where keyboards and mice can be damaged.
• Provide fast access to all types of digital
  content.
• Ensure that no space is wasted since the input
  device is completely integrated into the monitor.

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Elements of a touchscreen system

• The touchscreen itself.
• A computer whose display is fitted with the
  touchscreen interefacing with.
• A controller drives the touchscreen and converts
  each touch into X/Y coordinates.
• A software driver, which communicates between the
  controller card and the computer's operating
  system.
• Application-development software, which enables
  developers of touch programs to build their own
  applications and/or customize existing touch
  applications.

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How do Touchscreens Work?
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TOUCH TECHNOLOGIES

• Here are some technologies that are used in
  making touch screens
• Resistive
• Capacitive
• Surface Acoustic Wave (SAW)
• Scanning Infrared
• Near Field Imaging

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Resistive touch screen

• Made of a glass panel with a coating of uniform
  resistivity on which a voltage is applied. A
  polyester cover sheet is tightly suspended over
  the top of the glass, separated from it by small,
  transparent insulating dots.
• The cover sheet has a hard, durable coating on
  the outer side and a conductive coating on the
  inner side.

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• With a light touch, the conductive coating makes
  electrical contact with the coating on the glass.
  
•  The voltages at the point ofcontact are the
  analog representation of the position touched.
  The controller digitizes these voltages and
  transmits them to the computer for processing.

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• Advantages of Resistive
• High Resolution and Accuracy
• Fast Response
• Pressure-activated by finger or gloved hand with
  a very light touch
• Durable hard-coat front surface can be nonglare
  treated for     reflection control or polished
  for maximum clarity
• Touchscreens and controllers are safety
  agency-approved components,so certification of
  your system is easier
• Disadvantages of Resistive
• 80 Clarity
• Resistive layers can be damaged by a sharp object

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Capacitive Touch screen

• There are 2 types of capacitive touch screens
• Surface capacitive
• -consists of a uniform conductive coating on a
  glass panel on which a low voltage is evenly
  applied fromthe corners.
• -The touch location is measured from the ratio
  of the current flow from the corners

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• Projected Capacitive
• -Made of a front and back protective glass
  providing optical and strength enhancement
  options.
• -Its middle layer consists of a laminated sensor
  grid of micro-fine wires and optical enhancement
  options.

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• Advantages of Capacitive
• High Touch Resolution
• High Clarity
• Completely Sealable
• Disadvantages of Capacitive 
• Must be touched by finger- will not work with any
  non- conductive input
• Can be affected by electricity
• May need re-calibration often

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Surface Acoustic Wave Touch screen

• Made of a glass overlay with transmitting and
  receiving piezoelectric transducers for both the
  X and Y axes.
• When a touch occurs, the wave is absorbed
  shortening the echo time it takes to reach the
  receivers.

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• Advantages of Surface Acoustic Wave
• Excellent Image Clarity -Very High
  LightTransmission
• Excellent Durability -Stable "No-Drift"
  Operation
• High Resolution - Very Light Touch
• Fast Touch Response -X,Y and Z-axis Response
• Finger or Gloved-Hand Operation
• Disadvantages of Surface Acoustic Wave
• Must be touched by finger, gloved hand, or
  soft-tip stylus.  Something hard like a pen won't
  work
• Not completely sealable, can be affected by
  large  amounts of grease, water,  or dirt on the
  touchscreen

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Scanning Infrared touch screen

• Made of a grid of LEDs and detectors framed to
  the front of the display that projects horizontal
  and vertical beams of infrared light.
• The press location is determined since it
  obstructs the IR beam

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• Advantages
• Mostly used in manufacturing and medical
  applications since it can be completely sealed.
• operated using a stylus or a gloved finger.
• mechanically stronger
• Clearer
• more wear resistant
• Disadvantages
• it is very sensitive and can be activated by
  stray touches.
• Low resolution
• Parallax problems

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Near Field Imaging touch screen

• Made of two laminated glass sheets having a
  transparent metal oxide coating in between.
• An AC signal is applied to the patterned
  conductive coating creating an electrostatic
  field on the surface of the screen.
• It is used only in the toughest environments and
  applications due to its high cost.

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Applications of Touch Screens 

• Informational kiosks
• Trade show displays
• Museum / tourism displays
• Point-of-sale terminals
• Restaurant systems
• Employee time clocks
• Industrial process controls
• World Wide Web access kiosks
• Home automation systems
• Casino and other gaming systems
• Computer access for the physically disabled

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Thank you