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Touch screen technology
Researcher: Eng. Tamer Sherif Mohamed ElMasry.
Supervisor: Prof.D. Mohamed Besheer
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.
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
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.
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.
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
Application-development software, which
enables developers of touch programs to build
their own applications and/or customize existing
touch applications.
How do Touchscreens Work?
Here are some technologies that are used in
making touch screens:
– Resistive
– Capacitive
– Surface Acoustic Wave (SAW)
– Scanning Infrared
– Near Field Imaging
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.
• 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.
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
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
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
•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
Advantages of Capacitive
–High Touch Resolution
–High Clarity
–Completely Sealable
Disadvantages of Capacitive
–Must be touched by finger- will not work with any nonconductive input
–Can be affected by electricity
–May need re-calibration often
Surface Acoustic Wave Touch
• 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
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
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
–Mostly used in manufacturing and medical applications
since it can be completely sealed.
–operated using a stylus or a gloved finger.
–mechanically stronger
–more wear resistant
–it is very sensitive and can be activated by stray touches.
–Low resolution
–Parallax problems
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.
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
Thank you