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 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.
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 system.
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:
Surface Acoustic Wave (SAW)
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
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
Capacitive Touch screen
There are 2 types of capacitive touch screens:
-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
-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.
Advantages of Capacitive
High Touch Resolution
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
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.
Advantages of Surface Acoustic Wave
Excellent Image Clarity -Very High LightTransmission