Touch Screen Technology

RESEARCHER: RAZZESH SHAH.

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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 screenThere 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 Sir !

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