TOUCHSCREENBy – Fazle Qadir Chimthanawala

TOUCHSCREEN

A touchscreen is an electronic visual display that the user can control through simple or multi-touch gestures by touching the screen with a special stylus/pen or one or more fingers.

The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or any other device other than a stylus.

Touchscreens are common in devices such as game consoles, all-in-one computers, tablet computers, and smartphones. They can also be attached to computers or, as terminals, to networks.

HISTORY

Touch screens emerged from academic and corporate research labs

This sensor was known as “Elograph”.

Touch screens first gained some visibility with the invention of the computer-assisted learning terminal, which came out in 1975 as part of the PLATO project(Programmed Logic for Automatic Teaching Operations)[.

In 1971, the first "Touch Sensor" was developed by Doctor Sam Hurst (founder of Elographics) while he was an instructor at the University of Kentucky.

COMPONENTS

Touch sensor

Controller

Software driver

TYPESResistive

Surface acoustic wave

Capacitive

Infrared grid

Infrared acrylic projection

Acoustic pulse recognition

Dispersive signal technology

Optical imaging

RESISTIVE

Composed of several layers

Two Electrically conductive layers

SURFACE ACOUSTIC WAVESIt uses ultrasonic waves.

When the panel is touched, a portion of the wave is absorbed.

CAPACITIVE

Consist of an insulator such as glass

Coated with transparent conductor such as ITO (Indium Tin Oxide)

Touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance.

INFRARED GRIDAn infrared touch screen uses an array of X-Y infrared LED and photo detector pairs around the edges of the screen to detect a disruption in the pattern of LED beams.

ADVANTAGESUser friendly

Fast response

Error free input

Use finger , fingernail , gloved hands , stylus or any soft tip pointer

Easy to clean

Does not interfere mouse and keyboard

Make computing easy , powerful and fun

It benefits children

DISADVANTAGES

Finger stress

Fingerprints

Screen has to be really big not to miss things when pressing them with your finger

Big screen leads to low battery life

Touch screen means screen can’t be read too well in direct sunlight as it is not 100% transparent.

WORKING OF A IPHONE TOUCHSCREEN

Driving lines carry current.

Sensing lines detect the current at nodes.