Touch screen Technology

What is a touch screen ???

Well a touch screen is an electronic device that can detect the presence and location of atouch made by a user on the screen of a mobile or any other device.

The touch has two main attributes.. that is firstly it enables one to interact directly with what is displayed..

And secondly it lets one do so without requiring any intermediate device that would need to be held in the hand.

Touch screen are mainly of two types Resistive touch screen and Capacitive touch screen.

Capacitive Touch

A Capacitive touch screen consists of an insulator such as glass, coated with a transparent conductor.

The human body is an electrical conductor touching the surface of the screen resulting in a distortion of the screens electrostactic fields.

The location of the disruption is then sent to the controller for processing.

Unlike a resistive touch capacitive are very smooth and does not need pressing of the screen, but needs to be taken a extra care .

Projected Capacitance

Projected capacitance touch also known as pct is a technology involving permission of more accurate and flexible operations. An X-Y grid is formed either by etching a single conductive layer to form a grid pattern of electrodes or by etching two perpendicular layers of conductive materials..



Nowadays, Pct used mutual capacitance, which is more common projected approach and makes use of the fact that most conductive objects are able to hold a charge if they are very close together.

Mutual Capacitance

In mutal capacitance there is a capacitor at  every intrersection of each row and aeach column.


A 16 bit 14 array for examople would have 224 independent capacitors.

A voltage is applied to rows and columns bringing a finger or conductive stylus close to the surface of the sensor.


The capacitance change in every individual point on the grid can be measured to acurately determine the touch location by measuring the voltage in the other axis.

Infrared Touch Screen

An infrared touch uses an array of X-Y infrared LED and photo detector Pairs around the edgesof the touch screen. Photo detector pairs are used mainly to detect a disruption in the pattern of LED beams.



The LEDs cross each other in vertical and horizonatal patterns helping the sensors to pick up the exact location of the touch by trhe user.



Unlike capacitive touch screens , infrared touch screens does not require any patterning on the glass which increases durabilty and optical clarity of the overall system.

Dispersive technology

Dispersive signal technology was introduced in 2002 by 3M.  This sytem uses sensors to detect piezoelectricity in the glass caused by the touch a user makes.

This technology is unaffected by dust and any other outside elements, like sctratches etc..

Since mechanical vibrations are used to detect a touch event, therefore any object can be used to generate this event.