Touch Screen

  Now Ur touch can Xplore the world… 

Revolutionary idea of the modern era making technology smarter…






For instance :

• Ur Smartphone
• Ur Tablet PC
• Ur Desktop/Notebook PC etc.

But.. Have you ever wondered…??
How They Do It…??
LETS HAVE A LOOK….!!





There are three basic systems that are used to recognize our touch impressions :

• Resistive System
• Capacitive System
• Surface Acoustic Wave

RESISTIVE  SYSTEM

Working Mechanism of a Resistive Touch System



• Consists of a normal glass panel that is covered with a conductive and a resistive metallic layer.
• These two layers are held apart by spacers.
• scratch-resistant layer is placed on top of the whole setup.
• An electrical current runs through the two layers while the monitor is operational.

On touching the screen…

• The two layers make contact in that exact spot.
• The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer.
• Once the coordinates are known, a special driver translates the touch into data signals that the operating system can understand.
  (just as a computer mouse driver translates a mouse’s movements into a click or a drag).

CAPACITIVE  SYSTEM

Working Mechanism of a Capacitive Touch System

• The monitor has a layer of glass panel that stores electrical charge.

On touching the screen…

• some of the 1charge is transferred to the user, so the charge on the capacitive layer decreases.
• This decrease is measured in circuits located at each corner of the monitor.
• The computer precisely calculates the exact location of touch from the relative differences in charge at each corner.
• This information is now handed over to the touch-screen driver software.
• The driver software translates this information into data signals that the operating system can understand.

ADVANTAGEOUS OVER RESISTIVE SYSTEM..

• Transmits almost 90 percent of the light from the monitor,
  whereas the resistive system only transmits about 75 percent.
  This gives the capacitive system a much clearer picture than the resistive system.

  SURFACE  ACOUSTIC  WAVE  SYSTEM

Working Mechanism of a Surface Acoustic Wave System

• On the monitor of a surface acoustic wave system, two transducers (one receiving and one sending) are placed along the x and y axes of the monitor’s glass plate.
• Reflectors are also placed on the glass plate. – they reflect an electrical signal sent from one transducer to the other.

On touching the screen…

• The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly.
• Again this data is handed over to the driver software for further proceedings by operating system.

ADVANTAGES..

• The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity.
• This makes the surface acoustic wave system best for displaying detailed graphics (whereas both the above systems have a significant degradation in clarity).

Which STIMULI can register a touch..?

Is it possible to use any object for pointing on a Touch Screen..?
— NO….!!
WHY SO….??

The answer lies in the working mechanism of the devices….

A Resistive System registers a touch as long as the two layers make contact, which means that it doesn’t matter if you touch it with your finger or a rubber ball.

A Capacitive System, on the other hand, must have a CONDUCTIVE input, so that the screen is able to transfer some charge to the pointing object. Usually finger is used in order to register a touch.

The Surface Acoustic Wave System works much like the resistive system, allowing a touch with almost any object – except hard and small objects like a pen tip.

 

 

 

 

 

 

PRICE COMPARISIONS….

As far as price is concerned…
The Resistive System is the cheapest..
Its clarity is the lowest of the three.
and its layers can be damaged by sharp objects.
whereas…
The Surface Acoustic Wave Setup is usually the most expensive.