How does Touch Screen work

There is one technology that is
integrated in an increasing number of digital gadgets. MP3 players have it,
mobile phones have it and navigation equipment can never do  without it.

We are talking about the touch-sensitive screens, or touch screens if you want.
They have been operating since the late 60th century, but it is only in recent
years that they really have got their breakthrough in the consumer market.

This article takes you through the technologies that are appropriate for the
general consumer market. We will not go too deep into the technical aspect ,
but we’ll explains more overall how this different technologies work, what are
the benefits of them and what we can expect from them in the near future.


Why touch screens?

For most people both keyboards and mouse pointers have to be very simple and
easy to understand for navigation means. The ability to actually
physically press the option you want to do is something each and every one can
understand. The alternative is the mouse pointer, which can be moves by your hand,
which gets the pointer on the screen to do the same movement.

The advantages of touch screens are many. but The bottom line remains the same
that the natural senses must be fully exploited. Touch screens also saves
space. If we look at a desktop computer can such a screen replace both the
mouse and keyboard in several cases? When it comes to more portable devices
such as media players and mobile phones the benefits are more visible.
Here one can exploit the small space they have, by using a touch screen instead
of many buttons that take up valuable space on that small gadget

Today, there is a lots of different technologies behind the touch sensitive
surface. but only are Some are used in the industry; others have only been
projects to prove that the technology really works. In this guide we will
concentrate on the four main types of resistive, capacitive, infrared, and SAW.

Resistive technology

Resistive touch screens are one of the two most commonly used technologies in
the consumer market, primarily because of the low price. As the name implies,
uses this resistance method, it takes  the advantages of electrical
resistance to calculate where on the screen you have actually pressed.

A resistive touch surface consists of two main layers, where both layers
Resides over the screen. These layers are metallic, which means they can carry
a charge. The two layers are separated from each other, and when you tap the
screen, the top layer comes  in contact with the below layer .

The top layer is electrically charged, and when you press it down, there is a
change in the electrical current. this change is interpreted by a special
controller chip, Which send it to the X and Y coordinates. These coordianates
can can be used to tell the computer where to display the results.

The lifetime of such displays are not particularly long compared to other
technologies, mainly because minor injuries such as scratches, damage the
surface. The solution can however be of almost 5000 points in both directions,
but this depends on screen size. A major benefit of this technology is that one
does not have to rely on anything in particular to be able to touch the screen.
It reacts to everything, both the finger tips, pointers, keys, etc.

Capacitive technology

The other very popular technologies among consumers are capacitive touch. In
principle, this sensor is a capacitor, in that the vertical and horizontal
currents act as two plates. Since the human body conducts electricity, the
sensors measure the capacitive change when screen is touched.Now We Will
explain it in deeper way:

In front of the screen There is transparent, electrically conductive, material.
An electromagnetic field forms on the surface. The sensors are programmed to
react in exactly the same amount of capacitance as a human finger . As soon as
you press the surface, the electric field changes. this change is detected by
the sensors , before it is interpreted into signals , which you’ve clicked on
the screen.

These surfaces can withstand ten times as much pressure as a resistive surface,
but the resolution is five times as low. A small disadvantage is that this
technology can only responds to human flesh, or materials with approximately
the having the same amount of capacitance. that why Some point pens have a nib
which resembles exactly that .

Infrared technology

Infrared technology uses light to see where on the screen you press. This is
one of very few technologies that do not overlap the screen. All of the
components are located along the monitor’s frame. Man cannot see infrared
light, and  as Infrared technology does not overlap the image, this method
does not affect quality of image

A series of infrared LEDs extends along the screen edge. On the opposite page
there is a series of photo transistors. When you tap the screen, you are
violating one or more of the rays that extend both vertically and horizontally
across the screen.

The selected photo transistors lose when contact with corresponding LEDs. When
this occurs both vertically and horizontally, consider a small circle of the

With these technologies it has nothing to say what you tap the screen with.
Finger, stylus or a carrot for that matter, everything works just as well. Such
screens can withstand a little more rough treatment than others, and is often
used in public systems such as ticket vending machines. The resolution offer
here is very good, and life is long.

Infrared touch screens are not particularly cheap – in fact this is the most
expensive of the technologies mentioned so far,

Surface Acoustic Wave Technology

Surface Acoustic Wave, hereafter abbreviated SAW, is a great newcomer. This
technology came in the late 90’s, and uses sound waves to calculate where you
have pressed.

The screen is covered by a special glass.called as Small transducers, marked as
transmitters in the green on the image, it sends out sound waves. Using the
small "mirror" which are then reflected those beyond the screen
surface. When you press on the screen, the recipients by means of reflections
and delays calculate where you have pressed.

The sound waves are sent out from the transmitters, and for every mirror they
pass is a small part reflected over the surface, while the rest continue on to
the other mirrors. Since sound beam lose strength, are the mirrors at the end
of the range set closer together. In the same way the waves are reflected back
to the receiver on the opposite side of the glass.

The technology can withstand water,
but it must be wiped away from the area prior to use. The water, like all forms
of dirt, kills the signals leading to the touchpad and it will not work. This
is actually one of the very few technologies that are approved for use in
EX-zones, especially in the oil industry. The reason for this is that there is
electricity on the surface. Since the technology is still very new, it is also
very expensive.

What happens next?

As with all forms of technology, it is very easy to predict the future. But we
are still giving a few hints , Resistive screens are one of the technologies
where this is possible. You can hit multiple locations on the surface
simultaneously, and using the proper programming can then individual movements
are converted into other actions.

For example, you can zoom out if you
press the two punks and drag your fingers away from each other. Reverse motion
gives back the opposite action.

One thing is at least safe, and that this touch-sensitive screens will only
develop further and further. In future can we see this things on office desks,
like what Dr. Merrick uses in the movie "The Island". And by all
means, we must not forget all the cool things the gang research in CSI has
money to spend.



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