A touch screen is an input device normally layered on the top of an
electronic visual display of an information processing system. A
user can give input or control the information processing system
through simple or multi-touch gestures by touching the screen with
a special stylus/pen and-or one or more fingers. Some touch screens
use ordinary or specially coated gloves to work while others use a
special stylus/pen only. The user can use the touch screen to react
to what is displayed and to control how it is displayed (for
example by zooming the text size).
The touch screen enables the user to interact directly with what is
displayed, rather than using a mouse, touchpad, or any other
intermediate device (other than a stylus, which is optional for
most modern touch screens).
Touch screens are common in devices such as game consoles, personal
computers, tablet computers, and smart phones. They can also be
attached to computers or, as terminals, to networks. They also play
a prominent role in the design of digital appliances such as
personal digital assistants (PDAs), GPS navigation devices, mobile
phones, video games and some books (E-books).
The popularity of smart phones, tablets, and many types of
information appliances is driving the demand and acceptance of
common touch screens for portable and functional electronics. Touch
screens are found in the medical field and in heavy industry, as
well as for automated teller machines (ATMs), and kiosks such as
museum displays or room automation, where keyboard and mouse
systems do not allow a suitably intuitive, rapid, or accurate
interaction by the user with the display's content.
There are a variety of touch screen technologies with different
methods of sensing touch. In LUPHI we mainly provide the resistive
touch screen panels and capacitive touch screen panels.
Resistive Touch Screen Panels
A resistive touch screen panel comprises several layers, the most
important of which are two thin, transparent electrically-resistive
layers separated by a thin space. These layers face each other with
a thin gap between. The top screen (the screen that is touched) has
a coating on the underside surface of the screen. Just beneath it
is a similar resistive layer on top of its substrate. One layer has
conductive connections along its sides, the other along top and
bottom. A voltage is applied to one layer, and sensed by the other.
When an object, such as a fingertip or stylus tip, presses down
onto the outer surface, the two layers touch to become connected at
that point: The panel then behaves as a pair of voltage dividers,
one axis at a time. By rapidly switching between each layer, the
position of a pressure on the screen can be read.
Resistive touch is used in restaurants, factories and hospitals due
to its high resistance to liquids and contaminants. A major benefit
of resistive touch technology is its low cost. Additionally, as
only sufficient pressure is necessary for the touch to be sensed,
they may be used with gloves on, or by using anything rigid as a
finger/stylus substitute. Disadvantages include the need to press
down, and a risk of damage by sharp objects. Resistive touch
screens also suffer from poorer contrast, due to having additional
reflections from the extra layers of material (separated by an air
gap) placed over the screen.