Workings of Touch Screen
We all are very known to the word “Touch
Screen”, even today 95% of us totally related to their workings with touch
screen. But that’s a big question to us, are we know anything about Touch
Screen internal features?? Are we know anything about
Mobile Touch Screen and How It’s work??
Don’t worried about this, In my
today’s article I give you a little knowledge about Touch Screen and Some
knowledge about how it’s work on Mobile.
Defination : A touchscreen
is an input and output 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 or one or more fingers
There are many types of touch screens(Resistive,
Capacitive, Acoustic, Optical Imaging, Infrared) but if you're talking about
mobile phones there are basically two types of touch screens right now.
1.
Resistive Touch Screen:
The resistive touch
screen resists your touch literally and if you press harder you can feel the
screen bent slightly. This is what makes the resistive touch work. There are
two layers in the resistive touch, the resistive layer and the conducting
layer. These are separated by tiny dots called spacers. The electric current
flows through the conductive layer at all times but when you touch the screen
i.e. resistive layer, it comes in contact with the conducting layer. Thus the electric
current changes at that point and the function corresponding to that point is
carried out.
2.
Capacitive Touch Screen:
Unlike Resistive touch Screen, it does not use the pressure of your finger for the
flow of electricity. Instead, they work with anything that holds an electric
charge, including human skin. They are made from materials like copper and
indium tin oxide that hold electric charges in an electrostatic grid of wire
each smaller than a human hair. There's a glass substrate,a conductive layer , a protector, a controller and
electrodes at the corners. The electrodes apply a low voltage to the conductive
layer to form a electrostatic field. When a finger
hits the screen, a tiny electrostatic charge is transferred to the field that
completes the circuit. A voltage drop is created at that point. The location of
the voltage drop is reported by the controller.
Construction :
In the capacitive resistive approach, the most popular
technique, there are typically four layers:
·
Top polyester-coated
layer with a transparent metallic-conductive coating on the bottom.
·
Adhesive spacer
·
Glass layer coated with a
transparent metallic-conductive coating on the top
·
Adhesive layer on the
backside of the glass for mounting.
When a user touches the
surface, the system records the change in the electric current that flows
through the display.
Dispersive-signal
technology measures the piezoelectric effect—the voltage generated when
mechanical force is applied to a material—that occurs chemically when a
strengthened glass substrate is touched.
There are two
infrared-based approaches. In one, an array of sensors detects a finger
touching or almost touching the display, thereby interrupting infrared light
beams projected over the screen. In the other, bottom-mounted infrared cameras
record heat from screen touches.
3. Self-capacitance:
Self-capacitance sensors can have the same X-Y grid as mutual capacitance
sensors, but the columns and rows operate independently. With self-capacitance,
the capacitive load of a finger is measured on each column or row electrode by
a current meter, or the change in frequency of an RC
oscillator. This method produces a stronger signal than mutual capacitance, but
it is unable to accurately resolve more than one finger, which results in
"ghosting" or misplaced location sensing. However, in 2010 a new
method of sensing was patented [44] which allowed some parts
of the capacitance sensors to be sensitive to touch while other parts remained
insensitive. This enabled Self capacitance to be used for multi-touch without
"ghosting"
4. Infrared
Just like the magic eye
beams in an intruder alarm, an infrared touchscreen
uses a grid pattern of LEDs and light-detector photocells arranged on opposite
sides of the screen. The LEDs shine infrared light in front of the screen—a bit
like an invisible spider's web. If you touch the screen at a certain point, you
interrupt two or more beams. A microchip inside the screen can calculate where
you touched by seeing which beams you interrupted
5.
Surface Acoustic Wave:
Surprisingly, this touchscreen technology detects your fingers using sound
instead of light. Ultrasonic sound waves (too high pitched for humans to hear)
are generated at the edges of the screen and reflected back and forth across
its surface. When you touch the screen, you interrupt the sound beams and absorb
some of their energy. The screen's microchip controller figures out from this
where exactly you touched the screen.
6.
Near field imaging:
Have you noticed how an
old-style radio can buzz and whistle if you move your hand toward it? That's
because your body affects the electromagnetic field that incoming radio waves
create in and around the antenna. The closer you get,
the more effect you have. Near field imaging (NFI) touchscreens
work a similar way. As you move your finger up close, you change the electric
field on the glass screen, which instantly registers your touch. Much more
robust than some of the other technologies, NFI screens are suitable for
rough-and-tough environments (like military use). Unlike most of the other
technologies, they can also detect touches from pens, styluses, or hands
wearing gloves.