Inside cell phone:
A Touch screen is an
electronic visual display capable of detecting and locating a touch over its
display area. This means, touching the display of the device with a finger or
hand. This technology most widely used in computers, user interactive machines,
smartphones, tablets, etc. to replace most functions of the mouse and keyboard.
The three most common touch screen technologies include resistive, capacitive, and SAW (surface acoustic wave). Most low-end touch screen devices contain a standard printed circuit plug-in board and are used on SPI protocol. The system has two parts, namely; hardware and software. The hardware architecture consists of a stand-alone embedded system using an 8-bit microcontroller, several types of interface, and driver circuits. The system software driver is developed using an interactive C programming language.
Touch Screen Technology
A touch screen technology
is the assembly of a touch panel as well as a display device. Generally, a
touch panel is covered on an electronic visual display within a processing
system. Here the display is an LCD otherwise OLED whereas the system is
normally like a smartphone, tablet, or laptop. A consumer can give input
through simple touch gestures by moving the screen using a special stylus
otherwise fingers. In this way touch screen allows the operator to
communicate directly through the displayed information instead of using a
touchpad, mouse, etc.
Who Invented Touch Screen?
The first concept of a touch screen was described & published in the year 1965 by E.A. Johnson. So, the first touch screen was developed in the 1970s by CERN engineers. Bent Stumpe built in 1972, following an idea launched by Frank Beck, a capacitive touchscreen for controlling CERN's Super Proton Synchrotron accelerator. In 1973 Beck and Stumpe published a CERN report, outlining the concept for a prototype touchscreen as well as a multi-function computer-configurable knob. The first resistive touch screen was designed in 1975 by George Samuel Hurst.
How Does Touch Screen Technology Work?
Different types of
touchscreen technology work in different methods. Some can detect simply one
finger at a time & get very confused if you seek to push in two positions
at once. Other types of screens can simply notice and differentiate above one
key push at once.
Operation of Touch Screen Panel
A basic touch screen is
having a touch sensor, a controller, and a software driver as three main
components. The touch screen is needed to be combined with a display and a PC
to make a touch screen system.
Touch Sensor
The sensor generally has
an electrical current or signal going through it and touching the screen causes
a change in the signal. This change is used to determine the location of the
touch of the screen.
Controller
A controller will be
connected between the touch sensor and PC. It takes information from the sensor
and translates it for the understanding of PC. The controller determines what
type of connection is needed.
Software Driver
It allows computers and
touch screens to work together. It tells OS how to interact with the touch
event information that is sent from the controller.
Types of Touch Screen Technology
The Touch screen is a
2-dimensional sensing device made of 2 sheets of material separated by spacers.
There are four main touch screen technologies: Resistive, Capacitive, Surface
Acoustical wave (SAW), and infrared (IR).
Resistive
Resistive touchscreens
(currently the most popular technology) work a bit like "transparent
keyboards" overlaid on top of the screen. There's a flexible upper layer
of conducting polyester plastic bonded to a rigid lower layer of conducting
glass and separated by an insulating membrane. When you press on the screen,
you force the polyester to touch the glass and complete a circuit—just like
pressing the key on a keyboard. A chip inside the screen figures out the
coordinates of the place you touched.
These screens are made
from multiple layers of glass. The inner layer conducts electricity and so does
the outer layer, so effectively the screen behaves like two electrical
conductors separated by an insulator—in other words, a capacitor. When you
bring your finger up to the screen, you alter the electrical field by a certain
amount that varies according to where your hand is. Capacitive screens can be
touched in more than one place at once. Unlike most other types of touchscreens,
they don't work if you touch them with a plastic stylus (because the plastic is
an insulator and stops your hand from affecting the electric field).
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. The touchscreen on Sony Reader ebooks (like
the one pictured in our photo below) works this way. Since you're interrupting
a beam, infrared screens work just as well whether you use your finger or a
stylus.
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.
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.
I M Sc. Physics
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