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 the touchscreen. 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.
Definition: 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 touchscreens right now.
1. Resistive Touch Screen:
The resistive touchscreen 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 an 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.
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.
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  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”
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 the 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.