Today we are in the world of touch screen. Everyone when go to buy a mobile or tablet he/she should choose only touch type. In touch type the device the component is used touch screen sensor which is used to take the input from you gesture like fingers etc. The principle about the working of touch screen is i am going to tell you. This article is very much interesting because of it working. It is so most popular in the world. Now-a-days every mobile coming in the market has the facility of touch screen.
You can understand the fact that how can touch screen work. What is basic idea behind it.
A touch screen is a two dimensional sensing device which is made of two sheets of material separated by small spacers. Generally a sheet of glass is used as a bottom layer and a sheet of Polyethylene(PET) is used as a top layer. Polyethylene is a flexible material.
These two sheets are covered with a resistive substance which is usually a metal compound named Indium Tin Oxide (ITO). Thin layer of ITO is uniformly spreaded onto each glass and PET layer. Small bumps named spacer dots are added onto the glass over the resistive coating. This spacer dots creates space between two layers and prevents accidental or a false touch.
When someone touches the display, the PET film is pressed down so the two resistive surfaces touch each other which completes the circuit. The position of this touch can be calculated by a touch screen controller circuit.
The controller circuit uses two dimensional system to determine the point of touch. The basic two dimensional system is shown in the figure.
By measuring the value of X and Y you can determine the position of touch.
In a touch screen display there is two different circuit for measurement of X and Y position. The circuit for measuring X position is shown in the below figure.
The circuit for measuring Y position is shown in figure.
Thus the controller circuit can determine the position of touch in the display.
New Information Added!!
This is for every person who ever wondered how in the world the iPhones touch screen works!! Ill add more to how the GUI works and about the iPhone for all the noobs like me who had no idea how it works. until now...
The basic idea is pretty simple -- when you place your finger or a stylus on the screen, it changes the state that the device is monitoring. In screens that rely on sound or light waves, your finger physically blocks or reflects some of the waves. Capacitive touch-screens use a layer of capacitive material to hold an electrical charge; touching the screen changes the amount of charge at a specific point of contact. In resistive screens, the pressure from your finger causes conductive and resistive layers of circuitry to touch each other, changing the circuits' resistance.
Most of the time, these systems are good at detecting the location of exactly one touch. If you try to touch the screen in several places at once, the results can be erratic. Some screens simply disregard all touches after the first one. Others can detect simultaneous touches, but their software can't calculate the location of each one accurately. There are several reasons for this, including:
Many systems detect changes along an axis or in a specific direction instead of at each point on the screen.
Some screens rely on system-wide averages to determine touch locations.
Some systems take measurements by first establishing a baseline. When you touch the screen, you create a new baseline. Adding another touch causes the system to take a measurement using the wrong baseline as a starting point.
![[IMG]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_uNUBua_nid7xP-Opa6ZyMnuQSazH-fbAmgIMZGhO7rCXlOQ8TOqQU-XeQpq-uEvsfVaRgnSCPLrlYblPtRYBHQ7xa_uv987lHY1PIoCbzX49LmAu50rYLWKuNBs0t9_jDgrXjFNFFZ_-I=s0-d)
Multi-touch Systems
To allow people to use touch commands that require multiple fingers, the iPhone uses a new arrangement of existing technology. Its touch-sensitive screen includes a layer of capacitive material, just like many other touch-screens. However, the iPhone's capacitors are arranged according to a coordinate system. Its circuitry can sense changes at each point along the grid. In other words, every point on the grid generates its own signal when touched and relays that signal to the iPhone's processor. This allows the phone to determine the location and movement of simultaneous touches in multiple locations. Because of its reliance on this capacitive material, the iPhone works only if you touch it with your fingertip -- it won't work if you use a stylus or wear non-conductive gloves.
![[IMG]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_s-nLLM7NLle_A_A0plXR67x5EUhZeii0Q-avmBR9AwNqDuO4hkVSjAMP80ksYGxyws22QhNywqJdQmhAr3TtqrIwPBfYhoEzkh-hvDocyy87xs4Xz3ykA_zowqlvOsTnE6QEqG_4zwMOZM=s0-d)
Interpreting Touch-location Data
The iPhone's processor and software are central to correctly interpreting input from the touch-screen. The capacitive material sends raw touch-location data to the iPhone's processor. The processor uses software located in the iPhone's memory to interpret the raw data as commands and gestures. Here's what happens:
Signals travel from the touch screen to the processor as electrical impulses.
The processor uses software to analyze the data and determine the features of each touch. This includes size, shape and location of the affected area on the screen. If necessary, the processor arranges touches with similar features into groups. If you move your finger, the processor calculates the difference between the starting point and ending point of your touch.
![[IMG]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_u50F-CI3Y_LNe-3QC9auqIAA-fyWU30agQN-mkUeArwxygLKZW1GzqEU4xtu1InpyISUcmxDjTtZhuiKDJ77_Mg15_BSyHXImcJRdex9wj5SY02PjEFRvlV6_nWnAgR4-oqc-trP7TnTWW=s0-d)
The processor uses its gesture-interpretation software to determine which gesture you made. It combines your physical movement with information about which application you were using and what the application was doing when you touched the screen.
The processor relays your instructions to the program in use. If necessary, it also sends commands to the iPhone's screen and other hardware. If the raw data doesn't match any applicable gestures or commands, the iPhone disregards it as an extraneous touch.
![[IMG]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_sRFWQp3UoM0pWz-NglPj-V_RE5b0A6vNp6rJvDG2oizZ9BCsLWJKWT3ZBdcVJFGuYnJAr0r5w6_G3_dEfXHgV0F1cTHaNFb_plq81mZhH1op0vmkGigePnLxilOrDNh13eANCeVOksvIY4=s0-d)
All these steps happen in an instant -- you see changes in the screen based on your input almost instantly. This process allows you to access and use all of the iPhone's applications with your fingers. We'll look at these programs and the iPhone's other features in more detail in the next section, as well as how the iPhone's cost measures up to its abilities.
To all who read, well, you can thank www.howstuffworks.com for all of the above information.
This is for every person who ever wondered how in the world the iPhones touch screen works!! Ill add more to how the GUI works and about the iPhone for all the noobs like me who had no idea how it works. until now...
The basic idea is pretty simple -- when you place your finger or a stylus on the screen, it changes the state that the device is monitoring. In screens that rely on sound or light waves, your finger physically blocks or reflects some of the waves. Capacitive touch-screens use a layer of capacitive material to hold an electrical charge; touching the screen changes the amount of charge at a specific point of contact. In resistive screens, the pressure from your finger causes conductive and resistive layers of circuitry to touch each other, changing the circuits' resistance.
Most of the time, these systems are good at detecting the location of exactly one touch. If you try to touch the screen in several places at once, the results can be erratic. Some screens simply disregard all touches after the first one. Others can detect simultaneous touches, but their software can't calculate the location of each one accurately. There are several reasons for this, including:
Many systems detect changes along an axis or in a specific direction instead of at each point on the screen.
Some screens rely on system-wide averages to determine touch locations.
Some systems take measurements by first establishing a baseline. When you touch the screen, you create a new baseline. Adding another touch causes the system to take a measurement using the wrong baseline as a starting point.
Multi-touch Systems
To allow people to use touch commands that require multiple fingers, the iPhone uses a new arrangement of existing technology. Its touch-sensitive screen includes a layer of capacitive material, just like many other touch-screens. However, the iPhone's capacitors are arranged according to a coordinate system. Its circuitry can sense changes at each point along the grid. In other words, every point on the grid generates its own signal when touched and relays that signal to the iPhone's processor. This allows the phone to determine the location and movement of simultaneous touches in multiple locations. Because of its reliance on this capacitive material, the iPhone works only if you touch it with your fingertip -- it won't work if you use a stylus or wear non-conductive gloves.
Interpreting Touch-location Data
The iPhone's processor and software are central to correctly interpreting input from the touch-screen. The capacitive material sends raw touch-location data to the iPhone's processor. The processor uses software located in the iPhone's memory to interpret the raw data as commands and gestures. Here's what happens:
Signals travel from the touch screen to the processor as electrical impulses.
The processor uses software to analyze the data and determine the features of each touch. This includes size, shape and location of the affected area on the screen. If necessary, the processor arranges touches with similar features into groups. If you move your finger, the processor calculates the difference between the starting point and ending point of your touch.
The processor uses its gesture-interpretation software to determine which gesture you made. It combines your physical movement with information about which application you were using and what the application was doing when you touched the screen.
The processor relays your instructions to the program in use. If necessary, it also sends commands to the iPhone's screen and other hardware. If the raw data doesn't match any applicable gestures or commands, the iPhone disregards it as an extraneous touch.
All these steps happen in an instant -- you see changes in the screen based on your input almost instantly. This process allows you to access and use all of the iPhone's applications with your fingers. We'll look at these programs and the iPhone's other features in more detail in the next section, as well as how the iPhone's cost measures up to its abilities.
To all who read, well, you can thank www.howstuffworks.com for all of the above information.
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