Introduction to Touch Screen Technology
Nowadays our life is full of electronic gadgets like Smartphone, tablets, iPads and more. Each of these uses touch screen technology for input or for interaction with the operating system. Now what is the meaning of 'touch screen'? It is a screen that experiences the touch and detects the position of touch as well as calculates as user input. Touch screen technology is believed to be one of the most important inventions in this modern era of digital machines. For the last few years, the touch screen has used many technologies like mechanical, optical and electrical technologies to detect the sense of touch. By use of touch screen, mobile phones have turned compact and light due to omission of keypad or keyboard. Due to so many technological advantages of touch screen, almost everyone thinks how does touch screen technology work?. The recently new technology named 'dual touch screen technology' supports two different touch screens. One is for display which acts like monitor of laptop and other will act as virtual keypad or keyboard. Now, let us understand the overview of the working principle of Touch screen technology.
Different types of touch screen technologies
There are two main types of touch screen technologies, which include resistive touch screen technology and capacitive touch screen technology. First, let us understand the Resistive touch screen technology.
Resistive touch screen technology
In a resistive touch screen technology, the touch screen is a 2D sensing device having two sheets (top and bottom layer) separated by small spaces. Normally top layer is made up of PET or Polyethylene which is considered as a flexible material. The bottom layer is made up of glass material. These top and bottom layers are separated by two resistive coatings of ITO or Indium Tin Oxide. Spacers are provided between these two resistive coatings. The function of these spaces is to avoid any false touch or an accidental touch.
When screen display is touched, the top layer of a film made up of PET is pressed downward and two ITO resistive coatings complete the circuit by contact between them. The location or position of the touch is calculated by the controller circuit. These controller circuits work, based on the X and Y Cartesian coordinates system. It determines X and Y coordinate of a point under the touch. For this type of technology, one needs to use the stylus or hard press for completing the circuit for input. While in the case of capacitive only human touch can complete the touch circuit.
Capacitive touch screen technology
This capacitive touch screen technology solely depends on the physics of the capacitor used in electrical technology. This touch screen is made up of two conductive electrodes which are separated by an insulation gap. When DC current is passed, it cannot pass or straddle the gap between the two conductive electrodes but when AC current is passed, electrons flow from one side to the other side. This touch screen is fabricated with a grid of conductive electrodes. When this conductive touch screen experiences touch, a firm contact in form of capacitive contact is formed and AC current generated within the device produces the corresponding current in our body of the person touching the screen which spans the gap and completes the circuit to calculate the position of the touch.
Surface acoustic wave touch screen technology
This Surface Acoustic Wave (SAW) touch screen technology deals with the ultrasonic wave and related technology. In this technology, ultrasonic waves are continuously passed over the panel of a touch screen. When someone touches this screen/panel, some portion or part of the wave gets absorbed. This change in the ultrasonic wave incident transfers the touch information to the position controller. This touch screen can be damaged by exterior factors or elements.
Infrared Grid touch screen technology
This technology deals with XY infrared LED array and pairs of photo-detector near/around the edges of the touch screen to detect or sense the touch or disruption in the normal patterns of LED beams, which are continuously thrown from the source. This forms the rectangular patterns of LED which are arranged in a vertical and horizontal fashion and this tells the controller about the touch position.
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