Touch Screens are the most commonly used input devices. We can see most of the devices have touch screens say ATM’s, mobiles, ticket vending machines and many more. Touch screens are used instead of keyboards and mouse to accept input from the user. Here in this article we’ll discuss the technology behind the touch screens.
Types of Touch Screens
There are mainly four types of touch screen technologies depending on the application or cost. They are –
- Resistive Touch
- Capacitive Touch
- Surface Acoustic Wave Touch
- Infrared Touch
Resistive Touch Screen
Resistive touch screen technology consists of two transparent thin layers which are on top of the display which are electrically resistive. These layers are arranged so that there is a small gap between them where electric current is passed. When we apply any force on the top layer, then the layer makes contact with the bottom layer and making some sort of disturbance to the passage of current and registers the location of the contact made, which is then converted into the input by the device software.
We can find resistive touch screens in some old modal mobile phones, supermarkets, etc. Since it works with stylus or gloves it is most used technology. It is not that efficient for all the mobile applications, so most of the manufacturers preferring capacitive touch screens.
Capacitive Touch Screen
Capacitive touch screen consists of a transparent electrode layer which is mounted on the display and covered by a protective cover. This layer uses static electrical capacity of the human body as the input. When we touch the screen the electrical capacitance in the body is conducted and some of the electrical charge transfers from screen to the user, thus resulting some loss of charge in the screen and then the loss is calculated and registers the location with the sensors present at all the four corners of the screen. This is called Surface Capacitance.
There is other type in capacitive touch technology
Projected capacitance is similar to the surface capacitance but it can also be activated with the gloves and supports multi-touch. It consists of a thin sheet of glass with embedded transparent electrode ﬁlms and an IC chip, which creates a 3 dimensional electrostatic ﬁeld. When the user touches the screen, the ratios of the electrical currents change and the device will be able to detect the touch points. All the latest generation mobile phones are embedded with this touch screens.
Surface Acoustic Wave Touch Screen
Surface Acoustic Wave Touch technology includes two transducers to register the touch inputs. The 2 transducers are responsible for sending and receiving respectively, are placed along the X and Y axis of the screen. The receiver transducer checks the waves that are blocked when the user touches the screen and registers the location of the input.
Infrared Touch Screen
In infrared touch technology there is no extra layer. This technology consists of photo detectors and infrared LED which are aligned vertically and horizontally. When the user touches the screen, the infrared rays will be disturbed and the photo detectors point outs the location of the occurred disturbance. Then it registers the location and the input is given to the device.
These are the types of touch screens which are available.