Touchscreen

What is Touch Screen?
Touch-screen is an input device which allows us to operate a device by simply touching the screen. A touch screen enables us to directly interact with devices in an easy way, as it could be operated by the touch of a figure or stylus. Now a days the use of touch screen devices is rapidly increasing and they are used in devices like mobiles, computers, tablets, ATM’s, navigation systems, industrial and medical control panels.

Types of touch screens:

Resistive touch screen:
Resistive touch screen is widely used touch screens across the globe. It consists of two layers, a flexible layer and a rigid bottom layer separated by a gap with insulating dots, attached to a touch screen controller. The inner sides of the layers are coated with a thin metallic conductive material, when we press on flexible layer, the two layers will come into contact and there will be a change in voltage, then controller calculates the coordinates at which voltage change has occurred and this is how a resistive touch screen recognizes the input. Resistive touch screen gives only 75% clarity and cannot recognize multiple touches at same time but offer long durability and it is much cheaper.

Capacitive touch screen:

Surface Capacitive:
It consists of a transparent conductive coated glass and at the panel edges electrodes distribute low voltage creating a uniform electric field over the screen. When we touch, our finger draws some current then controller calculates the ratio of current flow from edges and finds out the touch point. This is how surface capacitive touch screen recognizes the input.

Projected Capacitive:
It consists of three layers, top and bottom layer consists of protective glass and middle layer consist a senor grid of micro fine wires laminated. Now when we touch the screen, capacitance is formed between our finger and sensor grid, controller finds out touch point by calculating coordinates where the capacitance is formed. This is how projected capacitive touch screen recognizes the input.
Capacitive touch screen emits 90% of light and has long life but it can sense only finger touch, stylus can’t be sensed.

Surface acoustic wave touch screen:
Surface acoustic wave touch screen has transmitting transducer that receives electrical signals from controller and transmits them to ultrasonic waves which are directed across the surface of screen. On the other end reflectors redirect these waves to the receiving transducer which reconverts ultra sonic waves into electrical signals and send them to the controller. When we touch the screen a portion of wave travelling across it will be absorbed by our finger. Then this change in signal is passed to controller and the controller finds out touch location. These screens are expensive and have short life but emit 100% light, so they offer good image quality.

Infrared touch screens:
Infrared touch screen consists of infrared LEDs and photo transistors on sides of the panel to create an invisible infrared light grid. Now when we touch the screen, light beam in that particular location gets interrupted and controller calculates the coordinates of point at which the interruption took place, and this is how infrared touch screen recognizes the input. This screen supports multi touch and it can take input with the tap of our finger, pen, gloved finger and stylus, there is no need to rely on a conductive material. It has a long life, resistant to moisture and also provides good image quality.