Touch Screen

Touch Screen is very user friendly, fast, accurate, easy to operate. It has been widely accepted. A touch screen is a display screen that is sensitive to human touch. The screen has a sensitive glass overlay placed on it and one can give desired input by touching it.

It is comprised of three basic components viz, touch screen panel, controller and software driver.

Touch Sensor

A touch screen sensor is a clear glass panel with a touch responsive surface. The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change.

Controller

The controller is a small PC card that connects between the touch sensor and the PC. The controller determines what type of interface/connection you will need on the PC.

Driver

The driver is a software that allows the touch screen and computer to work together. Most touch screen drivers today are a mouse-emulation type driver.

Schematic Diagram of Working of Touch Screen

Types of Touch Screen Technologies

• Resistive type

• Surface Acoustic wave type

• Capacitive type

• Infrared Grid

• Infrared Acrylic Projection type

• Optical Imaging type

• Dispersive Signal type

• Acoustic Pulse Recognition type

In general we use four types of touch screen technologies which are discussed below:

• Resistive type

A resistive touchscreen panel comprises of two transparent electrically resistive layers facing each other with a thin gap between. The top layer (that which is touched) has a coating on the underside surface; just beneath it is a similar resistive layer on top of its substrate. A voltage is applied to one layer, and sensed by the other. When fingertip or stylus tip, presses down onto the outer surface, the two layers touch to become connected at that point. The panel then behaves as a switch. And with the help of software the position of touch is determined and desired action is performed.

• Surface Acoustic Wave type

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. The change in ultrasonic waves is processed by the controller to determine the position of the touch.

• Capacitive type

A capacitive touchscreen panel consists of an insulator, such as glass, coated with a transparent conductor, The human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch.

• Infrared Touch Screen type

An infrared touchscreen uses an array of X-Y infrared LED and photo-detector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. These LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch.

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