Touchscreen technology

Touchscreen technology is the direct manipulation type gesture-based technology. A touchscreen is a source of input device and output device normally layered on the top of an electronic visual display of an information processing system.  As the name suggests touchscreen you have to touch the screen for any processing. It is sensitive to the touch of a human finger, hand, pointed figure nail and passive objects like a stylus. The user simply moves things on the screen, scroll them, make them bigger and much more.

History

The first ever touchscreen was developed by E. A. Johnson at the Royal radar establishment, Malvern, UK in late 1965. evidently, the first touchscreen was a capacitive type; the one widely used in smart phones now days. In 1971, a milestone in touchscreen technology was developed by doctor Sam Hurst, an instructor at the University of Kentucky research foundation. It was a touch sensor named ‘Elograph’. Later in 1974, Hurst in association with company Elographics came up with the first real touchscreen featuring a transparent surface.

Touchscreen displays are widely used in computers, user interactive machines, point of sale application, gaming consoles, PADs, smartphones, tablets. etc.

Types of touch screen technology

A touchscreen is a 2-dimensional sensing device made of 2 sheets of material separated by spacers. There are four main touchscreen technologies: 

1. Resistive 
2. Capacitive 
3. Surface Acoustic wave 
4. infrared

Resistive

A resistive touchscreen panel comprises panel comprises several layers, the most important of which are two thin, transparent electrically-resistive layers separated by a thin space. These layers face each other with a thin gap between. The top screen has a coating on the underside surface of the screen . just beneath it is a similar resistive layer on top of its substrate. One layer has conductive connections along its sides, the other along top and bottom. A voltage is applied to one layer and sensed by the other. When an object, such as a 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 pair of voltage dividers, one axis at a time. By rapidly switching between each layer, the position of a pressure on the screen can be read. Resistive touch is used in restaurants, factories, and hospitals due to its high resistance to liquids and contaminants. A major benefit of resistive touch technology is its low cost. Additionally, as only sufficient pressure is necessary for the touch to be sensed, they may be used with gloves on, or by using anything rigid as a finger/stylus substitute. Disadvantages include the need to press down and a risk of damage by sharp objects. Resistive touchscreens also suffer from poorer contrast, due to having additional reflections from the extra layers of material (separated by an air gap) placed over the screen.

Capacitive

A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As 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. The location is then sent to the controller for processing. This disadvantage especially affects usability in consumer electronics, such as touch tablet PCs and capacitive smartphones in cold weather. It can be overcome with a special capacitive stylus or a special­ application glove with an embroidered patch of conductive thread passing through it and contacting the user's fingertip.

Surface acoustic wave

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. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface acoustic wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.

Infrared grid

An infrared touchscreen uses an array of X­Y infrared LED and photodetector 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. A major benefit of such a system is that it can detect essentially any input including a finger, gloved finger, stylus or pen.