Touchscreen technology is the direct manipulation type gesture based technology. Direct manipulation is the ability to manipulate digital world inside a screen without the use of command-line-commands. A device which works on touchscreen technology is coined as Touchscreen. A touchscreen is an electronic visual display capable of 'detecting' and effectively 'locating' a touch over its display area. It is sensitive to the touch of a human finger, hand, pointed finger nail and passive objects like stylus. Users can simply move things on the screen, scroll them, make them bigger and many more.
Resistive Touchscreen Technology
Types of Touchscreen Technology
Resistive LCD touchscreen monitors rely on touch overlay, which is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touchscreen controller. The inside surface of each of the two layers is coated with a transparent metal oxide coating of Indium Tin Oxide (ITO) that facilitates a gradient across each layer when voltage is applied. Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. The
control electronics alternate voltage between the layers and pass the resulting X and Y touch coordinates to the touchscreen controller. The touchscreen controller data is then passed on to the computer operating system for processing. Resistive touch screen panels are generally more affordable but offer only 75% clarity and the layer can be damaged by sharp objects. Resistive touch screen panels are not affected by outside elements such as dust or water. Resistive touchscreens are used in food-service; retail Point-Of-Sale (POS), medical monitoring devices, portable and handheld products, industrial process control and instrumentation. Resistive Technology is divided into two broad categories:
Capacitive Touchscreen Technology
A capacitive touch screen panel is coated with a material that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact. Circuits located at each corner of the panel measure the charge and send the information to the controller for processing. Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus. Capacitive touch screens have excellent clarity, and there are no moving parts to wear out. Liquids, dirt, grease, or other contaminants do not affect them. Unfortunately, gloved fingers will not activate the system. It is divided into two broad categories as follows:
Infrared Touchscreen Technology
An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. A major benefit of such a system is that it can detect essentially any input including a finger, gloved finger, stylus or pen. It is generally used in outdoor
applications and Point-Of-Sale systems which can't rely on a conductor (such as a bare finger) to activate the touchscreen.Unlike capacitive touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system.
Surface Acoustic Wave Touchscreen Technology
The Surface Acoustic Wave (SAW) technology is one of the most advanced touch screen types. The technology is based on two transducers (transmitting and receiving) placed for the both of X and Y axis on the touch panel. The other important element of SAW is placed on the glass, called reflector. The controller sends electrical signal to the transmitting transducer, and transducer converts the signal into ultrasonic waves and emits to reflectors that are lined up along the edge of the panel. After reflectors
refract waves to the receiving transducers, the receiving transducer converts the waves into an electrical signal and sends back to the controller. When a finger touches the screen, the waves are absorbed, causing a touch event to be detected at that point.
Compared to Resistive and Capacitive technologies, SAW technology provides superior image clarity, resolution, and higher light transmission. Because the panel is all glass, there
are no layers that can be worn, giving this technology the highest durability factor and also the highest clarity. Disadvantages of Surface Acoustic Wave (SAW) technology include the facts that the touch screen must be touched by finger, gloved hand, or softtip stylus (something hard like a pen won't work) and that the touchscreen is not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environment. The Surface Acoustic Wave technology is recommended for ATMs, Amusement Parks, Banking and Financial Applications, public information kiosks, computer based training, or other high traffic indoor environments. Surface wave touch screen panels are the most advanced of the four types. SAW offers excellent clarity and durability and allows gloved hand use. However, SAW is expensive, is difficult to seal from the environment, and can be activated inadvertently by dirt, grease, or liquids and can
be damaged by outside elements.
ADVANTAGES AND DISADVANTAGES OVER OTHER POINTING DEVICES
- Touching a visual display of choices requires little
thinking and is a form of direct manipulation that is
easy to learn.
- Touch screens are the fastest pointing devices.
- Touch screens have easier hand eye coordination than
mice or keyboards.
- No extra work space is required as with other
- Touch screens are durable in public access and in
high volume usage.
- User's hand may obscure the screen.
- Screens need to be installed at a lower position and
tilted to reduce arm fatigue.
- Some reduction in image brightness may occur.
- They cost more than alternative devices.
- Screens get very dirty
- These devices require massive computing power
- which leads to slow devices and low battery life
Touchscreen devices usually has no additional keys (see the iPhone) and this means when an application crashes, without crashing the OS, you can?t get to the main menu as the whole screen becomes unresponsive