Touchscreen Gyaan

What is it ?

A technology which allows commands to be issued on an electronic device by merely touching the user-interactive display on the screen.


Who dunnit ?

Pretty mature stuff. Existing for around 30 years!!

In 1970 a professor from the University of Kentucky, Dr. Sam Hurst, filed a patent for a "touch sensor", called the Elograph. The "Elograph" was not transparent like modern touch screens; however, it was a significant milestone in touch screen technology.
Patent : US3662105: Electrical Sensor Of Plane Coordinates

The first true touchscreen patent was filed by Dr. Hurst in 1972. Using his patented five-wire resistive technology, this patent would go on to be the most widely used form of touchscreen technology. In 1974, the first true touch screen incorporating a transparent surface came on the scene.
Patent : US3798370: Electrographic Sensor For Determining Planar Coordinates


Technology

Consists of three main components :-

i) A “Touch Sensor” which is a clear glass panel with a touch responsive surface. The sensor has an electric current passing across it. Touching the screen causes a voltage change. This allows determining the exact position or coordinates of the touch. A Touch Sensor can function in three major ways namely resistive, capacitive and Surface Acoustic Wave (SAW). However, there are other technologies like Dispersive Signal (DST), Infrared and Optical too.

a) Resistive: It consists of conductive and resistive metallic layers separated by spacers and a scratch-   resistant layer is placed on top of this whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot to deliver the X and Y coordinates. It allows decent clarity allowing 75% light from the monitor.

b) Capacitive: It consists of a layer that stores electric charge placed on top of the monitor. When a user touches the panel, some of the capacitive charge gets dissipated to the user. This relative decrease in charge is measured using circuits at each corner of the monitor. This helps to pinpoint the exact coordinates of the human touch. It allows good clarity allowing 90% light from the monitor.

c) Surface Acoustic Wave: It consists of two transducers mounted at the edge of a glass overlay to emit ultrasonic sound waves along two sides. These waves are reflected across the surface of the glass and received by sensors. A finger or other soft tipped stylus absorbs some of the acoustic energy and the controller measures the amplitude change of the wave to determine touch location. It allows perfect clarity allowing almost 100% light from the monitor.

ii) A “Controller” which is small installable card to transmit touch information from the sensor to the OS. It can connect to a Serial or USB port on the PC running the OS.

iii) And ofcourse a “Software Driver” for successful installation of the controller peripheral. It allows for interpretation of touch event information by the OS.


Applications

Commercially, touch screen computers service a wide range of purposes. Most common public information booths such as information kiosks, customer self-service and various displays offer a way for almost anybody to access information with little or no experience using a computer. This is due to the fact that a touch screen interface allows the user to interact not with keyboard and mouse like a typical computer, but with tools they are most comfortable with-their fingers. The popularity of smart phones, PDAs, portable game consoles and many types of information appliances is driving the demand for, and acceptance of, touch screens. There are many pros and cons of the various touchscreen technologies based on which their deployment is considered. For e.g. highly durable and less expensive resistive technology is most often used in public ATMs and kiosks. Capacitive technology is being considered more for smart phones and mobile gaming devices due to their better clarity.

It is very likely to expect more innovative products applying the touch screen technology in the near future.