Resistive vs Capacitive touch screens


The worldwide market for touchscreen mobile devices was surpassing 362.7 million units in 2010, a 96.8 percent increase from 2009 sales of 184.3 million units, according to Gartner, Inc. By 2013, touchscreen mobile devices will account for 58 percent of all mobile device sales worldwide and more than 80 percent in developed markets such as North America and Western Europe.

shipments

Touch control modes:

Surface acoustic wave
A surface acoustic wave (SAW) is an acoustic wave traveling along the surface of a material exhibiting elasticity, with an amplitude that typically decays exponentially with depth into the substrate.

Discovery
SAWs were first explained in 1885 by Lord Rayleigh, who described the surface acoustic mode of propagation and predicted it's properties in his classic paper. Named after their discoverer, Rayleigh waves have a longitudinal and a vertical shear component that can couple with any media in contact with the surface. This coupling strongly affects the amplitude and velocity of the wave, allowing SAW sensors to directly sense mass and mechanical properties. This kind of wave is commonly used in devices called SAW devices in electronic circuits. SAW devices are used as filters, oscillators and transformers, devices that are based on the transduction of acoustic waves. The transduction from electric energy to mechanical energy (in the form of SAWs) is accomplished by the use of piezoelectric materials.
Application in electronic components Schematic picture of a typical SAW device design. Electronic devices employing SAWs normally use one or more interdigital transducers (IDTs) to convert acoustic waves to electrical signals and vice versa by exploiting the piezoelectric effect of certain materials (quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, etc.). These devices are fabricated by photolithography, the process used in the manufacture of silicon integrated circuits. SAW filters are now used in mobile telephones, and provide significant advantages in performance, cost, and size over other filter technologies such as quartz crystals (based on bulk waves), LC filters, and waveguide filters. Much research has been done in the last 20 years in the area of surface acoustic wave sensors. Sensor applications include all areas of sensing (such as chemical, optical, thermal, pressure, acceleration, torque and biological). SAW sensors have seen relatively modest commercial success to date, but are commonly commercially available for some applications such as touchscreen displays.

future

Infrared

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. 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. 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.


What is a resistive touchscreen?
Resistive touchscreens work on the basis of pressure applied to the screen. A resistive screen consists of a number of layers. When the screen is pressed, the outer later is pushed onto the next layer — the technology senses that pressure is being applied and registers input. Resistive touchscreens are versatile as they can be operated with a finger, a fingernail, a stylus or any other object.

What is a capacitive touchscreen?
Capacitive touchscreens work by sensing the conductive properties of an object, usually the skin on your fingertip. A capacitive screen on a mobile phone or smartphone usually has a glass face and doesn't rely on pressure. This makes it more responsive than a resistive screen when it comes to gestures such as swiping and pinching. Capacitive touchscreens can only be touched with a finger, and will not respond to touches with a regular stylus, gloves or most other objects.

The ClearPad 3000 is Synaptics' new top-of-the-line capacitive touchscreen, designed for high-end phones, gaming systems (PSP GoFaster?) and other fancy mobile gear. It has 48 sensing channels, so it'll pick up 10 fingers at once, and it scales up to 8-inch screens with narrower borders than their current ClearPad 2000 touchscreens (which senses two fingers and is used in HTC's Android handsets like the G1, among other phones).

Sources: http://www.pcworld.idg.com.au, http://www.gartner.com, wikipedia, http://gizmodo.com, http://www.seria.hu