Introduction
The PURPOSE of this brief report is to compare touch screen systems: infrared (IR) and surface acoustic wave (SAW), TO ASSIST in the process of SELECTING the best touch screen system for our company’s needs.

Similarities
Both touch screen systems have very high clarity because, unlike resistive or capacitive screens, there are no metallic layers over the screens. Both technologies use signals passing on or over the surface of the screen.

Differences in technology
With the IR system, LEDs send light beams which are picked up by detectors. A touch interrupts a light beam and causes a drop in the signal, which is processed by a controller that determines the location of the touch.
With the SAW system, on the other hand, transducers emit sound waves along the sides of the screen, which are then reflected back and forth across the surface. A touch absorbs some of the acoustic energy from the waves, and the controller then measures the wave amplitude change to determine the location.

Differences in performance resulting from technology
These differences in the technology GIVE RISE TO differences in performance between the two systems. SINCE any object can interrupt a light beam, the IR touch screen will respond to any input, whether it is a finger, a pen, a stylus or any other object. The SAW screen, however, will only respond to a touch by a soft object which can absorb sound, SUCH AS a finger or a soft stylus.
Because the IR system uses light beams, the screen can be badly affected by bright ambient light, WHILE the SAW system, depending on sound waves, can be negatively affected by loud noise around it.
Since the IR screen is separated from the light beams, the screen can be sealed and is therefore not affected by bad weather or contaminants. The SAW screen, however, cannot be sealed, since the waves travel across its surface, and so it can be badly affected by moisture and contaminants.
For this reason, IR touch screens are highly suitable for outdoor use (ALTHOUGH they will need some protection from bright sunlight), and also for use in medical or industrial environments. On the other hand, SAW touch screens are more suitable for indoor use.