Surface Acoustic Wave (SAW) touch screens work by using ultrasonic waves to detect touch events and the location of the user’s input. They operate in a similar way to beam break technology.
Like optical touch screens, the technology is also perimeter based, with the only difference being that sound waves are used instead of light.
A SAW touch screen is made up of a glass sheet with transmitting transducers, receiving transducers and reflectors. The transmitting transducers produce ultrasonic waves that skim over the surface of the screen, get reflected and are captured by the receiving transducers.
When a soft matter like human skin, touches the screen, the surface acoustic waves are absorbed, and the receiving transducers do not register any input. Based on this, sensors can calculate the location of the touch event.
Pros of SAW Touch Screens
The Baanto ShadowSense Advantage
SAW touch screens are not perfect and come with their own unique set of disadvantages that can hamper universal deployment. These disadvantages are addressed by Baanto ShadowSense technology, which uses high performance analog sensors coupled with sophisticated position detection algorithms.
|Cons of SAW Touch Screens||ShadowSense Benefits|
|Will not work with materials like pens that do not absorb ultrasonic waves||Works with any kind of input device because they depend on shadows cast by the input device|
|Can malfunction in the presence of foreign materials like water or oil droplets which can absorb the waves||Can ignore impurities like water, mud, dust, ketchup or grease by letting users set acceptable limits around shadow density, frequency of input and size|
|Display latency during multi touch operations||Have sensors that work at 10,000 fps giving near instantaneous response times of 6 to 8 ms|
|Attract dirt, water and impurities in the bezel area as the perimeter cannot completely be sealed off from the environment because transducers need to send and receive waves||Have sensors that are bezel-based and can be sealed off from the environment without affecting their performance|
|Does not support multi touch as the waves can be reflected off multiple objects, confusing the sensors||Screens support true multi touch gestures|