NEC AccuSync LCD72VX White Paper page 5

The IntelliTouch™ touchscreen is a glass overlay with transmitting and receiving
piezoelectric transducers for the both X and Y axes. The touchscreen controller sends a
five-megahertz (5 MHz) electrical signal to the transmitting transducer, which converts the
signal into ultrasonic waves within the glass. These waves are directed across the front
surface of the touchscreen by an array of reflectors. Reflectors on the opposite side gather
and direct the waves to the receiving transducer, which reconverts them into an electrical
signal - a digital map of the touchscreen surface. When you touch the screen, you absorb
a portion of the wave travelling across it. The received signal is then compared to the
stored digital map, the change recognized, and a coordinate calculated. This process
happens independently for both the X and Y axes. By measuring the amount of the signal
absorbed, a Z-axis is also determined. The digitized coordinates are transmitted to the
computer for processing.
HOW SURFACE WAVE TECHNOLOGY WORKS
The IntelliTouch touchscreen consists of a clear glass overlay formed to match the shape
of the display. Each axis on the overlay has a transmitting and receiving piezoelectric
transducer and a set of reflector stripes. The touchscreen controls sends a 5 MHz burst to
the transmitting transducers, which convert the signal into surface acoustic waves. Surface
acoustic waves are mechanical waves that propagate in the surface of materials such as
glass. The reflector stripes divert the burst across the face of the overlay. When a finger,
gloved hand or soft stylus touches the touchscreen, a portion of the wave is absorbed. The
resulting change in the received signal is analyzed by the controller and digitized into X
and Y coordinates. A Z-axis level is also determined by measuring how much signal was
absorbed. Unlike some other technologies, which depend upon ratios to determine touch
location and thus are prone to drift, IntelliTouch is an inherently stable technology offering
drift-free operation.
For more information please contact:
ELO TouchSystems: http://www.elotouch.com
Microtouch Systems: http://www.pixelinkcorp.com
This white paper was published in and based on information as of November 2001. Technical information is subject to
change.