interactive screens
fingers, such as pinching or zooming of
images. Larger displays might allow for
interaction using two hands or even two
users at the same time.
Surface acoustic wave, or SAW
displays, use piezoelectric transducers
and receivers along the sides of the
screen to create a grid of invisible
ultrasonic waves on the surface.
A portion of the wave is absorbed
when the screen is touched, with
this disruption tracked to locate the
touchpoint.
The transparency of the glass on
a SAW panel is pretty good and the
touch tends to be very stable and not
require frequent calibration. On the
other hand, it doesn’t work well outdoors
or anywhere there is grease or high
amounts of dust, such as near car parks
or in warehouses etc. Also, you can
apply 2-point touch on SAW, although
pinching, zooming, and applications
such as on-screen signatures don’t work
particularly well.
Last on the list of dominant touch
technologies is projected capacitive
technology. PCAP is a relative of
capacitive touch, with the key difference
being that they can be used with a
stylus or a gloved finger. Projected
capacitive touchscreens are built by
layering a matrix of rows and columns of
conductive material on sheets of glass.
32 KIOSK solutions
The Voltage applied to the matrix creates
a uniform electrostatic field, which is
distorted when a conductive object
comes into contact with the screen. That
distortion serves to pinpoint the touch.
Projected capacitive and its cousin
surface capacitive are relatively new
technologies, similar to what’s in a
smartphone. Both offer opportunities
not possible with resistive and infrared
touchscreens. Capacitive technology
is born and bred for multi-touch and
because the touch technology is
embedded in the glass it offers superior
resistance to wear and vandalism, plus
provides a clear, bright screen.
This type of screen is still fairly
expensive compared with other types
of touchscreens, mostly because the
technology is new and there isn’t a
ton of high-quality manufacturers out
there making them. Another important
consideration is that metal can interfere
with the function of the PCAP technology,
so the integrator or kiosk designer
should know what they are doing to
ensure the product works as advertised.
The final determination
Ultimately, the type of touchscreen a
deployer chooses to incorporate into
their application will be determined by
factors including budget, the environment
in which the device will be placed, the
function the device will perform and plans
for any future applications.
Order entry screens in the kitchens
of a small fast food restaurant chains
would obviously call for resistive touch
technology, for example, while a 72-inch
display in a hotel lobby or shopping mall
would call for infrared touch. An ‘endless
aisle’ or catalogue lookup kiosk where a
shopper may want to enlarge an image
of a particular product might work fine
with a surface acoustic wave or surface
capacitive screen, while wayfinding
kiosks on a college campus or city street
would likely call for projected capacitive
technology. If the deployer has plans to
implement more advanced functions
down the road and wants to future-
proof their investment, they may need to
choose between a surface capacitive or
projective capacitive screen. n