With the touch-screen sector now entering a new phase of innovation, the issue of applying multitouch operation to the larger format displays found in industrial and public use settings is becoming a key engineering concern. Designers must examine the sensor technology options available today and consider using new single-layer project capacitive sensing technology to enable sophisticated human-machine interactions in large displays destined for harsh environments.
Multitouch
sensor technology has the potential to revolutionize the way we connect
with all manner of electronics hardware, giving touch-screen-based
Graphical User Interfaces (GUIs) the ability to recognize complex
gestures using several fingers such as rotating, two-digit scrolling,
three-digit dragging, and pinch zoom, as well as allowing multiple users
to collaborate. Analyst firm Markets & Markets predicts that the
global multitouch business will reach $5.5 billion by 2016 (constituting
more than 30 percent of the total touch panel
market by this stage). The multitouch segment is currently exhibiting a
compound annual growth rate of more than 18 percent, with the portable
consumer sector driving the vast majority of this growth.
Moving
forward, the problem for design engineers is knowing how to bring the
multitouch capabilities that are already becoming commonplace in smartphones and tablet PCs to other areas that could also derive benefit from them. Digital signage, Point-Of-Sale (POS),
public information, and industrial control systems could profit greatly
from this sort of functionality. However, certain obstacles are
inhibiting the adoption of multitouch in these nonconsumer sectors.
The
larger format multitouch sensor options currently on the market, though
acceptable for personal use such as all-in-one touch PCs, have serious
shortcomings when applied to more demanding application scenarios. Both
infrared and camera-based systems require an exposed bezel for housing
sensor elements. This means that, in addition to increasing
vulnerability to damage from external forces, the buildup of dust or
dirt in the bezel recesses can hamper operational performance over time.
These systems also suffer from sensor drift and need regular
recalibration to rectify this.
Certain forms of projective capacitance such as self-capacitive types, which by their nature are extremely sensitive in
the Z-axis, have proved to be well suited for rugged touch-screen
implementations and can measure two independent touch points
simultaneously. Another form of projected capacitive sensing, mutual
capacitive, which measures charge/discharge across a crossover or node
between adjacent cells created by an X-Y grid, tends to be less
sensitive in the Z-axis and thus typically only works well with thin
glass. However, mutual capacitive sensing offers the ability to detect
more than two independent touch points when mated with the appropriate
control electronics and software. As a result, this technology has been
chosen in recent years as the principal method of bringing multitouch
functionality to consumer applications.
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