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Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

New Challenges in Handheld Touchscreens

Designing capacitive sensing into handhelds for the exploding mobile phone market
Synaptics
Figure 1. Until recently, the industry largely relied on resistive touchscreens, which require the force of a finger to activate a button on the screen.
Figure 2. Capacitive touchscreens use a thin layer of ITO to sense the presence of a finger by capacitive coupling. Capacitive sensors can be mounted underneath tough outer coatings such as hardened glass or scratch-resistant plastic, which makes the touchscreen more durable.
Figure 3. Synaptics’ ClearPad technology features a transparent sensor that can be mounted under curved plastic and glass.
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By Dr. Andrew Hsu

As we survey today’s technology landscape, touchscreens have become ubiquitous. We find them on ATM machines, gas pumps, airport check-in kiosks, as well as in games, navigation systems, digital cameras, smartphones, ovens, appliances, and more. Touch technology is everywhere, and this is only the beginning. The touchscreen has become ever more important in modern handheld design because the touchscreen is the interaction device—both input and output, and the stakes are high. The rapid adoption of capacitive touchscreen technology for handheld devices is introducing new challenges and opportunities for software designers.

Until recently, the industry largely relied on resistive touchscreens, which require the force of a finger to activate a button on the screen. Yet, many new high-profile smartphones, for example, now employ capacitive touch technology, which is gaining wide adoption. As devices such as smartphones have become richer and more complex, the demands for sophisticated touchscreen technology have only increased. The mobile phone market is exploding and more people are increasingly dependent on smartphones and other modern devices for work, productivity, relationships, and play.

Capacitive touchscreens use a thin layer of ITO to sense the presence of a finger by capacitive coupling. Capacitive sensors can be mounted underneath tough outer coatings such as hardened glass or scratch-resistant plastic, which makes the touchscreen more durable. As a result, product designers are no longer forced to choose between the convenience of an exposed display and the advanced user interface made possible by a touchscreen. Capacitive touchscreens are also inherently suited to multi-finger use. The detection of multiple contacts or touch points in a capacitive touchscreen enables multi-finger usage, such as pinching to zoom in or out on a screen or simultaneous use by multiple users. The ability to use a finger instead of a stylus, as in resistive touchscreens, provides better responsiveness, flexibility, and overall user experience. Further, the ability to use finger-based gestures such as flicking for scrolling, or dragging and dropping, makes for a richer end-user experience.

There have clearly been advances in hardware design in recent years. Today’s handhelds are thinner, flashier, and use new materials such as glass or PET, and even stainless steel. For a fashion-conscious industry, innovative and appealing hardware designs have helped fuel the handheld market. However, with adoption of capacitive touchscreen technology surging, there is a new emphasis today on software design. Software design is more important than ever, and it can make or break your product.

Capacitive touchscreen technology has opened up a whole new world for software designers. In earlier days designers working on a new mobile phone, for example, had a fixed amount of input buttons or controls to work with. The emphasis was on hardware. With modern devices, the touchscreen is like a blank canvas with infinite possibilities for software designers. The latitude and flexibility that designers have with touchscreens is remarkable, but it means that they must fill in that canvas like an artisan; they need to be skilled “painters.” The astonishing success of the iPhone is largely due to the exceptional interaction design based on its capacitive touchscreen.

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