Advanced Imaging


Advanced Imaging Magazine

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

A Touch of Glass

Touchscreen technology evolving from single touch to multitouch and gesturing
Ocular Inc.
Figure 1. Resistive touch screens have an outer layer of flexible film that must bend to make electrical contact. Projected capacitive touch screens feature a protective glass layer which conducts changes in the screen’s capacitance resulting from a touch.
Digital Dash
Figure 2. Digital Dash’s multifunctional solution uses familiar physical controls like knobs, buttons and sliders, with touch input, while remaining totally reconfigurable in software.

By Barry Hochfelder

The display market is expanding rapidly. Touchscreens are more and more popular. How popular?

According to Display Bank, a Seoul, Korea-based research organization, the touch screen panel market reached $2.45 billion in 2009 and is expected to create $3.6 billion in 2010 and $7.3 billion by 2013. Display Bank, which has offices in Castro Valley, Calif., Shanghai, Tokyo and Taiwan, also says that touch screen-enabled application products reached 280 million units in 2009 and are expected to reach 420 million this year and 800 million by 2013. That translates, the company says, to more than 30 percent compound annual growth rate (CAGR) by 2013.

One industry expert, Larry Mozdzyn, CTO of Ocular, Inc. (Richardson, Texas), points to one area that has driven the growth. “I think what’s driven this is the development of graphical user interfaces (GUIs) on electronic products,” he says. “Resistive touchscreens have been around for a long time [in cash registers and restaurant transactional systems, for example]. The development of the GUI has become integrated into display and opened up touchscreens. If you look at capacitive that’s been a more recent deployment into products, even though capacitive sensing has been around at least 10 years.”

There are two primary touchscreen technologies—resistive and capacitive. A resistive touchscreen panel has several layers, including two thin, metallic, electrically conductive layers separated by a narrow gap. When a finger presses down on the panel’s outer surface the two metallic layers become connected at that point and the panel acts as a pair of voltage dividers with connected outputs. This causes a change in the electrical current and is sent to the controller for processing.

A capacitive touch screen consists of an insulator, such as glass, and is coated with indium tin oxide (ITO) to serve as a conductive coating. The human body is also a conductor and touching the surface of a capacitive touch screen results in a distortion of the panel’s electrostatic field. Different controllers are used to determine the location of the touch and once the location is determined, it can be passed to a computer running a software application that calculates how the user’s touch relates to the computer software being utilized.

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