SJ Mercury News: Touch Screen technologies

From: Arthur Keller <arthur_at_kellers_dot_org>
Date: Mon Oct 12 2009 - 11:16:44 CDT

http://www.siliconvalley.com/latestheadlines/ci_13519506

Touch screen gamble: which technology to use

By Steve Johnson
sjohnson@mercurynews.com
Posted: 10/11/2009 04:00:00 PM PDT

Prompted partly by the iPhone's phenomenal popularity, consumers are
demanding and likely to get a wider range of touch screens on many
more electronic devices.

The screens have become wildly trendy by allowing people to operate
cell phones, bank teller machines, airport kiosks and other gadgets
by simply pressing a finger to a screen or, in some cases, merely
waiving their pinkie over it.

But the multibillion-dollar touch-screen market is awash with at
least a dozen competing technologies, each requiring a differently
designed microchip known as a controller to make their screens work.
And that poses considerable risk for any semiconductor company trying
to determine which technology to embrace.

"You're kind of having to make a gamble," said Randy Lawson, a senior
analyst with chip research firm iSuppli. "A lot of people are asking,
'Who's going to be the winner in five years?' "

Most touch screens today use what is known as resistive technology,
which incorporates two electrically conductive layers separated by
air. When a finger or stylus presses the screen, it compresses the
layers together and changes the electrical current, which the screen
recognizes as a touch.

One Silicon Valley chip maker long experienced with the resistive
approach is Maxim Integrated Products of Sunnyvale, which considers
the technology ideal for such things as printers, MP3 players,
digital photo frames and car entertainment systems.

"We've being doing resistive touch-screen controllers for the past
eight years," said Bart DeCanne, a Maxim business director, noting
that the technology is popular because it is relatively inexpensive
and adaptable for a variety of uses.

But resistive touch screens have their limits. They tend to wear out
with all the pounding they take and they aren't generally designed to
accommodate gestures with more than one finger, as is possible with
the Apple's iPhone. With that phone, for example, a person can zoom
into a picture or Web page by putting their thumb and index finger on
the screen and spreading them apart. To zoom back out, the fingers
are pinched together.

While companies are just beginning to explore multitouch
capabilities, experts say being able to operate screens with up to 10
fingers will enable people to play virtual piano, create elaborate
finger paintings, easily rearrange computerized photo albums and
enjoy new types of video games, among other possibilities.

The technology generally regarded as best suited for multiple-finger
commands - and the one the iPhone uses - is called capacitive touch,
which relies on the human body's electrical properties.

In a basic configuration, a capacitive screen is given a uniform
electric field by electrodes placed around its edges so that a finger
touch draws current from each corner of the screen. The controller
then measures the current flow from the corners to instantly
calculate the finger's location. Some capacitive designs can detect a
finger that comes close to the screen but doesn't actually make
contact with it.

While generally more expensive to make than resistive screens, the
capacitive kind are becoming more affordable and "getting a lot of
interest" from chip makers, said Jennifer Colegrove, an analyst with
the market research firm DisplaySearch.

One Silicon Valley company that has forged heavily into capacitive
technology over the past two years and has become a leading supplier
of capacitive chips is Cypress Semiconductor of San Jose.

Many chip companies, including Cypress, don't disclose how much they
earn specifically from touch-screen sales, which analysts say makes
it hard to calculate the overall size of the touch-screen controller
market. But the business "is on a very growth trajectory," said Gokul
Krishnan, Cypress' director of marketing user interface solutions,
adding that "almost everyone is switching from resistive to
capacitive."

Among those jumping on the capacitive train is Maxim. But because
resistive touch screens are likely to remain desirable for certain
consumer and industrial applications, said Maxim's DeCanne, "we
believe resistive is going to be the bulk of our business for the
next two years."

Hedging its bets even more is Elo TouchSystems of Menlo Park, which
has been developing touch-screen capabilities for about 40 years and
became part of Switzerland-based Tyco Electronics in 1999.

Besides selling resistive and capacitive controllers, Elo offers
products based on several other touch-screen technologies. Two of
them pass sound waves over the screen, so a finger touch is
identified by a change in the wave. Another creates a grid on the
screen with infrared light-emitting diodes. When a finger interrupts
the light, the touch is detected by photo sensors.

By offering several options, Elo differentiates itself from
competitors that "force-fit you into one type of technology," said
Lorna Wood, the company's global marketing manager.

More alternatives are probably coming, said Amy Leong, an analyst
with research firm Gartner.

"The touch market is still in its infancy stage," she said. "In the
next few years, we are going to see many types of touch technologies
being tested and deployed for various applications."

Contact Steve Johnson at 408-920-5043.

TWO TOUCH-SCREEN TECHNOLOGIES

Resistive technology incorporates two electrically conductive layers
separated by air. When a finger or stylus presses the screen, it
compresses the layers together and changes the electrical current,
which the screen recognizes as a touch.

Capacitive touch relies on the human body"s electrical properties and
is regarded as best suited for multiple-finger commands. In a basic
configuration, a capacitive screen is given a uniform electric field
by electrodes placed around its edges, so that a finger touch draws
current from each corner of the screen. The controller then measures
the current flow from the corners to instantly calculate the finger"s
location.

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Received on Sat Oct 31 23:17:02 2009

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