The Yulong CoolPad 858F GSM mobile phone features Atrua Wings touch control. The SenTru fingerprint sensor is located at the bottom part of the phone. Yulong is based in Shenzen, China.

Designers of mobile devices increasingly face a dilemma — to embed more functions in their products or to continue to make them smaller. Atrua Technologies, Campbell, Calif., has solved the nagging design question of how to provide user access to an ever-growing number of functions without the added buttons.

The Atrua SenTru fingerprint sensor provides data on the ridges and valleys on the finger as it moves across its surface. Internal circuits within the sensor convert the data into a stream of digital data (a frame) that is presented to the host microprocessor.

After focusing solely on this particular design issue for five years now, the company has come up with a haptic technology that improves the usability of mobile devices by providing more responsive, high-precision controls and advanced control functions, without rendering the products too cumbersome to market.

The touch technology allows users to emulate functions that they are already familiar with on mobile devices, like a touch pad or joy stick, as well as functions they may not have come into contact with before, such as a pivot control pressure button and fingerprint recognition.

Intelligent touch controls is a new category of user input device for cell phones, PDAs, mobile handsets and virtually any other mobile device the market can devise. The Atrua Wings intelligent touch controls solutions apply proprietary HaptorXD haptic processing technology to detect the features of the user’s finger.

HaptorXD uses an adaptive capacitive sensor that sees the fine features of the finger, where a typical touch sensor would simply look at the end of the finger. Because the sensor can actually see the fine ridges of the finger, small movements can be translated into signals that are registered by the sensor and navigation software. Different types of movements, such as twisting of the finger and pressing of the finger, are also readily detected.

Both the sensing technology and the software for mobile devices are created in-house at the company and are combined for the Atrua Wings solution. The SenTru Haptic sensor provides features and movement information to Hapticware software, which interprets data and converts it into commands that can be used for advanced game controls, flexible navigation and control of a handset in addition to secure access to mobile data services and transactions.

The SenTru sensor provides data on the ridges and valleys of the finger as it moves across its surface. Internal circuits within the sensor convert the data into a stream of digital data (a frame) that is presented to the host microprocessor via an 8-bit bidirectional bus interface that is compatible with most microprocessors or via a high-speed serial port.

Two key classes of algorithms are used to execute the core functions of the haptic processing system — fingerprint authentification and control and navigation. These algorithms operate on data streamed from the sensor. The authentification algorithms extract the minutiae features used for fingerprint verification, and match the pattern to the user’s template stored on the device. The navigation/control algorithms analyze finger motions to provide control functions.

Atrua’s haptic processing system captures an image of the finger’s features frame by frame as it is moved over the small, linear sensing area. When used for fingerprint recognition, proprietary reconstruction software using the automatic gain control (AGC) function in the sensor, processes the data of the finger’s features and movements from the received frames while maximizing contrast and sensitivity across a variety of environmental conditions.

The Atrua Wings touch control solution includes the SenTru haptic sensor, which can replace buttons on the interface of compact, portable devices where space is at a premium.

The implications for designers include the ability to have a high-precision, high-sensitivity control without sacrificing space. The sensing area is about as 14 mm long and 2 mm high. It runs on very low power, and its fingerprint recognition technology can be easily applied to services that require a user to navigate through a series of steps with a single touch.

Beyond the PDA and mobile phone, the haptic sensor is being used for improvements on current applications like the creation of phone game controls with the quality of those on a dedicated portable games console, easier picture editing; as well as to facilitate maneuverability through long MP3 play lists or through mapping services. It can also be used for PC security and data storage security.

With a sensor coating that is harder than quartz crystal, the durability of the mobile devices is superior to other products as well. Atrua tested the surfaces by swiping it with simulated fingers, and found a limit of 10 million swipes.

“You don’t have any mechanical parts to break on this,” says Atrua Marketing Director Marc Ostrowski. “That’s actually one of the largest sources of failure on mobile devices, is mechanical input. So, that cuts out a big loss factor in terms of those devices.”

The technology can be used in almost any type of mobile device, and Atrua working in collaboration with more than 20 partners for applications that include mobile network operators, game developers, security developers, integration, and hardware/software platform providers. Partners include Swisscom Mobile, MaxArtists, Sicap, Yulong, Pollex Mobile, Genesys Logic, BioAPI and Hitachi Engineering Corp.

“This can go for any type of mobile device — things like an MP3 player, GPS units — it can go for anything that is a portable unit that requires control beyond just a few simple on/off functions,” Ostrowski says.