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Motion-sensing comes to mobiles

The Sharp V603SH, sold by Vodafone in Japan since 2005, also uses three-axis accelerometers to allow users to scroll through menus by moving the handset up, down, left or right. Users can also use the motion-sensing technology to turn their phone into a controller for mobile games, including one that allows users to swing the handset like a golf club and hit golf balls on a virtual driving range.

While many of the cool new applications can be done using three-axis accelerometers, experts agree that combining that technology on a single chip with a gyroscope, which can be used to measure rotational speed, could provide even finer sensory control.

An opening for gyroscopes?
Gyroscopes are important for providing stabilisation, said Steve Nasiri, chief executive of Invensense. Like accelerometers, gyroscopes have been used for years in the automobile industry, where they are used to help stabilise cars so they don't roll over. Gyroscopes are also used in devices that require accurate balance sensing, such as the Segway.

Invensense is already supplying digital-camera companies with its tiny, MEM-based gyroscopes to help stabilise cameras and improve picture quality, especially on higher-megapixel cameras. This application alone could provide a huge opportunity to companies like Invensense, which is trying to combine gyroscopes with accelerometers.

"The mobile handset market is the ultimate market to be in," Nasiri said. "With 700 million camera phones sold each year and over 50 per cent of them with 3 megapixels or more, there is a real need for this technology."

In addition to image stabilisation, gyroscopes used in combination with three-axis accelerometers could also help deliver more-accurate location and navigational services. Today, GPS receivers use internal compasses to help get a fix on which direction the phone is pointing. So if you are using a navigation service to get directions to the closest Starbucks, the phone will know if you are facing north, south, east or west. But the compasses work better when the devices are held perfectly horizontal -- a position that can be difficult to maintain. A combination accelerometer and gyroscope could help stabilise the device to get a better read.

While Lemaire of Analog Devices agrees that integrating gyroscopes into a chipset that also has an accelerometer could improve accuracy, he also said that much of the improved functionality can be achieved with three-axis accelerometers alone, especially since gyroscopes are expensive, consume a lot of power and add bulkiness to devices.

"Gyroscopes provide greater range of motion, that's true," he said. "But the jury is still out on whether you can make a suitable gyroscope/accelerometer chip. Handset makers are looking for cheaper, lower-power and smaller components. That is their priority rather than adding more functionality, especially when it only adds marginal value."

But Invensense says it is developing a combined three-axis accelerometer and gyroscope that will meet price, power consumption and size constraints appropriate for mobile devices. Commercial products are at least a year away, but the company is already talking to major handset manufacturers, Nasiri said.

Whether handset makers use three-axis accelerometer chips only or a combination chip that has both an accelerometer and gyroscope, experts agree that the best way to ensure the technology is adopted and the market takes off is to enable applications that help mobile operators generate revenue.

"I don't think that handset makers will integrate a $2 (£1) sensor simply to allow people to scroll through screens better," said Marlene Bourne, president and principal analyst for Bourne Research. "But using it to improve picture quality, so that I actually want to send pictures I've taken on my phone to friends and family, which generates traffic on a carrier's network, might be worth it."