March 23, 2007 4:00 AM PDT
Motion sensing comes to mobile phones
Responding to a flick of the wrist or sweep of the arm, tiny sensors called accelerometers, which measure linear acceleration in the Wiimote game controller, translate motion into action on the screen. When the technology is added to a cell phone, the handset's utility changes in several intriguing ways. It can, for example, function as a motion-sensing mouse that lets you browse the mobile Internet by tilting the device left, right, up or down. It even can allow you to monitor a fitness workout by measuring the number of steps you take, your speed and the calories burned.
Experts say this is just the beginning. As accelerometers advanced from one-axis to two-axis to three-axis measurement capabilities, their accuracy has improved dramatically. And some companies, such as the 3-year-old start-up Invensense, are taking the technology a step further by combining three-axis accelerometers with gyroscopes, which measure rotation speed, to create even-more accurate sensors that could be used to improve photo stabilization and location and navigation services.
Analog Devices, one of the largest manufacturers of accelerometers, has already supplied more than 300 million of the devices to consumer electronics makers over the past decade, but Christophe Lemaire, the company's marketing manager, said the market is set to explode as more of these components make their way into cell phones.
"My sense is we are on the edge of seeing an explosion of more and more devices using motion sensors, and specifically MEM (microelectromechanical) accelerometers," he said. "We are already working with all the tier one phone manufacturers as well with other third-party application developers to fuel this explosion."
Accelerometers--especially those based on MEM systems, which combine electrical and mechanical components--have been used for years in airbag deployment in automobiles. For those applications the accelerometers are used to detect the rapid negative acceleration of the vehicle to determine when a collision has occurred and its severity.
But in the last few years the technology has also been incorporated into personal electronic devices, such as mobile phones, digital cameras, media players and handheld gaming devices. Several handset manufacturers including, Nokia, Samsung Electronics, LG Electronics, and even newcomer Apple have used accelerometer technology to provide some kind of motion-sensing capability in a handful of handset models.
Not in the U.S.--yet
Most of these phones have been available only in South Korea or Japan, where cutting-edge cell phone features typically originate. In the U.S., Apple's iPhone will be one of the first phones to use accelerometer technology.
The iPhone, set to debut in June on AT&T's wireless network, detects when the device is rotated, so it can tell whether to display what's on the screen in portrait (vertical) or landscape (horizontal) format. That allows the user to determine which format is best for viewing whatever is on the screen, be it a Web page, video or photo. The phone also can detect when it's being lifted to the ear, and responds by immediately turning off the display light to save power and preventing changes to the display image due to inadvertent contact with the touch-sensitive screen. The system restores screen power when the iPhone is moved away from the ear.
Lemaire said applications such as the ones employed by the iPhone are likely to become popular. He predicts handset makers will include accelerometers to detect if a phone is resting facedown, so that it can turn off the ringer or power down the display to conserve battery power. Accelerometers also could be used to shut off power on phones that have been left idle.
Those are a few basic applications for accelerometers. They can also be used to help people operate their phones without using a keypad. The Samsung SCH-S310, introduced in Asia in 2005, uses a three-axis accelerometer that allows a user to dial the phone by "writing" numbers in the air.
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