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Optical sensors let gadgets point their own way

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Hank Hogan,

With apologies to William Shakespeare, all the world’s a pad and all devices merely mice. At least, that could be the case if researchers Chris Harrison and professor Scott E. Hudson of the Human-Computer Interaction Institute at Carnegie Mellon University have their way. The duo has shown how gadgets too small for ordinary input methods can function as their own pointing devices, thanks to the latest in inexpensive optical sensor technology.

The approach could make possible much smaller audio players, phones and other gear, Harrison said. “If we can get rid of screens and buttons, we could make devices that are the size of a couple of pennies.”

Optical sensor technology mounted on the bottom of a small device provides it with mouselike pointing ability that makes input easier. Courtesy of Chris Harrison, Carnegie Mellon University.

Harrison, a graduate student, noted that getting information into electronic devices presents a fundamental challenge. Although electronic devices have gotten smaller, people have not. As a result, buttons and screens must be a certain size, placing a lower limit on the size of devices.

The solution devised by the Carnegie Mellon researchers is to change the input method. Conceptually, it is the same as turning a device into a mouse, with optical sensors mounted on the bottom of the device. With two sensors, this approach enables tracking X and Y movement, as well as rotation, on surfaces ranging from tabletops to shirtsleeves to the palm of a hand. Virtually any flat surface will work.

This tactic of turning devices into mice offers a number of advantages. One is that targeting with pixel-level accuracy is possible – something that cannot be done with comparatively fat fingers working a touch screen. Also, getting fingers off a screen improves the visibility of its output. A third plus is that it can transform a surface into a virtual control space, with some areas designated for functions such as horizontal or vertical scrolling.

The approach takes advantage of the sensor technology behind today’s optical mice. Over the past few years, the cost of such technology has dropped significantly. So, too, has its size. At the same time, the precision of the sensors and their ability to pinpoint a location have remained high.

The sensors and associated technology have another attribute that makes them useful in a handheld or portable device, Harrison said. “They consume almost no power and are fantastically precise.”

He noted that simply slapping sensors on a device isn’t enough, however. The technology must be married to software, other hardware and the right interface to be effective. Harrison and Hudson presented a prototype at the April 2010 Association for Computing Machinery’s annual Conference on Human Factors in Computing Systems in Atlanta.

In their prototype, they used the technology for gestures, with software that understood flicking and twisting. They demonstrated an audio player, with users able to scroll through a list, select a song and adjust the volume. All of this was done without the use of buttons.

Tests done with eight college-age subjects produced positive feedback. Certain motions, in particular those involving twisting, were particularly popular. The physical nature of the motion, such as flicking, also appealed to some of the testers.

As for the future, Harrison noted that talks with manufacturers to bring the technology to the mass market are under way. The approach could end up in a cell phone, which has the processing power to handle the interface.

With regard to the sensor technology itself, it’s good enough for many applications today but could be improved, Harrison said. “Further miniaturization is always welcome.”

Photonics Spectra
Jul 2010
The transfer of a part of a device's or circuit's output back to its input.
1. A generic term for detector. 2. A complete optical/mechanical/electronic system that contains some form of radiation detector.
Association for Computing Machineryaudio playerCarnegie MellonCarnegie Mellon UniversityChris Harriosnelectronic devicesfeedbackflickingHank Hoganhardwarehorizontal scrollingHuman Factors in Computing SystemsHuman-Computer Interaction Institutemiceoptical sensoropticsPALMpixelsprototypeResearch & TechnologyrotationScott HudsonscrollsensorSensors & DetectorstabletopTech Pulsetouch screenvertical scrollingvirtual control spaceWilliam Shakespearelasers

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