STMicro Could Enable Touchless Gesture Control of Smartphones
Touchless swipes, taps and double-taps can all be identified by STMicro's 'time-of-flight' proximity detector
Thu, February 27, 2014
IDG News Service (Paris Bureau) — Using an infrared laser, ST Microelectronics' new proximity detector for mobile phones can measure distances to within a centimeter or two.
The component could enable future smartphones to repond to more sophisticated touchless commands, distinguishing between as many as eight simple hand gestures, said company representatives on the STMicro stand at Mobile World Congress.
Traditional proximity detectors contain a sensor that detects when a beam of infrared light from an adjacent LED is reflected off a nearby object. While the intensity of the reflected light can give some information about the proximity of the object, this can also be affected by the object's color or surface finish. Typically, they are placed next to the phone's earpiece or front-facing camera.
Software running on a demo phone showed a traditional detector responding strongly to objects within about 5 cm, but barely reacting beyond that. The same app also showed the new detector's response varying proportionally with the distance to an obstacle, out to about 50 cm.
The new detector is much more precise because it calculates the time of flight of individual photons emitted by an infrared laser and reflected back to a sensor consisting of a single-photon avalanche diode (SPAD), said STMicro representative HervA(c) Grotard. He declined to explain exactly how the component measures the flight time, saying only that it was done by performing statistical calculations on a number of results gathered over time. Its power consumption will be equivalent to that of existing, less precise components, he said.
His colleague Jocelyn Leheup demonstrated how the detector can distinguish between gestures. Moving a hand in close towards a demo phone's screen and then briskly backing away again prompted an app to display a symbol representing a tap. Performing the same gesture twice in succession triggered the symbol for a double tap. Passing a hand from one side of the screen to the other, 10 or 20 cm in front of it, triggered a swipe symbol, while the same gesture from side to side and back was detected as a double swipe. The detector did not distinguish between left-to-right and right-to-left movements, however.
Leheup also showed how an app could distinguish between the broad obstacle of a swipe with all fingers extended, the narrow obstacle of a single finger extended, and the fluctuation in distance when two fingers extended in a V are swiped in front of the sensor. In all an app could distinguish between as many as eight gestures, he said.