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IR Lasers Enable Touchless Smartphones

GENEVA, March 3, 2014 — A new proximity detector could allow future smartphones to respond to touchless commands by distinguishing between as many as eight hand gestures. Using an IR laser, the detector is able to measure distances to within a centimeter or two.

The detector, developed by ST Microelectronics, calculates the time of flight of individual photons that are emitted by the IR laser and reflected back to a sensor consisting of a single-photon avalanche diode (SPAD).

Sensors in traditional proximity detectors identify when a beam of IR 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.

Using software on a demo phone, developers found that a traditional detector responds strongly to objects within about 5 cm, but barely reacted beyond that. The same software also found that the response of the new detector varied proportionally with the distance to an obstacle, out to about 50 cm.

The new detector can distinguish between as many as eight gestures, according to Jocelyn Leheup of ST Microelectronics, prompting commands including swiping and double tapping. However, it does not differentiate between left-to-right and right-to-left movements.

The new detector is smaller, too, and could be concealed in the earphone. Traditional detectors require obvious apertures — one for light leaving the LED and the other for its return to the sensor — in the front of the device.

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