Three dimensional ultrasound gestural interface

Tracking complex human body 3D gestures to realize human-computer interfaces is possible using the proposed localization system. It is composed of a number of low-cost 3D remote position sensors and of a set of beacons that emit a sequence of ultra-acoustic pulses in the space region containing the position sensors. When impinged by the acoustic wavefronts, each sensor sends back a signal to a central unit through a suitable transmission channel. The central unit, knowing the positions of the acoustic beacons and the time of arrival of the sensor signals, computes the positions of the sensors, identifying and discarding possible false signals due to echoes and environmental noise. In a first prototype implementation, four coplanar beacons, actually earphones, are placed at the corners of a PC screen, and are forced to emit pulses in the 20 - 40 kHz band. Each sensor is equipped with a wideband miniature microphone, which is wired to an acquisition board. All the computation, including signal filtering, time of arrival detection, localization and results display, is carried out by a notebook PC at 25 Hz.