Patent ID: 8139029

Claim:
An apparatus comprising: a touchless sensing unit to generate a three-dimensional ultrasonic sensing space and track a relative location and movement of an object in the three-dimensional ultrasonic sensing space; and a controller communicatively coupled to said touchless sensing unit for communicating a coordinate of said object within said three-dimensional space, wherein the sensing unit operates to: emit an ultrasonic pulse from a first ultrasonic transducer configured to transmit the ultrasonic pulse that reflects off the object in said three-dimensional space and generates a reflected ultrasonic signal; digitally sample the reflected ultrasonic signal to produce a sampled reflected ultrasonic signal; suppress a ringing distortion of the sampled reflected ultrasonic signal via digital signal processing wherein the ringing distortion is a result of the close proximity interference and residual ringing of the emitted ultrasonic pulse; and wherein the suppressing comprises subtracting a contribution of the ringing portion of the emitted ultrasonic pulse from the reflected signal to remove a ring-down effect; estimate a time of flight between when said ultrasonic pulse was transmitted from said first ultrasonic transducer and when the suppressed reflected ultrasonic signal was received for a plurality of ultrasonic transducers configured to receive the reflected ultrasonic signal; calculate a phase differential between the suppressed reflected ultrasonic signal and a previously received reflected ultrasonic signal both received at a same ultrasonic transducer for the plurality of ultrasonic transducers; and determine a location and relative displacement of said object by weighting said time of flight measurements and with said phase differential measurements for the plurality of ultrasonic transducers from repeated operation.