Patent ID: 7573467
Filing Date: 2009-08-11
Classification: G01S,G06F

Abstract:
1. A graphic input device for measuring a displacement of a pen-shaped pointing device, comprising: A. the pen-shaped pointing device moving about a writing surface and transmitting ultrasonic (US) continuous waves (CW) propagating in the air; B. two receivers close to the writing surface, each including means for receiving US waves from the pen-shaped pointing device and for measuring a phase of the received waves, wherein a change in the phase is proportional to the displacement of the pointing device relative to that receiver; C. means for a coarse measurement of a pen-shaped pointing device's location with respect to the two receivers; D. means for computing a displacement in fixed orthogonal (x-y) coordinates from the measured displacement relative to the two receivers and the measured coarse pen-shaped pointing device location.