Patent ID: 6703570
Filing Date: 2004-03-09
Classification: G01S,G06F,Y10S

Abstract:
A digital pen system, comprising:an elongated pen defining a writing tip; an ultrasonic (US) transducer oriented on the pen to direct frames of US energy outwardly from the pen; at least two detectors on a base receiving the US energy and outputting plural pulses, each pulse being associated with at least one pulse time of arrival (TOA) relative to at least one detector; and a processor on the base and receiving signals from the detectors and in response thereto outputting position signals representative of positions of the pen based on at least one frame TOA, the processor determining the frame TOA based at least in part on at least one of: determining that a TOA of a first pulse in a frame deviates from an expected TOA by at least a predetermined time period, and averaging together plural pulse TOAs associated with pulses in a single frame.