Digital pen using ultrasonic tracking
Number of patents in Portfolio can not be more than 2000
United States of America Patent
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-
Mar 9, 2004
Grant Date -
N/A
app pub date -
May 10, 2000
filing date -
May 10, 2000
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A digital pen that has a writing tip includes an ultrasonic (US) transducer on a pen body that generates frames of US pulses toward a receiver base in response to an infrared (IR) synchronizing signal from the base. The first pulse of a frame is adjusted by a modulo of the US period .tau. when the time of arrival (TOA) of the first pulse varies from an expected TOA by more than one-half .tau.. The TOAs of successive i.sup.th pulses in the frame, which are one wavelength apart from each other, are adjusted forward in time by subtracting from each pulse TOA (i-1).tau., and then several of the adjusted pulse TOAs in a single frame are averaged together to determine a frame TOA. The frame TOAs from plural receivers on the base are then triangulated to determine a pen position for that frame, with the pen positions being input to a handwriting recognition module.
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