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Tracking motion of a writing instrument

  • US 7,268,774 B2
  • Filed: 07/17/2003
  • Issued: 09/11/2007
  • Est. Priority Date: 08/18/1998
  • Status: Expired due to Fees
First Claim
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1. A method comprisingreceiving, from a writing instrument, light including a modulation frequency,sensing the light at each of two or more sensors each comprising sensitive pixels and generating a sequence of signals representative of the sensed light,determining the modulation frequency from the sensor signals using a phase lock loop,sampling a sensor signal at the times triggered by the phase lock loop, anddetermining a location of the writing instrument based on the sampled sensor signals.

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