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Marking system with pen-up/pen-down tracking

  • US 5,434,370 A
  • Filed: 11/05/1993
  • Issued: 07/18/1995
  • Est. Priority Date: 11/05/1993
  • Status: Expired due to Term
First Claim
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1. In a graphic data-acquisition system for tracking the position of an implement relative to a writing surface, a sub-system for distinguishing between a write mode and a non-write mode of the writing implement comprisingelectromagnetic-radiation-generating structure disposed adjacent the writing surface and operable to produce an expanse of radiation in a substantially planar zone near the writing surface,radiation-interactive structure associated with the implement and capable of interacting with the expanse to produce signals which vary depending on a relative distance between a writing tip on the implement and the writing surface,monitoring structure capable of detecting and converting the signals into an analog data stream, anda processor for receiving and processing the data stream to determine when the implement is in the write mode and when the implement is in the non-write mode.

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