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Camera-pen-tip mapping and calibration

  • US 7,136,054 B2
  • Filed: 01/06/2004
  • Issued: 11/14/2006
  • Est. Priority Date: 01/06/2004
  • Status: Expired due to Fees
First Claim
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1. A method of calibrating a digital pen, which includes a pen tip and a camera, and of mapping a location of a center of a camera-captured image to a location of the pen tip, the method comprising:

  • generating a calibration parameter based on a plurality of images captured by the digital pen'"'"'s camera by placing the pen in a plurality of different orientations while keeping the pen tip at a substantially fixed location Lpentip on a positionally encoded surface, wherein the calibration parameter is generated based on a plurality of iteratively generated estimates of the calibration parameter; and

    using the calibration parameter to map the location of the center of the camera-captured image to the location of the pen tip so that a stroke written by a user on the positionally encoded surface can be recovered at a location within an electronic copy of the positionally encoded surface, wherein the position of the recovered stroke within the electronic copy corresponds to a plurality of locations of the pen tip as the user was writing the stroke on the positionally encoded surface.

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