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Position determination

  • US 6,556,722 B1
  • Filed: 11/30/1999
  • Issued: 04/29/2003
  • Est. Priority Date: 05/30/1997
  • Status: Expired due to Term
First Claim
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1. A method of determining the three-dimensional position of an object in a reference frame, the method comprising:

  • providing three or more markers at respective reference positions, at least three of the markers being patterned as a series of concentric shapes encoding a plurality of bits of identification information in the darkness or color of the shapes, the center of the concentric shapes of each patterned marker providing a reference point for each marker, wherein each marker has a respective distance from a reference plane of the reference frame, the distances varying between the markers;

    storing information including a measure of the three-dimensional positions of the markers in the reference frame and information identifying the patterned markers;

    obtaining an image of at least a sub-set of said markers from a camera associated with the object;

    processing the image to identify the positions of said markers in the image and, for each patterned marker in the sub-set, identifying the respective reference point and decoding said identification information;

    determining a measure of the three-dimensional position of the object in the reference frame based on said processing and decoding and based on said stored information.

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