Nonfeedback-based machine vision methods for determining a calibration relationship between a camera and a moveable object

  • US 6,301,396 B1
  • Filed: 12/31/1998
  • Issued: 10/09/2001
  • Est. Priority Date: 11/21/1996
  • Status: Expired due to Term
First Claim
Patent Images

1. A method of determining a calibration relationship between a reference frame of motion of an object and an image coordinate system (hereinafter “

  • image reference frame”

    ) of each of plural image acquisition devices that generate images of the object, the method comprising the steps of;

    A. coupling plural targets to the object such that (i) the location and orientation of the targets on the object are not necessarily known, and (ii) the locations and orientations of the targets are any of fixed and known relative to one another;

    B. placing the object at plural known locations/orientations relative to the motion reference frame of the object such that at least one target is in a field of view of each respective image acquisition device for plural ones of those locations/orientations, where “

    location/orientation”

    refers to at least one of location and orientation, and where “

    locations/orientations”

    refers to the plural thereof;

    C. generating with each image acquisition device an image of the object at each of the plural known locations/orientations relative to the motion reference frame of the object, and determining a location/orientation of the target in each of those images relative to the image reference frame of the image acquisition device;

    D. determining a calibration relationship between the reference frame of motion of the object and the image reference frame of each of the image acquisition devices as a function of (i) the known locations/orientations of the object relative to the notion reference frame of the object and (ii) the locations of the targets in the corresponding images of the object relative to the image reference frame of the image acquisition device, and wherein step (D) comprises the step of determining the calibration relationship by minimizing an error between known locations/orientations of the object and estimates of those locations/orientations based on candidate calibration relationships.

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