3D Digitizing System for Reverse Engineering

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Camera Calibration

• In the field of machine vision, camera
  calibration refers to the experimental
  determination of a set of parameters which
  describe the image formation process for a given
  analytical model of the machine vision system.
• Ideally, camera calibration is performed without
  specialized optical equipment, without
  modifications to the hardware, and without a
  priori knowledge of the vision system.
• Most calibration techniques are based on the
  observation of planar (2D) targets with a large
  number of control points.

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Camera Calibration

• Camera Calibration is critical in many machine
  vision applications
• Photogrammetry determining geometric properties
  of objects from photographic image
• Stereoscopy determining the 3D coordinates of
  points of an object taken from two different
  positions
• Dimensional metrology the science of calibrating
  and using physical measurement equipment to
  quantify the physical size of or distance from
  any given object
• Multisensor Image fusion the process of
  combining relevant information from two or more
  images into a single image
• Robotics, navigation, reverse engineering

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Camera Calibration
3D Calibration target proposed by Prof.
Janne Heikkilä
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Camera Calibration
Orthogonal (Fig 8) versus perspective (Fig 9)
projection of a circular control point
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Camera Calibration
Checkerboard calibration target proposed by
Jean-Yves Bouguet (Caltech)
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Camera Calibration

• The machine vision parameters which must be
  identified include
• The scale factor (negligible on solid-state
  cameras)
• The principal point (i.e., the coordinates of the
  image center)
• The skew coefficients (negligible?)
• The effective focal length of the lens-camera
  assembly
• The radial and tangential lens distortion
  coefficients
• The pose (position and orientation) of the camera
• Parameters a) through d) are classified as
  intrinsic, e) as extrinsic.

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Camera Calibration