title: Low-distortion perturbative solutions in a camera calibration model including high-distortion radial effects.
abstract: OBJECTIVE
  An endoscope fisheye lens camera calibration model was extended using intuitive vector parameters to describe lens distortion with a fourth degree radial polynomial.
  
  
  METHODS
  An existing algorithm was expanded to the wider domain of applicability of the high endoscopic distorted lenses. By completely decoupling the computation of the camera distortion center obtained using general properties of distortion lines, even strong radial distortion effects can be perturbatively included into a pure perspective first guess zero-distortion solution.
  
  
  RESULTS
  A perturbative and iterative solution used to model small amounts of lens distortion can be maintained in case of strong distortion lenses, such as the endoscope fisheye, with satisfactory results.
  
  
  CONCLUSIONS
  We demonstrated that using an educated guess for the initial solution based on the final location of the lens distortion center, the intuitive vector-based model's full solution can be iteratively obtained starting from a purely perspective distortion-free first guess solution.
authors.affiliation: Institute for Process Control and Robotics, Karlsruhe Institute of Technology, Baden-Württemberg, Germany. ciucci@ira.uka.de
authors.forename: Matteo
authors.initials: M
authors.lastname: Ciucci
authors.forename: Daniel
authors.initials: D
authors.lastname: Stein
authors.forename: Joerg
authors.initials: J
authors.lastname: Raczkowsky
authors.forename: Heinz
authors.initials: H
authors.lastname: Wörn
mesh_terms: D000465:Algorithms; D002138:Calibration; D019723:Endoscopes; D019544:Equipment Failure Analysis / Q000379:methods; D007089:Image Enhancement / Q000379:methods*; D010781:Photography / Q000295:instrumentation*; D015203:Reproducibility of Results