New Approaches to Machine Vision Based Displacement Analysis

Richard Neumayr

Research output: ThesisDoctoral Thesis

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Abstract

This thesis describes new approaches to machine vision based measurement and displacement analysis. It deals with the design and manufacturing of optical components; calibration and evaluation procedures; together with thermally stable housings. All these elements are required for the implementation of accurate optical displacement and orientation sensors. Printed hexagonal and rectangular dot-patterns on optical glass are investigated with respect to their spatial scattering properties of an incident laser beam, and as a means of implementing semi-transparent windows to image laser spots on two parallel targets. The positions of the laser spots are observed by two cameras. The mapping from pixel coordinates to real world coordinates is implemented via a bivariate tensor polynomial product, whereby the calibration coefficients are determined in a manner such that the distortion associated with the optical component, e.g., lens distortion is compensated. The covariance propagation is explicitly computed for the calibration process and used to optimize the selection of the polynomial degree. This reflects the trade-off minimizing between the systematic and stochastic error. Two applications that incorporate the results of the theoretical approach are presented: (1) The new technique and methods are demonstrated in the design and implementation of an active optical laser target for machine guidance control. The unit measures the orientation and position of the machine using an off-vehicle reference laser beam that is projecting its laser spots on two parallel targets. Precise measurements of the spot positions are achieved, yielding a standard deviation of the displacement error of 0.05 [mm] and for yaw and pitch of 0.02 [degree]. (2) The second measurement system is a single, stationary camera setup for direct full pose determination of parallel manipulators. Light Emitting Diodes (LED) mounted on the End Effector are registered in the image to compute the mapping and the displacements. Poses could be quickly registered at sub-millimetre precision. This method simplifies the kinematic calibration structure of parallel manipulators considerably. Finally, a new viable component called electro-active glass - glass that exhibits selective reflection/transmission properties - is investigated as regards its potential as a laser reference spot target for precision camera based metrology.
Translated title of the contributionNeue Verfahrens- und Lösungsansätze in der optischen Messtechnik zur Bestimmung von Orientierung und Position von Objekten.
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • O'Leary, Paul, Assessor A (internal)
  • Zsombor-Murray, Paul J., Assessor A (external), External person
Publication statusPublished - 2011

Bibliographical note

no embargo

Keywords

  • Bivariate Tensor Polynomial Approximation
  • Optical Error Compensation
  • Vision Based Instrumentation for Machine Guidance Control

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